Next Article in Journal
RETRACTED: Rahman et al. An Overview of Antimicrobial Stewardship Optimization: The Use of Antibiotics in Humans and Animals to Prevent Resistance. Antibiotics 2022, 11, 667
Previous Article in Journal
Retrospective Study of Bacteriological Patterns and Antimicrobial Resistance Profiles of Mastitis in the Banat Region of Romania
Previous Article in Special Issue
Characterization of Salmonella spp. Isolates from European Hedgehogs (Erinaceus europaeus) in Italy: Serotypes and Antimicrobial Susceptibility Profiles
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Antibiotics
Volume 15
Issue 2
10.3390/antibiotics15020199
antibiotics-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Wild Fishes as Reservoirs of Gut Bacteria Carrying Antimicrobial Resistance Encoding Genes in Chilean Bays

by
Claudio D. Miranda
1,*,
Christopher Concha
1,
Luz Hurtado
1,
Rodrigo Rojas
1 and
Jaime Romero
2
1
Laboratorio de Patobiología Acuática, Departamento de Acuicultura, Universidad Católica del Norte, Coquimbo 1780000, Chile
2
Laboratorio de Biotecnología, Instituto de Nutrición y Tecnología de los Alimentos (INTA), Universidad de Chile, Macul, Santiago 7810000, Chile
*
Author to whom correspondence should be addressed.
Antibiotics 2026, 15(2), 199; https://doi.org/10.3390/antibiotics15020199
Submission received: 8 January 2026 / Revised: 4 February 2026 / Accepted: 9 February 2026 / Published: 11 February 2026
(This article belongs to the Special Issue Antimicrobial Resistance in the Wildlife)
Browse Figures
Versions Notes

Abstract

Objective: The main aim of the study was to evaluate the role of wild fishes inhabiting in three anthropogenic-impacted Bays in Chile as reservoirs of antimicrobial resistance genes (ARGs). Methods: A total of 245 antimicrobial-resistant isolates were isolated from fish captured in the Coquimbo (142 isolates), Concepción (44 isolates), and Puerto Montt (59 isolates) Bays, and were identified by 16S rRNA gene sequence analysis, Antimicrobial-resistant isolates were tested for susceptibility to 12 antimicrobials by an agar disk diffusion method, and the carriage of genes encoding for resistance to main antimicrobial classes, such as β-lactams, amphenicols, tetracyclines, and sulfonamides by PCR (Polymerase Chain Reaction). Results: A predominance of the Pseudomonas (37.04%), Vibrio (14.40%), and Shewanella (13.99%) genera. Antimicrobial-resistant isolates were tested for susceptibility to 12 antimicrobials by an agar disk diffusion method, showing highest resistance to streptomycin (82.4%), amoxicillin (67.4%), and furazolidone (63.3%), and lowest resistance to ciprofloxacin (3.7%), meropenem (22.5%), and oxytetracycline (29.8%) and exhibiting a high occurrence of the multi-drug resistance phenotype (76.9%). Furthermore, an important number of isolates recovered from sampled fish species carried plasmids (53.5%), floR gene (36.7%), and tet genes (19.2%), whereas the detection of sul genes and class 1-integron was rare. As an overall result, 10.6% of isolates carried at least one bla gene, encoding an extended-spectrum-β-lactamase, with a high predominance of the blaCTX-M1 gene (23 isolates), whereas 14 out of 245 isolates (5.7%) were positive for the carriage of carbapenemases encoding genes, which both groups exhibited the β-lactam resistance phenotype. Conclusions: The wide distribution of ARG-carrying bacteria in wild fishes from all sampled Bays provides evidence that wild fish are important reservoirs and drivers of spread of ARGs in the marine environment, prompting the need of a continuous surveillance of these genes in wild fishes inhabiting anthropic impacted coastal marine environments in Chile.

1. Introduction

The rapid global spread of antimicrobial resistant bacteria represents one of the most serious threats to human health today, resulting in approximately 700,000 deaths worldwide each year due to drug-resistant infections [1,2].
As noted, antimicrobial resistance is a growing public health concern worldwide, and it is now regarded as a critical One Health issue [3,4]. One Health is an interdisciplinary concept, which recognizes that interdependent human, animal, and environmental domains contribute to the emergence, evolution, and spread of antibiotic-resistant microorganisms, and their related antimicrobial-resistance genes (ARGs) on a local and global scale [3,4], which demands knowledge and understanding of their role in the dissemination of ARGs under a One-Health perspective. Thus, under a One Health approach, it is critical to understand the role of marine fishes residing in anthropic-impacted coastal waters in the spread of molecular elements involved in antimicrobial resistance and transfer [5,6,7]. Carriage of ARGs by resistant bacteria residing in wild fishes raises ecological and public health concerns, emphasizing the need for further studies, especially in relation to the ARGs of clinical importance [8,9].
Most of studies on the occurrence of ARGs in fish gut microbiota are related with aquaculture settings [10,11,12,13]. Otherwise, studies on the ARGs carried by bacteria composing the microbiota of wild fishes from non-aquaculture settings are scarce, and mostly related to freshwater and estuarine environments [8,9,14,15]. In this trend, Ballash et al. [16] concluded that fishes are effective bioindicators of freshwater environments contaminated with antimicrobial-resistant bacteria, and antimicrobial-resistance encoding genes. In another study, Sellera et al. [17] reported for the first time the occurrence of Escherichia coli carrying β-lactamase-encoding genes among gut bacteria from wild fishes from Brazilian polluted estuarine waters. Furthermore, Mills et al. [18] demonstrated that fish gut bacteria carry higher levels of genes encoding for carbapenem resistance than do the surrounding water and sediment of a human-impacted river.
Despite significant anthropogenic impacts in many coastal areas in Chile, which are usually used for human recreational activities and by artisanal fishing for capturing seafood, no studies of the resistome of gut bacteria inhabiting wild fishes have been previously performed. In Chile, only two studies, conducted more than two decades apart, on the occurrence of antimicrobial resistant bacteria by marine wild fishes have been performed, confirming the role of these species as reservoirs of antimicrobial resistant bacteria [19,20]. We reported a high incidence of multi-drug-resistant bacteria among gut microbiota of wild fishes captured in Southern [19] and Northern [20] Bays in Chile; however, to date no studies have been conducted in this country, to evaluate the occurrence of antimicrobial-resistance encoding genes carried by gut bacteria recovered from marine wild fishes.
The main aim of the study was to evaluate the role of marine wild fishes residing in three main human-impacted Chilean Bays as reservoirs and routes for the spread of genes encoding antimicrobial resistance against antimicrobials important in human and animal therapy, posing a significant public health risk.
It is expected that marine wild fishes residing in different bays impacted with anthropogenic contaminants, will carry a high taxonomic diversity of antimicrobial resistant bacteria carrying diverse ARGs, as well as plasmids, confirming the role of wild fishes as highly important contributors of maintenance and spread of main antimicrobial resistant genes of clinical importance in marine environments. Thus, this study will address a critical knowledge gap and emphasizes the public health risks posed by anthropogenic contamination in coastal ecosystems.

2. Results

2.1. Bacterial Identification

The identification of 245 antimicrobial-resistant isolates recovered from the Coquimbo, Concepción, and Puerto Montt Bays showed a high predominance of Pseudomonas genus (36.7%), and a lesser proportion the Vibrio and Shewanella genus (14.3 and 13.9%, respectively), as is described in Table 1. All Bays exhibited a dominance of Pseudomonas representatives, comprising the 38.7%, 43.2%, and 27.1%, of antimicrobial resistant isolates recovered from intestinal content of wild fishes from Coquimbo, Concepción, and Puerto Montt Bays, respectively, whereas Vibrio (21.1%), Psychrobacter (13.6%), and Shewanella (18.6%) were the second largest predominant genus in wild fishes recovered from these Bays (Table 1). Antimicrobial-resistant isolates from wild fishes belonged from ten to fourteen different genera, and from these, only Pseudomonas, Psychrobacter, Shewanella and Photobacterium, Vibrio and Brochothrix genera were detected in fishes from all sampled Bays (Supplementary Tables S1–S3).

2.2. Antimicrobial Resistance Patterns

Antimicrobial resistance patterns of the recovered strains were not related to specific bacterial species or Bay sampled. Overall, highest percentages of antimicrobial resistance among Chilean isolates were observed against streptomicin (82.4%), amoxicillin (67.4%), and furazolidone (63.3%), whereas the lowest incidence of resistance to ciprofloxacin (3.7%), meropenem (22.5%), and oxytetracycline (29.8%), was detected among the studied isolates (Figure 1a). When sampled Bays were compared, isolates recovered from Concepción and Puerto Montt Bays exhibited the lowest proportions of resistance to the antimicrobials, meropenem (11.4% and 3.6%), ciprofloxacin (4.5% and 12.5%), and kanamycin (22.7% and 30.4%), whereas isolates from Coquimbo Bay evidenced lowest resistance proportions against the antimicrobials ciprofloxacin (0.7%), oxytetracycline (23.2%), and trimethoprim/sulfamethoxazole (28.9%) (Figure 1a). Conversely, isolates recovered from fishes captured at Coquimbo, Concepción, and Puerto Montt Bays, exhibited highest proportions of resistance to the antimicrobials streptomycin (85.2%, 63.6% and 83.9%), amoxicillin (64.8%, 70.4% and 73.2%), and furazolidone (56.6%, 85.5% and 73.2%), as shown in Figure 1a.
High levels of multiresistance among antimicrobial-resistant isolates from sampled Bays were detected, observing that 29.6%, 54.8% and 33.9% of isolates from Coquimbo Bay, Concepción Bay, and Puerto Montt Bay, respectively, showed simultaneous resistance to 7–11 antimicrobials (Figure 1b). In this trend, similar antimicrobial resistance indexes (ARI) were observed among the antimicrobial-resistant bacteria isolated from the studied Bays, exhibiting ARI values of 0.37, 0.47, and 0.44 for isolates recovered from Coquimbo, Concepción, and Puerto Montt Bays, respectively. Otherwise, a high proportion of isolates from all Bays showed high levels of simultaneous resistance to at least three antimicrobial classes (71.1%, 81.8%, and 89.3% of isolates recovered from Coquimbo, Concepción, and Puerto Montt Bays, respectively), thus exhibiting a multi-drug resistance phenotype. Reference strain Escherichia coli ATCC 25922 was used for quality control in all susceptibility assays exhibited. Antimicrobial inhibition values within the ranges were considered acceptable by CLSI [21].

