Epidemiology of Staphylococcus aureus food isolates: Comparison of conventional methods with whole genome sequencing typing methods.

A variety of methods exists for typing bacteria. However, guidelines for the application and interpretation of typing tools in epidemiologic investigations of Staphylococcus aureus are lacking. This study aimed to identify appropriate typing methods for S. aureus population studies and outbreak investigation. We compared pulsed-field gel electrophoresis (PFGE), seven loci multi-locus sequence typing (MLST), core genome MLST (cgMLST), core single nucleotide polymorphism (cSNP), and enterotoxin (se/SE) profiles on 351 S. aureus isolates. The discriminatory power, concordance, and congruence of typing results were assessed. cgMLST, cSNP, and PFGE yielded the highest discrimination value, followed by se/SE typing and MLST. The best concordance of results was found between cgMLST and cSNP, while the best congruence was observed for cgMLST and cSNP with all methods, followed by PFGE with MLST. The strengths and weaknesses of each method are highlighted. For population structure, cgMLST and cSNP performed better than PFGE and MLST in terms of resolution of clusters and in phylogenetic inference. Enterotoxin profiles matched with MLST groups, suggesting the use of se/SE typing to predict MLST results. For the retrospective analysis of 31 outbreaks, all methods performed almost equally to discriminate epidemiologically related strains and can be used to unambiguously distinguish outbreak strains.

Comparative Evaluation of the Antibiotic Resistance Profile of Staphylococcus aureus Isolated From Breeders and Livestock.

Objectives: Animals are a potential source of Methicillin Resistant Staphylococcus aureus. This study evaluated the antibiotics susceptibility pattern of S. aureus isolates from breeders and livestock. Methods: S. aureus strains were isolated from 180 livestock and 48 livestock farmers and identified using standard methods. Antibiotic susceptibility profiles and MRSA status were determined via disk diffusion susceptibility method. Results: Among farm workers, 37.5% were colonized by S. aureus, with pig farm workers exhibiting the highest prevalence (56.2%), cattle herders (37.5%), and goat farm workers (18.7%). MRSA carriage among livestock isolates was 41.3%, while, six isolates from the poultry farm worker were MRSA, representing a carriage of 33.3%. Drug susceptibility profiles revealed differential patterns between isolates from breeders and animals. Gentamicin and levofloxacin demonstrated higher efficacy against farm worker isolates compared to animal isolates. Resistance to cefuroxime was higher among animal isolates (84.1%) as against the 66.7% for the breeders. Conclusion: The identification of multidrug-resistant S. aureus strains underscores the risk posed to humans in contact with animals. These findings stress the importance of monitoring and managing MRSA transmission between animals and humans.

Presence of multiple van genes among glycopeptide non-susceptible Staphylococcus aureus exhibiting in vitro MIC creep phenomenon: A study from north-east India.

Background & objectives The global prevalence of vancomycin-resistant Staphylococcus aureus (VRSA) has increased two fold since 2010, accounting for 2.4 per cent of S. aureus infections. The emerging hVISA isolates and their increasing trends pose a serious therapeutic challenge. The present study investigated in vitro vancomycin and teicoplanin minimum inhibitory concentration (MIC) creep in S. aureus and assessed their revertants. Methods A total of 845 isolates were collected for this study, and 246 were confirmed as S. aureus. Molecular characterization of vancomycin resistance was carried out by PCR assay targeting genes types viz: vanA, vanB, vanC, vanC2/C3, vanD, vanE, and vanG. MIC was determined for vancomycin and teicoplanin by agar dilution method. MIC creep and revertant analysis were done by broth dilution method in the presence and absence of antibiotics. Results PCR assay confirmed 12 isolates were harboured vanA, followed by vanD (n=8) and vanB (n=7). The study showed 69 isolates were screened positive for glycopeptide non-susceptibility. While analyzing vancomycin MIC creep, four isolates showed a significant increase in MIC, whereas no creep phenomenon was observed for the rest. In the case of teicoplanin, seven isolates showed the MIC creep phenomenon. Revertant analysis of all the isolates that showed MIC creep phenomenon for vancomycin and teicoplanin reverted to their original MIC when the antibiotic pressure was withdrawn. Interpretation & conclusions In the present study setting, glycopeptide non-susceptibility was found in eight per cent of the isolates, and the present study found the occurrence of multiple van genes from isolates calculated from a single study center will impose a serious challenge in infection control and antibiotic policy. This study also underscores that heterogenic resistant isolates, upon exposure to vancomycin and teicoplanin at a minimum level, exhibited an increase in MIC, which will impact individuals receiving glycopeptide therapy.

