Genotypic and Phenotypic Markers of Livestock-Associated Methicillin-Resistant Staphylococcus aureus CC9 in Humans

Molecular Characterization of Chimeric Staphylococcus aureus Strains from Waterfowl

Staphylococcus aureus is a versatile pathogen that does not only occur in humans but also in various wild and domestic animals, including several avian species. When characterizing S. aureus isolates from waterfowl, isolates were identified as atypical CC133 by DNA microarray analysis. They differed from previously sequenced CC133 strains in the presence of the collagen adhesin gene cna; some also showed a different capsule type and a deviant spa type. Thus, they were subjected to whole-genome sequencing. This revealed multiple insertions of large regions of DNA from other S. aureus lineages into a CC133-derived backbone genome. Three distinct strains were identified based on the size and extent of these inserts. One strain comprised two small inserts of foreign DNA up- and downstream of oriC; one of about 7000 nt or 0.25% originated from CC692 and the other, at ca. 38,000 nt or 1.3% slightly larger one was of CC522 provenance. The second strain carried a larger CC692 insert (nearly 257,000 nt or 10% of the strain's genome), and its CC522-derived insert was also larger, at about 53,500 nt or 2% of the genome). The third strain carried an identical CC692-derived region (in which the same mutations were observed as in the second strain), but it had a considerably larger CC522-like insertion of about 167,000 nt or 5.9% of the genome. Both isolates of the first, and two out of four isolates of the second strain also harbored a hemolysin-beta-integrating prophage carrying "bird-specific" virulence factors, ornithine cyclodeaminase D0K6J8 and a putative protease D0K6J9. Furthermore, isolates had two different variants of SCC elements that lacked mecA/mecC genes. These findings highlight the role of horizontal gene transfer in the evolution of S. aureus facilitated by SCC elements, by phages, and by a yet undescribed mechanism for large-scale exchange of core genomic DNA.

Virulence attributes of successful methicillin-resistant Staphylococcus aureus lineages

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of severe and often fatal infections. MRSA epidemics have occurred in waves, whereby a previously successful lineage has been replaced by a more fit and better adapted lineage. Selection pressures in both hospital and community settings are not uniform across the globe, which has resulted in geographically distinct epidemiology. This review focuses on the mechanisms that trigger the establishment and maintenance of current, dominant MRSA lineages across the globe. While the important role of antibiotic resistance will be mentioned throughout, factors which influence the capacity of S. aureus to colonize and cause disease within a host will be the primary focus of this review. We show that while MRSA possesses a diverse arsenal of toxins including alpha-toxin, the success of a lineage involves more than just producing toxins that damage the host. Success is often attributed to the acquisition or loss of genetic elements involved in colonization and niche adaptation such as the arginine catabolic mobile element, as well as the activity of regulatory systems, and shift metabolism accordingly (e.g., the accessory genome regulator, agr). Understanding exactly how specific MRSA clones cause prolonged epidemics may reveal targets for therapies, whereby both core (e.g., the alpha toxin) and acquired virulence factors (e.g., the Panton-Valentine leukocidin) may be nullified using anti-virulence strategies.

Heterogeneity and transmission of food safety-related enterotoxigenic Staphylococcus aureus in pig abattoirs in Hubei, China

The dissemination of Staphylococcus aureus in the pork production chain is a major food safety concern. Abattoirs can serve both as disruptor and transmitter for S. aureus. In this study, we conducted a systematic genomic epidemiology research on the prevalence, heterogeneity, and transmission of S. aureus in 3,638 samples collected from four pig abattoirs in Hubei province, China. Our findings revealed substantial heterogeneity between S. aureus recovered from samples collected at upstream (from stunning step to head-removal step) and downstream (from splitting step to chilling step) locations within the slaughter process. Overall, 966 (26.6%) samples were positive for S. aureus, with significantly higher overall prevalence for upstream samples (29.0%, 488/1,681) compared to downstream samples (24.4%, 478/1,957). Antimicrobial susceptibility testing demonstrated that the isolates from the upstream exhibited significantly higher resistance proportions to different antimicrobials than those from the downstream. Whole-genome sequencing of 126 isolates revealed that ST398 (32.9%, 23/70) and ST9 (22.9%, 16/70) were more common among upstream isolates, while ST7 (35.7%, 20/56) and ST97 (28.6%, 16/56) were most frequently observed among downstream isolates. Additionally, molecular characterization analysis demonstrated that upstream isolates possessed significantly higher enterotoxigenic potential, more antimicrobial resistance genes, and S. aureus pathogenicity islands than downstream isolates. Notably, we discovered that enterotoxigenic S. aureus could be transmitted across different slaughter stages, with knives, water, and air serving as vectors. Although slaughtering processes had a substantial effect on reducing the food safety risk posed by enterotoxigenic S. aureus, the possibility of its widespread transmission should not be disregarded. IMPORTANCE Staphylococcus aureus (S. aureus) is one of the most important foodborne pathogens, and can cause foodborne poisoning by producing enterotoxins. Pork is a preferable reservoir and its contamination often occurs during the slaughter process. Our findings revealed significant differences in the prevalence, antimicrobial resistance, and enterotoxigenic potential between the upstream and downstream isolates within the slaughter process. Also, it is imperative not to overlook enterotoxigenic S. aureus transmitted across all stages of the slaughter process, with notable vectors being knives, water, and air. These findings hold significant implications for policy-makers to reassess their surveillance projects, and underscore the importance of implementing effective control measures to minimize the risk of S. aureus contamination in pork production. Moreover, we provide a more compelling method of characterizing pathogen transmission based on core-SNPs of bacterial genomes.

The Epidemiology of Animal-Associated Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important etiological factor of human and animal infectious diseases, causing significant economic losses not only in human healthcare but also in the large-scale farming sector. The constantly changing epidemiology of MRSA observed globally affects animal welfare and raises concerns for public health. High MRSA colonization rates in livestock raise questions about the meaning of reservoirs and possible transmission pathways, while the prevalence of MRSA colonization and infection rates among companion animals vary and might affect human health in multiple ways. We present the main findings concerning the circulation of animal-associated MRSA (AA-MRSA) in the environment and factors influencing the direction, mechanisms, and routes of its transmission. Studies have shown it that S. aureus is a multi-host bacterial pathogen; however, its adaptation mechanisms enabling it to colonize and infect both animal and human hosts are still rarely discussed. Finally, we elaborate on the most successful strategies and programs applied limiting the circulation of AA-MRSA among animals and humans. Although MRSA strains colonizing animals rarely infect humans, they undergo host-adaptive evolution enabling them to spread and persist in human populations.

