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10 pages, 251 KB  
Brief Report
In Vitro Antimicrobial Activity of Taurolidine Against Isolates Associated with Catheter-Related Bloodstream Infections
by Jared L. Crandon, Xing Tan, Paul R. Rhomberg, Mariana Castanheira and S. J. Ryan Arends
Antibiotics 2026, 15(8), 785; https://doi.org/10.3390/antibiotics15080785 - 14 Aug 2026
Abstract
Background: Catheter-related bloodstream infections are common in patients receiving hemodialysis through a central venous catheter. Taurolidine, a novel broad-spectrum antimicrobial catheter lock solution, is FDA-approved in combination with heparin for reducing the incidence of such infections. Methods: In vitro activity of taurolidine was [...] Read more.
Background: Catheter-related bloodstream infections are common in patients receiving hemodialysis through a central venous catheter. Taurolidine, a novel broad-spectrum antimicrobial catheter lock solution, is FDA-approved in combination with heparin for reducing the incidence of such infections. Methods: In vitro activity of taurolidine was assessed against 442 bacterial and 50 yeast clinical bloodstream infection isolates selected from the SENTRY Antimicrobial Surveillance Program and tested according to the Clinical and Laboratory Standards Institute methodology. Multidrug-resistant species and phenotypes were included. Results: Taurolidine was highly active against all isolates, with MIC50/MIC90 values of ≤1024/1024 μg/mL for most species. The highest MICs observed were among isolates of Mycobacterium avium complex and Burkholderia cepacia complex (MIC90, 2048 μg/mL) and Candida albicans (MIC90, 4096 μg/mL). All isolates were inhibited by 13,500 μg/mL of taurolidine, the concentration of the commercially available product. Conclusions: Taurolidine activity was very similar among Gram-positive, Gram-negative, and yeast clinical isolates, with the activity of taurolidine being unaffected by phenotypic resistance to other antimicrobials. Taken together with clinical efficacy data from clinical trials, this provides a theoretical basis for the idea that taurolidine-based lock solutions may be able to reduce the risk of catheter-related bloodstream infections from a wide variety of pathogens and resistance phenotypes. Full article
(This article belongs to the Section Novel Antimicrobial Agents)
22 pages, 1893 KB  
Article
Glycosylated Delphinidins, Natural Antioxidants, Functionally Modulate the COX-2/PGE2 Axis and Downregulate MDR1 in Glioblastoma Cells
by Constanza Cuevas, Yessica Nahuelpan, Darling Haro, Pamela Silva, Vicente Villagran, María A. Gleisner, Flavio Salazar-Onfray, Juan P. Muñoz, Christian Pávez, Noemi Garcia-Romero, Angel Ayuso-Sacido, Rody San Martin, Diego Carrillo-Beltrán and Claudia Quezada-Monrás
Antioxidants 2026, 15(8), 1005; https://doi.org/10.3390/antiox15081005 - 13 Aug 2026
Abstract
The multidrug resistance (MDR) phenotype, mediated by transporters such as MDR1/P-glycoprotein (P-gp), represents a critical obstacle in the treatment of glioblastoma (GB). Natural antioxidants such as glycosylated delphinidins—anthocyanins abundant in Chilean berries, particularly the native species Aristotelia chilensis (maqui)—have emerged as bioactive compounds [...] Read more.
The multidrug resistance (MDR) phenotype, mediated by transporters such as MDR1/P-glycoprotein (P-gp), represents a critical obstacle in the treatment of glioblastoma (GB). Natural antioxidants such as glycosylated delphinidins—anthocyanins abundant in Chilean berries, particularly the native species Aristotelia chilensis (maqui)—have emerged as bioactive compounds that modulate inflammation and cancer-related pathways. In this context, the regulation of inflammation-associated signaling pathways, including COX-2 and NF-κB, represents a potential strategy to overcome chemoresistance. In this study, we evaluated the effect of delphinidin-3-glucoside (DEL-3) on the COX-2/PGE2 axis, MDR1 expression, and sensitivity to chemotherapeutic agents in U87-MG and GBM38 glioblastoma cells and in an NOD-SCID xenograft model using ELISA, RT-qPCR, Western blot, and luciferase reporter assays. DEL-3 reduced PGE2 production, consistent with functional modulation of the COX-2/PGE2 pathway, and downregulated MDR1 expression at both transcriptional and protein levels, in agreement with reduced promoter activity. Functionally, combined treatment with DEL-3 and MDR1-substrate chemotherapeutic agents enhanced cytotoxicity in U87-MG cells. Although DEL-3 did not significantly reduce tumor growth in a NOD-SCID xenograft model, MDR1 expression was reduced in treated tumors, indicating in vivo modulation of the target. Overall, these findings suggest that DEL-3, as a natural antioxidant, modulates inflammation-associated mechanisms and downregulates MDR1, thereby potentially enhancing the sensitivity of glioblastoma cells to MDR1-substrate chemotherapeutic agents. Full article
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22 pages, 14122 KB  
Article
Mapping the Thematic Structure and Evolution of AmpC β-Lactamase Research: A Bibliometric Analysis
by Ahmet Doğukan Bayrak and Okan Derin
Antibiotics 2026, 15(8), 777; https://doi.org/10.3390/antibiotics15080777 - 13 Aug 2026
Viewed by 64
Abstract
Background: AmpC β-lactamases are complex resistance determinants due to inducible chromosomal expression, stable derepression, plasmid-mediated dissemination, potential for co-resistance, and diagnostic interpretation challenges. Nevertheless, the scientific production, citation structure, and thematic evolution of the AmpC β-lactamase literature have not been comprehensively mapped. This [...] Read more.