Occurrence, genetic diversity, and antimicrobial resistance of methicillin-resistant Staphylococcus spp. in hospitalized and non-hospitalized cats in Brazil.

Methicillin-resistant Staphylococci (MRS) cause infections at various sites and exhibit multidrug resistance. Despite their importance in veterinary medicine, only little is known about Staphylococcus spp. colonizing and infecting cats. Therefore, in this study, we aimed to isolate and identify Staphylococcus spp. colonizing hospitalized and non-hospitalized domestic cats and analyze their antimicrobial resistance profiles, genetic diversity, and risk factors associated with MRS colonization. A total of 218 oral and axillary swabs were obtained from 109 cats, including 77 non-hospitalized and 32 hospitalized cats. After plating on selective media, the isolates were identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and rpoB and 16S rRNA gene sequencing. Subsequently, antimicrobial sensitivity of the strains was assessed, and they were screened for mecA gene. Methicillin-resistant S. haemolyticus (MRSH) isolates were subjected to multilocus sequence typing, whereas methicillin-resistant S. pseudintermedius (MRSP) and S. felis isolates were subjected to whole genome sequencing. S. felis was most commonly isolated from non-hospitalized cats (28.1%), whereas S. pseudintermedius and MRS were commonly isolated from hospitalized cats (25%). MRSH isolates from hospitalized animals were classified as ST3. The identified MRSP strains belonged to two well-known sequence types, ST551 and ST71. Moreover, antimicrobial use (p = 0.0001), hospitalization (p = 0.0141), and comorbidities (p = 0.002) were associated with increased MRS prevalence in cats.

Role of Xpert PCR kit in assessing MRSA colonization in medical and surgical units of a tertiary care teaching hospital.

BACKGROUND AND RATIONALE: Methicillin resistant Staphylococcus aureus (MRSA) colonization increases the risk of MRSA infection. Detecting MRSA colonization can influence postoperative outcomes and prolong hospital stay. The conventional standard culture method for detecting MRSA colonization has limitations in terms of sensitivity and turnaround time. Hence, we sought out use of Xpert PCR kit for prompt evaluation of MRSA colonization to support MRSA prevention in a tertiary care hospital in Karachi, Pakistan. MATERIALS AND METHODS: During 1st April-31st December 2022, 290 nasal and skin swab samples were collected from 257 patients and processed using routine culture (as gold standard method) and PCR-based MRSA detection assay (MRSA Xpert). RESULTS: A total of two hundred and ninety (290) swab samples from 257 patients were obtained, 33 of which were paired. The overall prevalence of MRSA colonization was 12% by both methods, with 90% of cases classified as community-associated (CA-MRSA) whereas 10% as hospital-acquired (HA-MRSA). The colonized group showed a higher subsequent MRSA infection rate (11% vs. 3.5%) compared to the noncolonized group. Culture identified 11% of screening samples as MRSA positive, Xpert MRSA assay showed 100% sensitivity and 95% specificity. The cost of a single MRSA Xpert assay was $50 while MRSA culture cost around $7.50. CONCLUSION: Our study findings suggest that the presence of MRSA colonization in our cohort of patients is consistent with the existing trends in hospital epidemiology. Both conventional culture and Xpert MRSA methods showed comparable efficacy for detection of MRSA colonization. Larger-scale studies are recommended to validate these findings conclusively.

Methicillin-Resistant Staphylococcus aureus among Students: Nasal Carriage Rate, Contributing Factors, and Antimicrobial Susceptibility.