Comparative review of the nasal carriage and genetic characteristics of Staphylococcus aureus in healthy livestock: Insight into zoonotic and anthroponotic clones

Given the central role of livestock in understanding the genomic epidemiology of S. aureus, the present study systematically reviewed and synthesized data on the nasal S. aureus carriage, resistance patterns to critical antimicrobial agents, virulence factors and genetic lineages among healthy livestock. Bibliographical databases were searched for published studies from May 2003 to May 2022 on nasal S. aureus carriage, their phenotypic and genetic characteristics among healthy pigs (A), sheep and goats (B), cattle (C), poultry (D), camels (E) and buffaloes (F). Special focus was given to the prevalence of nasal MRSA, MRSA-CC398, MRSA-CC9, mecC-MRSA, MSSA-CC398, and resistance to linezolid (LZD^R), chloramphenicol (CLO^R) and tetracycline (TET^R) in S. aureus isolates. Of the 5492 studies identified, 146 comprised groups A(83)/B(18)/C(33)/D(4)/E(5)/F(3), and were found eligible. The overall pooled nasal prevalence of MRSA in healthy livestock was 13.8% (95% CI: 13.5-14.1) among a pooled 48,154 livestock population. Specifically, the pooled prevalence in groups A to F were: 16.0% (95% CI: 15.6-16.4), 3.7% (95% CI: 2.9-4.6), 13.6% (95% CI: 12.8-14.4), 5.8% (95% CI: 5.1-6.5), 7.1% (95% CI: 6.1-10.7), and 2.8% (95% CI: 1.5-4.8), respectively. These values varied considerably by continent. Varied pooled prevalences of CC398 lineage with respect to MRSA isolates were obtained, with the highest from pigs and cattle (>70%). Moreover, other classical animal-adapted MRSA as well as MSSA-CC398-t1928 were reported. TET^R-MSSA was lowest in cattle (18.9%) and highest in pigs (80.7%). LZD^R-S. aureus was reported in 8 studies (mediated by optrA and cfr), mainly in pigs (n = 4), while CLO^R-S. aureus was reported in 32 studies. The virulence genes luk-S/F-PV, tst, etd, sea, see were sparsely reported, and only in non-CC398-MRSA lineages. Certain S. aureus clones and critical AMR appeared to have predominance in some livestock, as in the case of pigs that are high nasal carriers of MRSA-CC398 and -CC9, and MSSA-CC398. These findings highlight the need for adequate prevention against the transmission of zoonotic S. aureus lineages to humans.

Tracking Infection and Genetic Divergence of Methicillin-Resistant Staphylococcus aureus at Pets, Pet Owners, and Environment Interface

Staphylococcus aureus (S. aureus) has become a leading animal and public health pathogen that keeps on transferring from one host to other, giving rise to newer strains by genetic shifts. The current study was designed to investigate the epidemiology and genetic relatedness of mecA gene in S. aureus isolated from pets, immediate individuals in contact with pets, and veterinary clinic environments. A total of n = 300 samples were collected from different veterinary hospitals in Pakistan using convenience sampling. The collected samples were subjected to microbiological and biochemical examination for the isolation of S. aureus. Methicillin resistance was investigated by both phenotypically using oxacillin disk diffusion assay and by genotypically targeting mecA gene by PCR. PCR amplicons were subjected for sequencing by Sanger method of sequencing, which were subsequently submitted to NCBI GenBank under the accession numbers MT874770, MT874771, and MT874772. Sequence evolutionary analysis and mecA gene characterization was done using various bioinformatics tools. Overall, 33.66% mecA genes harboring S. aureus strains were isolated from all sources (33.33% from pets, 46.0% from surrounding, and 28.0% from immediate contact individuals). The bioinformatics analysis noted that one SNP was identified at position c.253C>A (Transvertion). The phylogenetic tree (two clades) of S. aureus mecA revealed a possibility of inter-transmission of disease between the environment and pets. Frequency of adenine and thymine nucleotide in motifs were found to be the same (0.334). Cytosine and guanine frequency were also the same (0.166). Threonine was replaced by asparagine (p.T84D) in each sample of cat, environment, and human. On the other hand, protein structures ofcat-1 and cat-2 proteins were found identical while cat-3, environmental, and human proteins shared identical structures. The study thus concludes rising circulation of methicillin-resistant S. aureus (MRSA) strains in animal-human-environment interfaces, forecasting the development of novel strains withmodified range of resistance.

Transmission routes of antibiotic resistant bacteria: a systematic review

Background

Quantification of acquisition routes of antibiotic resistant bacteria (ARB) is pivotal for understanding transmission dynamics and designing cost-effective interventions. Different methods have been used to quantify the importance of transmission routes, such as relative risks, odds ratios (OR), genomic comparisons and basic reproduction numbers. We systematically reviewed reported estimates on acquisition routes’ contributions of ARB in humans, animals, water and the environment and assessed the methods used to quantify the importance of transmission routes.

Methods

PubMed and EMBASE were searched, resulting in 6054 articles published up until January 1st, 2019. Full text screening was performed on 525 articles and 277 are included.

Results

We extracted 718 estimates with S. aureus (n = 273), E. coli (n = 157) and Enterobacteriaceae (n = 99) being studied most frequently. Most estimates were derived from statistical methods (n = 560), mainly expressed as risks (n = 246) and ORs (n = 239), followed by genetic comparisons (n = 85), modelling (n = 62) and dosage of ARB ingested (n = 17). Transmission routes analysed most frequently were occupational exposure (n = 157), travelling (n = 110) and contacts with carriers (n = 83). Studies were mostly performed in the United States (n = 142), the Netherlands (n = 87) and Germany (n = 60). Comparison of methods was not possible as studies using different methods to estimate the same route were lacking. Due to study heterogeneity not all estimates by the same method could be pooled.