2.3. Carriage of Antimicrobial Resistance Genes (ARGs)

From a comprehensive perspective, isolates recovered from wild fishes residing in Chilean anthropogenically impacted waters evidenced the carriage of a wide variety of ARGs encoding for resistance to antimicrobial classes of critical importance for human and animal health, confirming the role of wild fishes as reservoirs of these elements. Geographically, no significant differences in the distribution of studied ARGs among the studied Chilean Bays were observed.
As shown in Table 2, a considerable number of gut isolates from wild fishes carried at least one bla gene (37 isolates), encoding for resistance against cephalosporins (10.6%), exhibiting a high predominance of representatives of the Pseudomonas genus (28 isolates). Among the bla-carrying isolates, a high predominance of the blaCTX-M1 gene (23 isolates), followed by the carriage of the blaCTX-M4 gene (four isolates), was observed. All of these bla-carrying isolates exhibited a positive resistance phenotype.
As an overall result, 15 out of 245 isolates (6.1%) were positive for the carriage of a gene, encoding for the synthesis of a metallo-β-lactamase, observing the highest carriage of the blaSPM gene (eight isolates). Among the five assayed carbapenemase-producing genes, four of them were detected among some isolates from wild fishes, and only the blaGYM gene was not detected in any isolate (Table 2). It is important to note that all bla-carrying isolates encoding for cephalosporinases and carbapenemases exhibited the resistant phenotype against the third-generation cephalosporin cefotaxime, and the carbapenem meropenem, respectively. In addition, the phenotypic detection of Extended-Spectrum-β-Lactamase (ESBL) and carbapenemases activity were demonstrated in all of these isolates.
When the carriage of chromosomal Ampc β-lactamase was investigated, only five isolates from wild fishes were captured at Coquimbo Bay (three isolates carrying blaCMY, and one isolate carrying blaFOX or blaDHA) and two resistant isolates recovered from fishes captured at Concepción (one isolate carrying blaFOX or blaACC) Bay were positive for this β-lactamase group, whereas no carriage of this β–lactamase enzyme was detected among isolates from Puerto Montt Bay (Table 3).
Additionally, resistance against phenicols was extensively detected among the studied bacterial isolates (Table 2). A high percentage of antimicrobial-resistant isolates from wild fishes from the studied Bays carried the floR gene (31.7% of isolates from Coquimbo Bay, 52.3% of isolates from Concepción Bay, and 37.3% of isolates from Puerto Montt Bay), whereas none of the isolates was positive for the fexA gene, encoding for another florfenicol specific exporter (Table 2).
A high diversity of tetracycline resistance (tet) genes was detected among the gut bacteria from wild fish species, with at least four different tet genes detected in isolates from each Bay, as shown in Table 2. Overall, 47 out of 245 isolates (19.2%) were positive for the carriage of a tet gene, and seven out of the nine assayed tet genes were detected in the resistant bacteria recovered from wild fishes inhabiting the sampled Bays (Table 2). Only the tet(34) and tet(35) genes were not detected among assayed isolates. A high occurrence of resistant isolates carrying a tet gene was observed among isolates from wild fish species captured at Puerto Montt Bay, with a remarkable predominance of the tet(E) gene (18.6% of isolates). In accordance, tet(E) gene was the predominant tet gene among isolates from wild fishes from Coquimbo and Concepción Bays, but at lesser percentages.
The occurrence of sulfonamide-resistance encoding genes was infrequent, and only two isolates from each Bay were carrying the sul1 gene, whereas only one isolate from Coquimbo and Puerto Montt Bays were positive for the sul2 gene, as shown in Table 2.

2.4. Plasmid Content

A considerable number of isolates from gut microbiota of wild fishes captured from Chilean Bays carried plasmids (114 out of 245), and from these, 34 isolates contained two or more plasmid bands (Figure 2). Thus, the percentage of plasmid carrying isolates from studied Bays varied between 31.8% and 53.5%. As previously reported, a high percentage of isolates from wild fishes captured at Coquimbo Bay harbored plasmid content (76 out of 142 isolates), observing a predominance of plasmid weighting 20, 50, and 100 kb (11, 22, and 16 isolates, respectively), and from these, 18 and four isolates contained two and three plasmids, respectively [20]. Plasmid DNA was detected in 14 out of 44 isolates from fishes captured at Concepción Bay, and from these, four and one isolates carried two and three plasmids, respectively. Among the plasmid-carrying isolates, a high diversity of plasmid bands with molecular weights in the range from 10 to 80 kb was observed, exhibiting plasmid bands with molecular weight of 10 kb (two isolates), 15 kb (three isolates), 50 kb (two isolates), 60 kb (two isolates), and 80 kb (two isolates) followed by plasmids with a lower molecular weight. Plasmid DNA was detected in 24 out of 59 resistant isolates recovered from wild fishes captured at Puerto Montt Bay, and of these, seven isolates contained two plasmid bands. Among these isolates, the most found plasmid band had a molecular weight of 50 kb (18 isolates), followed by plasmids of 100 kb (three isolates).
As is shown in Table 3, gut bacteria from Chilean wild fishes carrying at least one β-lactamase encoding gene were predominantly identified as belonging to the Pseudomonas genus, comprising the 75.7%, and Shewanella, in a lower percent (16.2%) of the isolates positive for a bla gene. Furthermore, an important percentage of bla-carrying isolates were also harboring plasmid elements (48.6%), suggesting the feasibility of their horizontal dissemination in the aquatic system (Table 3).
Additionally, wild fish species, where bla-carrying bacteria were isolated vary greatly, and eight out of nine studied fish species carried isolates, at least observing that these bacteria were recovered from eight different fish species, confirming the widespread of fish species acting as reservoirs of these genes (Table 3).
Moreover, among bla-carrying isolates, a high percentage (70.3%), carried simultaneously the florfenicol resistance gene, floR, whereas only three of these isolates carried simultaneously a tet gene (Table 3).

2.5. Carriage of Class-1 Integron

As was previously reported by Miranda et al. [20], only two out of 142 isolates from wild fishes captured at Coquimbo Bay carried a class 1 integron, which were identified as Pseudomonas sp. NCIA62 and Pseudomonas sp. NCIF20, recovered from fish species Trachurus murphyi and Menticirrhus ophicephalus, respectively. Isolate NCIF20 harbored two plasmids (1.5 and 50 kb), whereas no plasmid content was detected in isolate NCIA62. Among the isolates from wild fishes captured at Concepción Bay, only the isolates Pseudomonas CCIA1 from Merluccius gayi and Pseudomonas CCIA12 from Pinguipes chilensis were positive for carrying of a class 1 integron. Isolates CCIA1 and CCIA12 carried plasmids of 50 kb and 2 kb, respectively. Otherwise, only the isolate Vibrio CIF31 from T. murphyi captured at Puerto Montt Bay carried a class 1 integron, as well as carrying a plasmid element of 100 kb. It must be noted that none of the studied bacterial isolates carried a class 2 integron. Therefore, this study show that integron-carrying bacterial isolates from wild fishes inhabiting anthropogenically impacted Chilean coasts are very rare, because only five out of 245 isolates (2.0%) were positive for carriage of this mobilome element, evidencing a wide geographic distribution at very low levels.