Background: AmpC β-lactamases are complex resistance determinants due to inducible chromosomal expression, stable derepression, plasmid-mediated dissemination, potential for co-resistance, and diagnostic interpretation challenges. Nevertheless, the scientific production, citation structure, and thematic evolution of the AmpC β-lactamase literature have not been comprehensively mapped. This study aimed to evaluate this literature using bibliometric methods. Methods: Original articles and reviews indexed in SCI-E and ESCI within the Web of Science Core Collection were evaluated when “AmpC” appeared in the title field. After an additional microbiological filter, 1183 documents published between 1980 and 2026 were included. Analyses were performed using R, bibliometrix, and Biblioshiny. Results: Scientific production increased from the 2000s onward. Antimicrobial Agents and Chemotherapy and Journal of Antimicrobial Chemotherapy were among the most productive and most locally cited sources, while the United States ranked first in publication output and total citation impact. The most frequent keywords were Escherichia coli, ESBL, Klebsiella pneumoniae, and Enterobacterales. Conceptual analyses showed that the literature was structured around chromosomal AmpC biology, plasmid-mediated dissemination, resistance ecology intersecting with ESBLs, a cluster interpretable as a One Health axis, and clinical management themes. Trend topic analysis showed that multidrug resistance, carbapenemase, and virulence have become more visible in recent years. Conclusions: AmpC β-lactamase literature has broadened from an earlier emphasis on chromosomal resistance biology toward a multidimensional research field encompassing plasmid-mediated dissemination, resistance ecology, One Health-related themes, and clinical management. The recent prominence of concepts related to multidrug resistance phenotypes, the concurrent dissemination of resistance determinants, and pathogen virulence may suggest that the field is increasingly being addressed within a broader antimicrobial resistance context. Full article
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21 pages, 709 KB  
Article
Occurrence, Species Distribution, and Antimicrobial Resistance of Listeria spp. in Foods from Retail and Farm Outlets in North Carolina, USA
by Akbar Bahrami, Shurrita Davis, Erute Magdalene Adongbede, Janak Raj Khatiwada, Rishipal Rastrapal Bansode and Leonard Lamont Williams
Microorganisms 2026, 14(8), 1769; https://doi.org/10.3390/microorganisms14081769 - 11 Aug 2026
Viewed by 197
Abstract
Contamination of retail foods by Listeria species, compounded by emerging antimicrobial resistance (AMR), presents a critical public health challenge that demands continuous surveillance. This study evaluated prevalence, species distribution, and AMR profiles of Listeria spp. isolated from 861 retail food samples in North [...] Read more.
Contamination of retail foods by Listeria species, compounded by emerging antimicrobial resistance (AMR), presents a critical public health challenge that demands continuous surveillance. This study evaluated prevalence, species distribution, and AMR profiles of Listeria spp. isolated from 861 retail food samples in North Carolina, USA, (2018 and 2020). Isolation and molecular characterization were achieved through selective culturing, multiplex PCR, and antimicrobial susceptibility profiling via disk diffusion. Listeria was detected in 8.48% (73/861) samples, with 68 isolates identified to species level. Non-pathogenic strains predominated, led by L. welshimeri (24.66% of isolates) and L. innocua (21.92%). Pathogenic species (L. monocytogenes; L. ivanovii) represented 17.81% of isolates and were recovered exclusively from raw commodities. Vegetables yielded the most positive samples overall, but raw milk showed the highest individual category prevalence. Processed foods remained largely uncontaminated. Unprocessed foods were 27 times more likely to harbor Listeria than processed alternatives (RR = 27.19; 95% CI: 3.84–192.51. p < 0.0001). Phenotypic resistance was most frequent to Penicillin G (33.82%). Multidrug resistance (MDR) was identified in 64.71% of isolates, encompassing 84.62% of pathogenic and 60.00% of non-pathogenic species. Raw agricultural commodities serve as critical reservoirs for resistant Listeria, emphasizing the need for integrated surveillance frameworks. Full article
(This article belongs to the Section Food Microbiology)
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14 pages, 2135 KB  
Article
Associations of Biofilm Capacity with Antimicrobial Resistance and Virulence Genes in Klebsiella pneumoniae from Chickens in Henan, China, 2023–2025
by Han Zhang, Jiayi Li, Shiqi Deng, Jiani Lei, Liping Gao, Xiangyang Li, Lili Gao, Yuyang Yuan, Hua Wu, Yajun Zhai and Jianhua Liu
Antibiotics 2026, 15(8), 767; https://doi.org/10.3390/antibiotics15080767 - 10 Aug 2026
Viewed by 113
Abstract
Background: Klebsiella pneumoniae is an opportunistic zoonotic pathogen that can cause respiratory diseases in chickens. The aim of this study was to investigate the biofilm formation, resistance, and virulence of K. pneumoniae isolates from chickens in Henan Province, China, between 2023 and [...] Read more.