Background and Objectives: Staphylococcus aureus is a prominent component of the human flora; however, it can cause various pathological conditions. The emergence of methicillin-resistant S. aureus (MR-SA) has been significantly influenced by the overuse and inappropriate administration of antibiotics. The frequency of MR-SA nasal colonization among healthcare workers (HCWs) is increasing, and MR-SA is not restricted to hospital settings, with a notable rise in infections among individuals unrelated to HCWs. This study aimed to assess the prevalence of S. aureus nasal carriage among students at Government College University Faisalabad (GCUF), University of Agriculture Faisalabad (UAF), a Government School (GS), and a Private School (PS) to characterize the phenotypic traits of isolates and evaluate antimicrobial resistance profiles. Materials and Methods: A total of 1200 nasal swabs were inoculated on blood and mannitol salt agar, followed by phenotypic identification of S. aureus and MR-SA using biochemical tests. Antimicrobial susceptibility testing was conducted via the Kirby-Bauer disk diffusion method, and minimum inhibitory concentration (MIC) determination was performed using the broth dilution method. Additionally, nuc and mecA gene amplification through PCR aided in isolate identification. Results: The results revealed that 14% (168) of students harbored S. aureus in their nasal cavities, with 8.5% (102) carrying methicillin-sensitive S. aureus (MSSA) and 5.5% (66) carrying MR-SA. Male students exhibited higher S. aureus (57.7%) and MR-SA (21.4%) prevalence compared to females (42.3% and 17.9%, respectively). Urban students showed a higher S. aureus prevalence (54.2%), while rural students exhibited a higher MR-SA rate (22%). Overall, 80.3% of S. aureus isolates displayed resistance to erythromycin followed by fluoroquinolones (47.6%) and clindamycin (42.2%). All the S. aureus isolates, including MR-SA, remained susceptible to vancomycin and linezolid. PCR results revealed that 95.5% (63) of MR-SA isolates carried the mecA gene. Conclusions: The high prevalence of multi-drug-resistant (MDR) S. aureus raises significant public health concerns, with educational institutions potentially serving as reservoirs for bacterial transmission. The improper use of antibiotics contributes to bacterial resistance and increased infection rates. It is crucial to implement measures to prevent antibiotic misuse and develop comprehensive strategies within educational settings to effectively combat S. aureus and MR-SA prevalence.

Characterization of Staphylococcus aureus isolated from milk samples for their virulence, biofilm, and antimicrobial resistance.

The Staphylococcus aureus (S. aureus) one of the important food borne pathogen from milk, which was investigated in this study. The isolates were screened for antimicrobial resistance, enterotoxin genes, biofilm formation, spa typing, coagulase gene polymorphism and accessory gene regulator types. The prevalence of S. aureus in milk samples was 34.4% (89/259). Methicillin resistant S. aureus (MRSA) was found at 27% (24/89) of the isolates, were classified as community acquired based on SCCmec typing. The 24.71% (22/89) isolates demonstrated multiple antimicrobial resistance (MAR) pattern. However, none of the isolates carried vancomycin and mupirocin resistance genes. The isolates were positive for sea and sed enterotoxin genes and exhibited high frequency of biofilm formation. The High-Resolution Melting and conventional spa typing revealed that the isolates had both animal and community-associated S. aureus clustered origins. Coagulase gene polymorphism and agr typing demonstrated variable genotypic patterns. The finding of this study establishes the prevalence of community associated, enterotoxigenic, biofilm forming and antimicrobial resistance among S. aureus from milk in Chennai city. This emphasizing a potential threat to public health which needs a continuous monitoring system and strategies to mitigate their spread across the food chain and achieve food safety.

Clinical, demographic characteristics and antimicrobial resistance profile of Staphylococcus aureus isolated in clinical samples from pediatric patients in a tertiary hospital in Rio de Janeiro: 7-year longitudinal study.