3. Discussion

To our knowledge, this is the first report of the occurrence of ARGs carried by gut bacteria of marine wild fishes in Chile, despite the extensively impacted coastal waters in this country. As we previously noted [20], the high incidence of untreated urban effluents disposed into aquatic waters in Chile [22], demands performing studies to assess the spread of bacteria carrying genes encoding antimicrobial resistance which could be spread in these water bodies. Some aspects of the anthropic impact on each sampled Bay that must be considered to explain differences among them is that, in addition to disposal of urban effluents in all three Bays, Concepción Bay is subject to the intense impact of industrial discharges due to the intensive activity of fishing and fish processing companies producing fishmeal, while Coquimbo and Puerto Montt Bays mainly receives domestic and gastronomic wastes, because of their high importance as tourism sites.
In agreement with the present results, ARGs have been frequently reported in isolates belonging to the Pseudomonadaceae family [23]. However, the high predominance of antimicrobial resistant isolates belonging to the Pseudomonas genus contrasted with the study of Miranda and Zemelman [19], who found that among the antimicrobial resistant gut bacteria from wild fish inhabiting the Concepción Bay in Chile, Pseudomonas representatives were almost absent. However, that study was developed 20 years ago, when the consumption by Chilean population of antimicrobials was not regulated and not requiring a medical prescription, thus favoring self-medication and excessive consumption of these drugs, suggesting that higher levels of antimicrobial residues were entering into coastal waters by disposal of urban effluents, most probably influencing the structure and levels of antimicrobial resistant microbiota residing in the ecosystems.
As previously noted by Muziasari et al. [11], fish gut has been found to contain much more abundant ARGs than the other parts of the fish body, such as skin and gills, thus we investigated the carriage of ARGs by gut microbiota of wild fishes. ARGs encoding resistance to cephalosporins of second to fourth generation, carbapenems, amphenicols, tetracyclines, and sulfonamides were investigated. These antimicrobials have been classified as critically important (cephalosporins of third to fourth generation, quinolones, and carbapenems), or highly important (amphenicols, tetracyclines, and sulfonamides), for human health, according the WHO classification [24,25].
As a major concern, the most widespread mode of clinical resistance development to β–lactam antibiotics is the expression of β–lactamases that hydrolyze the β–lactam ring [26,27], which are increasingly being reported among environmental bacteria, and exhibiting a transmissible antimicrobial resistance to third and fourth-generation cephalosporins mostly mediated by Extended Spectrum Beta-Lactamases (ESBL).
In a recent study, using functional metagenomic analysis, Ren et al. [28] demonstrated that wildlife are natural reservoirs of novel β–lactamases declaring that ARGs develop subtly in wildlife, which may interplay with human resistome over time, thus concluding that wildlife and associated environments serve as natural reservoirs for novel β–lactamases. In another study, de Araujo et al. [29], found that operating wastewater treatment plants are not sufficient to eliminate the carbapenemase genes, finding the occurrence of various carbapenemase genes in two important aquatic environments in Brazil, highlighting the role of aquatic environments as gene pools.
The only few studies investigating ARGs in wild fishes, found a predominance of blaCTX-M and blaTEM genes among gut microbiota [30,31,32,33]. Baothman et al. [30] investigated the incidence of ESBL-expressing Enterobacteriaceae in the gut of wild fish species from the Red Sea coastal region of Saudi Arabia, concluding that the evolution of the blaCTX-M gene in Morganella morganii is a consequence of aquatic pollution. Furthermore, Brahmi et al. [31] studied the prevalence of extended-spectrum β-lactamase-producing Enterobacteriaceae in wild fish from the Mediterranean Sea in Algeria, observing a predominance of the blaCTX-M gene.
In contrast, in disagreement with the results of this study, most of the studies describing ARGs among fish gut microbiota reported the carriage of blaTEM gene, encoding for a β–lactamase [28,30,31,32], but surprisingly none of the isolates from this study carried that gene. In this trend, Sellera et al. [17] reported for the first time the occurrence of Escherichia coli carrying β-lactamases genes among gut bacteria from wild fishes from Brazilian polluted waters, observing an important carriage of blaTEM and intI1-integrase genes. In this trend, Ryu et al. [34] suggested that commercial fish and seafood may act as the reservoir for multi-resistant bacteria and facilitate the dissemination of the resistance genes, mostly blaTEM genes [31].
Furthermore, Khurana et al. [35] found that extended-spectrum β-lactamase (ESBL) was predominantly associated with Klebsiella pneumoniae present in the gut of Tor putitora, whereas Tyagi et al. [36] found that genes encoding extended spectrum β-lactamase (blaTEM, blaCTX-M-1) were also found in the gut microbiome of freshwater Indian carp [36]. When studied common antibiotic resistance genes and integrons among antimicrobial-resistant bacteria isolated from eels and aquaculture ponds in China, Lin et al. [36] found that genes blaTEM, tet(C), sul1, aadA, floR, and qnrB were detected at high percentages, whereas class-1 integrons were present in 79.6% of the isolates [37].
This study demonstrated the occurrence and distribution of diverse β–lactamase-encoding genes, and among them, blaCTX-M1 gene was predominant in wild fishes from all Bays, followed by blaSPM and blaCTX-M4 genes.
This is the first report of the presence of gut bacteria carrying ARGs encoding the production of β-lactamases in wild fish in Chile. Compared to other studies investigating the carriage of ARGs by gut bacteria from wild fish recovered in other countries, the predominance of the gene blaCTX-M is in agreement with many of these studies [16,17,30,31,32,33,34], whereas the absence of the blaTEM gene in this study is contrary to other studies, usually reporting a predominance of this gene [34]. On the other hand, the diversity and low incidence of ARGs, encoding the synthesis of metallo-β-lactamases, which included the blaSPM, blaSIM, blaVIM, and blaIMP genes detected in Chilean wild fish, is contrasting with other studies in which a complete absence or predominance of a particular metallo-β-lactamase encoding-gene is commonly observed [29].
In agreement with the results of this study, which have shown that integron-carrying antimicrobial-resistant bacteria from wild fishes are very rare, previous studies have demonstrated that carriage of integrons is not usually detected among wild fish gut bacteria [38,39,40,41,42]. In this context, Jia et al. [38] found a low abundance of intI1–integrase gene in the gut of guppies (Poecilia reticulata), demonstrating that intI1 is not the main element in diffusing ARGs in this ecosystem.
Furthermore, Barraud et al. [39] did not detect integrons among bacteria from wild fish, in comparison with farmed fish, with a moderate prevalence of integrons; and diseased fish, in which integron prevalence was high. In another study, Vivant et al. [40] studied Enterobacterales resistant to antimicrobials, isolated from gut microbiota of wild fish inhabiting a highly urbanized river in France, not detecting ESBL-producing bacteria, and only few of them carried a class-1 integron, whereas Bollache et al. [41] observed a high spread of blaCTX-M carrying E. coli in freshwater fishes from French watershed. In another study, the abundances of ARGs were quantified in the gut of Chinese freshwater carp, observing that sul1, blaTEM-1, and tet(A) genes were the most prevalent ARG [42].
Additionally, floR gene, encoding a phenicol-specific exporter was detected among gut bacteria from wild fishes from all Bays, despite that only Puerto Montt Bay is located at south of Chile, near salmon farming settings. Apparently, this gene is ubiquitous in microbiota associated to marine wild fishes in Chile.
A high percentage of antimicrobial-resistant bacteria from wild fish from all sampled Bays are carrying plasmid elements, as was previously reported for gut bacteria from Coquimbo Bay [20], which could provide very favorable conditions for genetic exchange through conjugative plasmids among gut microbiota of wild fishes destined for human consumption. Thus, it can be concluded that wild fishes along Chilean coasts are highly relevant as reservoirs of these mobilome elements, although it should be mentioned as a limitation of this study the analysis of only three bays along the long Chilean coast.
As previously noted, bacterial pathogens are the main pathway for the spread of ARGs [43], thus it is highly expected that antimicrobial resistant fecal bacteria carrying ARGs encoded on mobile DNA elements, such as conjugative plasmids, integrons, or transposons [44], from domestic and wastewater treatment plant discharges might transfer their ARGs to indigenous bacteria of fish provoking their spread and prevalence in the marine environment, as well as their potential transfer to fish handlers and consumers.
Fu et al. [45] investigated the dissemination of ARGs in microbial communities of zebrafish guts after the introduction in the aquaria of bacterial donors carrying self-transferring plasmids that encode ARGs, observing that 15% of fecal bacteria obtained ARGs through conjugal transfer, concluding that aquatic animal guts contribute to the spread of ARGs in water environments. Thus, the high carriage of plasmid elements among the antimicrobial-resistant bacteria associated with wild fish guts prompts the need of further studies to elucidate which ARGs are carried by these plasmids, and their capability to be horizontally transferred, in order to confirm that carriage of ARGs by wild fishes have ecological and public health implications, emphasizing the need for further studies related to ARGs of human clinical importance.
Although the occurrence of antimicrobial resistant bacteria carrying ARGs has been attributed mainly to the extensive and indiscriminate use of antibiotics in human and animal therapies the role of other contaminants usually entering to the marine coastal waters, such as biocides and heavy metals as significant contributors to this selective pressure in water systems must be highlighted [46,47]. As previously reported, heavy-metals and biocides are introduced into aquatic environment via discharges from pharmaceutical industries, hospital effluents, direct excretion from humans and livestock, and runoff from farms [48], and creating environmental reservoirs of these contaminants [49]. These agents could drive the selection and proliferation of ARGs through cross-resistance and co-resistance mechanisms, even without direct antibiotic exposure, because metal and biocide resistance genes could be co-located with ARGs on mobile genetic elements, such as plasmids, facilitating their spread [46,47].
Antimicrobial resistant bacteria carrying ARGs in commercial fish intestines have ecological and public health implications, raising questions on the origin of these ARGs, their spread and prevalence in the marine environment as well as fish handlers and consumers, as well as the possibility of the returning of ARGs to human population through fish handling and consuming, considering as potential pathways of passing ARGs to transient zoonotic bacterial pathogens that cause disease in humans, an improperly cooking or otherwise mishandling, demanding further epidemiological and molecular investigations to evaluate their public health importance, especially in relation to the ARGs of clinical importance. In this context, we are currently studying, antimicrobial resistant bacteria carrying ARGs isolated from wild fish mucus.

4. Materials and Methods

4.1. Bacterial Isolates

A total of 245 antimicrobial-resistant isolates were obtained by selecting different-looking colonies grown on plates with Tryptic soy agar (BBL BD Becton Dickinson™, Sparks, MD, USA), added with 2% NaCl (TSA2) containing an antimicrobial agent and seeded with intestinal content samples, as described in Miranda et al. [20]. Antimicrobial resistant isolates were recovered from various marine fish species as shown in Supplementary Tables S1–S3, captured by artisanal fishing from three main Chilean bays located along the country (Figure 3). Antimicrobial resistant isolates were recovered from wild fishes captured at Coquimbo Bay (142 isolates), Concepción Bay (44 isolates), and Puerto Montt Bay (59 isolates) (Supplementary Tables S1–S3). Fish samples were obtained from the fishermen’s boats, transported on ice to the Aquatic Pathobiology Lab of the Universidad Católica del Norte, and processed as described [20]. Sampled fishes were aseptically eviscerated, collecting and processing intestinal content samples, as previously described [20]. Bacterial isolates were purified using plates with TSA2 medium and stored at −85 °C in CryoBankTM vials (Mast Diagnostica, Reinfeld, Germany) before being grown in TSA2 at 20 °C for 24–48 h until use.

4.2. Bacterial Identification

Antimicrobial-resistant isolates were identified using bacterial 16S rRNA gene sequence analysis. Isolates were cultured in Tryptic soy broth (TSB2, BBL BD Becton Dickinson™, Sparks, MD, USA), with 2% NaCl at 22 °C for 12–24 h and pellets were obtained centrifuging bacterial cultures at 9000× g for 3 min using an Eppendorf 5415D (Eppendorf AG, Hamburg, Germany) microcentrifuge. DNA extraction was performed using the WizardR Genomic DNA Purification commercial kit (Promega, Madison, WI, USA) following the supplier’s instructions. The amplification of the 16S ribosomal genes of isolates was performed using PCR, using the procedure described by Opazo et al. [50]. The resulting amplified PCR products were sequenced by Macrogen (Rockville, MD, USA), using the ABI PRISM 373 DNA Sequencer (Applied Biosystems, Foster City, CA, USA). The sequences were edited and matched to the Silva database (https://www.arb-silva.de/aligner, accessed on 26 November 2025) to identify the bacterial isolates, and 16S rDNA gene sequences were deposited in the GenBank database (Supplementary Tables S1–S3).