Background: Klebsiella pneumoniae is an opportunistic zoonotic pathogen that can cause respiratory diseases in chickens. The aim of this study was to investigate the biofilm formation, resistance, and virulence of K. pneumoniae isolates from chickens in Henan Province, China, between 2023 and 2025, and to analyze the associations among these characteristics. Methods: We identified the isolates through blood agar culture, Gram staining and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Hypermucoviscosity phenotype, biofilm-forming ability, antimicrobial resistance and virulence genes were assessed by the string test, crystal violet assay, disk diffusion and polymerase chain reaction (PCR), respectively. Results: A total of 102 K. pneumoniae isolates were identified. Of these, 81.4% were biofilm-forming strains, and 15.7% exhibited the hypermucoviscosity phenotype. The susceptibility profiles of the K. pneumoniae isolates indicated high resistance to penicillins (>90.0%) and low resistance to carbapenems (<10%), with 88.2% identified as multidrug-resistant. The results of virulence gene detection indicated that luxS (79.4%), mrkD (75.5%), and uge (73.5%) were the most prevalent virulence genes, followed by wabG (49.0%), ybtA (34.3%), and iucA (20.6%). The association analysis indicated that biofilm formation was significant association with multidrug-resistant and the carriage of virulence genes. Compared with non–biofilm–forming isolates, biofilm–forming isolates showed significantly higher resistance to ceftiofur and florfenicol, as well as higher detection rates of luxS, mrkD, and uge (p < 0.05). Conclusions: The data obtained in this study reveal the pathogenic potential and multidrug–resistant characteristics of this pathogen, highlighting the need for surveillance and monitoring. Full article
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15 pages, 280 KB  
Article
Antimicrobial Resistance and Species Dynamics of Enterococcus faecalis and Enterococcus faecium in Breeding Hens: Phenotypic and Genotypic Characterization
by Alejandro Fenollar, María A. Ferrús, Pablo Catalá-Gregori, Vicente Tallá-Ferrer, Miguel García-Ferrús and Ana Isabel Jiménez-Belenguer
Vet. Sci. 2026, 13(8), 795; https://doi.org/10.3390/vetsci13080795 - 9 Aug 2026
Viewed by 146
Abstract
Enterococcus faecalis and Enterococcus faecium are commensal bacteria of poultry but also important opportunistic pathogens and key indicators for antimicrobial resistance (AMR) surveillance within a One Health framework. However, data on the occurrence and antimicrobial resistance of enterococci in breeding hens remain limited [...] Read more.
Enterococcus faecalis and Enterococcus faecium are commensal bacteria of poultry but also important opportunistic pathogens and key indicators for antimicrobial resistance (AMR) surveillance within a One Health framework. However, data on the occurrence and antimicrobial resistance of enterococci in breeding hens remain limited despite their critical role in the poultry production pyramid. This study evaluated the prevalence, antimicrobial resistance profiles, and resistance genes of Enterococcus faecalis and Enterococcus faecium isolated from two commercial breeding hen farms in eastern Spain. A total of 330 isolates were obtained from different production stages and sample types. Species identification was performed by multiplex PCR, antimicrobial susceptibility was assessed using disk diffusion according to Clinical and Laboratory Standards Institute (CLSI) guidelines, and resistance genes (erm and tet) were detected by PCR. A significant age-related shift from E. faecalis in early production stages to E. faecium in adult hens was observed. High resistance rates were detected for tetracycline (up to 95.2%) and erythromycin, whereas resistance to critically important antimicrobials such as vancomycin, aminoglycosides, and ampicillin was rare or absent. Significant differences between farms were identified in both antimicrobial resistance levels and the prevalence of multidrug resistance. The most prevalent resistance genes were ermB, tetL, and tetM, frequently co-occurring. This study shows that breeding hens constitute a relevant reservoir of AMR within poultry production systems. Species dynamics and resistance patterns appear to be influenced by age and farm-related factors. These findings underscore the need for continuous AMR surveillance integrating phenotypic and genotypic approaches from a One Health perspective. Full article
(This article belongs to the Section Veterinary Food Safety and Zoonosis)
15 pages, 1128 KB  
Article
Antimicrobial Resistance and Selected Virulence-Associated Genes Escherichia coli Pathotypes in Free-Living Cats from Southern Spain
by Gómez-Gascón Lidia, Romero-Salmoral Antonio, Huerta Lorenzo Belén, Galán-Relaño Ángela, Marco-Fuertes Ana, Mena-Rodríguez Mª Ángeles, Molina Guillén Eva and Rafael J. Astorga Márquez
Animals 2026, 16(15), 2435; https://doi.org/10.3390/ani16152435 - 6 Aug 2026
Viewed by 194
Abstract
Stray cats may act as reservoirs of antimicrobial-resistant and potentially pathogenic bacteria, representing a potential public health concern within a One Health framework. This study investigated the occurrence of antimicrobial resistance (AMR), multidrug resistance (MDR), and virulence-associated traits in commensal Escherichia coli isolated [...] Read more.