Conclusion

Despite an abundance of published data the relative importance of transmission routes of ARB has not been accurately quantified. Links between exposure and acquisition are often present, but the frequency of exposure is missing, which disables estimation of transmission routes’ importance. To create effective policies reducing ARB, estimates of transmission should be weighed by the frequency of exposure occurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07360-z.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014–2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

First Report of Antimicrobial Susceptibility and Virulence Gene Characterization Associated with Staphylococcus aureus Carriage in Healthy Camels from Tunisia

Simple Summary

The one-humped camel (Camelus dromedarius) is an important livestock species and is present in more than 46 national entities, with 80% of the camel population inhabiting Africa. In these regions, the role of camels in the livestock economy is highly valuable and a part of this camel herd is valorized on national or international markets for meat production, live animal export or milk production. Even if camels are the species that is most adapted to the harsh conditions of arid/semi-arid rangelands, they can be susceptible to a high number of pathogens, including S. aureus. This latter is often associated with asymptomatic carriage but can also be responsible for several diseases, therefore causing considerable economical losses. Continued monitoring and control assume particular importance in containing the spread of the bacterium since it constitutes an important zoonotic disease.

Abstract

A total of 318 nasal and rectal swabs were collected from 159 apparently healthy camels (Camelus dromedarius) randomly selected from five regions in southern and central Tunisia and screened for Staphylococcus aureus carriage. Staphylococcus spp. were recovered from 152 of 159 camels studied (95.6%) and in total 258 swabs (81%) were positive. Among these isolates, 16 were coagulase positive Staphylococcus (CoPS) (6.2%) and were characterized by biochemical and molecular tests as S. aureus. These were isolated from 14 camels (8.8%) with co-carriage in nasal and rectal mucosa by two camels. All S. aureus isolates recovered were methicillin-susceptible Staphylococcus aureus (MSSA) and were characterized by spa typing and PFGE. Three different spa types were recovered: t729, t4013 and a spa type newly registered as t19687, which was the most common. PFGE analysis revealed seven different patterns and these were characterized by MLST, which revealed five different sequence types (ST6, ST88, ST3583 and two new sequences, ST6504 and ST6506). All isolates harbored different virulence genes, including hld, encoding delta hemolysin; lukE–lukD, encoding bicomponent leukotoxin LukE–LukD; the clfB gene, encoding clumping factor B; the laminin gene, encoding laminin-binding protein; and cap8, encoding capsule type 8. Fifteen isolates harbored hemolysin beta (hlb) and fourteen encoded hemolysin alpha (hla) and hemolysin G2 (hlg_v). Adhesin factors, including clfA and fnbB, were detected in five and four isolates respectively. Binding proteins, including collagen (cbp) and elastin-binding protein (ebp), were detected in two S. aureus isolates while fibrinogen-binding protein (fib) was identified in four isolates. This study provides the first set of genotyping data on the population structure and presence of toxin genes of S. aureus strains in Tunisian camels.

Staphylococcus aureus and Cystic Fibrosis-A Close Relationship. What Can We Learn from Sequencing Studies?

Staphylococcus aureus is next to Pseudomonas aeruginosa the most isolated pathogen from the airways of cystic fibrosis (CF) patients, who are often infected by a dominant S. aureus clone for extended periods. To be able to persist, the pathogen has to adapt to the hostile niche of the airways to counteract host defence, antibiotic therapy and the competition with coinfecting pathogens. S. aureus is equipped with many virulence factors including adhesins, toxins that are localized on the chromosome, on plasmids or are phage-related. S. aureus is especially versatile and adaptation and evolution of the pathogen occurs by the acquisition of new genes by horizontal gene transfer (HGT), changes in nucleotides (single nucleotide variations, SNVs) that can cause a selective advantage for the bacteria and become fixed in subpopulations. Methicillin-resistant S. aureus are a special threat to CF patients due to the more severe lung disease occurring in infected patients. Today, with decreasing costs for sequencing, more and more studies using S. aureus isolates cultured from CF patients are being published, which use whole genome sequencing (WGS), multilocus sequence typing (MLST) or spa-sequence typing (spa-typing) to follow the population dynamics of S. aureus, elucidate the underlying mechanisms of phenotypic variants, newly acquired resistance or adaptation to the host response in this particular niche. In the first part of this review, an introduction to the genetic make-up and the pathogenesis of S. aureus with respect to CF is provided. The second part presents an overview of recent studies and their findings using genotypic methods such as single or multilocus sequencing and whole genome sequencing, which identify factors contributing to the adaptation of S. aureus and its evolution in the airways of individuals with CF.

Cross-species transmission risk of livestock-associated MRSA: A systematic review and Bayesian meta-analysis of global data

Although increasing studies have indicated a strong relationship between livestock exposure and methicillin-resistant Staphylococcus aureus (MRSA) carriage in humans, the risk magnitude of cross-species transmission of livestock-associated MRSA (LA-MRSA) is still unclear. This meta-analysis aimed to evaluate the potential effect of livestock exposure on LA-MRSA (including CC398/CC9, scn-negative, and tetracycline-resistant isolates) transmission. The summary estimates were pooled by random-effects models using the DerSimonian & Laird (DL) method and the Bayesian method. Twenty-two studies were included in this meta-analysis. Livestock-exposed people demonstrated a significantly higher rate of livestock-associated S. aureus (LA-SA) carriage than non-exposed people (Bayesian estimates: OR = 5.23 for CC398/CC9; OR = 2.35 for scn-negative isolates; OR = 3.86 for tetracycline-resistant isolates). Similarly, there was a greater positive association between livestock exposure and LA-MRSA carriage in humans ((Bayesian estimates: OR = 7.64 for CC398/CC9; OR = 7.54 for scn-negative isolates; OR = 9.89 for tetracycline-resistant isolates), indicating that livestock exposure increases the risk of LA-MRSA carriage in humans. These findings provide evidence for revealing the high risk of cross-species LA-MRSA transmission by livestock exposure.

Genomic Insights into Methicillin-Resistant Staphylococcus aureus spa Type t899 Isolates Belonging to Different Sequence Types

This study showed the genetic diversity and population structure of S. aureus presenting the same spa type, t899, but belonging to different STs. Our findings revealed that these isolates vary deeply in their core and accessory genomes, contrary to what is regularly inferred from studies using spa typing only.

