Search Results (349)

Background/Objectives: Extraintestinal pathogenic Escherichia coli (ExPEC) strains, particularly those belonging to phylogenetic group B2, are clinically significant due to their frequent involvement in urinary tract infections (UTIs) and display antimicrobial resistance profiles. While the association of phylogroup B2 E. coli with human urinary tract infections is well established, the growing number of reports of ExPEC strains in canine UTIs highlights their clinical relevance in small animal medicine and raises concerns about their potential role in zoonotic transmission. This study investigated the microbiological and genomic features of E. coli strains isolated from dogs with UTIs in São Paulo, Brazil. Methods: Between March and May 2023, a total of 60 E. coli strains from canine UTIs were screened for antimicrobial susceptibility and phylotyping. Accordingly, four strains (6.6%) were identified as multidrug-resistant (MDR) or belonging to phylogroup B2 and, therefore, were submitted for characterization by whole-genome sequencing. Results: The four E. coli strains exhibited diverse antimicrobial resistance profiles, including resistance to third- and fourth-generation cephalosporins and fluoroquinolones. Phylogenetic groups B1, B2, and G, and sequence types (ST) 73, ST224, ST1193, and ST12960 were identified. The resistome included clinically important β-lactam resistance genes, such as bla_CTX-M-55 and bla_CMY-2, as well as mutations in the quinolone-resistance-determining region. Virulence factors associated with ExPEC pathogenesis, including adhesion, iron acquisition, immune evasion, and toxin, were detected. Plasmid sequences were identified as carrying antimicrobial resistance and virulence genes, highlighting the potential for horizontal gene transfer. Conclusions: Our findings underscore the importance of genomic surveillance in companion animals to better understand the epidemiology of ExPEC strains and monitor the spread of MDR strains. Full article

Background: Pigs and cattle have been implicated as reservoirs of antimicrobial resistance genes (ARGs) that can spread to humans, and houseflies are considered potential carriers of bacteria with ARGs that could contribute to their spread to the environment, including food, animals, and humans. Methods: In this study, 107, 145, and 127 Escherichia coli strains were isolated from houseflies, pigs, and cattle, respectively, from a slaughterhouse in Lima, Peru. Antimicrobial susceptibility testing was performed using the Kirby–Bauer method, where thirteen antibiotics were used. Strains were also plated on CHROMagar COL-APSE agar, and colistin’s minimum inhibitory concentration (MIC) was determined. Colistin-resistant E. coli strains were subjected to whole genome sequencing. Results: 7.8% (8/107), 1.38% (2/145), and 0.79% (1/127) of E. coli strains isolated from houseflies, pigs, and cattle, respectively, were resistant to colistin (MIC ≥ 4 µg/mL). ARGs associated with resistance to more than 6 different antibiotic classes were identified, including tetracyclines, beta-lactams, fluoroquinolones, nitroimidazoles, trimethoprim and amphenicols. Conclusions: This study suggests that flies could contribute to the dissemination of ARG carrying bacteria and shows the potential risk of animals and meat production systems as reservoirs of ARG carrying bacteria. Full article

Bovine mastitis, particularly that caused by Staphylococcus aureus, presents a major challenge to dairy production worldwide due to its economic impact, animal welfare concerns, and zoonotic potential. This narrative review synthesizes current literature on the epidemiology, pathogenesis, resistance patterns, and control strategies related to S. aureus-associated mastitis in dairy cattle. It highlights the pathogen’s virulence mechanisms, such as biofilm formation, immune evasion, and toxin production, that facilitate persistent infections. The review compiles global prevalence data, revealing significant geographic variation and disparities between clinical and subclinical cases. Antimicrobial resistance, especially the emergence of methicillin-resistant S. aureus (MRSA), is extensively examined alongside resistance gene profiles. Diagnostic approaches, including culture, PCR, MALDI-TOF MS, and AI-based systems, are evaluated for their sensitivity and field applicability. Additionally, the review addresses public health implications, zoonotic risks, and One Health perspectives, culminating in an exploration of prevention strategies, including improved hygiene, vaccination, dry cow therapy, and AI-driven herd management. The findings emphasize the urgent need for integrated surveillance, precision diagnostics, and targeted interventions to mitigate the burden of S. aureus mastitis. Full article