4.3. Antimicrobial Susceptibility Patterns

The antimicrobial susceptibility of resistant isolates was determined using a disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guideline M02-A12 [51], using plates containing Cation-Adjusted Mueller–Hinton agar (CAMH, BBL BD Becton Dickinson™, Sparks, MD, USA), and disks (Oxoid Ltd., Basingstoke, Hampshire, UK) containing the antimicrobials amoxicillin (AML, 25 µg), cefotetan (CTT, 30 µg), cefotaxime (CTX, 30 µg), meropenem (MEM, 10 µg), streptomycin (S, 10 µg), kanamycin (K, 30 µg), chloramphenicol (CM, 30 µg), florfenicol (FFC, 30 µg), oxytetracycline (OTC, 30 µg), ciprofloxacin (CIP, 5 µg), furazolidone (FR, 100 µg), and sulfamethoxazole-trimethoprim (SXT, 25 µg), as described in Miranda et al. [20]. Plates were incubated at 22 °C for 24 h, and isolates were considered resistant according to the CLSI criteria [52]. As suggested by the CLSI guideline M02-A12, the quality control strain Escherichia coli ATCC 25922 was included in all antimicrobial susceptibility test groups, and results were accepted when results of E. coli ATCC 25922 were within the Disk diffusion QC ranges recommended by CLSI [53]. All isolates were re-examined to check the assay reproducibility. Isolates showing resistance to at least three groups of antimicrobials were considered exhibiting the Multi-Drug Resistance (MDR) phenotype. In addition, the antimicrobial resistance index (ARI) of sampled Bays were determined according to Hinton et al. [54].

4.4. Phenotypic Detection of Extended-Spectrum-β-Lactamase (ESBL) Activioty

The production of ESBL was investigated in isolates showing reduced susceptibility (≤23 mm), to cefotaxime [55], using two phenotypic methods, as described in Miranda et al. [20]. ESBL production was detected by the Combination Disc Diffusion Test (CDDT) method, according to CLSI guidelines [56,57], using disks containing cefotaxime, both alone (CTX, 30 µg) and in combination with clavulanic acid (CTL), placed onto agar plates 15 mm apart. Plates were incubated at 22 °C for 24 h and production of ESBL was confirmed in the isolates exhibiting a ≥5 mm increase in the inhibition zone diameter of the CTL, compared with the CTX disc [58]. Furthermore, ESBL production was phenotypically detected by using the Double Disc Synergy Test (DDST) method [59]. An amoxicillin–clavulanic acid disc (AMC, 20/10 µg) was placed at the center of the CAMHA plate inoculated with the test isolate, and a ceftazidime disc (CAZ, 30 µg), ceftriaxone disc (CRO, 30 µg), and cefotaxime disc (CTX, 30 µg) were each placed 25–30 mm apart from the center disk. Plates were incubated at 22 °C for 24 h, and an increase of inhibition zone towards the AMC disc was considered positive for ESBL production [60]. In all assays, Klebsiella pneumoniae ATCC 700603 (ESBL producing strain) and E. coli ATCC 25922 (susceptible strain) were used as positive and negative control strains for the ESBL production, respectively [61].

4.5. Phenotypic Detection of Carbapenemase Activity

Bacterial isolates showing inhibition zones of ≤23 mm to meropenem were considered likely to produce a Metallo-β-Lactamase (MBL) enzyme [62], and were screened for MBL production using two methods. The production of MBLs, was investigated employing a combined disc diffusion test (CDDT) method [52], using discs containing meropenem, both alone (MRP, 10 µg) and combined with the metal chelator, ethylene diamine tetra-acetic acid (EDTA) (MRP EDTA, 30 µg), placed 15 mm apart. Plates were incubated at 22 °C for 24 h [63], and a ≥7 mm increase in the inhibition zones of discs of MRP EDTA compared with those from MRP discs phenotypically confirmed the production of MBLs [64,65,66]. Furthermore, MBL production was assayed using the modified Hodges test [67,68], aseptically swabbing CAMHA plates with the E. coli ATCC 25922 strain, and then meropenem (MRP, 10 µg) discs were aseptically placed at the center of the plates, and finally assayed isolates were heavily streaked on a straight line from the edge of the meropenem disc to the edge of the plate. Plates were incubated at 22 °C for 24 h and a clover-leaf-type indentation or flattening at the intersection of the tested isolate and the E. coli ATCC 25922 within the zone of inhibition of the meropenem disc was considered positive for MBL production [66].

4.6. Detection of Antimicrobial Resistance Genes

The carriage of genes encoding for resistance to main antimicrobial classes, such as β-lactams, amphenicols, tetracyclines, and sulfonamides was investigated, using primers previously described, as shown in Supplementary Table S4.

4.6.1. Genes Encoding for β-Lactam Resistance

The occurrence of various bla genes, encoding resistance against β-lactams, was detected using the procedure described by Dey et al. [57]. The amplification conditions for blaTEM and blaSHV genes were as described in Kojima et al. [69], for the blaCTX-M1, blaCTX-M2, blaCTX-M3, and blaCTX-M4 genes were as described in Pitout et al. [70], and for the blaFOX, blaMOX, blaEBC, blaACC, blaDHA, and blaCMY genes were as described in Pérez-Pérez and Hanson [71], whereas for the carbapenemase-encoding genes blaIMP, blaVIM, blaGIM, blaSIM, and blaSPM, were as described in Mendes et al. [72]. The amplification conditions were as follows: denaturation at 94 °C for 5 min; 30 cycles of denaturation at 94 °C for 60 s, annealing at 60 °C (blaTEM, blaSHV, blaCTX-M1, blaCTX-M2, blaCTX-M3, and blaCTX-M4), 53 °C (blaIMP, blaVIM, blaGIM, blaSIM, and blaSPM), or 64 °C (blaFOX, blaMOX, blaEBC, blaACC, blaDHA, and blaCMY) for 40 s, and elongation at 72 °C for 60–65 s; and finally, extension at 72 °C for 7 min using the GE-96G thermocycler (BIOER Technology, Hangzhou, China) using the primers described in Supplementary Table S4.

4.6.2. Genes Encoding for Amphenicol Resistance

The carriage of floR and fexA genes conferring resistance to amphenicols, was investigated using PCR assays according to Hurtado et al. [73]. The amplification conditions were as described in Hurtado et al. [73], for the floR gene, and Higuera-Llantén et al. [10] for the fexA gene, using the primers shown in Supplementary Table S4. Briefly, the amplification conditions were denaturation at 95 °C for 4 min; 30 cycles of denaturation at 95 °C for 40 s, annealing at 58 °C for 30 s, elongation at 72 °C for 60 s; and finally, extension at 72 °C for 5 min using the GE-96G thermocycler (BIOER Technology, China). The positive controls Citrobacter freundii FB98 for floR gene, and Vibrio tasmaniensis AVF09 for fexA gene [73], were included in each gel run.

4.6.3. Genes Encoding for Tetracycline Resistance

The occurrence of the tet genes, encoding for tetracycline resistance was investigated using PCR using the procedure described by Ng et al. [74] for tet(A), tet(C), tet(G), and tet(E) genes, whereas tet(D), tet(34), and tet(35) genes were investigated using the methodology described by Miranda et al. [75]. The presence of the tet(B) gene was investigated following the methodology described by Higuera-Llantén et al. [10], whereas tet(39) gene was detected using the methodology described by Hamidian et al. [76]. Primers used are shown in Supplementary Table S4. Briefly, the amplification conditions for tet(A), tet(C), tet(G), and tet(E) genes were denaturation at 95 °C for 5 min; 30 cycles of denaturation at 94 °C for 60 s, annealing at 55 °C for 40 s, elongation at 72 °C for 60 s; and finally, extension at 72 °C for 7 min using the GE-96G thermocycler (BIOER Technology, China), whereas amplification conditions for tet(B), tet(D), tet(34), tet(35), and tet(39) were as previously described [10,75,76].

4.6.4. Genes Encoding for Sulfonamide Resistance

The occurrence of sul1 and sul2 genes, encoding for resistance to sulfonamides, was investigated using PCR according to procedures described by Domínguez et al. [77], using the primers previously described [77], as shown in Supplementary Table S4. Briefly, amplifications were performed in a GE-96G thermocycler (BIOER Technology, China). with one cycle of 95 °C for 10 min, 30 cycles of 94 °C for 45 s, annealing at 64 °C for 30 s, elongation at 51 °C for 45 s and 72 °C for 2 min, with a final extension at 72 °C for 10 min. The control strain Citrobacter gillenii FP75, positive for both genes was included in each assay [77].

4.7. Detection of Class-1 Integron

The carriage of intl1 gene (class 1 integron integrase) was investigated using the methodology and primers described in Domínguez et al. [77]. Briefly, the amplification of the intI1-integrase gene was performed using a BIOER TechnologyTM model GE-96G thermal cycler using the cycle conditions, 95 °C for 30 min, followed by 30 cycles of 95 °C for 30 s, 58 °C for 30 s (annealing temperature), 72 °C for 1 min, and a final extension at 72 °C for 5 min. The production of two fragments (393 and 499 bp) from the intl1 amplicon treated with the restriction enzyme, SphI confirmed the presence of the intl1 gene [20]. The strain Citrobacter gillenii FP75 was used as positive control for intl1 gene [77].

4.8. Plasmid Content

Isolates were cultured in TSB2, for 12 h at 22 °C and pellet was obtained by centrifugation at 9000× g for 5 min using an Eppendorf 5415D microcentrifuge to obtain a pellet. Plasmid DNA was extracted by using the Wizard® Plus SV Minipreps DNA Purification System (Promega, Madison, WI, USA) following the supplier’s instructions. Plasmid DNA was ran on 1.5% agarose gel electrophoresis for plasmids less than 20 kb and 0.8% agarose gel for plasmid greater than 20 kb, as described by Domínguez et al. [77]. Gels were stained with GelRedTM (Biotium, Fremont, CA, USA), viewed by UV transillumination, and plasmid size was estimated by comparing with standard molecular weight markers Quick-Load® 1 kb Extend DNA Ladder and known plasmid weight standards [73].

