Abstract
New human pathogens can emerge from the livestock-human interface and spread into human populations through many pathways including livestock products. Occupational contact with livestock is a risk factor for exposure to those pathogens and may cause further spreading of those pathogens in the community. The current study used whole genome sequencing to explore nasal Staphylococcus aureus obtained from hog slaughterhouse workers and their community members, all of whom resided in a livestock-dense region in rural North Carolina. Sequence data were analyzed for lineage distribution, pathogenicity-related genomic features, and mobile genetic elements. We observed evidence of nasal S. aureus differences between hog workers and non-workers. Nasal S. aureus from hog workers showed a greater lineage diversity than nasal S. aureus from community residents. Hog worker isolates were less likely to carry the φSa3 prophage and human-specific immune evasion cluster genes than community resident isolates (φSa3 prophage: 54.5% vs. 91.7%, Benjamini-Hochberg (BH) corrected p = 0.035; immune evasion cluster genes: 66.7% vs. 100%, BH p = 0.021). Hog worker isolates had a lower prevalence and diversity of enterotoxins than community resident isolates, particularly lacking the enterotoxin gene cluster (39.4% vs. 70.8%, BH p = 0.125). Moreover, hog worker isolates harbored more diverse antibiotic resistance genes, with a higher prevalence of carriage of multiple resistance genes, than community resident isolates (75.8% vs. 29.2%, BH p = 0.021). Phylogenetic analysis of all ST5 isolates, the most abundant lineage in the collection, further supported separation of isolates from hog workers and non-workers. Together, our observations suggest impact of occupational contact with livestock on nasal S. aureus colonization and highlight the need for further research on the complex epidemiology of S. aureus at the livestock-human interface.
Highlights
Staphylococcus aureus is an important pathogen causing significant clinical and public health burdens
In our previous cross-sectional study conducted at a hog slaughter/processing plant in a livestock-dense region in North Carolina, we found that the prevalence of nasal carriage of S. aureus was similar in hog workers and their household and community members, S. aureus isolates from hog workers were resistant to a greater number of antibiotic classes [9]
We successfully sequenced 77 of the 79 nasal isolates that were obtained from 336 residents in rural North Carolina (WGS statistics in S4 Table)
Summary
Staphylococcus aureus is an important pathogen causing significant clinical and public health burdens. This situation is more serious because of the global emergence of antibiotic resistance, including methicillin resistance, in S. aureus [1, 2]. Certain risk factors for infections by CA-MRSA have been characterized [3], reservoirs of resistant and/or virulent S. aureus outside of health care settings remain poorly understood, and the origins and transmission routes of S. aureus in the community are not elucidated [5]. Recent studies further show that livestock-associated occupational groups are at increased risk of nasal carriage of antibiotic resistant S. aureus, including MRSA and multidrug resistant S. aureus (MDRSA), compared to the general population [8,9,10]. While findings to date indicate that occupational contact with livestock is a risk factor for exposure to livestockassociated S. aureus, including resistant strains, few studies have examined influences of such exposure on the S. aureus population in human nostrils, this information could have important implications for the epidemiology of S. aureus
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