Methicillin-resistant Staphylococcus aureus (MRSA) presenting spa type t899 is commonly associated with sequence type 9 (ST9) but is also increasingly linked to ST398. This study provides genomic insight into the diversity of t899 isolates using core genome multilocus sequence typing (cgMLST), single nucleotide polymorphism (SNP)-based phylogeny, and the description of selected antimicrobial resistance and virulence markers. The SNP-based phylogenic tree showed that isolates sharing the same spa type (t899) but different STs highly diverged in their core and accessory genomes, revealing discriminant antimicrobial resistance (AMR) and virulence markers. Our results highlighted the idea that in a surveillance context where only spa typing is used, an additional multiplex PCR for the detection of the tet(M), sak, and seg genes would be valuable in helping distinguish ST9 from ST398 isolates on a routine basis.

IMPORTANCE This study showed the genetic diversity and population structure of S. aureus presenting the same spa type, t899, but belonging to different STs. Our findings revealed that these isolates vary deeply in their core and accessory genomes, contrary to what is regularly inferred from studies using spa typing only. Given that identical spa types can be associated with different STs and that spa typing only is not appropriate for S. aureus isolates that have undergone major recombination events which include the passage of the spa gene (such as in t899-positive MRSA), the combination of both MLST and spa typing methods is recommended. However, spa typing alone is still largely used in surveillance studies and basic characterization. Our data suggest that additional markers, such as tet(M), sak, and seg genes, could be implemented in an easy and inexpensive manner in order to identify S. aureus lineages with a higher accuracy.

Livestock-Associated and Non-Livestock-Associated Staphylococcus aureus Carriage in Humans is Associated with Pig Exposure in a Dose-Response Manner

Background

The distinction between livestock-associated and human-associated methicillin-resistant Staphylococcus aureus (MRSA) has become more and more blurred. This study aimed to reveal the transmission risk of livestock-associated and non-livestock-associated S. aureus (including MRSA and multidrug-resistant S. aureus [MDRSA]) by occupational pig exposure.

Methods

A total of 591 pig-exposed workers and 1178 non-exposed workers were enrolled in this study. All nasal S. aureus isolates were tested for antibiotic susceptibility and molecular characteristics. Logistic regression models were used to examine the dose–response relationships between occupational pig exposure and S. aureus carriage.

Results

Pig-exposed workers had significantly higher carriage rates of MRSA (OR=6.29, 95% CI: 3.38~11.68) and MDRSA (OR=3.17, 95% CI: 2.03~4.96) than non-exposed workers. Notably, we found dose–response relationships between occupational pig exposure and MRSA or MDRSA carriage. Using genotypic and phenotypic markers for differentiating livestock-associated and non-livestock-associated S. aureus, we also revealed dose–response relationships occupational pig exposure and livestock-associated or non-livestock-associated S. aureus carriage.

Conclusion

Our findings provide sufficient epidemiological evidence for revealing the high transmission risk of livestock-associated S. aureus and the low transmission risk of non-livestock-associated S. aureus by occupational pig exposure.

Linezolid-resistant MRSA-CC398 carrying the cfr gene, and MRSA-CC9 isolates from pigs with signs of infection in Spain

AIMS

To perform the molecular characterization of 23 Staphylococcus aureus isolates from pigs with signs of infections recovered in Spanish farms during 2018-2019.

METHODS AND RESULTS

The antimicrobial resistance pattern and virulence profile were determined. The molecular typing was performed by different molecular techniques. The transferability of the cfr gene was assessed by conjugation and its genetic environment was determined by PCR mapping. In all, 21 isolates were methicillin-resistant S. aureus (MRSA) carrying the mecA gene (SCCmecV or non-typeable SCCmec), whereas the remaining two were methicillin-susceptible (MSSA). All but one MRSA isolates (n = 20) belonged to the CC398, being the spa t011 the most prevalent (n = 11). The remaining MRSA and the two MSSA isolates were ascribed to ST9/CC9. The S. aureus isolates exhibited resistance to (number of resistant isolates): β-lactamics (21), erythromycin and/or clindamycin (20), aminoglycosides (7), tetracycline (22), fluoroquinolones (14), chloramphenicol (5) and linezolid (1). The S. aureus isolates did not carry any of the virulence genes studied. One MRSA belonging to the CC398 showed linezolid resistance mediated by the cfr gene. The cfr gene was co-located with fexA in the Tn558 variant previously reported in the S. aureus plasmid pSCFS7.

CONCLUSIONS

Two major livestock-associated genetic lineages were detected among pigs with signs of infection in Spain. The presence of the cfr gene among LA-MRSA-CC398 is of great concern not only for veterinary medicine, but also for humans in close contact.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work describes the molecular characterization of S. aureus isolates recovered from pigs with signs of infection and we report, as far as we know, the first description of MRSA-CC9 from pigs in Spain. Moreover, the detection of a MRSA-CC398 isolate carrying the multiresistance cfr gene highlights the need for continuous surveillance and awareness of LA-MRSA.

Human mecC-Carrying MRSA: Clinical Implications and Risk Factors

A new methicillin resistance gene, named mecC, was first described in 2011 in both humans and animals. Since then, this gene has been detected in different production and free-living animals and as an agent causing infections in some humans. The possible impact that these isolates can have in clinical settings remains unknown. The current available information about mecC-carrying methicillin resistant S. aureus (MRSA) isolates obtained from human samples was analyzed in order to establish its possible clinical implications as well as to determine the infection types associated with this resistance mechanism, the characteristics of these mecC-carrying isolates, their possible relation with animals and the presence of other risk factors. Until now, most human mecC-MRSA infections have been reported in Europe and mecC-MRSA isolates have been identified belonging to a small number of clonal complexes. Although the prevalence of mecC-MRSA human infections is very low and isolates usually contain few resistance (except for beta-lactams) and virulence genes, first isolates harboring important virulence genes or that are resistant to non-beta lactams have already been described. Moreover, severe and even fatal human infection cases have been detected. mecC-carrying MRSA should be taken into consideration in hospital, veterinary and food safety laboratories and in prevention strategies in order to avoid possible emerging health problems.