5. Conclusions

The impact of anthropogenic activities in marine coastal waters in Chile is undeniable but to date there are no studies of the resistome associated with wild fishes residing in these systems. This study demonstrated that intestinal contents of wild fishes inhabiting Chilean Bays impacted by diverse anthropogenic activities are acting as reservoirs of antimicrobial-resistant bacteria carrying a plethora of antimicrobial-resistant genes (ARGs) encoding for resistance against various classes of antimicrobials of human and animal importance, as well as plasmids, becoming important drivers of spread of resistome and mobilome components, even in the absence of antimicrobial use, threatening human health safety.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/antibiotics15020199/s1, Table S1: Identification and source of resistant isolates from intestinal content of wild fishes from Coquimbo Bay; Table S2: Identification and source of resistant isolates from intestinal content of wild fishes from Concepción Bay; Table S3: Identification and source of resistant isolates from intestinal content of wild fishes from Puerto Montt Bay; Table S4: Primers used to amplify antimicrobial resistance genes.

Author Contributions

Conceptualization, C.D.M.; methodology, C.C., L.H., R.R. and J.R.; software, C.C. and J.R.; validation, C.D.M. and C.C.; formal analysis, C.C., L.H., R.R. and J.R.; investigation, C.D.M., C.C., L.H. and J.R.; resources, C.D.M.; data curation, C.C.; writing—original draft preparation, C.D.M. and C.C.; writing—review and editing, C.D.M.; visualization, C.D.M. and C.C.; supervision, C.D.M. and J.R.; project administration, C.D.M.; funding acquisition, C.D.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Chilean National Research and Development Agency (ANID), grant number 1211950.

Informed Consent Statement

Not applicable.

Data Availability Statement

The 16S RNA sequences of isolates have been deposited at DDBJ/ENA/GenBank under the accession numbers described in Tables S1–S3.