Stray cats may act as reservoirs of antimicrobial-resistant and potentially pathogenic bacteria, representing a potential public health concern within a One Health framework. This study investigated the occurrence of antimicrobial resistance (AMR), multidrug resistance (MDR), and virulence-associated traits in commensal Escherichia coli isolated from free-living cat colonies in southern Spain. A total of 169 rectal swabs were collected from cats belonging to feline colonies and shelters in Benalmádena (Málaga, Spain). Bacterial isolation and identification were performed using selective culture media, conventional biochemical tests, and MALDI-TOF mass spectrometry. Antimicrobial susceptibility was determined by minimum inhibitory concentration (MIC) testing against 15 antimicrobial agents, and isolates were screened for selected virulence-associated genes associated with major diarrheagenic E. coli pathotypes. A total of 68 E. coli isolates (40.2%) were recovered. The highest resistance frequencies were observed for sulfamethoxazole (25.0%) and ampicillin (20.6%), whereas all isolates showed high susceptibility rates to most of the antimicrobials tested, including azithromycin (100%), as well as gentamicin, amikacin, cefotaxime, ceftazidime, meropenem, colistin, chloramphenicol and tigecycline (98.5%). Six isolates (8.8%) were classified as multidrug-resistant. In addition, six isolates (8.8%) were identified as atypical enteropathogenic E. coli (aEPEC), although none exhibited a multidrug resistance phenotype. These findings demonstrate the presence of both AMR and virulence-associated traits among commensal E. coli circulating in free-living cats. The inclusion of feline colonies or shelters in AMR surveillance programmes may contribute valuable information for integrated One Health monitoring strategies. Full article
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19 pages, 1089 KB  
Article
Clinical Impact of Multidrug-Resistant Bacterial Infections in Critically Ill Patients: A Retrospective Cohort Study
by Mateusz Bartoszewicz, Ewa Płonowska, Marta Krysik, Jerzy Robert Ładny and Sławomir Lech Czaban
J. Clin. Med. 2026, 15(15), 6110; https://doi.org/10.3390/jcm15156110 - 6 Aug 2026
Viewed by 219
Abstract
Background/Objectives: Antimicrobial-resistant bacterial infections are frequent in intensive care units (ICUs), but the independent effect of multidrug resistance relative to infection with susceptible organisms remains uncertain. We compared clinical characteristics, microbiology, treatment intensity, and in-hospital mortality among patients with no documented bacterial infection, [...] Read more.
Background/Objectives: Antimicrobial-resistant bacterial infections are frequent in intensive care units (ICUs), but the independent effect of multidrug resistance relative to infection with susceptible organisms remains uncertain. We compared clinical characteristics, microbiology, treatment intensity, and in-hospital mortality among patients with no documented bacterial infection, antimicrobial-susceptible infection, or multidrug-resistant (MDR) infection. Methods: We conducted a single-center retrospective cohort study of the first eligible ICU hospitalization for each patient at the University Clinical Hospital in Bialystok, Poland, from 1 January 2017 to 1 June 2023. Infection groups were assigned using clinical documentation, microbiological results, and local laboratory resistance-phenotype coding; patients with multiple isolates were classified according to the most resistant clinically relevant isolate. Multivariable logistic regression evaluated associations with in-hospital mortality. Results: Among 3326 patients, 1413 (42.5%) had a documented bacterial infection: 481 (34.0% of infected patients) had susceptible infection and 932 (66.0%) had MDR infection. Crude mortality was 45.5%, 46.8%, and 48.4% in the no-infection, susceptible-infection, and MDR-infection groups, respectively (p = 0.354), whereas mean ICU length of stay was 10.0, 15.5, and 25.2 days (p < 0.001). In the complete-case whole-cohort model (n = 678), MDR infection (adjusted OR 2.70, 95% CI 1.84–3.96) and susceptible infection (adjusted OR 2.16, 95% CI 1.26–3.69) were associated with in-hospital death versus no infection. Within the infected cohort (n = 352), MDR status was not independently associated with mortality versus susceptible infection (adjusted OR 1.09, 95% CI 0.61–1.93). Conclusions: MDR infection identified patients with prolonged ICU exposure and greater organ-support requirements but did not independently increase mortality relative to susceptible infection. Interpretation is limited by the retrospective single-center design, complete-case analysis, and absence of time-resolved MDR acquisition data. Full article
(This article belongs to the Section Infectious Diseases)
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14 pages, 4019 KB  
Article
Environmental and Clinical Spread of MDR Acinetobacter baumannii: A Genomic Epidemiology Investigation
by Alice Caramaschi, Marianna Farotto, Marta Mellai, Francesco Favero, Davide Corà, Paolo Bottino, Christian Leli, Lidia Ferrara, Chiara Bazzano, Silvio Collani, Valeria Bonato, Andrea Rocchetti, Marinella Bertolotti, Annalisa Roveta, Antonio Maconi and Elisa Bona
Microbiol. Res. 2026, 17(8), 150; https://doi.org/10.3390/microbiolres17080150 - 3 Aug 2026
Viewed by 208
Abstract
During the COVID-19 pandemic, healthcare systems experienced significant disruption, increasing the risk of multidrug-resistant (MDR) pathogen transmission. Acinetobacter baumannii, a critical-priority MDR pathogen, is known for its ability to persist in hospital environments and rapidly acquire resistance. To investigate the genomic characteristics, [...] Read more.