BACKGROUND: In the pediatric population, Staphylococcus aureus infections are responsible for increased morbidity and mortality, length of hospitalization and the cost of inpatient treatment. The aim of this study is to describe the antimicrobial resistance profile of S. aureus isolated in clinical specimens from pediatric patients admitted to a tertiary hospital in Rio de Janeiro, Brazil. METHODS: Culture reports and medical records of hospitalized patients under 18 years of age with S. aureus infections between January 2015 and December 2022 were retrospectively analyzed. Information was collected on recent antibiotic use, previous hospital admission, inpatient unit, clinical specimen, time of infection (community or nosocomial), classification according to susceptibility to methicillin (methicillin sensitive - MSSA or methicillin resistant - MRSA) and sensitivity to other antimicrobials. We analyzed the distribution of the sensitivity profile of S. aureus infections over the 7 years evaluated in the study. RESULTS: Were included 255 unique clinical episodes, among which the frequencies of MSSA and MRSA were 164 (64%) and 91 (36%), respectively. Over the 7 years evaluated, there was stability in the prevalence percentage, with a predominance of MSSA in the range of 60 to 73.3%, except in 2020, when there was a drop in the prevalence of MSSA (from 73.3% in 2019 to 52.5%) with an increase in MRSA (from 26.7% in 2019 to 47.5%). Ninety-seven (38%) infections were community-acquired and 158 (62%) were healthcare-associated. The main clinical specimens collected were blood cultures (35.2%) and wound secretions (17%). The MRSA isolates presented percentages of sensitivity to trimethoprim-sulfamethoxazole from 90.4 to 100%, and to clindamycin from 77 to 89.8% in MRSA healthcare associated and MRSA community respectively. CONCLUSION: There was a constant predominance in the prevalence of MSSA with percentage values ​​maintained from 2015 to 2022, except in 2020, in which there was a specific drop in the prevalence of MSSA with an increase in MRSA. MSSA infections are still predominant in the pediatric population, but MRSA rates also present significant values, including in community infections, and should be considered in initial empiric therapy.

Penicillin susceptibility among Staphylococcus aureus skin and soft tissue infections at a children's hospital.

Shortly after its introduction into clinical practice, Staphylococcus aureus isolates gained resistance to penicillin via the acquisition of ß-lactamases. A number of centers have recently described an increase in the proportion of invasive methicillin-susceptible S. aureus (MSSA), which are also susceptible to penicillin (PSSA). Little data are available regarding the prevalence or impact of PSSA in skin and soft tissue infections (SSTI). Community-acquired MSSA SSTI isolates were obtained through a surveillance study at Texas Children's Hospital from January 2017 to December 2021. A total of 200 random isolates underwent PCR for blaZ ß-lactamase; blaZ-negative isolates then underwent penicillin susceptibility testing using macrobroth dilution. Isolates which were blaZ negative and had a penicillin MIC ≤0.125 µg/mL were regarded as PSSA with the remainder regarded as penicillin-resistant MSSA (PR-MSSA). All PSSA underwent multilocus sequence typing. Medical records were reviewed. The median age of subjects was 4.2 years (IQR: 1.6-10.5). PSSA accounted for 9% of isolates during the study period. PSSA and PR-MSSA cases were similar with respect to age, demographics, and rates of prior antibiotic exposure. PSSA isolates less often had vancomycin MIC ≥1.5 µg/mL. Furthermore, 39% of PSSA were variants of sequence type 1. In multivariable analyses, penicillin susceptibility was independently associated with both hospital admission and surgical intervention. PSSA account for a small but significant proportion of MSSA SSTI in children. Clinically distinguishing patients with PSSA and PR-MSSA SSTI is challenging. However, PSSA SSTI were independently associated with higher rates of hospital admission as well as the need for surgical intervention suggesting a significant clinical impact.IMPORTANCEThe vast majority of Staphylococcus aureus in the US are penicillin resistant with most clinical labs no longer reporting penicillin susceptibility for this organism. A number of centers, however, have reported increasing penicillin susceptibility among invasive S. aureus infections. Skin and soft tissue infections (SSTI) are far more common than invasive infections, yet the frequency and impact of penicillin-susceptible S. aureus (PSSA) in this population are uncertain. Through active surveillance at a children's hospital, we found that 9% of methicillin-susceptible S. aureus SSTI isolates were PSSA. PSSA were independently associated with hospital admission for the management of SSTI as well as the need for debridement in the operating room. Given that most SSTI are managed in the outpatient setting, these findings suggest a clinical impact of this phenotype and the need for a reassessment of the value in susceptibility testing and potentially even treatment with penicillin.