Acknowledgments

The authors acknowledge Industrial Biotechnology Technician Katherine Castro for her valuable technical assistance.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Dadgostar, P. Antimicrobial resistance: Implications and costs. Infect. Drug Resist. 2019, 12, 3903–3910. [Google Scholar] [CrossRef]
  2. Fongang, H.; Mbaveng, A.T.; Kuete, V. Chapter One—Global burden of bacterial infections and drug resistance. Adv. Bot. Res. 2023, 106, 1–20. [Google Scholar] [CrossRef]
  3. Aslam, B.; Asghar, R.; Muzammil, S.; Shafique, M.; Siddique, A.B.; Khurshid, M.; Ijaz, H.; Rasool, M.H.; Chaudhry, T.H.; Aamir, A.; et al. AMR and Sustainable Development Goals: At a crossroads. Global Health 2014, 20, 73. [Google Scholar] [CrossRef] [PubMed]
  4. Ajayi, A.O.; Odeyemi, A.T.; Akinjogunla, O.J.; Adeyeye, A.B.; Ayo-Ayayi, I. Review of antibiotic-resistant bacteria and antibiotic resistance genes within the One Health framework. Infect. Ecol. Epidemiol. 2024, 14, 2312953. [Google Scholar] [CrossRef] [PubMed]
  5. Varol, M.; Rasit, M. Environmental contaminants in fish species from a large dam reservoir and their potential risks to human health. Ecotoxicol. Environ. Saf. 2019, 169, 507–515. [Google Scholar] [CrossRef]
  6. Griboff, J.; Carrizo, J.C.; Bonansea, R.I.; Valdés, M.E.; Wunderlin, D.A.; Amé, M.V. Multiantibiotic residues in commercial fish from Argentina. The presence of mixtures of antibiotics in edible fish, a challenge to health risk assessment. Food Chem. 2020, 332, 127380. [Google Scholar] [CrossRef]
  7. Zhang, R.; Yu, K.; Li, A.; Wang, Y.; Pan, C.; Huang, X. Antibiotics in coral reef fishes from the South China Sea: Occurrence, distribution, bioaccumulation, and dietary exposure risk to human. Sci. Total Environ. 2020, 704, 135288. [Google Scholar] [CrossRef]
  8. Zhou, Z.-C.; Lin, Z.-J.; Shuai, X.-Y.; Zheng, J.; Meng, L.-X.; Zhu, L.; Sun, Y.-J.; Shang, W.-C.; Chen, H. Temporal variation and sharing of antibiotic resistance genes between water and wild fish gut in a peri-urban river. J. Environ. Sci. 2021, 103, 12–19. [Google Scholar] [CrossRef]
  9. Xu, Y.; Chen, R.; Shi, C.-W.; Li, C.; Wang, W.; Zhang, Q.-S.; Liu, X.-H.; Xiao, T.-Y.; Song, R.; Li, D.-L.; et al. Comparative analysis of antibiotic resistance gene (ARG) profiles and microbial communities in the Xiangjiang River highlights fish gut opportunistic pathogens as potential reservoir of high-risk ARGs. Water Biol. Sec. 2025; in press. [Google Scholar] [CrossRef]
  10. Higuera-Llantén, S.; Vásquez-Ponce, F.; Barrientos-Espinoza, B.; Mardones, F.O.; Marshall, S.H.; Olivares-Pacheco, J. Extended antibiotic treatment in salmon farms select multiresistant gut bacteria with a high prevalence of antibiotic resistance genes. PLoS ONE 2018, 13, e0203641. [Google Scholar] [CrossRef]
  11. Muziasari, W.I.; Pitkänen, L.K.; Sørum, H.; Stedtfeld, R.D.; Tiedje, J.M.; Virta, M. The Resistome of Farmed Fish Feces Contributes to the Enrichment of Antibiotic Resistance Genes in Sediments below Baltic Sea Fish Farms. Front. Microbiol. 2017, 7, 2137. [Google Scholar] [CrossRef]
  12. Zhang, M.; Hou, L.; Zhu, Y.; Zhang, C.; Li, W.; Lai, X.; Yang, J.; Li, S.; Shu, H. Composition and distribution of bacterial communities and antibiotic resistance genes in fish of four mariculture systems. Environ. Pollut. 2022, 311, 119934. [Google Scholar] [CrossRef]
  13. Vásquez-Ponce, F.; Higuera-Llantén, S.; Parás-Silva, J.; Gamboa-Acuña, N.; Cortés, J.; Opazo-Capurro, A.; Ugalde, J.A.; Alcalde-Rico, M.; Olivares-Pacheco, J. Genetic characterization of clinically relevant class 1 integrons carried by multidrug resistant bacteria (MDRB) isolated from the gut microbiota of highly antibiotic treated Salmo salar. J. Glob. Antimicrob. Resist. 2022, 29, 55–62. [Google Scholar] [CrossRef]
  14. Marti, E.; Huerta, B.; Rodríguez-Mozaz, S.; Barceló, D.; Marcé, R.; Balcázar, J.L. Abundance of antibiotic resistance genes and bacterial community composition in wild freshwater fish species. Chemosphere 2018, 196, 115–119. [Google Scholar] [CrossRef]
  15. Xue, X.; Jia, J.; Yue, X.; Guan, Y.; Zhu, L.; Wang, Z. River contamination shapes the microbiome and antibiotic resistance in sharpbelly (Hemiculter leucisculus). Environ. Pollut. 2021, 268, 115796. [Google Scholar] [CrossRef]
  16. Ballash, G.A.; Baesu, A.; Lee, S.; Mills, M.C.; Mollenkopf, D.F.; Sullivan, S.M.P.; Lee, J.; Bayen, S.; Wittum, T.E. Fish as sentinels of antimicrobial resistant bacteria, epidemic carbapenemase genes, and antibiotics in surface water. PLoS ONE 2022, 17, e0272806. [Google Scholar] [CrossRef]
  17. Sellera, F.P.; Fernandes, M.R.; Moura, Q.; Carvalho, M.P.N.; Lincopan, N. Extended-spectrum-β-lactamase (CTX-M)-producing Escherichia coli in wild fishes from a polluted area in the Atlantic Coast of South America. Mar. Pollut. Bull. 2018, 135, 183–186. [Google Scholar] [CrossRef]
  18. Mills, M.; Lee, S.; Mollenkopf, D.; Wittum, T.; Sullivan, S.M.P.; Lee, J. Comparison of environmental microbiomes in an antibiotic resistance-polluted urban river highlights periphyton and fish gut communities as reservoirs of concern. Sci. Total Environ. 2022, 851, 158042. [Google Scholar] [CrossRef]
  19. Miranda, C.D.; Zemelman, R. Antibiotic Resistant Bacteria in Fish from the Concepción Bay, Chile. Mar. Pollut. Bull. 2001, 42, 1096–1102. [Google Scholar] [CrossRef]
  20. Miranda, C.D.; Concha, C.; Hurtado, L.; Urtubia, R.; Rojas, R.; Romero, J. Occurrence of Antimicrobial-Resistant Bacteria in Intestinal Contents of Wild Marine Fish in Chile. Antibiotics 2024, 13, 332. [Google Scholar] [CrossRef]
  21. Clinical and Laboratory Standards Institute (CLSI). Methods for Antimicrobial Broth Dilution and Disk Diffusion Susceptibility Testing of Bacteria Isolated from Aquatic Animals, 2nd ed.; CLSI Guideline VET03; CLSI: Wayne, PA, USA, 2020. [Google Scholar]
  22. Bueno, I.; Verdugo, C.; Jimenez-Lopez, O.; Alvarez, P.P.; Gonzalez-Rocha, G.; Lima, C.A.; Travis, D.A.; Wass, B.; Zhang, Q.; Ishii, S.; et al. Role of wastewater treatment plants on environmental abundance of antimicrobial resistance genes in chilean rivers. Int. J. Hyg. Environ. Health 2020, 223, 56–64. [Google Scholar] [CrossRef] [PubMed]
  23. Gerzova, L.; Videnska, P.; Faldynova, M.; Sedlar, K.; Provaznik, I.; Cizek, A.; Rychlik, I. Characterization of microbiota composition and presence of selected antibiotic resistance genes in carriage water of ornamental fish. PLoS ONE 2014, 9, e103865. [Google Scholar] [CrossRef]
  24. World Health Organization (WHO); World Organisation for Animal Health (OIE). OIE List of Antimicrobial Agents of Veterinary Importance; OIE: Paris, France, 2015; p. 9. [Google Scholar]
  25. World Health Organization (WHO); Advisory Group on Integrated Surveillance of Antimicrobial Resistance (AGISAR). Critically Important Antimicrobials for Human Medicine; 5th Revision; World Health Organization: Geneva, Switzerland, 2016; p. 41. [Google Scholar]
  26. Camargo, C.H.; Yamada, A.Y.; De Souza, A.R.; Cunha, M.P.V.; Ferraro, P.S.P.; Sacchi, C.T.; Dos Santos, M.B.; Campos, K.R.; Tiba-Casas, M.R.; Freire, M.P.; et al. Genomic analysis and antimicrobial activity of β-lactam/β-lactamase inhibitors and other agents against KPC-producing Klebsiella pneumoniae clinical isolates from Brazilian hospitals. Sci. Rep. 2023, 13, 14603. [Google Scholar] [CrossRef]
  27. Zhuang, Q.; Guo, H.; Peng, T.; Ding, E.; Zhao, H.; Liu, Q.; He, S.; Zhao, G. Advances in the detection of β-lactamase: A review. Int. J. Biol. Macromol. 2023, 251, 126159. [Google Scholar] [CrossRef]
  28. Ren, H.; Lu, Z.; Sun, R.; Wang, X.; Zhong, J.; Su, T.; He, Q.; Liao, X.; Liu, Y.; Lian, X.; et al. Functional metagenomics reveals wildlife as natural reservoirs of novel β-lactamases. Sci. Total Environ. 2023, 868, 161505. [Google Scholar] [CrossRef]
  29. de Araujo, C.F.M.; Silva, D.M.; Carneiro, M.T.; Ribeiro, S.; Fontana-Maurell, M.; Alvarez, P.; Asensi, M.D.; Zahner, V.; Carvalho-Assef, A.P.D. Detection of carbapenemases genes in aquatic environments in Río de Janeiro, Brazil. Antimicrob. Agent. Chemother. 2016, 60, 4380–4383. [Google Scholar] [CrossRef]
  30. Baothman, O.A.; Alshamrani, Y.A.; Al-Talhi, H.A. Prevalence of Extended-Spectrum β-lactamases in Enterobacteriaceae Isolated from Polluted Wild Fish. The Open Biochem. J. 2020, 14, 14–19. [Google Scholar] [CrossRef]
  31. Brahmi, S.; Touati, A.; Dunyach-Remy, C.; Sotto, A.; Pantel, A.; Lavigne, J.P. High prevalence of extended-spectrum β-lactamase-producing Enterobacteriaceae in wild fish from the Mediterranean Sea in Algeria. Microb. Drug Resist. 2018, 24, 290–298. [Google Scholar] [CrossRef] [PubMed]
  32. Hassen, B.; Jouini, A.; Elbour, M.; Hamrouni, S.; Maaroufi, A. Detection of Extended-Spectrum β-Lactamases (ESBL) Producing Enterobacteriaceae from Fish Trapped in the Lagoon Area of Bizerte, Tunisia. Biomed. Res. Int. 2020, 2020, 7132812. [Google Scholar] [CrossRef]
  33. Moremi, N.; Manda, E.V.; Falgenhauer, L.; Ghosh, H.; Imirzalioglu, C.; Matee, M.; Chakraborty, T.; Mshana, S.E. Predominance of CTX-M-15 among ESBL Producers from Environment and Fish Gut from the Shores of Lake Victoria in Mwanza, Tanzania. Front. Microbiol. 2016, 7, 1862. [Google Scholar] [CrossRef] [PubMed]
  34. Ryu, S.H.; Park, S.G.; Choi, S.M.; Hwang, Y.O.; Ham, H.J.; Kim, S.U.; Lee, Y.K.; Kim, M.S.; Park, G.Y.; Kim, K.S.; et al. Antimicrobial resistance and resistance genes in Escherichia coli strains isolated from commercial fish and seafood. Int. J. Food Microbiol. 2012, 152, 14–18. [Google Scholar] [CrossRef]