During the COVID-19 pandemic, healthcare systems experienced significant disruption, increasing the risk of multidrug-resistant (MDR) pathogen transmission. Acinetobacter baumannii, a critical-priority MDR pathogen, is known for its ability to persist in hospital environments and rapidly acquire resistance. To investigate the genomic characteristics, antimicrobial resistance determinants, and phylogenetic relationships of outbreak-associated Acinetobacter baumannii isolates, whole-genome sequencing (WGS) and comparative genomic analyses on 24 clinical and environmental strains collected during the COVID-19 period were performed. Twenty-four A. baumannii isolates collected between August 2020 and February 2021 from clinical and environmental samples were analyzed by WGS. All isolates displayed an MDR phenotype, with uniform resistance to carbapenems and aminoglycosides, and preserved colistin susceptibility. One environmental strain showed extreme drug resistance. WGS confirmed medium-quality genome assemblies and the clonal spread of a single A. baumannii lineage. Most resistance genes, including OXA-23, ADC-type β-lactamases, and ade efflux pumps, were chromosomally encoded and shared across all isolates. Plasmid-mediated resistance genes were variably distributed. This outbreak of MDR A. baumannii was driven by the clonal dissemination of a genomically stable lineage. Combined genomic and epidemiological analyses underscore the importance of integrated surveillance and environmental decontamination to prevent the spread of MDR pathogens. Full article
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29 pages, 3999 KB  
Article
Virulence and Invasion Profiles of Escherichia coli Across One Health Reservoirs: Genomic Insights into High-Risk Clones and Their Defense Systems
by Sandra Martínez-Álvarez, Soraya Herrera-Espejo, Myriam Zarazaga, Ursula Höfle, María Eugenia Pachón-Ibáñez and Carmen Torres
Pathogens 2026, 15(8), 812; https://doi.org/10.3390/pathogens15080812 - 1 Aug 2026
Viewed by 269
Abstract
Escherichia coli is a genetically diverse species encompassing both commensal and pathogenic lineages capable of transitioning among various hosts. Within a One Health framework, we conducted a targeted screening of 38 E. coli strains isolated from wildlife, livestock, and food reservoirs to characterize [...] Read more.
Escherichia coli is a genetically diverse species encompassing both commensal and pathogenic lineages capable of transitioning among various hosts. Within a One Health framework, we conducted a targeted screening of 38 E. coli strains isolated from wildlife, livestock, and food reservoirs to characterize their pathogenic potential by integrating genomic and phenotypic approaches. In vitro functional assays, including biofilm formation, surface motility, and adherence and invasion of HEK-293 epithelial cells, were statistically evaluated using the non-parametric Mann–Whitney U test. Phenotypic analyses revealed that extraintestinal pathogenic (ExPEC) and uropathogenic E. coli (UPEC) strains, particularly those belonging to the high-risk ST117 clone, exhibited significantly enhanced adherence and internalization capacities. These virulent phenotypes strongly correlated with specific genetic signatures involved in iron acquisition and epithelial invasion (chuA, fyuA, vat, and tia), underscoring that the convergence of ExPEC/UPEC determinants drives increased colonization potential. Genomic characterization further revealed that despite high virulence and widespread antimicrobial resistance, the CRISPR/Cas subtype I-E system was highly prevalent (93.8%), displaying structural variations frequently driven by insertion sequences. Spacer analyses identified limited homology to plasmids and phages, suggesting past mobilome interactions rather than active restriction of current horizontal gene transfer. Overall, these findings illustrate how phenotypic traits of high-risk clones match their genomic virulence platforms. The convergence of multidrug resistance and pathogenic fitness across human, animal, and environmental interfaces underscores the need for integrated molecular surveillance in a One Health context. Full article
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32 pages, 15961 KB  
Article
Isolation, Identification, and Biological Characterization of Proteus mirabilis Isolated from Beef Cattle in China
by Xueli Ge, Rongjun Gong, Jiamin Ma, Yangsini Fu, Jiahao Chen, Manting Li, Qinghong Guo, Xinchao Liu and Wenchao Li
Microorganisms 2026, 14(8), 1668; https://doi.org/10.3390/microorganisms14081668 - 30 Jul 2026
Viewed by 292
Abstract
Proteus mirabilis, a member of the family Enterobacteriaceae, is widely distributed in the environment and commonly colonizes the gastrointestinal tract of animals. Although traditionally regarded as an opportunistic zoonotic pathogen, increasing evidence suggests that it may also contribute to bovine diseases. [...] Read more.