Occurrence and characterisation of methicillin-resistant Staphylococcus aureus isolated from bovine milk in Hungary

The last surveys on methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine milk in Hungary took place in the 2000s. To elucidate the genetic variability and to estimate the burden of the pathogen, MRSA from our strain collection and prospectively collected Staphylococcus aureus (SA) isolates originating from two milk hygiene laboratories were investigated. Between 2003 and 2018, 27 MRSA strains originating from 10 dairy farms were deposited and characterised. Most strains (n = 20) belonged to ST1-t127-SCCmecIV and were recovered from three unrelated farms. From other farms, variable genotypes were identified sporadically: ST22-t032-SCCmecIV from three farms; a newly described double locus variant of ST97, ST5982-t458-SCCmecIV from two farms; and ST398-t011-SCCmecIV and ST398-t011-SCCmecV from two respective farms. The prospective screening of 626 individual SA isolates originating from 42 dairy farms resulted in four (0.48 %) MRSA strains from three (7.14 %) farms. All MRSA isolates belonged to the clonal complex 398 and a novel spa-type t19251 was also identified. Most isolates were resistant to three or more antimicrobial classes. The occurrence and significance of MRSA of dairy origin seems to be unchanged in the past decade in Hungary. However, the low host specificity and multiresistance of the identified genotypes calls for periodic revision on the role and distribution of the pathogen in the Hungarian dairy sector.

Acquisition Risk Factors of the SCCmec IX-Methicillin-Resistant Staphylococcus aureus in Swine Production Personnel in Chiang Mai and Lamphun Provinces, Thailand

Methicillin-resistant Staphylococcus aureus (MRSA) harboring the type-IX staphylococcal cassette chromosome mec (SCCmec) has been found in pigs and humans in Northern Thailand. However, knowledge of the prevalence and acquisition risk factors of this MRSA strain among swine production personnel (SPP) are needed. The nasal swab samples and data were collected from 202 voluntary SPP and 31 swine farms in Chiang Mai and Lamphun Provinces, Thailand in 2017. MRSA were screened and identified using mannitol salt agar, biochemical and antimicrobial susceptibility testing, multiplex PCR, and the SCCmec typing. The prevalence of MRSA was 7.9% (16/202) and 19.3% (6/31) among SPP and swine farms. All isolates were multidrug-resistant, and 55 of 59 isolates (93%) contained the type-IX SCCmec element. Data analysis indicated that education, working time, contact frequency, working solely with swine production, and personal hygiene were significantly related to MRSA acquisition (p < 0.05). The multivariate analysis revealed that pig farming experience, working days, and showering were good predictors for MRSA carriage among SPP (area under the curve (AUC) = 0.84). The biosecurity protocols and tetracycline use were significantly associated with MRSA detection in pig farms (p < 0.05). Hence, the active surveillance of MRSA and further development of local/national intervention for MRSA control are essential.

Characteristics of methicillin-resistant Staphylococcus aureus from broiler farms in Germany are rather lineage- than source-specific

Methicillin-resistant Staphylococcus aureus (MRSA) are a major concern for public health, and broiler farms are a potential source of MRSA isolates. In this study, a total of 56 MRSA isolates from 15 broiler farms from 4 different counties in Germany were characterised phenotypically and genotypically. Spa types, dru types, SCCmec types, and virulence genes as well as resistance genes were determined by using a DNA microarray or specific PCR assays. In addition, PFGE profiles of isolates were used for analysis of their epidemiological relatedness. While half of the isolates belonged to spa type t011, the other half was of spa types t1430 and t034. On 3 farms, more than 1 spa type was found. The most common dru type was dt10a (n = 19), followed by dt11a (n = 17). Susceptibility testing of all isolates by broth microdilution revealed 21 different resistance phenotypes and a wide range of resistance genes was present among the isolates. Up to 10 different resistance phenotypes were found on individual farms. Resistance to tetracyclines (n = 53), MLS_B antibiotics (n = 49), trimethoprim (n = 38), and elevated MICs of tiamulin (n = 29) were most commonly observed. Microarray analysis detected genes for leucocidin (lukF/S), haemolysin gamma (hlgA), and other haemolysines in all isolates. In all t1430 isolates, the egc cluster comprising of genes encoding enterotoxin G, I, M, N, O, U, and/or Y was found. The splitstree analysis based on microarray and PCR gene profiles revealed that all CC9/SCCmec IV/t1430/dt10a isolates clustered apart from the other isolates. These findings confirm that genotypic patterns were specific for clonal lineages rather than for the origin of isolates from individual farms.

The Genomic Context for the Evolution and Transmission of Community-Associated Staphylococcus aureus ST59 Through the Food Chain

Sequence type 59 (ST59) is a predominant clonal lineage of community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA) in Asia. Despite its increasing clinical relevance in China, the evolution and geographic expansion of ST59 has been relatively uncared for. Previous study has shown that ST59 was the predominant clone in food-related MRSA in China. This study compared the genomes of 87 clonal complex (CC) 59 S. aureus isolates sourced from food chain and infection cases to reconstruct the molecular evolution and geographical spread of ST59. Accordingly, three major sub-clades of ST59 were identified and these did not correlate with isolation source or location. Phylogenetic analysis estimated that ST59 in mainland China diverged from a most common recent ancestor around 1974, and most of the cases of cross-country transmission occurred between 1987 and 2000. Notably, two recent events of cross-country transmission through the food chain were observed, the isolates from these events diverged within relatively short time intervals. These isolates also showed high similarity in terms of their core genome, accessory genes, and antibiotic resistance patterns. These findings provide a valuable insight into the potential route of ST59 expansion in China and indicate a need for robust food chain surveillance to prevent the spread of this pathogen.

High concentration of coagulase-negative staphylococci carriage among bioaerosols of henhouses in Central China

Background

Coagulase-negative staphylococci (CoNS) are a group of opportunistic pathogens, which are widely spread in the environment. Animal breeding is an important source of pathogen spreading. However, the concentration and characteristics of CoNS in the bioaerosols of henhouses are unclear.