Occurrence, multidrug resistance and potential risk factors for Staphylococcus aureus infection at worker-animal and working equipment interfaces: a systematic review and meta-analysis of the Ethiopian literature.

Background: Staphylococcus aureus (S. aureus) infecting animals and humans via close contact, handling, or consuming contaminated products is a growing public health concern. In Ethiopia, it is important to examine the overall prevalence of S. aureus, patterns of multidrug resistance, and potential risks in human-animal interface settings. Thus, this review was conducted to estimate the pooled prevalence of S. aureus, its multidrug resistance, and potential risk factors for worker-animal-working equipment interactions. Methods: This systematic review and meta-analysis were carried out by the PRISMA guidelines. The research articles were searched from PubMed, HINARI, Web of Sciences, and Google Scholar databases. Results: This meta-analysis included 13 independent articles and 52 dependent studies. In total, 5,329 humans, 5,475 animals, and 5,119 samples of working equipment were analyzed. The pooled prevalence of S. aureus at the interfaces between humans, animals, and working equipment was 22%, there was a high level of heterogeneity (I2 = 94%: p < 0.01). The overall pooled prevalence of S. aureus in dairy farm sources was 23% (95% CI, 17-30%) compared to 18% in abattoirs. The pooled prevalence of S. aureus was estimated to be 25% for human sources, 23% for animal sources, and 19% for working equipment. The total multidrug resistance (MDR) rate was 27%. The present study illustrates that a predominant antimicrobials comprising ampicillin, penicillin, chloramphenicol, tetracycline, and ciprofloxacin, accounts for the development of resistance in S. aureus strains, with a prevalence of 72%. According to the qualitative assessment of potential risk factors, animal age, worker education, lactation stage, and hand washing by milkers influenced the circulation of S. aureus at animal-worker and working equipment interfaces. Conclusion: The pooled prevalence of S. aureus at the interface of human,-and animal-working equipment was quantified at 22%. S. aureus was found in humans, animals, and equipment at nearly the same rate. The results of this study demonstrate that S. aureus is hazardous and circulates among animals, workers, and equipment: farmers, animal owners, employees, and the public need to be educated about S. aureus. Moreover, animals and work equipment should be included in the control and prevention of S. aureus infection.

Clinical presentation and microbiological characteristics of community-acquired Staphylococcus aureus bacteraemia at a tertiary hospital in Costa Rica.

Introduction. Staphylococcus aureus is a leading agent in community-acquired bacteraemia (CAB) and has been linked to elevated mortality rates and methicillin resistance in Costa Rica.Gap statement and aim. To update and enhance previous data obtained in this country, we analysed the clinical manifestations of 54 S. aureus CAB cases in a tertiary hospital and delineated the sequence types (STs), virulome, and resistome of the implicated isolates.Methodology. Clinical information was retrieved from patient files. Antibiotic susceptibility profiles were obtained with disc diffusion and automated phenotypic tests. Genomic data were exploited to type the isolates and for detection of resistance and virulence genes.Results. Primary infections predominantly manifested as bone and joint infections, followed by skin and soft tissue infections. Alarmingly, 70% of patients continued to exhibit positive haemocultures beyond 48 h of treatment modification, with nearly a quarter requiring mechanical ventilation or developing septic shock. The 30-day mortality rate reached an alarming 40%. More than 60% of the patients were found to have received suboptimal or inappropriate antibiotic treatment, and there was an alarming tendency towards the overuse of third-generation cephalosporins as empirical treatment. Laboratory tests indicated elevated creatinine levels, leukocytosis, and bandaemia within the first 24 h of hospitalization. However, most showed improvement after 48 h. The isolates were categorized into 13 STs, with a predominance of representatives from the clonal complexes CC72 (ST72), CC8 (ST8), CC5 (ST5, ST6), and CC1 (ST188). Twenty-four isolates tested positive for mecA, with ST72 strains accounting for 20. In addition, we detected genes conferring acquired resistance to aminoglycosides, MLSB antibiotics, trimethoprim/sulfamethoxazole, and mutations for fluoroquinolone resistance in the isolate collection. Genes associated with biofilm formation, capsule synthesis, and exotoxin production were prevalent, in contrast to the infrequent detection of enterotoxins or exfoliative toxin genes.Conclusions. Our findings broaden our understanding of S. aureus infections in a largely understudied region and can enhance patient management and treatment strategies.