Proteus mirabilis, a member of the family Enterobacteriaceae, is widely distributed in the environment and commonly colonizes the gastrointestinal tract of animals. Although traditionally regarded as an opportunistic zoonotic pathogen, increasing evidence suggests that it may also contribute to bovine diseases. However, information regarding the antimicrobial resistance, virulence determinants, and genomic characteristics of bovine-associated P. mirabilis in China remains limited. In this study, a P. mirabilis strain, designated A3, was isolated from one of 19 diarrheic adult beef cattle sampled in Anhui Province, China, and comprehensively characterized through phenotypic, genomic, and pathogenicity analyses. Strain A3 exhibited typical swarming motility and a multidrug-resistant phenotype. PCR screening identified the resistance genes aac(6′)-Ib and qnrA, together with seven virulence genes (pmfA, atfA, ureC, mrpA, ucaA, zapA, and atfC) involved in adhesion and colonization. Whole-genome sequencing generated a 3,965,086 bp draft genome with a GC content of 38.37% and identified 85 resistance-associated genes and 147 virulence-associated genes, including multidrug efflux pumps and virulence factors related to adhesion, motility, iron acquisition, secretion systems, and host interaction. Comparative genomic analysis demonstrated high genomic similarity to other bovine-derived P. mirabilis isolates, with average nucleotide identity (ANI) values ranging from 99.06% to 99.32%, while pangenome analysis identified 5680 orthologous gene clusters, including 2959 core genes, indicating an open pangenome structure. Multiple insertion sequences, prophages, and genomic islands were identified, highlighting substantial genomic plasticity and adaptive potential. In a mouse infection model, strain A3 exhibited clear dose-dependent pathogenicity. All eight mice challenged with 2.22 × 109 CFU/mL died within 12 h post-infection and developed severe pathological lesions in multiple organs, whereas only one of eight mice in the low-dose group died during the same period. Collectively, these findings indicate that bovine-derived P. mirabilis A3 combines multidrug resistance, genomic plasticity, and opportunistic pathogenic potential. This study expands current knowledge of bovine-associated P. mirabilis and provides a genomic and experimental basis for surveillance, risk assessment, and prevention strategies in cattle production systems. Full article
(This article belongs to the Section Veterinary Microbiology)
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17 pages, 1101 KB  
Article
Phenotypic and Genetic Profile, Biofilm-Forming Ability and Antibiotic Sensibility of ESBL-Producing Klebsiella pneumoniae Complex from Fecal Samples of Cats in Italy
by Alessia Facchin, Gabriele Ratti, Irene Mauri, Alessia L. Gazzonis, Paola Dall’Ara, Claudia Pollera, Maria Cristina Rapi and Stefania Lauzi
Antibiotics 2026, 15(8), 735; https://doi.org/10.3390/antibiotics15080735 - 29 Jul 2026
Viewed by 212
Abstract
Background: Antimicrobial resistance mediated by ESBL-producing Klebsiella pneumoniae is an emerging concern in both human and veterinary medicine, with companion animals increasingly considered relevant within the One Health framework. This study aimed to investigate the fecal carriage of ESBL-producing K. pneumoniae complex in [...] Read more.
Background: Antimicrobial resistance mediated by ESBL-producing Klebsiella pneumoniae is an emerging concern in both human and veterinary medicine, with companion animals increasingly considered relevant within the One Health framework. This study aimed to investigate the fecal carriage of ESBL-producing K. pneumoniae complex in cats from Italy and to characterize the strains by the phenotypic and genetic profile of ESBL production, virulent pathotypes, antibiotic resistance profile and biofilm production. Methods: Fecal samples collected from cats admitted to the Veterinary Teaching Hospital of Milan (Italy) in 2020–2026 were bacteriologically and genetically analyzed. Results: All the Klebsiella pneumoniae strains isolated [4/200 (2%, 95% CI: 0.06–3.94%)] were ESBL-producing K. pneumoniae complex isolates harboring blaCTX-M-15, blaSHV, and blaTEM genes. The isolates were detected with higher presence in cats with diarrhea and were found only in cats treated with antibiotics and hospitalized. All four ESBL-producing isolates were classified as the classical K. pneumoniae pathotype based on the negative string test results, the absence of reliable virulence genes used for pathotype identification (peg-344, iucA, rmpA and rmpA2), and the lack of K1 and K2 serotypes, despite the detection of terB and irp2 virulence genes in one and two isolates, respectively. All four ESBL-producing K. pneumoniae complexes were classified as multidrug-resistant, with resistance mainly observed to β-lactams, fluoroquinolones, quinolones and folate antagonists. All four ESBL-producing K. pneumoniae complexes demonstrated biofilm-forming abilities, with two isolates showing weak adhesion, one moderate adhesion, and one strong adhesion. Conclusions: The detection of ESBL genes together with the MDR pattern, biofilm-forming capacity and selected virulence determinants suggests the potential epidemiological relevance of cats in the dissemination of antimicrobial-resistant K. pneumoniae complexes, underscoring the need for strengthened surveillance and prevention strategies in veterinary settings to provide information to pet cat owners and children who may interact with stray cats, in full implementation of the One Health approach. Full article
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13 pages, 859 KB  
Article
Resistance to Human-Reserved Antimicrobials in Clinical and Commensal Enterococcus faecalis and Enterococcus faecium from Dogs and Cats
by Giulia Iamone, Alessandro Bellato, Ilaria Prandi, Maria Cristina Stella, Simona Paparone, Simona Zoppi, Cristina Marra, Renato Zanatta, Rosario Musumeci, Patrizia Robino and Patrizia Nebbia
Antibiotics 2026, 15(8), 732; https://doi.org/10.3390/antibiotics15080732 - 29 Jul 2026
Viewed by 265
Abstract
Background/Objectives: Although companion animals are recognized as reservoirs of antimicrobial resistant enterococci, it remains unclear whether antimicrobial resistance differs between clinical and commensal isolates, particularly for antimicrobials reserved for human medicine. This study compared antimicrobial susceptibility profiles of clinical and commensal E. faecalis [...] Read more.