Results

In this study, we showed that CoNS were significantly increased in bioaerosols of henhouses during the first 60 days, and reached 2.0 × 10⁶ CFU/m³, which account for 75.4% of total bacteria. One hundred and two CoNS isolates from bioaerosols and nasal swabs of farmers were further identified, covering seven species. Among these, 41.2% isolates were Staphylococcus sciuri, which was the predominant species, followed by S. equorum, S. saprophyticus, S. haemolyticus, S. xylosus, S. arlettae and S. gallinarum. There were high rates of resistance to oxacillin in CoNS (49.0%), which were defined as Methicillin-Resistant CoNS (MRCoNS), and 36.3% isolates contained resistance gene mecA. Bioaerosol infection models showed that, chickens exposed to aerosolized S. sciuri had significant induction of inflammatory cytokines interleukin (IL)-1β, IL-6, IL-8 and IL-10 at 5 days post-infection (dpi) in lungs and at 7 dpi in spleens.

Conclusions

We reported a high concentration of CoNS in henhouses, and S. sciuri was the preponderant CoNS species. Antibiotic resistance analysis and bioaerosols infection of CoNS further highlighted its hazards on resistance and immunological challenge. These results suggested that, CoNS in bioaerosols could be one serious factor in the henhouses for not only poultry industry but also public health.

Staphylococcus aureus Isolated from Skin from Atopic-Dermatitis Patients Produces Staphylococcal Enterotoxin Y, Which Predominantly Induces T-Cell Receptor Vα-Specific Expansion of T Cells

While investigating the virulence traits of Staphylococcus aureus adhering to the skin of atopic-dermatitis (AD) patients, we identified a novel open reading frame (ORF) with structural similarity to a superantigen from genome sequence data of an isolate from AD skin. Concurrently, the same ORF was identified in a bovine isolate of S. aureus and designated SElY (H. K. Ono, Y. Sato'o, K. Narita, I. Naito, et al., Appl Environ Microbiol 81:7034-7040, 2015, https://doi.org/10.1128/AEM.01873-15). Recombinant SElY_bov had superantigen activity in human peripheral blood mononuclear cells. It further demonstrated emetic activity in a primate animal model, and it was proposed that SElY be renamed SEY (H. K. Ono, S. Hirose, K. Narita, M. Sugiyama, et al., PLoS Pathog 15:e1007803, 2019, https://doi.org/10.1371/journal.ppat.1007803). Here, we investigated the prevalence of the sey gene in 270 human clinical isolates of various origins in Japan. Forty-two strains were positive for the sey gene, and the positive isolates were from patients with the skin diseases atopic dermatitis and impetigo/staphylococcal scalded skin syndrome (SSSS), with a detection rate of ∼17 to 22%. There were three variants of SEY (SEY₁, SEY₂, and SEY₃), and isolates producing SEY variants formed three distinct clusters corresponding to clonal complexes (CCs) 121, 59, and 20, respectively. Most sey ⁺ isolates produced SEY in broth culture. Unlike SEY_bov, the three recombinant SEY variants exhibited stability against heat treatment. SEY predominantly activated human T cells with a particular T-cell receptor (TCR) Vα profile, a unique observation since most staphylococcal enterotoxins exert their superantigenic activities through activating T cells with specific TCR Vβ profiles. SEY may act to induce localized inflammation via skin-resident T-cell activation, facilitating the pathogenesis of S. aureus infection in disrupted epithelial barriers.

Staphylococci: Evolving Genomes

Staphylococci, and in particular Staphylococcus aureus, cause an extensive variety of infections in a range of hosts. The comprehensive analysis of staphylococcal genomes reveals mechanisms controlling the organism's biology, pathobiology, and dissemination. Whole-genome sequencing technologies led to a quantum leap in our understanding of bacterial genomes. The recent cost reduction of sequencing has resulted in unprecedented volumes of genomic information about S. aureus, one of the most sequenced bacterial species. Collecting, comparing, and interpreting big data is challenging, but fascinating insights have emerged. For example, it is becoming clearer which selective pressures staphylococci face in their habitats and which mechanisms allow this pathogen to adapt, survive, and spread. A key theme is the constant evolution of staphylococci as they alter their genome, exchange DNA, and adapt to new environments, leading to the emergence of increasingly successful, antibiotic-resistant, immune-evading, and host-adapted colonizers and pathogens. This article introduces the structure of staphylococcal genomes, details how genomes vary between strains, outlines the mechanisms of genetic variation, and describes the features of successful clones.

Comparison of livestock-associated and community-associated Staphylococcus aureus pathogenicity in a mouse model of skin and soft tissue infection

Industrial hog operation (IHO) workers are at increased risk of carrying Staphylococcus aureus in their nares, particularly strains that are livestock-associated (LA) and multidrug-resistant. The pathogenicity of LA-S. aureus strains remains unclear, with some prior studies suggesting reduced transmission and virulence in humans compared to community-associated methicillin-resistant (CA-MRSA) S. aureus. The objective of this study was to determine the degree to which LA-S. aureus strains contracted by IHO workers cause disease relative to a representative CA-MRSA strain in a mouse model of skin and soft tissue infection (SSTI). Mice infected with CC398 LA-S. aureus strains (IHW398-1 and IHW398-2) developed larger lesion sizes with higher bacterial burden than mice infected with CA-MRSA (SF8300) (p < 0.05). The greatest lesion size and bacterial burden was seen with a CC398 strain that produced a recurrent SSTI in an IHO worker. The LA-S. aureus infected mice had decreased IL-1β protein levels compared with CA-MRSA-infected mice (p < 0.05), suggesting a suboptimal host response to LA-S. aureus SSTIs. WGSA revealed heterogeneity in virulence factor and antimicrobial resistance genes carried by LA-S. aureus and CA-MRSA strains. The observed pathogenicity suggest that more attention should be placed on preventing the spread of LA-S. aureus into human populations.

