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Animals can act as a reservoir and source for the emergence of novel meticillin-resistant Staphylococcus aureus (MRSA) clones in human beings. Here, we report the discovery of a strain of S aureus (LGA251) isolated from bulk milk that was phenotypically resistant to meticillin but tested negative for the mecA gene and a preliminary investigation of the extent to which such strains are present in bovine and human populations. Isolates of bovine MRSA were obtained from the Veterinary Laboratories Agency in the UK, and isolates of human MRSA were obtained from diagnostic or reference laboratories (two in the UK and one in Denmark). From these collections, we searched for mecA PCR-negative bovine and human S aureus isolates showing phenotypic meticillin resistance. We used whole-genome sequencing to establish the genetic basis for the observed antibiotic resistance. A divergent mecA homologue ( mecA LGA251) was discovered in the LGA251 genome located in a novel staphylococcal cassette chromosome mec element, designated type-XI SCC mec. The mecA LGA251 was 70% identical to S aureus mecA homologues and was initially detected in 15 S aureus isolates from dairy cattle in England. These isolates were from three different multilocus sequence type lineages (CC130, CC705, and ST425); spa type t843 (associated with CC130) was identified in 60% of bovine isolates. When human mecA-negative MRSA isolates were tested, the mecA LGA251 homologue was identified in 12 of 16 isolates from Scotland, 15 of 26 from England, and 24 of 32 from Denmark. As in cows, t843 was the most common spa type detected in human beings. Although routine culture and antimicrobial susceptibility testing will identify S aureus isolates with this novel mecA homologue as meticillin resistant, present confirmatory methods will not identify them as MRSA. New diagnostic guidelines for the detection of MRSA should consider the inclusion of tests for mecA LGA251. Department for Environment, Food and Rural Affairs, Higher Education Funding Council for England, Isaac Newton Trust (University of Cambridge), and the Wellcome Trust.

Antimicrobial resistance is a global threat, and pet-associated strains may pose a risk to human health. Equine veterinarians are at high risk of carrying methicillin-resistant staphylococci (MRS), but specific risk factors remain elusive, and few data are available for other personnel involved in the horse industry. The prevalence, characteristics, and risk factors for nasal carriage of MRS in horses and their caregivers were studied in northwestern Italy. Nasal swabs from 110 asymptomatic horses housed at 21 barns and 34 human caregivers were collected. Data on barns, horses, and personnel were acquired through questionnaires. The samples were incubated in selective media, and the bacterial isolates were identified by mass spectrometry. Risk factors were investigated by Poisson regression. MRS were isolated from 33 horses (30%), 11 humans (32.4%) and 3 environmental samples (14.2%). Most isolates were multidrug resistant (MDRS). The prevalence of MRS and MDRS was greater in racehorses and their personnel than in pleasurable and jumping/dressing horses. MRS carriage in caregivers was associated with an increased prevalence of MRS carriage in horses. The frequency of antimicrobial treatments administered in the barn during the last 12 months was a risk factor for MRS carriage in horses [prevalence ratio (PR) 3.97, 95% CI 1.11, 14.13] and caregivers (PR 2.00, 95% CI 1.05, 3.82), whereas a good ventilation index of the horse tabling environment was a protective factor (PR 0.43, 95% CI 0.20, 0.92). Our data reveal relevant interactions occurring between bacterial communities of horses and humans that share the same environment, suggesting that One Health surveillance programs should be implemented.

Although the role of pets in household transmission of meticillin-resistant Staphylococcus aureus (MRSA) has been examined previously, only minor attention has been given to the role of the abiotic household environment independent of, or in combination with, colonisation of pets and human beings to maintain transmission cycles of MRSA within the household. This report reviews published work about household transmission of S aureus and other staphylococci and describes contamination of household environmental surfaces and colonisation of pets and people. Household microbial communities might have a role in transfer of antimicrobial resistance genes and could be reservoirs for recolonisation of people, although additional research is needed regarding strategies for decontamination of household environments. Household-based interventions should be developed to control recurrent S aureus infections in the community, and coordination between medical and veterinary providers could be beneficial.

Background The value of repeated nasopharyngeal lavage (NPL) to detect silent carriers of Streptococcus equi has not been investigated. Hypothesis/Objectives Determine if results of serial testing for S. equi by NPL predicts subsequent true carrier status as determined by both NPL and guttural pouch lavage. Animals An outbreak of strangles with 100% morbidity in 41 mature Icelandic horses was followed prospectively to investigate development of silent carriers. All were initially positive to S. equi on NPL. The farm was closed to horse movement during the entire study. Methods Prospective observational study. Testing for S. equi was performed by NPL at weeks 18, 28, 29, and 30 postindex case and subsequently at week 45 by both NPL and guttural pouch lavage. Carrier status at week 45 was compared to results obtained at weeks 18, 28, 29, and 30. Descriptive statistics were calculated. Comparisons were made using Fisher's exact test or the Freeman‐Halton extension with a P < .05 level of significance. Results Of 24 noncarriers at week 45, only 4 horses were negative on all 3 consecutive weekly NPL samples at weeks 28 to 30. However, 10 of the 11 horses with at least 3 negative NPL obtained from weeks 18, 28, 29, and 30 were S. equi‐free at week 45 (P = .03). Conclusions and Clinical Importance Repeated NPL on at least 3 separate occasions can assist in predicting S. equi carrier‐free status in horses after recovery from a strangles outbreak.