Background/Objectives: Although companion animals are recognized as reservoirs of antimicrobial resistant enterococci, it remains unclear whether antimicrobial resistance differs between clinical and commensal isolates, particularly for antimicrobials reserved for human medicine. This study compared antimicrobial susceptibility profiles of clinical and commensal E. faecalis and E. faecium isolates from dogs and cats, focusing on antimicrobials reserved for human medicine under European regulation and EMA/AMEG classification. Methods: A total of 99 isolates (49 E. faecalis and 50 E. faecium) collected between 2022 and 2025 were analysed by broth microdilution, gradient diffusion, and disk diffusion methods. Antimicrobial resistance patterns were compared according to bacterial species and isolate origin. Results:E. faecium exhibited significantly higher resistance rates than E. faecalis, particularly to ampicillin, fluoroquinolones, erythromycin, nitrofurantoin, and vancomycin. Multidrug resistance was widespread, affecting all clinical E. faecium isolates and 72.2% of commensal E. faecium, whereas corresponding proportions in E. faecalis were 64.1% and 40.0%, respectively. Clinical E. faecium isolates showed significantly higher resistance than commensal isolates to antimicrobials commonly used in veterinary medicine, including ampicillin, fluoroquinolones, erythromycin, gentamicin, streptomycin, and tetracycline. Conversely, no significant differences were observed for antimicrobials reserved for human medicine, including linezolid, vancomycin, teicoplanin, tigecycline, daptomycin, rifampicin, and quinupristin/dalfopristin. Conclusions: The higher resistance observed in clinical isolates to veterinary antimicrobials is consistent with the selective pressure exerted by antimicrobial use in veterinary clinical settings, whereas resistance to human-reserved agents may reflect epidemiological processes that are independent of antimicrobial exposure in veterinary clinical settings. Continuous integrated One Health surveillance is essential to monitor the emergence and dissemination of these resistance phenotypes. The AMR profiles observed in companion animals further support the need for integrated One Health surveillance, combining veterinary, human, and environmental data to better understand the emergence and dissemination of resistant enterococci. Full article
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17 pages, 1522 KB  
Article
Phenotypic Antimicrobial Resistance in Escherichia coli and Salmonella spp. Recovered from Broiler-Farm Environmental Matrices in Morocco
by Walid Atiki, Najia Ameur, Atika Zidouh, Abdelmoula Elouardi and Latifa Tahri
Antibiotics 2026, 15(8), 731; https://doi.org/10.3390/antibiotics15080731 - 28 Jul 2026
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Abstract
Background/Objectives: Antimicrobial resistance (AMR) in poultry-production environments is an important One Health concern. This phenotypic baseline study investigated the detection and antimicrobial-resistance profiles of Escherichia coli and Salmonella spp. recovered from broiler-farm environmental matrices in the Rabat–Salé–Kénitra region of Morocco. Methods: [...] Read more.