Prevalence and Characterization of Food-Related Methicillin-Resistant Staphylococcus aureus (MRSA) in China

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen that is difficult to treat due to the multiresistance of the bacteria upon infection. From 2011 to 2016, 1581 S. aureus strains were isolated from 4300 samples from retail foods covering most provincial capitals in China. To determine the prevalence of food-related MRSA and its genetic background in China, antibiotic resistance, staphylococcal toxin genes, staphylococcal cassette chromosome mec (SCCmec) typing, spa-typing and MLST were carried out in this study. In total, 108 (7.4%) isolates were confirmed for MRSA by phenotyping (cefoxitin) and genotyping (mecA/mecC gene). A total of 52.8% (57/108) of the MRSA isolates belonged to clonal complex 59 (CC59) (ST59, ST338, and ST3355), which was the predominant clone in this study. These CC59 isolates carried SCCmec elements of type IV, V, or III and exhibited spa type t437, t441, t543, t163, t1785, or t3485, and half of them carried major virulence genes, such as the Panton-Valentine leucocidin (PVL) gene. The secondary clones belonged to ST9 (15.7%, 17/108) with a type of t899-SCCmec III and showed a broader range of antimicrobial resistance. The remaining MRSA isolates (31.5%, 34/108) were distributed in 12 different STs and 18 different spa types. All isolates harbored at least one of the enterotoxin genes, whereas only 4 isolates (3.70%) were positive for the toxic shock syndrome toxin tsst alleles. For antibiotic susceptibility testing, all isolates were resistant to more than three antibiotics, and 79.6% of the isolates were resistant to more than 10 antibiotics. Amoxycillin/clavulanic acid, ampicillin, cefoxitin, penicillin, ceftazidime, kanamycin, streptomycin, clindamycin, and telithromycin was the most common antibiotic resistance profile (55.6%, 60/108) in the study. In summary, the results of this study implied that the major food-related MRSA isolate in China was closer to community-associated MRSA, and some of the remaining isolates (ST9-t899-SCCmec III) were supposed to livestock-associated MRSA. In addition, most MRSA isolates showed resistance to multiple drugs and harbored staphylococcal toxin genes. Thus, the pathogenic potential of these isolates cannot be ignored. In addition, further studies are needed to elucidate the transmission routes of MRSA in relation to retail foods and to determine how to prevent the spread of MRSA.

High Genetic Similarity of MRSA ST88 Isolated From Pigs and Humans in Kogi State, Nigeria

We determined the prevalence and genetic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolated from pigs and humans between September 2013 and February 2015 in Kogi State, a central region in Nigeria. A total of 680 nasal swabs were collected and analyzed from pigs (n = 425) and “pig-contact” humans (n = 55) on 35 farms, and “non-pig-contact” humans (n = 200). MRSA was recovered from 20 (4.7%) pigs on 12 farms and 18 (7.0%) humans. Six (2.4%) of the human isolates were recovered from “pig-contact” humans, of which only three work on farms also harboring MRSA positive pigs. All 38 MRSA were resistant to β-lactams only, belonged to spa type t1603, sequence type (ST) 88, and mecA was associated with a SCCmec IVa element. Four isolates from a pig, a pig-contact human from the same farm, a pig-contact human from a pig farm in a different district, and a non-pig-contact human were subjected to whole genome sequencing (WGS). Core genome SNP analysis revealed high genetic similarity between strains (3–11 SNP differences), despite the temporal (2 year gap) and geographic (165 km) differences between isolates. Furthermore, these Nigerian isolates form a distinct clade when compared to other African MRSA ST88 isolates. All but one porcine strain was positive for scn suggesting a possible human origin and that pigs were either transiently contaminated by humans or result of a very recent human-to-pig transmission event. To our knowledge, this is the first report of genetically confirmed MRSA in pigs in Nigeria, which appear to be a typical CA-MRSA clone present in the human population.

Occurrence of Staphylococcus aureus in swine and swine workplace environments on industrial and antibiotic-free hog operations in North Carolina, USA: A One Health pilot study

Occupational exposure to swine has been associated with increased Staphylococcus aureus carriage, including antimicrobial-resistant strains, and increased risk of infections. To characterize animal and environmental routes of worker exposure, we optimized methods to identify S. aureus on operations that raise swine in confinement with antibiotics (industrial hog operation: IHO) versus on pasture without antibiotics (antibiotic-free hog operation: AFHO). We associated findings from tested swine and environmental samples with those from personal inhalable air samplers on worker surrogates at one IHO and three AFHOs in North Carolina using a new One Health approach. We determined swine S. aureus carriage status by collecting swab samples from multiple anatomical sites, and we determined environmental positivity for airborne bioaerosols with inhalable and impinger samplers and a single-stage impactor (ambient air) cross-sectionally. All samples were analyzed for S. aureus, and isolates were tested for antimicrobial susceptibility, absence of scn (livestock marker), and spa type. Seventeen of twenty (85%) swine sampled at the one IHO carried S. aureus at >1 anatomical sites compared to none of 30 (0%) swine sampled at the three AFHOs. All S. aureus isolates recovered from IHO swine and air samples were scn negative and spa type t337; almost all isolates (62/63) were multidrug resistant. S. aureus was recovered from eight of 14 (67%) ambient air and two (100%) worker surrogate personal air samples at the one IHO, whereas no S. aureus isolates were recovered from 19 ambient and six personal air samples at the three AFHOs. Personal worker surrogate inhalable sample findings were consistent with both swine and ambient air data, indicating the potential for workplace exposure. IHO swine and the one IHO environment could be a source of potential pathogen exposure to workers, as supported by the detection of multidrug-resistant S. aureus (MDRSA) with livestock-associated spa type t337 among swine, worker surrogate personal air samplers and environmental air samples at the one IHO but none of the three AFHOs sampled in this study. Concurrent sampling of swine, personal swine worker surrogate air, and ambient airborne dust demonstrated that IHO workers may be exposed through both direct (animal contact) and indirect (airborne) routes of transmission. Investigation of the effectiveness of contact and respiratory protections is warranted to prevent IHO worker exposure to multidrug-resistant livestock-associated S. aureus and other pathogens.

Parallel susceptibility testing of bacteria through culture-quantitative PCR in 96-well plates

OBJECTIVE

The methods combining culture and quantitative PCR(qPCR) offer new solutions for rapid antibiotic susceptibility testing(AST). However, the multiple steps of DNA extraction and cold storage of PCR reagents needed make them unsuitable for rapid high throughput AST. In this study, a parallel culture-qPCR method was developed to overcome above problems.

METHOD

In this method, bacteria culture and DNA extraction automatically and simultaneously completed through using a common PCR instrument as a controllable heating device. A lyophilized 16S rDNA targeted qPCR reagent was also developed, which was stable and could be kept at 4°C for long time and at 37°C for about two months.