Genomic approach to determine sources of neonatal Staphylococcus aureus infection from carriage in the Gambia.

Staphylococcus aureus is a major cause of neonatal infections in various anatomical sites, resulting in high morbidity and mortality in The Gambia. These clinical infections are often preceded by nasal carriage of S. aureus, a known risk factor. To determine whether potential sources of newborn S. aureus infections were from carriage, and to characterize S. aureus present in different anatomical sites (blood, ear, eye, umbilical cord, skin, pus, oropharynx, breast milk and vagina), we performed whole-genome sequencing of 172 isolates from clinical sites as well as from healthy and unhealthy carriage. A random selection of mothers (n = 90) and newborns (n = 42) participating in a clinical trial and testing positive for S. aureus were considered for this study. Sequence data were analyzed to determine S. aureus multilocus sequence types and selected antimicrobial and virulence gene profiles. Our findings revealed that in The Gambia, ST15 is the dominant sequence type associated with both carriage and clinical infection. In addition, S. aureus isolates causing clinical infection among neonates were genetically similar to those colonizing their oropharynx, and the different anatomical sites were not found to be uniquely colonized by S. aureus of a single genomic profile. Furthermore, while S. aureus associated with clinical infection had similar antimicrobial resistance gene profiles to carriage isolates, only hemolysin and adhesive factor virulence genes were significantly higher among clinical isolates. In conclusion, this study confirmed S. aureus oropharyngeal colonization among neonates as a potential source of clinical infection in The Gambia. Hence, interventions aiming to reduce neonatal clinical infections in The Gambia should consider decreasing oropharyngeal S. aureus carriage.Trial registration The trial was registered at ClinicalTrials.gov NCT03199547.

Inducible clindamycin-resistant and biofilm formation in the Staphylococcus aureus isolated from healthcare worker's anterior nasal carriage.

OBJECTIVE: The purpose of this study is a new update on the resistance profile, Macrolide-Lincosamide-Streptogramin B resistance mechanisms and biofilm formation in the Staphylococcus aureus isolated from health care workers (HCWs) nasal carriage at a children's teaching hospital in Babol (Northern Iran). RESULTS: A total of 143 non-repetitive nasal swab samples were collected from volunteers, where 53.8% (n; 77/143) were HCWs, 33.6% (n; 48/143) medical students, and 12.6% (n; 18/143) resident students. The prevalence of nasal carriers of S. aureus was 22.4% (n; 32/143), among them, 40.6% (n; 13/32) were identified as methicillin-resistant Staphylococcus aureus (MRSA( carriers. Antimicrobial susceptibility testing showed that erythromycin (68.8%, n; 22/32) and ciprofloxacin (15.6%, n; 5/32) had the highest and lowest resistance rate, respectively. The frequency of resistance genes in the strains was as follows; ermC (n; 17/32, 53.1%), ermA (n; 11/32, 34.4%), ermB (n; 6/32, 18.7%), ereA (n; 3/32, 9.4%). Moreover, 50.0% (n; 16/32), 28.1% (n; 9/32) and 21.8% (n; 7/32) of isolates were strongly, weakly and moderately biofilm producer, respectively. Macrolides-lincosamides-streptogramins B (MLSB) antibiotic resistance among S. aureus isolates from HCWs nasal carriage have found significant prevalence rates throughout the globe. It is crucial to remember that the development of biofilms and MLS B antibiotic resistance are both dynamic processes.

Prevalence and risk factors associated with nasal carriage of methicillin-resistant staphylococci in horses and their caregivers.

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.

Methicillin-resistant Staphylococcus aureus in diabetic and non-diabetic foot infections.