Background/Objectives: Antimicrobial resistance (AMR) in poultry-production environments is an important One Health concern. This phenotypic baseline study investigated the detection and antimicrobial-resistance profiles of Escherichia coli and Salmonella spp. recovered from broiler-farm environmental matrices in the Rabat–Salé–Kénitra region of Morocco. Methods: A cross-sectional field study was conducted in 13 broiler farms on 35 sampling dates between 24 November 2023 and 28 April 2025. A total of 543 samples were collected from poultry manure, drinking troughs, farm soil, soils approximately 200 and 500 m from the poultry houses, and well water. Isolates were identified by culture and API 20E; Salmonella spp. identification was additionally confirmed by real-time PCR. Disk-diffusion results were interpreted using applicable CLSI M100, 31st edition, criteria, and colistin was tested by the colistin broth disk elution MIC method. Multidrug resistance (MDR) was defined as resistance to at least one agent in three or more antimicrobial classes. ResultsEscherichia coli and Salmonella spp. were detected in 190/543 (35.0%) and 127/543 (23.4%) samples, respectively. Among E. coli isolates, 115/190 (60.5%) were MDR; the highest matrix-specific proportions occurred in farm soil (85.7%), drinking troughs (83.3%), and poultry manure (75.7%). Among Salmonella spp. isolates, 82/127 (64.6%) were MDR, with the highest proportions in poultry manure (92.9%) and drinking troughs (78.3%). The predominant resistance rates were ampicillin (84.7%), tetracycline (61.6%), and chloramphenicol (55.8%) in E. coli, and nalidixic acid (73.2%), ampicillin (61.4%), and tetracycline (55.9%) in Salmonella spp. Resistant isolates were also detected in surrounding soils and well water; however, the study design did not permit source attribution or inference of transmission direction. Conclusions: Broiler-farm environmental matrices in the study area may represent reservoirs of phenotypically antimicrobial-resistant E. coli and Salmonella spp. The findings provide baseline evidence supporting integrated One Health surveillance, improved biosecurity, manure and litter management, water-system sanitation, and responsible veterinary antimicrobial use. Genomic typing and environmental source-tracking are required to determine persistence and transmission pathways. Full article
(This article belongs to the Special Issue Advances in Antimicrobial Action and Resistance)
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14 pages, 8093 KB  
Article
Characterization of blaNDM-1 and blaOXA-23-Type Carbapenemases in Acinetobacter baumannii Isolated from Post-Surgical Patients
by Sana Gul, Nawab Ali, Muhammad Qasim, Maali Alahmad, Muhammad Saeed Khan, Zull E. Nourain, Sadir Zaman, Yar Muhammad and Waheed Ullah
Antibiotics 2026, 15(8), 722; https://doi.org/10.3390/antibiotics15080722 - 24 Jul 2026
Viewed by 327
Abstract
Background: Acinetobacter baumannii is an important opportunistic pathogen responsible for healthcare-associated infections, particularly among critically ill, intensive care unit (ICU), and post-surgical patients. The emergence of carbapenem-resistant A. baumannii (CRAB) has become a major therapeutic challenge worldwide because of its multidrug-resistant nature [...] Read more.
Background: Acinetobacter baumannii is an important opportunistic pathogen responsible for healthcare-associated infections, particularly among critically ill, intensive care unit (ICU), and post-surgical patients. The emergence of carbapenem-resistant A. baumannii (CRAB) has become a major therapeutic challenge worldwide because of its multidrug-resistant nature and limited treatment options. Despite the increasing prevalence of CRAB in Pakistan, information regarding the molecular characterization of carbapenem resistance genes among isolates recovered from surgical site infections (SSIs) remains limited. Methods: A cross-sectional study was conducted from November 2023 to February 2024 at Khalifa Gul Nawaz Hospital, Bannu, Khyber Pakhtunkhwa, Pakistan. A total of (n = 118) surgical wound specimens were collected from patients with clinically diagnosed SSIs. A. baumannii isolates were identified using standard biochemical tests and confirmed by 16S rRNA gene sequencing. In vitro antimicrobial susceptibility was determined by Kirby–Bauer disk diffusion according to CLSI 2024 guidelines. In addition, the concentration-dependent inhibition-zone response of imipenem and meropenem against carbapenem-resistant isolates was evaluated using an agar well diffusion assay. Molecular detection of blaNDM-1 and blaOXA-23 was performed by polymerase chain reaction (PCR), and representative amplicons were subjected to Sanger sequencing for further analysis. Results: In the current study, the total number of (n = 118) wound specimens from healthcare-associated patients were processed, in which A. baumannii-positive isolates (n = 23, 19.5%) were documented. Its prevalence was higher in males (69.6%) compared to females, and was strongly associated (78.2%) with elderly patients (aged 51–68 years). In vitro susceptibility testing revealed that 91.3% of isolates harbored multidrug-resistant (MDR) attributes. Antimicrobial susceptibility profiling revealed high levels of multidrug resistance, with 82.6% of isolates resistant to imipenem and meropenem, as well as 100% resistance to aztreonam and gentamicin. Colistin showed the highest activity, with 87.0% of isolates remaining susceptible. In the agar well diffusion assay, measurable inhibition of the carbapenem-resistant isolates by imipenem and meropenem occurred only at higher concentrations. Molecular screening of resistance genes identified blaOXA-23 in 60.9% and blaNDM-1 in 30.4% of isolates. Co-expression of both genes was detected in some (n = 4) isolates. Among the selected MDR isolates included in the gene resistance analysis, imipenem and meropenem resistance were recorded in 9/14 blaOXA-23-positive isolates and 5/7 blaNDM-1-positive isolates. Conclusions: This study substantiates an escalated incidence of carbapenem-resistant, MDR A. baumannii in post-surgical infections. blaOXA-23 were documented as the predominant carbapenemase gene, with co-expression of blaNDM-1 in a substantial proportion of isolates. These findings provide an important phenotypic and molecular characterization of selected carbapenemase genes in healthcare-associated infections, highlighting the exigency for strengthened antimicrobial stewardship and infection control strategies in the hospitals of the region. Full article
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