  35. Khurana, H.; Singh, D.N.; Singh, A.; Singh, Y.; Lal, R.; Negi, R.K. Gut microbiome of endangered Tor putitora (Ham.) as a reservoir of antibiotic resistance genes and pathogens associated with fish health. BMC Microbiol. 2020, 20, 249. [Google Scholar] [CrossRef]
  36. Tyagi, A.; Singh, B.; Billekallu Thammegowda, N.K.; Singh, N.K. Shotgun metagenomics offers novel insights into taxonomic compositions, metabolic pathways and antibiotic resistance genes in fish gut microbiome. Arch. Microbiol. 2019, 201, 295–303. [Google Scholar] [CrossRef]
  37. Lin, M.; Wu, X.; Yan, Q.; Ying Ma, Y.; Huang, L.; Qin, Y.; Xu, X. Incidence of antimicrobial-resistance genes and integrons in antibiotic-resistant bacteria isolated from eels and aquaculture ponds. Dis. Aquat. Org. 2016, 120, 115–123. [Google Scholar] [CrossRef]
  38. Jia, J.; Gomes-Silva, G.; Plath, M.; Pereira, B.B.; Vieira, C.U.; Wang, Z. Shifts in bacterial communities and antibiotic resistance genes in surface water and gut microbiota of guppies (Poecilia reticulata) in the upper Rio Uberabinha, Brazil. Ecotoxicol. Environ. Saf. 2021, 211, 111955. [Google Scholar] [CrossRef]
  39. Barraud, O.; Laval, L.; Le Devendec, L.; Larvor, E.; Chauvin, C.; Jouy, E.; Le Bouquin, S.; Vanrobaeys, Y.; Thuillier, B.; Lamy, B.; et al. Integrons from Aeromonas isolates collected from fish: A global indicator of antimicrobial resistance and anthropic pollution. Aquaculture 2023, 576, 739768. [Google Scholar] [CrossRef]
  40. Vivant, A.-L.; Marchand, E.; Janvier, B.; Berthe, T.; Guigon, E.; Grall, N.; Alliot, F.; Goutte, A.; Petit, F. Wild fish from a highly urbanized river (Orge, France) as vectors of culturable Enterobacterales resistant to antibiotics. Can. J. Microbiol. 2024, 70, 63–69. [Google Scholar] [CrossRef]
  41. Bollache, L.; Bardet, E.; Depret, G.; Motreuil, S.; Neuwirth, C.; Moreau, J.; Hartmann, A. Dissemination of CTX-M-producing Escherichia coli in freshwater fishes from a French watershed (burgundy). Front. Microbiol. 2019, 9, 3239. [Google Scholar] [CrossRef]
  42. Yuan, L.; Wang, L.; Li, Z.H.; Zhang, M.Q.; Shao, W.; Sheng, G.P. Antibiotic resistance and microbiota in the gut of Chinese four major freshwater carp from retail markets. Environ. Pollut. 2019, 255, 113327. [Google Scholar] [CrossRef]
  43. Ravi, A.; Avershina, E.; Ludvigsen, J.; L’Abee-Lund, T.M.; Rudi, K. Integrons in the Intestinal Microbiota as Reservoirs for Transmission of Antibiotic Resistance Genes. Pathogens 2014, 3, 238–248. [Google Scholar] [CrossRef]
  44. Gillings, M.R. Lateral gene transfer, bacterial genome evolution, and the Anthropocene. Annal. N. Y. Acad. Sci. 2017, 1389, 20–36. [Google Scholar] [CrossRef]
  45. Fu, J.; Yang, D.; Jin, M.; Liu, W.; Zhao, X.; Li, C.; Zhao, T.; Wang, J.; Gao, Z.; Shen, Z.; et al. Aquatic animals promote antibiotic resistance gene dissemination in water via conjugation: Role of different regions within the zebra fish intestinal tract, and impact on fish intestinal microbiota. Molec. Ecol. 2017, 26, 5318–5333. [Google Scholar] [CrossRef]
  46. Murray, L.M.; Hayes, A.; Snape, J.; Kasprzyk-Hordern, B.; Gaze, W.H.; Murray, A.K. Co-selection for antibiotic resistance by environmental contaminants. NPJ Antimicrob. Resist. 2024, 2, 9. [Google Scholar] [CrossRef]
  47. Colclough, A.; Corander, J.; Sheppard, S.K.; Bayliss, S.C.; Vos, M. Patterns of Cross-Resistance and Collateral Sensitivity between Clinical Antibiotics and Natural Antimicrobials. Evol. Appl. 2019, 12, 878–887. [Google Scholar] [CrossRef]
  48. Ebele, A.J.; Oluseyi, T.; Drage, D.S.; Harrad, S.; Abou-Elwafa Abdallah, M. Occurrence, Seasonal Variation and Human Exposure to Pharmaceuticals and Personal Care Products in Surface Water, Groundwater and Drinking Water in Lagos State, Nigeria. Emerg. Contam. 2020, 6, 124–132. [Google Scholar] [CrossRef]
  49. Chukwu, K.B.; Abafe, O.A.; Amoako, D.G.; Essack, S.Y.; Abia, A.L.K. Antibiotic, Heavy Metal, and Biocide Concentrations in a Wastewater Treatment Plant and Its Receiving Water Body Exceed PNEC Limits: Potential for Antimicrobial Resistance Selective Pressure. Antibiotics 2023, 9, 1166. [Google Scholar] [CrossRef]
  50. Opazo, R.; Ortúzar, F.; Navarrete, P.; Espejo, R.; Romero, J. Reduction of soybean meal non-starch polysaccharides and α-Galactosides by solid-state fermentation using cellulolytic bacteria obtained from different environments. PLoS ONE 2012, 7, e44783. [Google Scholar] [CrossRef]
  51. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Disk Susceptibility Test; Approved Standard, 12th ed.; M02-A12; CLSI: Wayne, NJ, USA, 2015. [Google Scholar]
  52. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing, 30th ed.; CLSI document M100-S27; CLSI: Wayne, PA, USA, 2020. [Google Scholar]
  53. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing of Bacteria Isolated from Aquatic Animals, 3rd ed.; CLSI Supplement VET04; CLSI: Wayne, PA, USA, 2020. [Google Scholar]
  54. Hinton, M.; Hedges, A.J.; Linton, A.H. The ecology of Escherichia coli in market claves fed a milk-substitute diet. J. Appl. Bacteriol. 1985, 58, 27–35. [Google Scholar] [CrossRef]
  55. Ogochukwu, E.C.; Regina, A.N.; Nkpeh, U.S.; Macmagnus, A.I.; Grace, E.; Ikenna, U.; Peter, E.C. Detection of ESBL, AmpC, and MBL-Producing Chryseobacterium indologenes Isolates Recovered from Hospital Environment in a Tertiary Health Care Facility. Am. J. Infect. Dis. Microbiol. 2021, 9, 129–135. Available online: http://pubs.sciepub.com/ajidm/9/4/4 (accessed on 8 February 2026).
  56. De Gheldre, Y.; Avesani, V.; Berhin, C.; Delmée, M.; Glupczynski, Y. Evaluation of Oxoid combination discs for detection of extended-spectrum β-lactamases. J. Antimicrob. Chemother. 2003, 52, 591–597. [Google Scholar] [CrossRef]
  57. Dey, T.K.; Lindahl, J.F.; Lundkvist, Å.; Grace, D.; Deka, R.P.; Shome, R.; Bandyopadhyay, S.; Goyal, N.K.; Sharma, G.; Shome, B.R. Analyses of Extended-Spectrum-β-Lactamase, Metallo-β-Lactamase, and AmpC-β-Lactamase Producing Enterobacteriaceae from the Dairy Value Chain in India. Antibiotics 2023, 12, 1449. [Google Scholar] [CrossRef]
  58. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing, 29th ed.; CLSI Document M100; CLSI: Wayne, PA, USA, 2019. [Google Scholar]
  59. El Aila, N.A.; Al Laham, N.A.; Ayesh, B.M. Prevalence of extended spectrum beta lactamase and molecular detection of blaTEM, blaSHV and blaCTX-M genotypes among Gram negative bacilli isolates from pediatric patient population in Gaza strip. BMC Infect. Dis. 2023, 23, 99. [Google Scholar] [CrossRef]
  60. Mohammed, A.B.; Anwar, K.A. Phenotypic and genotypic detection of extended spectrum beta lactamase enzyme in Klebsiella pneumoniae. PLoS ONE 2022, 17, e0267221. [Google Scholar] [CrossRef]
  61. Lawrence, J.; O’Hare, D.; van Batenburg-Sherwood, J.; Sutton, M.; Alison Holmes, A.; Rawson, T.M. Innovative approaches in phenotypic beta-lactamase detection for personalised infection management. Nat. Commun. 2024, 15, 9070. [Google Scholar] [CrossRef]
  62. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing Disk Susceptibility Test; Twenty-First Informational Supplement, CLSI document M100-S21; CLSI: Wayne, PA, USA, 2011. [Google Scholar]
  63. Anwar, M.; Ejaz, H.; Zafar, A.; Hamid, H. Phenotypic Detection of Metallo-Beta-Lactamases in Carbapenem Resistant Acinetobacter baumannii Isolated from Pediatric Patients in Pakistan. J. Pathog. 2016, 2016, 8603964. [Google Scholar] [CrossRef]
  64. Kulkarni, S.S.; Mulay, M.V. Phenotypic detection of metallo-beta-lactamase production in clinical isolates of Escherichia coli and Klebsiella pneumoniae in a tertiary care hospital. MGM J. Med. Sci. 2022, 9, 149–153. [Google Scholar] [CrossRef]
  65. Khosravi, Y.; Loke, M.F.; Chua, E.G.; Tay, S.T.; Vadivelu, J. Phenotypic Detection of Metallo-β-Lactamase in Imipenem-Resistant Pseudomonas aeruginosa. Sci. World J. 2012, 2012, 654939. [Google Scholar] [CrossRef]
  66. Chika, E.; Chigozie, U.; Carissa, D.; Moses, I. Phenotypic Detection of Metallo-B-lactamase Enzyme in Enugu, Southeast Nigeria. Afr. J. Basic Appl. Sci. 2013, 5, 214–219. [Google Scholar] [CrossRef]
  67. Egbule, O.S. Antimicrobial Resistance and β-Lactamase Production among Hospital Dumpsite Isolates. J. Environ. Prot. 2016, 7, 1057–1063. [Google Scholar] [CrossRef]
  68. Ejikeugwu, C.; Esimone, C.; Iroha, I.; Eze, P.; Ugwu, M.; Adikwu, M. Genotypic and Phenotypic Characterization of MBL Genes in Pseudomonas aeruginosa Isolates from the Non-hospital Environment. J. Pure Appl. Microbiol. 2018, 12, 1877–1885. [Google Scholar] [CrossRef]
  69. Kojima, A.; Ishii, Y.; Ishihara, K.; Esaki, H.; Asai, T.; Oda, C.; Tamura, Y.; Takahashi, T.; Yamaguchi, K. Extended-spectrum-beta-lactamase-producing Escherichia coli strains isolated from farm animals from 1999 to 2002: Report from the Japanese Veterinary Antimicrobial Resistance Monitoring Program. Antimicrob. Agents Chemother. 2005, 49, 3533–3537. [Google Scholar] [CrossRef]
  70. Pitout, J.D.; Hossain, A.; Hanson, N.D. Phenotypic and molecular detection of CTX-M-beta-lactamases produced by Escherichia coli and Klebsiella spp. J. Clin. Microbiol. 2004, 42, 5715–5721. [Google Scholar] [CrossRef]
  71. Pérez-Pérez, F.J.; Hanson, N.D. Detection of plasmid-mediated AmpC β-lactamase genes in clinical isolates by using multiplex PCR. J. Clin. Microbiol. 2002, 40, 2153–2162. [Google Scholar] [CrossRef]