To identify the incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection, reinfection and clinical outcomes. Four hundred forty-six patients that were admitted to the hospital with moderate or severe foot infections were retrospectively reviewed. Tissue and bone cultures were obtained from the index hospital admission. Conversion was defined as methicillin susceptible Staphylococcus aureus in the first culture and subsequently MRSA when there was a reinfection. The incidence of MRSA was 7.8% (n = 35), with no significant difference between soft tissue infections (7.7%) and osteomyelitis (8.0%). MRSA incidence was 9.4 times higher in non-diabetics (23.8% vs. 3.2%, p = <0.01). The incidence of reinfection was 40.8% (n = 182). Conversion to MRSA was seen in 2.2% (n = 4) total, occurring in 5.4%. Non-diabetics were 20.1 times more likely to have MRSA reinfection than people with diabetes (28.6% vs. 1.9%, p < 0.001). MRSA patients had a higher proportion of healed wounds (82.4% vs. 69.3%, p = 0.02). There were no differences in other clinical outcomes in MRSA vs. other infections in reinfection (28.6% vs. 24.3%, p = 0.11), amputation (48.6% vs. 52.0%, p = 0.69) or hospitalization (28.6% vs. 42.6, p = 0.11). The incidence of MRSA for the first infection (7.8%), reinfection (6.0%) and conversion to MRSA (2.2%) was low. MRSA was 9.4 times more common in people without diabetes.

Microbiology of catheter-associated bloodstream infection: differences according to catheter type.

OBJECTIVES: Catheter-associated bloodstream infections (CABSI) cause preventable morbidity. We compared the microbiological etiology of CABSI across different types of central and peripherally-inserted catheters. METHODS: We analyzed prospectively collected CABSI data in a 2100-bed hospital network in Switzerland between 2016 and 2022. We included: short-term non-tunneled central venous catheters (CVC); long-term catheters (tunneled, or peripherally-inserted central catheters); arterial catheters; dialysis catheters; and peripheral venous catheters (PVC). We used multivariable logistic regression models to describe the risk of Staphylococcus aureus and Gram-negative pathogens according to catheter type. RESULTS: Overall, 416 CABSI episodes were included, including 60 episodes of S. aureus and 92 episodes of Gram-negative CABSI. Microbiological profiles differed between catheter types. Together, PVC and dialysis catheters accounted for 43/60 (72%) of all S. aureus CABSI. After adjusting for age, sex, and hematology/oncology care, the odds of S. aureus were higher for hemodialysis catheters (odds ratio [OR] 17.3, 95% confidence interval [CI] 5.75-52.2, P <0.01) and PVC (OR 2.96, 95% CI 1.22-7.20, P = 0.02) compared to short-term non-tunneled CVC. Odds of Gram-negative organism as the cause of CABSI were higher in long-term catheters versus short-term non-tunneled CVC (OR 2.70, 95% CI 1.37-5.24). CONCLUSIONS: CABSI in catheters other than short-term non-tunneled CVC is more commonly caused by virulent organisms including S. aureus and Gram-negative bacteria. Catheter type should be considered when selecting empirical antimicrobial therapies.

Hospitalizations among family members increase the risk of MRSA infection in a household.

OBJECTIVE: Estimate the risk for household transmission of Methicillin-Resistant Staphylococcus aureus (MRSA) following exposure to infected family members or family members recently discharged from a hospital. DESIGN: Analysis of monthly MRSA incidence from longitudinal insurance claims using the Merative MarketScan Commercial and Medicare (2001-2021) databases. SETTING: Visits to inpatient, emergency department, and outpatient settings. PATIENTS: Households with ≥2 family members enrolled in the same insurance plan for the entire month. METHODS: We estimated a monthly incidence model, where enrollees were binned into monthly enrollment strata defined by demographic, patient, and exposure characteristics. Monthly incidence within each stratum was computed, and a regression analysis was used to estimate the incidence rate ratio (IRR) associated with household exposures of interest while accounting for potential confounding factors. RESULTS: A total of 157,944,708 enrollees were included and 424,512 cases of MRSA were identified. Across all included enrollees, exposure to a family member with MRSA in the prior 30 days was associated with significantly increased risk of infection (IRR: 71.03 [95% CI, 67.73-74.50]). After removing enrollees who were hospitalized or exposed to a family member with MRSA, exposure to a family member who was recently discharged from the hospital was associated with increased risk of infection (IRR: 1.44 [95% CI, 1.39-1.49]) and the risk of infection increased with the duration of the family member's hospital stay (P value < .001). CONCLUSIONS: Exposure to a recently hospitalized and discharged family member increased the risk of MRSA infection in a household even when the hospitalized family member was not diagnosed with MRSA.

