Search Results (1,788)

Diarrhea in neonatal dairy goat kids is a major disease affecting the dairy goat industry, yet the predominant bacterial pathogens in Inner Mongolia remain unclear. This study investigated the main bacterial pathogens and characterized the toxin genotypes, antimicrobial resistance, and metabolic features of Clostridium perfringens. A total of 1169 fecal samples from diarrheic kids (<15 days old) were analyzed. C. perfringens showed the highest positive rate (56.06%), followed by Escherichia coli (46.71%) and Salmonella spp. (24.54%), and was positively correlated with bloody diarrhea (r = 0.31). Among 73 isolates, type B (67.1%) was predominant. Most isolates were highly susceptible to tetracycline, cefoxitin, penicillin, and metronidazole, while resistance to ampicillin was relatively high. Metabolomic analysis revealed that type B strains exhibited enhanced metabolic activity compared with type C strains. In conclusion, type B C. perfringens is the predominant pathogen and shows metabolic advantages, providing a basis for targeted control strategies. Full article

The escalating global concern regarding bacterial antibiotic resistance in animal production has intensified the search for sustainable and effective alternatives to conventional antimicrobials. In this study, two L. reuteri strains (LBM-Ti195 and LBM-Ti173) are isolated from broiler cecal microbiota that were characterized through an integrated approach, combining phenotypic assays with comparative genomic analysis. Both strains exhibited antibacterial activity against relevant veterinary and foodborne pathogens, including Listeria monocytogenes CECT 934, Staphylococcus aureus CECT 239, Clostridium perfringens Type A, and Campylobacter jejuni CCAMP 162. The inhibitory activity anti-S. aureus increased by more than 10% modifying cultivation conditions, while comparative genomic analysis identified an M23-family metallopeptidase as a potential candidate for pathogen inhibition. Phenotypically, both strains produced folate and metabolized fructooligosaccharides (FOS) and inulin, supporting their potential compatibility with synbiotic formulations. Genome reconstruction reinforces these functional findings by revealing a complete predicted de novo folate biosynthesis pathway. In addition, CAZyme annotation identified higher copy numbers of glycosyltransferases GT2 and GT4 compared with the reference strains, suggesting differences in cell-surface carbohydrate metabolism and exopolysaccharide (EPS)-associated traits. Safety profiling revealed no hemolytic activity or conserved virulence factors under the tested conditions. However, phenotypic tetracycline resistance was detected, and in silico analysis identified an acquired tetW gene in a putative plasmid-associated context, highlighting the importance of an in-depth evaluation of strains with probiotic potential. Collectively, these findings position LBM-Ti195 and LBM-Ti173 as promising avian-derived L. reuteri candidates for next-generation zootechnical probiotic development, while highlighting antimicrobial resistance (AMR) mitigation and further functional validation as essential steps toward safe application. Full article

Antimicrobial resistance (AMR) in Escherichia coli (E. coli) from companion dogs is an emerging One Health concern because dogs may serve as asymptomatic reservoirs of multidrug-resistant (MDR) and potentially pathogenic bacteria that can be transmitted to humans. This study aimed to determine antimicrobial susceptibility profiles, characterize antimicrobial resistance and virulence associated genes, and identify nucleotide substitutions in resistance determinants of E. coli isolated from healthy dogs in Thailand. Fecal samples (n = 200; 100 samples per province) were collected from healthy dogs attending a total of 50 small animal clinics located in Nakhon Si Thammarat and Chiang Mai provinces between January and March 2026. E. coli isolates were identified by culture and polymerase chain reaction (PCR) confirmation. Antimicrobial susceptibility was evaluated against 12 antimicrobial agents using the disk diffusion method according to CLSI guidelines. Thirty randomly selected isolates were further screened for resistance and virulence-associated genes by PCR, and the tetA gene was sequenced to identify nucleotide substitutions. Differences in gene distributions between provinces were assessed using Fisher’s exact test. A total of 66 E. coli isolates were recovered. High resistance rates were observed for ampicillin (100%), piperacillin (84.85%), ceftriaxone (60.61%), tetracycline (56.06%), and aztreonam (46.97%). Multidrug resistance was identified in 47% of the isolates. The 30 isolates exhibiting the highest levels of antimicrobial resistance were selected for molecular characterization. Among these, the β-lactam resistance gene bla_TEM was significantly more prevalent in Nakhon Si Thammarat than in Chiang Mai (60% vs. 0%; p = 0.022). The virulence gene stx2 was also detected significantly more frequently in isolates from Nakhon Si Thammarat (93.33% vs. 26.67%; p < 0.001). Sequence analysis of tetA revealed multiple nucleotide substitutions in two isolates, suggesting ongoing genetic variation within tetracycline resistance determinants that may contribute to the evolution and persistence of antimicrobial resistance. These findings demonstrate that healthy dogs in Thailand can act as reservoirs of MDR and potentially virulent E. coli. The observed geographic variation in resistance and virulence gene distributions highlights the importance of antimicrobial stewardship and continuous molecular surveillance in companion animals within a One Health framework. Full article