RESULT

Testing of 36 P. aeruginosa isolates and 28 S. aureus isolates showed that the method had good agreements with the standard broth microdilution method, with an overall agreement of 97.22% (95% CI, 85.83-99.51) for P. aeruginosa and 96.43% (95% CI, 79.76-99.81) for S. aureus. This method could test 12 samples against a panel of up to 7 antibiotics simultaneously in two 96-well PCR plates within 4h, which greatly improves the testing efficiency of the culture-qPCR method.

CONCLUSION

With rapidness to obtain results and the capabilities for automation and multiple-sample testing, the parallel culture-qPCR method would have great potentials in clinical labs.

Epidemiology and Antibiotic Resistance Phenotypes of Diarrheagenic Escherichia Coli Responsible for Infantile Gastroenteritis in Ouagadougou, Burkina Faso

The emergence and persistence of multidrug-resistant (MDR) diarrheagenic Escherichia coli (DEC) causing acute diarrhea is a major public health challenge in developing countries. The aim of this study was to evaluate the resistance phenotypes of DEC isolated from stool samples collected from children less than 5 years of age with acute diarrhea living in Ouagadougou/Burkina Faso. From August 2013 to October 2015, this study was carried out on 31 DEC strains of our study conducted in "Centre Médical avec Antenne Chirurgicale (CMA)" Paul VI and CMA of Schiphra. DEC were isolated and identified by standard microbiological methods and polymerase chain reaction (PCR) method was used to further characterize them. Antimicrobial susceptibility testing was done based on the disk diffusion method. DEC isolates were high resistant to tetracycline (83.9%), amoxicillin (77.4%), amoxicillin clavulanic acid (77.4%), piperacillin (64.5%), and colistin sulfate (61.3%). The most resistant phenotype represented was the extended spectrum β-lactamase (ESBL) phenotype (67.7%). Aminoglycosides were 100% active on enteroinvasive E. coli (EIEC) and enterohemorrhagic E. coli (EHEC). All the DEC isolates exhibited absolute (100%) sensitivity to ciprofloxacin. Monitoring and studying the resistance profile of DEC to antibiotics are necessary to guide probabilistic antibiotic therapy, especially in pediatric patients.

The Prevalence of Antibiotic-Resistant Staphylococcus aureus Nasal Carriage among Industrial Hog Operation Workers, Community Residents, and Children Living in Their Households: North Carolina, USA

BACKGROUND

Antibiotic use in industrial hog operations (IHOs) can support the emergence of antibiotic-resistant (ABR) Staphylococcus aureus. The extent of ABR S. aureus exposure in IHO workers and children living in their households remains unclear.

OBJECTIVE

We investigated ABR S. aureus nasal carriage prevalence among adults with versus without occupational exposure to IHOs and among children living in their households.

METHODS

In total, 198 IHO worker-child household pairs and 202 community referent (CR) adult-child household pairs completed a questionnaire and provided a nasal swab which was analyzed for S. aureus, methicillin-resistant S. aureus (MRSA), multidrug-resistant S. aureus (MDRSA), absence of scn (putative marker of livestock association), and spa type.

RESULTS

S. aureus nasal carriage prevalence was higher among IHO (53%) compared with CR (31%) adults [adjusted prevalence ratio (aPR): 1.40; 95% confidence interval (CI): 1.07, 1.83], but MRSA nasal carriage prevalence was uncommon (2-3%) in IHO and CR adults. MDRSA nasal carriage prevalence was similar among IHO workers and CR adults (12% vs. 8%; aPR: 1.14; 95% CI: 0.56, 2.29). Nasal carriage prevalence was higher among IHO compared with CR children for S. aureus (49% vs. 31%; aPR: 1.50; 95% CI: 1.13, 1.99), MRSA (14% vs. 6%; aPR: 2.37; 95% CI: 1.14, 4.92), and MDRSA (23% vs. 8%; aPR: 2.64; 95% CI: 1.47, 4.75). We also found suggestive evidence of a higher prevalence of S. aureus, MRSA, and MDRSA among children living with an IHO worker who did versus did not report taking personal protective equipment (PPE) home from the IHO. Livestock-associated S. aureus nasal carriage predominated among IHO workers.

CONCLUSION

Our findings support the importance of further research on the prevalence and potential sources of exposure to ABR S. aureus among children living with IHO workers.

Livestock-Associated, Antibiotic-Resistant Staphylococcus aureus Nasal Carriage and Recent Skin and Soft Tissue Infection among Industrial Hog Operation Workers

Swine production work is a risk factor for nasal carriage of livestock-associated (LA-) Staphylococcus aureus and also for skin and soft tissue infection (SSTI). However, whether LA-S. aureus nasal carriage is associated with increased risk of SSTI remains unclear. We aimed to examine S. aureus nasal carriage and recent (≤3 months prior to enrollment) SSTI symptoms among industrial hog operation (IHO) workers and their household contacts. IHO workers and their household contacts provided a nasal swab and responded to a questionnaire assessing self-reported personal and occupational exposures and recent SSTI symptoms. Nasal swabs were analyzed for S. aureus, including methicillin-resistant S. aureus (MRSA), multidrug-resistant-S. aureus (MDRSA), absence of scn (livestock association), and spa type. S. aureus with at least one indicator of LA was observed among 19% of 103 IHO workers and 6% of 80 household members. Prevalence of recent SSTI was 6% among IHO workers and 11% among 54 minor household members (0/26 adult household members reported SSTI). Among IHO workers, nasal carriers of MDRSA and scn-negative S. aureus were 8.8 (95% CI: 1.8, 43.9) and 5.1 (95% CI: 1.2, 22.2) times as likely to report recent SSTI as non-carriers, respectively. In one household, both an IHO worker and child reported recent SSTI and carried the same S. aureus spa type (t4976) intranasally. Prevalence of scn-negative S. aureus (PR: 5.0, 95% CI: 1.2, 21.4) was elevated among IHO workers who reported never versus always wearing a face mask at work. Although few SSTI were reported, this study of IHO workers and their household contacts is the first to characterize a relation between nasal carriage of antibiotic-resistant LA-S. aureus and SSTI. The direction and temporality of this relation and IHO workers' use of face masks to prevent nasal carriage of these bacteria warrant further investigation.