Background/Objectives: Staphylococcus aureus is a major pathogen of concern in raw milk due to its potential to cause foodborne illness and its increasing antimicrobial resistance (AMR). In Romania, data on the occurrence and resistance patterns of S. aureus in raw sheep milk from traditional farming systems remain limited. This study investigated the presence and antimicrobial resistance of S. aureus in 106 raw sheep milk samples collected from traditional farms in the Banat region of western Romania. Methods: Coagulase-positive staphylococci (CPS) were enumerated using ISO 6888-1:2021 protocols. Isolates were identified at the species level using the Vitek 2 system and molecularly confirmed via PCR targeting the 16S rDNA and nuc genes. Methicillin resistance was assessed by detecting the mecA gene. Antimicrobial susceptibility was determined using the Vitek 2 AST-GP79 card. Results: CPS were detected in 69 samples, with S. aureus confirmed in 34.9%. The mecA gene was identified in 13.5% of S. aureus isolates, indicating the presence of methicillin-resistant S. aureus (MRSA). Resistance to at least two antimicrobials was observed in 97.3% of isolates, and 33 strains (89.2%) met the criteria for multidrug resistance (MDR). The most frequent MDR phenotype involved resistance to lincomycin, macrolides, β-lactams, tetracyclines, and aminoglycosides. Conclusions: The high prevalence of S. aureus, including MRSA and MDR strains, in raw sheep milk from traditional farms represents a potential public health risk, particularly in regions where unpasteurized dairy consumption persists. These findings underscore the need for enhanced hygiene practices, prudent antimicrobial use, and AMR monitoring in small-scale dairy systems. Full article

Background/Objectives: As bacteriophage-based strategies to control bacterial pathogens continue to gain momentum, phage therapy is increasingly being explored across various fields. In the poultry industry, efforts to minimize the public health impact of Salmonella have spurred growing interest in phage applications, particularly as prophylactic and disinfecting agents. Although the disinfecting potential of bacteriophages has been recognized, in-depth studies examining their efficacy under varying environmental conditions remain limited. This study focused on evaluating the effectiveness of bacteriophages as disinfecting agents against biofilm-forming Salmonella Infantis under different environments. Methods: A comprehensive screening of biofilm-producing strains was conducted using Congo Red Agar and 96-well plate assays. Two strains with distinct biofilm-forming capacities were selected for further analysis under different environmental conditions: aerobic and microaerobic atmospheres at both 25 °C and 37 °C. The resulting biofilms were then treated with four phage preparations: three individual phages and one phage cocktail. Biofilm reduction was assessed by measuring optical density and CFU/well. Additionally, scanning electron microscopy was used to visualize both untreated and phage-treated biofilms. Results: The results demonstrated that all S. Infantis strains were capable of forming biofilms (21/21). All three phage candidates exhibited biofilm-disrupting activity and were able to lyse biofilm-embedded Salmonella cells. Notably, the lytic efficacy of the phages varied depending on environmental conditions, highlighting the importance of thorough phage characterization prior to application. Conclusions: These findings underscore that the effectiveness of bacteriophages as surface disinfectants can be significantly compromised if inappropriate phages are used, especially in the presence of biofilms. Full article

Background/Objectives: Increasing levels of antimicrobial resistance (AMR) have recently been observed at the human–domestic animal–wildlife interface. Wild birds have been identified as carriers of antimicrobial-resistant bacteria and serve as excellent biomarkers for epidemiological studies. This study assessed the current AMR presence in Eastern Spain’s commensal Escherichia coli isolated from free-ranging Bonelli’s eagles (Aquila fasciata). Methods: Nestlings and their nests were intensively sampled between 2022 and 2024 to determine their AMR profile and characterize E. coli. AMR testing was conducted using the broth microdilution method, following the European Committee on Antimicrobial Susceptibility Testing guidelines. Additionally, the presence of eaeA (intimin gene) and stx-1 and stx-2 (shiga toxins) was analyzed by real-time PCR to classify E. coli strains into enteropathogenic (EPEC) and Shiga-toxigenic (STEC) pathotypes. Results: Of all E. coli isolates, 41.7% were resistant to at least one antimicrobial, and 30% were multidrug-resistant. Only two strains were classified as EPEC and none as STEC. The highest resistance rates were observed for amoxicillin and tetracycline (19.6% each). Alarmingly, resistance to colistin and meropenem, last-resort antibiotics in human medicine, was also detected. Conclusions: Although the mechanisms of resistance acquisition remain unclear, transmission is likely to occur through the food chain, with synanthropic prey acting as intermediary vectors. These results highlight the role of Bonelli’s eagles as essential sentinels of environmental AMR dissemination, even in remote ecosystems. Strengthening One Health-based surveillance is necessary to address AMR’s ecological and public health risks in wildlife. Full article

Pseudomonas aeruginosa is a highly adaptable opportunistic pathogen with significant clinical relevance in both human and veterinary medicine. Despite its well-documented role in hospital-acquired infections in human healthcare settings, its persistence and transmission within veterinary clinics remain underexplored. This review highlights the overlooked status of veterinary facilities as environmental reservoirs and amplification points for multidrug-resistant (MDR) P. aeruginosa, emphasizing their relevance to One Health surveillance. We examine the bacterium’s environmental survival strategies, including biofilm formation, resistance to disinfectants, and tolerance to nutrient-poor conditions that facilitate the long-term colonization of moist surfaces, drains, medical equipment, and plumbing systems. Common transmission vectors are identified, including asymptomatic animal carriers, contaminated instruments, and the hands of veterinary staff. The review synthesizes current data on antimicrobial resistance in environmental isolates, revealing frequent expression of efflux pumps and mobile resistance genes, and documents the potential for zoonotic transmission to staff and pet owners. Key gaps in environmental monitoring, infection control protocols, and genomic surveillance are identified, with a call for standardized approaches tailored to the veterinary context. Control strategies, including mechanical biofilm disruption, disinfectant cycling, effluent monitoring, and staff hygiene training, are evaluated for feasibility and impact. The article concludes with a One Health framework outlining cross-species and environmental transmission pathways. It advocates for harmonized surveillance, infrastructure improvements, and intersectoral collaboration to reduce the risk posed by MDR P. aeruginosa within veterinary clinical environments and beyond. By addressing these blind spots, veterinary facilities can become proactive partners in antimicrobial stewardship and global resistance mitigation. Full article

Background/Objectives: This review aimed to compare the efficacy of antibiotic treatment vs. non-antibiotic treatment in mild and moderate clinical mastitis in lactating dairy cows, categorized by the causative pathogen. Methods: The initial systematic review plan, which resulted in only four relevant articles, was altered due to limited available studies and significant heterogeneity among them. Consequently, five additional articles, closely meeting our criteria with minor differences, were included to ensure comprehensive analysis, resulting in nine included articles. Due to these pragmatic constraints, this review represents a hybrid between a systematic and a narrative review. The outcome of interest was the bacteriological cure (BC). Results: The findings revealed that antibiotic treatment resulted in improved BC rates for cases caused by Streptococci. For cases caused by Escherichia (E.) coli, antibiotic therapy showed no significant improvement in BC rates compared to non-antibiotic treatment, suggesting that antibiotics may be often unnecessary for these cases due to self-limiting tendencies. However, severe E. coli mastitis warrants systemic antibiotic treatment due to potentially life-threatening complications. Klebsiella spp. mastitis showed better cure rates with antibiotic therapy. Conclusions: This study underscores the importance of regular pathogen diagnostics to guide appropriate treatment, advocating for the use of on-farm rapid tests to reduce unnecessary antibiotic use while ensuring effective treatment outcomes. Full article

Background: Canine pyoderma and otitis externa are prevalent bacterial skin infections in veterinary practice, frequently complicated by the emergence of multidrug-resistant (MDR) pathogens. Objectives: To investigate the frequency, antimicrobial resistance (AMR) profiles, and frequency of MDR bacterial isolates from dogs with pyoderma or otitis externa in Hong Kong. Methods: A retrospective study of bacterial isolates from 215 clinical samples collected from dogs presenting with pyoderma (n = 63) or otitis externa (n = 152) at veterinary clinics across Hong Kong between 2018 and 2022. Bacterial isolates were identified and subjected to antimicrobial susceptibility testing against 13 antimicrobial classes. Results: Staphylococcus spp., particularly S. pseudintermedius, were the most commonly isolated species, followed by Pseudomonas spp. and Proteus spp. High resistance rates were observed for orbifloxacin (61.3% in pyoderma; 76.7% in otitis externa), doxycycline (59.3%; 69.2%), clindamycin (62%; 68.9%), and enrofloxacin (50%; 55.5%). Most isolates were sensitive to ofloxacin, ticarcillin–clavulanate, tobramycin, ciprofloxacin, cefpodoxime, cefuroxime, and cefixime. MDR was detected in 67.5% of pyoderma and 66.8% of otitis externa isolates. Gram-negative bacteria exhibited significantly higher MDR rates than Gram-positive isolates. The multiple antibiotic resistance (MAR) index averaged 0.41 for pyoderma and 0.52 for otitis externa isolates. We found no significant associations between MDR and non-modifiable risk factors (i.e., age, sex, breed, and reproductive status). Conclusions: These findings highlight the critical need for prudent antimicrobial use and continuous surveillance of AMR trends in companion animals. A higher focus should be placed on topical antiseptic therapy, with oral antibiotics used only in exceptional cases and after susceptibility testing. From a One Health perspective, the potential transmission of MDR bacteria between companion animals and humans underscores the importance of a coordinated approach to antimicrobial stewardship across both veterinary and human medicine. Full article

Bovine uterine infections remain a widespread challenge in dairy production systems, contributing to reduced fertility and overall herd performance. Background/Objectives: Postpartum uterine infections significantly affect dairy cattle fertility and productivity. This study aimed to identify aerobic bacterial pathogens associated with clinical endometritis in Romanian dairy cows and evaluate their antimicrobial resistance profiles. Methods: Uterine swab samples (n = 348) were collected from clinically affected cows across multiple farms. Bacteria were isolated and identified using conventional culture methods and MALDI-TOF MS. Antimicrobial susceptibility testing was performed using the VITEK^® 2 system with GN 96 and GP 79 cards. Statistical analysis was conducted using the chi-square (χ²) test. Results: A total of 387 bacterial isolates were recovered, with over half of the samples showing mixed bacterial contamination. Escherichia coli was the most frequently identified pathogen (44.9%), followed by Staphylococcus spp. (17.3%) and Klebsiella spp. (14.5%). Gram-negative isolates showed high resistance to tetracycline and ampicillin, while retaining susceptibility to imipenem and polymyxin B. Among Gram-positive isolates, Streptococcus spp. were highly susceptible to β-lactams, while Staphylococcus spp. showed moderate resistance to penicillin and macrolides. Conclusions: This study highlights the prevalence of key aerobic pathogens and their resistance profiles in Romanian dairy herds. These findings support the need for targeted diagnostics and rational antimicrobial use to improve uterine health and therapeutic outcomes in dairy cattle. Full article

Background: Pyoderma is a superficial bacterial infection that is considered the formation of pus-containing lesions on the skin occurring in animals. Staphylococci, including Staphylococcus aureus and Staphylococcus pseudintermedius, that cause pyoderma in pet animals is a global health concern. The objectives of this study were to investigate antibiotic-resistant staphylococci isolated from pyoderma in dogs and cats and to analyse whole genome sequences of multidrug-resistant (MDR) staphylococci. Methods: A total of 56 pyoderma swabbing samples from 42 dogs and 14 cats located in Southern Thailand was collected to isolate staphylococci. Antibiotic susceptibility and antibiotic-resistant genes of staphylococcal isolates were investigated. Furthermore, the representative MDR isolates were investigated using whole genome sequence analysis. Results: 61 isolates were identified as staphylococci, which can be classified into 12 different species, mostly including 13 S. intermedius (13.26%), 13 S. saprophyticus (13.26%), 8 S. sciuri (8.16%), and Staphylococcus cohnii (8.16%). Remarkably, the main pyoderma-causing species that were isolated in this study were S. aureus (5.10%) and S. pseudintermedius (3.06%). Most staphylococci were resistant to penicillin G (30%), and the blaZ gene was found to be the highest prevalence of the resistance genes. Both MDR-S. aureus WU1-1 and MDR-S. pseudintermedius WU48-1 carried capsule-related genes as main virulence factor genes. Interestingly, MDR-S. pseudintermedius WU48-1 was resistant to seven antibiotic classes, which simultaneously carried blaZ, mecA, aac, dfrK, aph3, and tetM. Genes related to antibiotic efflux were the highest proportion of the mechanism found in both representatives. Remarkably, SCCmec cassette genes were found in both isolates; however, the mecA gene was found only in MDR-S. pseudintermedius WU48-1. In addition, these were mostly carried by macrolide- and tetracycline-resistance genes. Mobile gene transfer and horizontal gene transfer events frequently contain genes involved in the antibiotic target alteration mechanism. Conclusions: This study found that MDR staphylococci, especially S. aureus and S. pseudintermedius, are important in animals and owners in terms of One Health concern. The information on whole genome sequences of these MDR staphylococci, particularly antimicrobial resistance genes, mobile genetic elements, and horizontal gene transfer events, can help to understand gene transmission and be applied for antibiotic resistance surveillance in veterinary medicine. Full article

Background/Objectives: The present study was aimed at documenting S. maltophilia occurrence in dogs with skin ailments, investigating its virulence, biofilm-forming ability, antimicrobial susceptibility, and zoonotic potential to inform preventive and therapeutic strategies against multidrug resistant S. maltophilia infections. Methods: Skin swabs (n = 300) were collected from dogs with dermatological ailments. Isolation was performed using selective media and confirmed with molecular methods, validated by MALDI Biotyper. Antimicrobial susceptibility testing and efflux activity assessment were conducted. Resistance genes related to sulfonamides, quinolones, and β-lactams were screened. Virulence was assessed by biofilm formation, motility, and virulence gene profiling. Results: In total, 15 S. maltophilia (5%) isolates were identified. All 15 isolates were susceptible to trimethoprim-sulfamethoxazole, enrofloxacin, gatifloxacin, levofloxacin, minocycline, and tigecycline, but resistant to cefpodoxime and aztreonam. The following resistance genes qnr (93.3%), bla_OXA-48 (46.7%), bla_KPC (33.3%), bla_NDM (33.3%), bla_CTX-M (20%), bla_SHV (20%), and bla_TEM (6.7%) were detected. All 15 isolates displayed high efflux activity. Overall, 9 isolates (60%) were strong biofilm producers, and 6 (40%) were moderate. Virulence genes such as virB, motA, rmlA, and fliC were present in all 15 isolates, with others varying in frequency. All isolates exhibited swimming motility. Heat map clustering showed diverse profiles, with no identical isolate patterns. Correlation analysis indicated positive associations between several antimicrobial resistance and virulence genes. Conclusions: This study underscores the zoonotic potential of S. maltophilia from dogs, advocating for a One Health approach to mitigate infection risks and limit the spread of virulent multidrug resistant pathogens. Full article

Background/Objectives: Antibiotic resistance or antimicrobial resistance (AMR) in livestock is a growing global concern that threatens both human and animal health. The overuse and misuse of antibiotics in livestock production have led to an increased propensity for the development of AMR bacterial strains in animals, which can be spread to humans through the consumption of contaminated animal products, direct contact, or environmental exposure. This review aims to summarize the development and transmission of AMR in livestock, explore its underlying mechanisms and impact on human and animal health, and discuss current practices and potential strategies for mitigation and prevention. Methods: For this narrative review, we searched articles on PubMed and Google Scholar using the terms antibiotic resistance, livestock, and environment, alone or in combination. Results: The history of antibiotic use in livestock and its link to increased AMR, along with the involved mechanisms, including the enzymatic breakdown of antibiotics, alterations in bacterial targets, horizontal gene transfer, and efflux pumps, are important. Antibiotics in livestock are used for growth promotion, disease prevention and control, and metaphylactic use. The role of livestock and the environment as reservoirs for resistant pathogens, their impact on human health, chronic infections, allergic reactions, toxicity, and the development of untreatable diseases is important to understand AMR. Conclusions: Given the widespread use of antibiotics and the potential consequences of AMR, collaborative global efforts, increased public awareness, coordinated regulations, and advancements in biological technology are required to mitigate the threat AMR poses to human and animal health. Regulatory solutions and the development of new therapeutic alternatives like antimicrobial peptides and bacteriophage therapy, and preventive measures such as DNA and mRNA vaccines, are future perspectives. Full article

Antibiotic overuse in livestock is a major concern, as it contributes to the emergence of antibiotic resistance and may adversely affect both animal and human health. One important consequence is its impact on the gut microbiota, a complex microbial ecosystem essential for maintaining host health. A growing body of research highlights the critical role of a balanced gut microbiota in maintaining the integrity of the gut-microbiota–brain axis, a bidirectional communication network between the gastrointestinal tract and the central nervous system (CNS). Antibiotics introduced through the food chain and the environment can disrupt microbial balance, leading to dysbiosis and systemic inflammation. In this context, the concept of “One Health” is emphasized, which recognizes the deep interconnection between the health of humans, animals, and the environment to address the global problem of antibiotic resistance. Several animal studies highlight how dysbiosis can induce neuroinflammation and potentially damage the gut–brain barrier. This review explores the mechanisms by which antibiotic use in livestock alters the gut microbiota and compromises the gut-microbiota–brain axis integrity, outlining the implications for public health and the possible link with neurodegenerative conditions. Full article

The accelerated spread of bacterial resistance has been demonstrated to reduce the effectiveness of antibiotic treatments for infections, resulting in higher morbidity and mortality rates, as well as increased costs for livestock producers. It is expected that the majority of future antimicrobial use will be in animal production. The management of antimicrobial resistance (AMR) in the livestock sector poses significant challenges due to the multifaceted nature of the problem. In order to identify appropriate solutions to the rise of antimicrobial resistance, it is imperative that we have a comprehensive understanding of the disease dynamics underpinning the ways in which antimicrobial resistance is transmitted between humans and animals. Furthermore, in consideration of the anticipated requirement to satisfy the global demand for food, it is imperative that we guarantee that resistance is not transmitted or propagated during the treatment and disposal of animal waste, particularly from intensive farming. It is also crucial to formulate a research agenda to investigate how antibiotic resistance in animal faeces from livestock farming is affected by intensified farming activities. The review analyses the environment’s role in the transmission resistance chain and reviews methodologies for disrupting the link. A particular focus is placed on the limitations of the applied methodologies to reduce antimicrobial resistance in global animal production. Full article