Background Methicillin‐resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections, including in veterinary settings. Hypothesis/Objectives To investigate the prevalence, risk factors for Staphylococcus aureus (SA) and MRSA colonization, and the duration of MRSA colonization. Animals Elective cases admitted to the Veterinary Teaching Hospital were recruited (228 horses). Methods A cross‐sectional study was conducted over 3 years. Nasal swabs were collected at admission and cultured for SA. Methicillin‐resistant isolates were identified using matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) technology, oxacillin minimal inhibitory concentration (MIC), and PCR testing. Horses colonized with MRSA were resampled until two negative cultures were obtained. Stabling management, activity, and medical history were obtained from owners and medical files. Multivariable logistic regressions were used to model associations between risk factors and colonization. Results The prevalence of SA and of MRSA nasal carriage was 17.5% (95% CI: 12.4–22.7) and 6.2% (95% CI: 2.9–9.4), respectively. Of the 10 horses colonized by MRSA and monitored over time, only one tested positive after 3 months. More than 10 horses on the premises (OR 6.0 – 95% CI 1.1–64.2), previous hospitalization (OR 6.0 – 95% CI 1.0–35.2), and year of admission (2022 vs. 2020–2021; OR 9.0 – 95% CI 1.7–92.2) were associated with MRSA nasal carriage. Conclusions and Clinical Importance The prevalence of MRSA nasal colonization is of concern; however, the carriage seems transitory. Apart from the medical risk factors, the importance of social interactions in MRSA transmission needs to be elucidated in horses.

Background Mycoplasma bovis probably enters dairy herds when carrier animals are introduced. Comingled calves that become subclinical M. bovis carriers could promote cross-dairy transmission. A prospective cohort study in Holstein heifers from two unrelated herds (Farms A and B previously M. bovis positive and negative, respectively) comingled at a facility raising only their calves assessed: 1). prevalence of asymptomatic M. bovis infection; 2). associations between four anatomic sites (nares, eyes, ear canal, vagina; M. bovis culture with PCR confirmation). Fifteen calves per farm were enrolled every 4 months. Swabbing solutions were first collected at parent farms, thereafter monthly for 6 months, then quarterly to 21 months. Results Three heifers from each dairy were lost after enrollment leaving 144 heifers (72 per farm) in the analysis. On day 1, a Farm A calf vaginal sample was the single M. bovis positive. While comingled, positives increased dramatically. Days of age to first positive were not different between farms (Farm A median = 109, range 42–561 days; Farm B median = 110, range 33–404 days; P  = 0.96). Overall, 125/144 heifers yielded 634 positive samples, intranasal (46.7%), ocular (25.7%), vaginal (17.8%), ear canal (9.8%). The most common combinations were eye/nose (55/634, 43.3%) and nose/vagina (21/634, 16.5%). Intranasal positives increased exponentially at 2–3 months of age, plateauing over 4–10 months, and were more frequent than non-nose (Incidence Rate Ratio 1.44, 95% CI 1.41–1.47; P  < 0.001). Positive combinations involving the nose temporally lagged the intranasal alone positives, but eventually reached similar frequencies. After returning to the parent farms, frequency of intranasal positives declined more rapidly than did non-nose. Conclusions M. bovis was cultured from all sites, but the nose appears most critical for transmission. Once intranasal carriage escalated, virtually all calves were subsequently positive at least once at one or more sites, indicating how readily asymptomatic M. bovis can disseminate in a population of animals and potentially manifest as clinical disease later in life.

Background Leptospirosis, caused by pathogenic Leptospira spp., is an important zoonotic disease that is found globally, with recent outbreaks posing a major public health challenge. This disease affects a wide range of mammalian species. While rodents, dogs, cattle, and buffaloes are recognized reservoirs of Leptospira , the role of swine in transmission in Sri Lanka remains unclear. This study aimed to investigate the carrier status of Leptospira spp. in swine raised for human consumption in Sri Lanka, and to assess potential zoonotic risks. Results Analysis of livestock data revealed the highest density of pigs in the Gampaha, Colombo, and Puttalam districts. Kidney ( n =  181) and blood ( n =  25) samples were collected from swine slaughtered for human consumption in the Colombo and Kegalle districts. Leptospiral DNA was detected in 25 of the kidney samples (13.8%), identifying Leptospira interrogans ( n =  21), P1 (pathogenic) subclade, and L. licerasiae ( n =  4), P2 (intermediate) subclade. Serological analysis revealed seropositivity to the serogroups Autumnalis, Icterohaemorrhagiae, Canicola, and Sejroe. Conclusions This study demonstrates that swine reared for human consumption in Sri Lanka serve as an important reservoir of Leptospira spp. All pigs sampled were clinically healthy at ante-mortem inspection, confirming their role as asymptomatic carriers of Leptospira spp. The detection of strains identical to those previously reported in human infections suggests a potential zoonotic threat exacerbated by inadequate farm hygiene and environmental contamination. These findings highlight the need for comprehensive research from a One Health perspective to gain a deeper understanding of the epidemiology of leptospirosis in Sri Lanka.

Red-eared sliders (RES; Trachemys scripta elegans ) are a globally invasive species that can impact native chelonian populations through resource competition and disease introduction. In Cook County, Illinois, invasive RES co-occur with, and greatly outnumber, a species of conservation priority in the Great Lakes region: the Blanding’s turtle ( Emydoidea blandingii ). This study sampled free-ranging RES in Cook County during spring, summer, and fall in four unique locations to characterize the possible effect of this non-native species on the health of regional, sympatric, aquatic chelonians. RES (n = 242) were captured and sampled for qPCR pathogen detection, clinical pathology, and necropsy from 2018 to 2022. Multiple pathogens were detected, including Mycoplasma spp., multiple adenoviruses, Trachemys herpesvirus 1 (TrHV-1), frog virus 3, human-pathogenic Leptospira spp., Emydomyces testavorans , and Salmonella typhimurium . Mycoplasma spp. prevalence was significantly higher (p < 0.05) at one isolated site with a suspected greater density of turtles. Detection of TrHV-1 was significantly associated with season (p < 0.001), with detections occurring only in spring and fall. For the 28 hematology, plasma biochemistry, and protein electrophoresis analytes assayed, significant and variable associations occurred based on sample year, season, pathogen detection, age, and sex. Population-based reference intervals were created for hematologic, plasma biochemistry, and plasma protein electrophoresis analytes. Common necropsy findings included mild endoparasitism and related vascular lesions such as endarteritis. Notably, qPCR detection of above pathogens was not associated with any gross or histologic lesions indicative of clinically relevant disease. This study indicates that invasive RES in Cook County may be infected with pathogens of concern for co-occurring turtle species, and absence of associated lesions in the RES suggests they likely serve as carrier species for these pathogens. Continued health monitoring of this species is important as interactions with chelonians of conservation priority increase.

Background The equine faecal microbiota is very complex and remains largely unknown, while interspecies interactions have an important contribution to animal health. Clostridium difficile has been identified as an important cause of diarrhoea in horses. This study provides further information on the nature of the bacterial communities present in horses developing an episode of diarrhoea. The prevalence of C. difficile in hospitalised horses at the time of admission is also reported. Results Bacterial diversity of the gut microbiota in diarrhoea is lower than that in non-diarrhoeic horses in terms of species richness (p-value <0.002) and in population evenness (p-value: 0.02). Statistical differences for Actinobacillus , Porphyromonas, RC9 group , Roseburia and Ruminococcaceae were revealed. Fusobacteria was found in horses with diarrhoea but not in any of the horses with non-diarrheic faeces. In contrast, Akkermansia was among the three predominant taxa in all of the horses studied. The overall prevalence of C. difficile in the total samples of hospitalised horses at admission was 3.7 % (5/134), with five different PCR-ribotypes identified, including PCR-ribotype 014. Two colonised horses displayed a decreased bacterial species richness compared to the remaining subjects studied, which shared the same Bacteroides genus. However, none of the positive animals had diarrhoea at the moment of sampling. Conclusions The abundance of some taxa in the faecal microbiota of diarrhoeic horses can be a result of microbiome dysbiosis, and therefore a cause of intestinal disease, or some of these taxa may act as equine enteric pathogens. Clostridium difficile colonisation seems to be transient in all of the horses studied, without overgrowth to trigger infection. A large proportion of the sequences were unclassified, showing the complexity of horses’ faecal microbiota.

Equine arteritis virus (EAV) has the unique ability to establish long-term persistent infection in the reproductive tract of stallions and be sexually transmitted. Previous studies showed that long-term persistent infection is associated with a specific allele of the CXCL16 gene (CXCL16S) and that persistence is maintained despite the presence of local inflammatory and humoral and mucosal antibody responses. Here, we performed transcriptomic analysis of the ampullae, the primary site of EAV persistence in long-term EAV carrier stallions, to understand the molecular signatures of viral persistence. We demonstrated that the local CD8+ T lymphocyte response is predominantly orchestrated by the transcription factors eomesodermin (EOMES) and nuclear factor of activated T-cells cytoplasmic 2 (NFATC2), which is likely modulated by the upregulation of inhibitory receptors. Most importantly, EAV persistence is associated with an enhanced expression of CXCL16 and CXCR6 by infiltrating lymphocytes, providing evidence of the implication of this chemokine axis in the pathogenesis of persistent EAV infection in the stallion reproductive tract. Furthermore, we have established a link between the CXCL16 genotype and the gene expression profile in the ampullae of the stallion reproductive tract. Specifically, CXCL16 acts as a \"hub\" gene likely driving a specific transcriptional network. The findings herein are novel and strongly suggest that RNA viruses such as EAV could exploit the CXCL16/CXCR6 axis in order to modulate local inflammatory and immune responses in the male reproductive tract by inducing a dysfunctional CD8+ T lymphocyte response and unique lymphocyte homing in the reproductive tract.