Antimicrobial resistance (AMR) and virulence have traditionally been viewed as competing traits in bacterial evolution due to fitness costs. However, Streptococcus pneumoniae has emerged as a paradigm of successful coevolution, with multidrug-resistant clones simultaneously maintaining or enhancing pathogenic potential. This review examines the molecular mechanisms, epidemiological patterns, and clinical consequences of the convergence between AMR and virulence in Streptococcus pneumoniae. Resistance to β-lactams is driven by mosaic penicillin-binding protein genes (pbp1a, pbp2b, pbp2x), while macrolide resistance is mediated primarily by the erm(B) gene (MLS phenotype) and mef(A/E)–msr(D) genes encoding an efflux system. These determinants are frequently co-localized on integrative and conjugative elements, ICEs, (e.g., Tn916 family) within successful clonal complexes such as CC271/320 and lineages including ST320 and GPSC10. Contrary to the classical fitness cost hypothesis, compensatory epistasis, capsular recombination, metabolic adaptations, and intra-serotype phenotypic variation enable certain clones to combine high-level resistance to β-lactams, macrolides, and tetracyclines with enhanced colonization, biofilm formation, immune evasion, and invasive capacity. Post-pneumococcal conjugate vaccine (PCV) surveillance reveals the persistence and expansion of these high-risk lineages, contributing to treatment-refractory invasive pneumococcal disease (IPD), increased morbidity, and mortality. Although PCVs have reduced vaccine-type resistant strains in some settings, serotype replacement and emerging metabolic genotypes continue to drive adaptation. This review highlights the need for integrated genomic surveillance, novel therapeutics (e.g., omadacycline, lefamulin, endolysins), monoclonal antibodies, and next-generation vaccines targeting both resistance and conserved virulence determinants. A multifaceted strategy combining antimicrobial stewardship, strengthened surveillance, and innovative interventions is essential to curb the evolving threat of resistant and virulent S. pneumoniae. Full article

Six lactic acid bacteria isolated from São Jorge PDO cheese were characterised for technological, safety, antimicrobial, and probiotic properties. All isolates fermented a broad range of carbohydrates and lacked lipolytic activity, while SJC115 and SJC119 showed proteolysis. Safety profiling (γ-haemolysis, no DNase or gelatinase activity, and generally favourable antibiotic susceptibility) is promising, but tetracycline resistance warrants caution and genomic confirmation. L. paracasei and L. brevis isolates inhibited a wide range of foodborne pathogens (Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Bacillus spp.) and spoilage fungi (Penicillium and Aspergillus spp.). Notably, two isolates (SJC117 and SJC120) exhibited antibacterial activity in neutralized cell-free supernatants, indicating putative bacteriocin-like inhibitory substances (BLIS). The isolates survived intestinal conditions above the probiotic threshold, yet only SJC117 and SJC120 tolerated gastric acidity (pH 2.5, 1 h) with >5 log CFU/mL. Despite low hydrophobicity, strains showed good autoaggregation and pathogen coaggregation. All isolates produced exopolysaccharides (EPS) and angiotensin-converting enzyme (ACE) inhibitory peptides, whereas some exhibited moderate conjugated linoleic acid (CLA) production and glutamate decarboxylase (GAD) activity. L. paracasei SJC117 stood out by combining BLIS/antifungal activity, superior gastric tolerance, and an exceptional bioactive profile, making it a promising candidate for biopreservation and functional food applications that warrants further in vivo validation to confirm its efficacy and safety. Full article

Introduction: Several Enterobacterales species harboring New Delhi metallo-β-lactamase (NDM-1) have been reported worldwide. Among them is Providencia stuartii (P. stuartii), an emerging pathogen in nosocomial infections. Objective: This study aimed to perform the clinical and genomic characterization of NDM-1-producing P. stuartii isolates recovered from hospitalized patients during the COVID-19 pandemic in Southern Brazil. Materials and Methods: A retrospective observational study was conducted between April and September 2021 at a Brazilian teaching hospital. Fifty P. stuartii isolates were identified, and carbapenem-resistant isolates underwent phenotypic and molecular characterization. Genetic relatedness was assessed by Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR), and selected isolates were subjected to whole-genome sequencing using the Illumina NextSeq platform to determine sequence types, resistance genes, virulence determinants, and plasmid content. Statistical analyses were performed using SPSS version 20.0. Results: Among the 50 isolates, 21 (42%) harbored the blaNDM-1 gene. Most isolates were recovered from tracheal aspirates (57.2%), followed by blood (23.8%), urine (9.5%), and skin and soft tissue samples (9.5%). Significant associations were observed between NDM-1-producing isolates and SARS-CoV-2 infection (p = 0.013), central venous catheter use (p = 0.012), mechanical ventilation (p = 0.006), hemodialysis (p = 0.033), previous antimicrobial exposure, and mortality (p = 0.021). Genomic analysis revealed the presence of blaNDM-1, blaOXA-1, and multiple resistance determinants associated with aminoglycosides, fluoroquinolones, macrolides, tetracyclines, and folate pathway inhibitors. ERIC-PCR demonstrated low genetic variability among isolates, suggesting possible clonal dissemination within the hospital environment. Conclusions: This study reports the emergence of NDM-1-producing P. stuartii during the COVID-19 pandemic in a Brazilian teaching hospital. The low genetic variability among isolates and the multidrug-resistant profile highlight the potential for nosocomial dissemination and reinforce the importance of genomic surveillance and infection control strategies. Full article

Background: Despite its typically self-limiting course, acute diarrheal disease continues to be clinically relevant from an antimicrobial resistance surveillance perspective. In-depth analyses at a national level remain limited, with available Romanian studies from the last decade focusing on individual pathogens, often relying on a restricted isolate collection. In this context, we aimed to evaluate antimicrobial resistance profiles and distribution of Salmonella spp., Campylobacter spp., Escherichia coli, Yersinia spp. and Shigella spp. Methods: Data was obtained from records from the Microbiology Laboratory of a tertiary-care hospital serving the south region of Romania, over a 3-year period. Results: Campylobacter spp. had high resistance rates to ciprofloxacin (81.65% for C. jejuni; 85.15% for C. coli) and tetracycline (44.65% for C. jejuni; 56.07% for C. coli). Erythromycin resistance remained low and stable over the study period, with no statistically significant temporal variation; however, C. coli isolates demonstrated significantly higher erythromycin (p = 0.001) and tetracycline (p = 0.008) resistance rates compared to C. jejuni. Overall Salmonella spp. resistance rate to ciprofloxacin was 46.00%, with higher resistance observed in serogroups C (63.64%) and D (52.53%) (p < 0.01). Ampicillin (AMP) resistance varied significantly across years and serogroups, with serogroup B consistently demonstrating higher resistance rates (40.48%) (p < 0.001). E. coli isolates reacting with pathotype-associated O antisera revealed high resistance levels to ampicillin (41.57%), amoxicillin–clavulanic acid (AMC) (38.73%) and sulfamethoxazole–trimethoprim (SXT) (19.25%), with low resistance levels to ciprofloxacin (9.04%) and ceftriaxone (CRO) (9.71%); no significant variation in resistance patterns was identified across years or serological pools, suggesting a relatively stable resistance profile over the study period. Yersinia spp. isolates showed no notable antimicrobial resistance levels. Shigella spp. isolates exhibited high resistance for ampicillin (78.57%), sulfamethoxazole–trimethoprim (68.75%), amoxicillin–clavulanic acid (50.00%) and ceftriaxone (35.41%). Conclusions: This study addressed a recognized gap in Romanian and Eastern European surveillance data and aims to contribute to a stronger evidence base for future epidemiological investigations and antimicrobial stewardship efforts. Resistance rates identified in our study may provide valuable information for comparison with data generated from veterinary, food and environmental surveillance programs, thereby supporting a more comprehensive understanding of antimicrobial resistance (AMR) epidemiology. These findings may additionally contribute to the development of coordinated strategies aimed at mitigating the emergence and spread of AMR. Full article

Background/Objectives: Antimicrobial resistance (AMR) in Staphylococcus spp. associated with poultry production is an emerging concern with implications for animal and public health. This study aimed to characterize antimicrobial susceptibility patterns and detect targeted methicillin resistance determinants in Staphylococcus isolates recovered from broiler chickens affected by bacterial chondronecrosis with osteomyelitis (BCO). Methods: A total of 200 bacterial isolates were evaluated, of which 167 were confirmed as Staphylococcus spp. Species identification was performed using presumptive phenotypic characterization followed by 16S rRNA gene sequencing. Antimicrobial susceptibility was assessed using disk diffusion, while presumptive methicillin-resistant phenotypes were evaluated using oxacillin screening and CHROMagar MRSA. Targeted molecular detection of mecA and mecC was performed by PCR. Results: The isolates demonstrated substantial species diversity, with S. aureus as the predominant species. Antimicrobial resistance was mainly observed against β-lactam antibiotics, particularly penicillin (33.5%), whereas high susceptibility was retained for non-β-lactam agents, including ciprofloxacin, tetracycline, trimethoprim–sulfamethoxazole, and azithromycin. A targeted PCR detected mecA in 7.2% of isolates, while mecC was not detected. The detection of mecA in oxacillin-susceptible isolates suggested genotype–phenotype discordance. Conclusions: BCO-associated Staphylococcus spp. from broiler chickens showed diverse species distribution, penicillin-dominant resistance, and targeted mecA detection across multiple species, supporting the use of combined phenotypic and molecular approaches for methicillin resistance surveillance. Full article

Subclinical bovine mastitis (SBM) is an inflammatory condition of the udder that remains a major concern for the dairy industry due to its high incidence and the direct and indirect associated costs. Antibiotics are widely used for prophylaxis and therapy in livestock, especially for SBM. However, overuse and misuse have contributed to the emergence of antimicrobial resistance (AMR), enabling resistant bacteria to enter the food chain and potentially spread to humans. This study aimed to detect antibiotic-resistant Staphylococcus and Streptococcus associated with SBM in dairy cows from Pioter, north-central Ecuador. For this, a commercial screening test, morphological and biochemical assays, standard culture techniques, mass spectrometry, and PCR (polymerase chain reaction) were applied. Among 99 isolates, 77 were Staphylococcus and 22 were Streptococcus. Among the identified Staphylococcus isolates, S. aureus was the predominant species (36.4%). Resistance in Staphylococcus exceeded 70% for fosfomycin and was under 30% for the other antibiotics tested. In Streptococcus, S. uberis predominated (54.5%), with resistance primarily to penicillin and tetracycline (>50%). PCR identified mecA, nuc, and lukSF-PV genes in 7.8%, 29.9%, and 6.5% of Staphylococcus isolates, respectively. In Streptococcus, the ermB and blaZ genes were found in 18.2% and 50% of isolates, respectively. These data provide a baseline on SBM-associated AMR in the study area and highlight the need for ongoing surveillance and improved milking practices to mitigate risks to the dairy sector and public health. Full article

This study aimed to investigate the molecular basis of high-level tetracycline resistance to tetracycline antibiotics in Aeromonas hydrophila isolated from fish farming. Comparative genomic analysis of the tetracycline-sensitive strain NJ-35 and the tetracycline-resistant strain AH823 revealed that the tetracycline repressor gene tetR in AH823 had undergone base mutations, resulting in premature translational termination. The tetR gene in NJ-35 was inhibited using a plasmid-based antisense RNA strategy, and the knockdown efficiency was confirmed by RT-qPCR. The resulting tetR antisense RNA-expressing strain, AHtetR-as, exhibited significantly increased resistance to tetracycline antibiotics (minocycline, tetracycline, and doxycycline), but did not affect biofilm formation or hemolysis. Moreover, tetR knockdown in NJ-35 was associated with increased efflux activity and reduced intracellular doxycycline accumulation. Transcriptomic analysis revealed that genes encoding the 30S ribosomal subunit proteins showed a differential expression pattern, with rpsO upregulated and rpsD and rpsP downregulated. These findings suggest that tetR contributes to tetracycline resistance in A. hydrophila and is associated with broad transcriptional changes related to cellular transport and ribosomal function. Full article

Enterococci are among the most frequently isolated environmental bacteria that cause mastitis in cows. This study aimed to determine the prevalence of virulence genes, as well as phenotypic and genotypic antibiotic resistance, among eighty enterococcal isolates from cases of bovine mastitis in Polish herds. The presence of virulence and antibiotic resistance genes was determined by PCR. E. faecalis isolates were found to carry more virulence genes than E. faecium isolates, including the efaA_fs (100%), ace (98.1%), gelE (86.5%), asa1 (63.5%), esp (57.7%) and cylA (17.3%) genes. The efaA_fm gene was the only virulence gene detected in E. faecium isolates. This study revealed that E. faecalis showed a higher virulence gene burden. The ermB gene was present in 90.9% of the Enterococcus spp. that were phenotypically resistant to erythromycin. Almost all tetracycline-resistant Enterococcus isolates carried the tet(M) gene (94.3%), either alone or in combination with the tet(L) and tet(O) genes. Three isolates harboured vanC genes and were susceptible to vancomycin (MIC = 4 μg/mL). The results confirm the high level of antimicrobial resistance of enterococci isolated from cows with mastitis and indicate the genes that may be responsible for this resistance. Full article

Background/Objectives: Listeria monocytogenes is a critical foodborne pathogen, with poultry products serving as a potential reservoir. Its ability to form biofilms may aid in its persistence on processing equipment and food-contact surfaces, while antibiotic resistance complicates efforts to control and treat infections. This study aimed to characterize, in parallel, the biofilm-forming capacity and antibiotic susceptibility of a large collection of poultry-derived L. monocytogenes isolates (n = 93) to better understand their potential for persistence and to clarify how the biofilm phenotype may relate to the bacterial antibiotic response and to inform risk assessment and targeted control strategies along poultry processing and supply chains. Methods: Biofilms were evaluated on polystyrene microtiter plates at 12 and 30 °C in a nutrient-rich laboratory medium. Susceptibility to eight clinically and food-relevant antibiotics was tested using disk diffusion and interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints when available. Results: At 30 °C for 48 h, 69.9% of isolates were classified as weak biofilm formers and 30.1% as non-biofilm formers, whereas at 12 °C for 120 h, 55.9% were weak, 16.1% moderate, and 28.0% non-biofilm formers, with no strong biofilm producers identified under either condition. Overall, the isolates remained largely susceptible to ampicillin, penicillin G, vancomycin, tetracycline, and chloramphenicol, with 87.3% of inhibition zones across all drugs falling within the 20–29 mm and 30–39 mm categories, while small subpopulations showed reduced susceptibility or resistance to trimethoprim–sulphamethoxazole (TMP-SMX) and, particularly, erythromycin and streptomycin. No consistent correlation was found between biofilm-forming ability and antibiotic susceptibility, indicating that these phenotypic traits are largely independent in this collection. Conclusions: These findings reveal that poultry-derived L. monocytogenes isolates can form weak to moderate biofilms under the tested monoculture conditions while generally maintaining susceptibility to first-line antibiotics. However, the development of macrolide- and aminoglycoside-resistant subpopulations, along with the potential for increased colonization within complex multispecies biofilms in real processing environments, emphasizes the importance of ongoing integrated surveillance across animal food systems. Full article

The widespread use of antibacterial agents in livestock production is associated with antibiotic residues in animal products and feed, posing a potential threat to food safety and contributing to antimicrobial resistance. The aim of this study was to assess contamination levels of beef, pork, and feed with antibiotic residues in the Kostanay region. The results demonstrated the presence of antibiotic residues in beef, pork, and feed, while all detected concentrations remained below established maximum residue limits. Despite compliance with regulatory standards, residues were detected frequently, and their levels differed significantly depending on feed type (p < 0.001). Microbiological analysis confirmed the presence of Escherichia coli and Staphylococcus aureus in meat samples, with isolates exhibiting moderate to high antimicrobial resistance, particularly in pork. The highest resistance was observed to tetracycline, streptomycin, and thiamphenicol. The obtained data indicate that even trace antibiotic concentrations entering the “feed–animal–product” chain may be associated with selective pressure on microbiota and the circulation of resistant microorganisms. The results highlight the need for comprehensive monitoring of feed and animal products to assess and mitigate antimicrobial resistance spread within the food chain. Full article

Helicobacter pylori (H. pylori) antimicrobial resistance is a key driver of eradication failure in children and adults. Recognizing factors associated with H. pylori antimicrobial resistance may help identify individuals at risk for treatment failure and tailor management. We conducted a retrospective cohort study of patients with H. pylori-positive gastric biopsy culture and available antimicrobial susceptibility data at a large pediatric tertiary care center between 2020 and 2025. Descriptive statistics and logistic regression models were used to assess associations among demographic characteristics, prior treatment history, and antimicrobial resistance. Of 174 patients (56.1% male, median 14 years), 50.3% were resistant to at least one antimicrobial. Resistance rates included metronidazole (28.3%), clarithromycin (18.5%), rifampin (12.7%), fluoroquinolones (11.6%), amoxicillin (4%), and tetracycline (0.6%). The multidrug resistance rate was 17.3%. Prior H. pylori treatment was the most consistent predictor of antimicrobial resistance on both bivariate and multivariable analyses. Race was independently associated with metronidazole resistance, with Black patients exhibiting the highest rates and significantly greater odds compared to White patients. Hispanic ethnicity was also independently associated with increased odds of metronidazole resistance. Careful consideration of prior treatment history, race, and ethnicity is warranted when managing pediatric H. pylori infection, given their association with increased antimicrobial resistance. Full article

Facklamia species are Gram-positive, catalase-negative cocci within the family Aerococcaceae. Historically misidentified as streptococci or enterococci due to phenotypic similarity and conventional biochemical testing limitations, their clinical significance remains incompletely defined. This narrative review synthesizes the current literature on the microbiology, epidemiology, clinical manifestations, diagnostic challenges, and antimicrobial susceptibilities of Facklamia infections, with emphasis on urogynecologic relevance. A structured literature search identified peer-reviewed reports of microbiologically confirmed human infection published through December 2025. These reports indicate global distribution and a broad clinical spectrum. Invasive infections were reported most often in older adults and individuals with structural abnormalities, chronic comorbidities, or recent surgical interventions; however, cases in otherwise healthy patients are described. Emerging microbiome data suggest that F. hominis may be enriched in adult females with lower urinary tract symptoms, supporting the possibility that the female urogenital tract functions as a potential reservoir and site of pathogenic activity. Antimicrobial susceptibility patterns vary, with documented resistance to penicillin, macrolides, clindamycin, and tetracyclines, and susceptibility to cephalosporins, vancomycin, and linezolid. Overall, Facklamia species should be recognized as underdiagnosed opportunistic pathogens with both invasive and urogynecologic relevance. Increased awareness, improved diagnostic identification, and systematic susceptibility profiling are needed to clarify their pathogenic role and guide appropriate antimicrobial therapy. Full article