Rate of nosocomial MRSA transmission evaluated via contact screening.

BACKGROUND: The prevention of methicillin-resistant S. aureus (MRSA) transmission in the healthcare setting is a priority in Infection Control practices. A cornerstone of this policy is contact tracing of nosocomial contacts after an unexpected MRSA finding. The objective of this retrospective study was to quantify the rates of MRSA transmission in different clinical settings. METHODS: This multi-centre study included MRSA contact screening results from two regional hospitals and one academic hospital. MRSA contact tracing investigations from 2000 until 2019 were reviewed and post-contact screening results were included of index patients with an MRSA-positive culture and their unprotected contacts. Available typing results were used to rule out incidental findings. RESULTS: Of 27,377 contacts screened after MRSA exposure, 21,488 were Health Care Workers (HCW) and 4816 patients. Post-contact screening was initiated for a total of 774 index cases, the average number of screened contacts per index case was 35.7 (range 1 to 640). MRSA transmission was observed in 0.15% (41) of the contacts, 19 (0.09%) HCW and 22 (0.46%) patients. The number needed to screen to detect one MRSA transmission was 667. The highest risk of MRSA transmission occurred during patient-to-patient contacts, with transmission rates varying from 0.32 to 1.32% among the participating hospitals. No transmissions were detected in HCW (n=2834) in the outpatient setting, and the rate of transmissions among HCW contacts on the wards was 0.13% (19 of 15,874). Among 344 contacts of patients with contact precautions, no transmissions were detected. CONCLUSIONS: Reconsidering current MRSA contact tracing practices may lead to a more targeted approach with a lower number needed to screen.

Phenotypic and genomic analysis of the hypervirulent methicillin-resistant Staphylococcus aureus ST630 clone in China.

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is a rarely reported lineage worldwide. This study aimed to trace the dissemination of the emerging MRSA ST630 clones in China and investigate their virulence potential. We collected 22 ST630-MRSA isolates from across China and performed whole-genome sequencing analysis and virulence characterization on these isolates. Epidemiological results showed that MRSA ST630 isolates were primarily isolated from pus/wound secretions, mainly originating from Jiangxi province, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type V (SCCmec V) predominated (11/22, 50.0%) among the MRSA ST630 isolates. Interestingly, nearly half (45.5%) of the 22 ST630-MRSA isolates tested lacked intact SCCmec elements. Phylogenetic analysis demonstrated that ST630-MRSA could be divided into two distinct clades, with widespread dissemination mainly in Chinese regions. Five representative isolates were selected for phenotypic assays, including hemolysin activity, real-time fluorescence quantitative PCR, western blot analysis, hydrogen peroxide killing assay, blood killing assay, cell adhesion and invasion assay, and mouse skin abscess model. The results showed that, compared to the USA300-LAC strain, ST630 isolates exhibited particularly strong invasiveness and virulence in the aforementioned phenotypic assays. This study described the emergence of a highly virulent ST630-MRSA lineage and improved our insight into the molecular epidemiology of ST630 clones in China.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) sequence type 630 (ST630) is an emerging clone with an increasing isolation rate in China. This study raises awareness of the hypervirulent MRSA ST630 clones in China and alerts people to their widespread dissemination. ST630-staphylococcal cassette chromosome mec V is a noteworthy clone in China, and we present the first comprehensive genetic and phenotypic analysis of this lineage. Our findings provide valuable insights for the prevention and control of infections caused by this emerging MRSA clone.