  72. Mendes, R.E.; Kiyota, K.A.; Monteiro, J.; Castanheira, M.; Andrade, S.S.; Gales, A.C.; Pignatari, A.C.C.; Tufik, S. Rapid Detection and Identification of Metallo-β-Lactamase-Encoding Genes by Multiplex Real-Time PCR Assay and Melt Curve Analysis. J. Clin. Microbiol. 2007, 45, 544–547. [Google Scholar] [CrossRef]
  73. Hurtado, L.; Miranda, C.D.; Rojas, R.; Godoy, F.A.; Añazco, M.A.; Romero, J. Live Feeds Used in the Larval Culture of Red Cusk Eel, Genypterus chilensis, Carry High Levels of Antimicrobial-Resistant Bacteria and Antibiotic-Resistance Genes (ARGs). Animals 2020, 10, 505. [Google Scholar] [CrossRef]
  74. Ng, L.K.; Martin, I.; Alfa, M.; Mulvey, M. Multiplex PCR for the detection of tetracycline resistant genes. Mol. Cell. Probes 2001, 15, 209–215. [Google Scholar] [CrossRef]
  75. Miranda, C.D.; Kehrenberg, C.; Ulep, C.; Schwarz, S.; Roberts, M.C. Diversity of tetracycline resistance genes in bacteria from Chilean salmon farms. Antimicrob. Agents Chemother. 2003, 47, 883–888. [Google Scholar] [CrossRef]
  76. Hamidian, H.; Holt, K.E.; Pickard, D.; Hall, R.M. A small Acinetobacter plasmid carrying the tet39 tetracycline resistance determinant. J. Antimicrob. Chemother. 2016, 71, 269–271. [Google Scholar] [CrossRef]
  77. Domínguez, M.; Miranda, C.D.; Fuentes, O.; de la Fuente, M.; Godoy, F.A.; Bello-Toledo, H.; González-Rocha, G. Occurrence of transferable integrons and sul and dfr genes among sulfonamide-and/or trimethoprim-resistant bacteria isolated from Chilean salmonid farms. Front. Microbiol. 2019, 10, 748. [Google Scholar] [CrossRef]
Antibiotics 15 00199 g001
Figure 1. Antimicrobial resistance pattern (a), and simultaneous antimicrobial resistance (b) of bacterial isolates recovered from intestinal content of wild fishes captured at the Coquimbo Bay (COQ, 142 isolates), Concepción Bay (COC, 44 isolates), and Puerto Montt Bay (PMC, 59 isolates). Antimicrobial abbreviations: AMO, Amoxicillin; CTX, Cefotaxime; CTT, Cefotetan; MEM, Meropenem; STR, Streptomycin; KAN, Kanamycin; CHL, Chloramphenicol; FLO, Florfenicol; OXY, Oxytetracycline; CIP, Ciprofloxacin; FUR, Furazolidone; SXT, Sulfamethoxazole-trimethoprim.
Figure 1. Antimicrobial resistance pattern (a), and simultaneous antimicrobial resistance (b) of bacterial isolates recovered from intestinal content of wild fishes captured at the Coquimbo Bay (COQ, 142 isolates), Concepción Bay (COC, 44 isolates), and Puerto Montt Bay (PMC, 59 isolates). Antimicrobial abbreviations: AMO, Amoxicillin; CTX, Cefotaxime; CTT, Cefotetan; MEM, Meropenem; STR, Streptomycin; KAN, Kanamycin; CHL, Chloramphenicol; FLO, Florfenicol; OXY, Oxytetracycline; CIP, Ciprofloxacin; FUR, Furazolidone; SXT, Sulfamethoxazole-trimethoprim.
Antibiotics 15 00199 g001
Antibiotics 15 00199 g002
Figure 2. Plasmid content of bacterial isolates recovered from intestinal content of wild fishes captured at the Coquimbo Bay (COQ, 142 isolates), Concepción Bay (COC, 44 isolates), and Puerto Montt Bay (PMC, 59 isolates).
Figure 2. Plasmid content of bacterial isolates recovered from intestinal content of wild fishes captured at the Coquimbo Bay (COQ, 142 isolates), Concepción Bay (COC, 44 isolates), and Puerto Montt Bay (PMC, 59 isolates).
Antibiotics 15 00199 g002
Antibiotics 15 00199 g003
Figure 3. The geographic location of the Coquimbo Bay, Concepción Bay, and Puerto Montt Bay, where the wild fishes were captured.
Figure 3. The geographic location of the Coquimbo Bay, Concepción Bay, and Puerto Montt Bay, where the wild fishes were captured.
Antibiotics 15 00199 g003
Table 1. Source and molecular identification of bacterial isolates.
Table 1. Source and molecular identification of bacterial isolates.
GenusBay
CoquimboConcepciónPuerto Montt
Acinetobacter2
Aeromonas 11
Aliivibrio82
Brevibacterium1
Brochothrix656
Carnobacterium 1
Glutamicibacter 1
Lelliottia 1
Myroides1
Moellerella2
Morganella 1
Photobacterium527
Proteus1
Providencia13
Pseudoalteromonas2
Pseudomonas551916
Psychrobacter967
Serratia 1
Shewanella19411
Staphylococcus 2
Tatumella 1
Vibrio3014
Total1424459
Table 2. Carriage of antimicrobial resistance genes by resistant isolates recovered from intestinal contents of wild fishes captured from Chilean Bays.
Table 2. Carriage of antimicrobial resistance genes by resistant isolates recovered from intestinal contents of wild fishes captured from Chilean Bays.
Resistance to:GeneCoquimbo BayConcepción BayPuerto Montt BayTotal
CephalosporinsblaCTX-M1144523
blaCTX-M20000
blaCTX-M30000
blaCTX-M45106
blaTEM0000
blaSHV1001
blaFOX1102
blaMOX0000
blaEBC0000
blaACC0101
blaDHA1001
blaCMY3003
CarbapenemsblaIMP1001
blaVIM1102
blaGIM0000
blaSIM1304
blaSPM2428
PhenicolsfloR45232290
fexA0000
Tetracyclinestet(A)1146
tet(B)3148
tet(C)0011
tet(D)5207
tet(E)921122
tet(G)0101
tet(34)0000
tet(35)0000
tet(39)2002
Sulfonamidessul12226
sul21012
Table 3. Carriage of genes encoding the production of β-lactamases by gut bacterial isolates from wild fishes captured from Chilean Bays.
Table 3. Carriage of genes encoding the production of β-lactamases by gut bacterial isolates from wild fishes captured from Chilean Bays.
IsolateGenusBayFish SpeciesAntimicrobial Resistance PatternPlasmid No
(in kb)		Beta-Lactamase Gene (bla)Other ARG
ESBLMBLAMC
NCIS20ShewanellaCOQ S. lalandiAML-MEM-STR-KAN-FUR1 (50) VIM/IMP
NCIS7MyroidesCOQS. chiliensisCTX-CTT-MEM-STR-KAN-FUR SPM
NCIA61ShewanellaCOQT. murphyiAML-MEM-STR1 (100) SIM
NCIA26PseudomonasCOQS. lalandiAML-CTX-CTT-STR-KAN-CHL-FLO-FUR2 (50/100)CTX-M1/M4 CMYfloR
NCIA27ShewanellaCOQS. lalandiAML-CTX-CTT-MEM-STR-KAN-FUR1 (20)CTX-M1/M4 DHA
NCIS25PseudomonasCOQS. lalandiAML-CTX-CTT-STR-CHL-FLO-FUR2 (50/100)CTX-M1/M4 floR
NCIA59PseudomonasCOQS. japonicusAML-CTX-CTT-STR-KAN-CHL-FLO-FUR-SXT1 (50)CTX-M1 floR
NCIA1PseudomonasCOQS. chiliensisAML-CTX-CTT-STR-CHL-FUR-SXT CTX-M1 floR
NCIA5PseudomonasCOQS. chiliensisAML-CTX-STR-KAN-CHL-FLO-FUR-SXT2 (5/50)CTX-M1/M4 CMYfloR
NCIF5PseudomonasCOQS. chiliensisAML-CTX-CTT-MEM-STR-CHL-FLO-FUR2 (6/10)CTX-M1 floR
NCIF7PseudomonasCOQS. chiliensisAML-CTX-CTT-STR-KAN-CHL-FLO-FUR FOX
NCIF22PseudomonasCOQM. ophicephalusAML-CTX-CTT-MEM-CHL-FLO-OXY-FUR-SXT2 (3/8) SPM floR/tet(D)
NCIA8PseudomonasCOQM. gayiAML-CTX-CTT-MEM-STR-KAN-CHL-FLO-FUR1 (10)CTX-M1 floR
NCIA9PseudomonasCOQM. gayiAML-CTX-CTT-STR-CHL-FLO-FUR CTX-M1/M4 CMYfloR
NCIA10PseudomonasCOQM. gayiAML-CTX-CTT-STR-KAN-CHL-FLO-FUR-SXT CTX-M1 floR
NCIA11PseudomonasCOQM. gayiAML-CTX-CTT-STR-KAN-FUR1 (50)CTX-M1/SHV
NCIF12PseudomonasCOQM. gayiAML-CTX-CTT-MEM-CHL-FLO-FUR-SXT2 (50/100)CTX-M1 floR
NCIF19PseudomonasCOQM. ophicephalusAML-CTX-CTT-STR-KAN-CHL-FLO-FUR-SXT1 (20)CTX-M1 floR
NCIF21PseudomonasCOQM. ophicephalusAML-CTX-CTT-STR-KAN-CHL-FLO-FUR2 (6/20)CTX-M1 floR
CCIF7PseudomonasCOCT. atunAML-CTX-CTT-MEM-STR-FLO-OXY-FUR-SXT SIM floR
CCIF9PseudomonasCOCT. atunAML-CTX-CTT-MEM-STR-CHL-FLO-FUR-SXT SIM floR
CCIO7ProvidenciaCOCT. atunMEM-CHL-FLO-OXY-FUR2 (8/60) SIM floR
CCIF14PseudomonasCOCT. murphyiAML-CTX-CTT-MEM-CHL-FLO-FUR-SXT VIM floR
CCIA1PseudomonasCOCM. gayiAML-CTX-CTT-STR-CHL-FLO-FUR-SXT1 (50) SPM tet(A)
CCIF3PseudomonasCOCM. gayiAML-CTX-CTT-MEM-CHL-FLO-FUR-SXT CTX-M1SPM floR/tet(B)
CCIF4PseudomonasCOCM. gayiAML-CTX-CTT-MEM-STR-CHL-FLO-OXY-FUR-SXT SPM floR
CCIF6PseudomonasCOCM. gayiAML-CTX-CTT-MEM-STR-CHL-FLO-FUR-SXT CTX-M1SPM floR
CCIF10PseudomonasCOCT. murphyiAML-CTX-CTT-CHL-FLO-OXY-FUR CTX-M4 floR
CCIF11PseudomonasCOCT. murphyiAML-CTX-CTT-STR-KAN-CHL-FLO-FUR-SXT FOXfloR
CCIO2ShewanellaCOCM. gayiAML-CTX-CTT-OXY CTX-M1 ACC
CCIO12ShewanellaCOCP. chilensisAML-CTX-CTT-OXY CTX-M1
CIA42MorganellaPMCT. murphyiAML-CTT-MEM-STR-CHL-FLO-FUR-SXT SPM floR
CIS55ShewanellaPMCT. murphyiAML-CTX-CTT-MEM-STR-KAN-FUR CTX-M1SPM
CIA43PseudomonasPMCT. murphyiAML-CTX-CTT-STR-CHL-FLO-FUR-SXT1 (50)CTX-M1 floR
CIF16PseudomonasPMCT. murphyiAML-CTX-CTT-STR-CHL-FLO-FUR-SXT CTX-M1 floR
CIF18PseudomonasPMCT. murphyiAML-CTX-CTT-STR-CHL-FLO-FUR-SXT2 (3/50)CTX-M1
CIF29PseudomonasPMCT. murphyiAML-CTX-CTT-STR-CHL-FLO-FUR-SXT CTX-M1 floR
Abbreviations: CTX, Cefotaxime; CTT, Cefotetan; MEM, Meropenem; STR, Streptomycin; KAN, Kanamycin; CHL, Chloramphenicol; FLO, Florfenicol; OXY, Oxytetracycline; FUR, Furazolidone; SXT, Sulfamethoxazole-trimethoprim; COQ, Coquimbo; COC, Concepción; PMC, Puerto Montt; ESBL, Extended-Spectrum-β-Lactamase; MBL, Metallo-β-Lactamase; AMC, AmpC-type β-Lactamase.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Miranda, C.D.; Concha, C.; Hurtado, L.; Rojas, R.; Romero, J. Wild Fishes as Reservoirs of Gut Bacteria Carrying Antimicrobial Resistance Encoding Genes in Chilean Bays. Antibiotics 2026, 15, 199. https://doi.org/10.3390/antibiotics15020199

AMA Style

Miranda CD, Concha C, Hurtado L, Rojas R, Romero J. Wild Fishes as Reservoirs of Gut Bacteria Carrying Antimicrobial Resistance Encoding Genes in Chilean Bays. Antibiotics. 2026; 15(2):199. https://doi.org/10.3390/antibiotics15020199

Chicago/Turabian Style

Miranda, Claudio D., Christopher Concha, Luz Hurtado, Rodrigo Rojas, and Jaime Romero. 2026. "Wild Fishes as Reservoirs of Gut Bacteria Carrying Antimicrobial Resistance Encoding Genes in Chilean Bays" Antibiotics 15, no. 2: 199. https://doi.org/10.3390/antibiotics15020199

APA Style

Miranda, C. D., Concha, C., Hurtado, L., Rojas, R., & Romero, J. (2026). Wild Fishes as Reservoirs of Gut Bacteria Carrying Antimicrobial Resistance Encoding Genes in Chilean Bays. Antibiotics, 15(2), 199. https://doi.org/10.3390/antibiotics15020199

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop