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.
Keywords: livestock, human, methicillin-resistant S. aureus , multidrug-resistant S. aureus , transmission