6.4 Environmental and occupational exposures to antimicrobial-resistant Staphylococcus aureus related to livestock agriculture

摘要

Background: Administration of antimicrobials to food animals, including non-therapeutically, can select for drug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA). In the United States, understanding of environmental and occupational MRSA exposure in settings related to livestock agriculture is improving, but evidence about occurrence of multidrug-resistant S. aureus (MDRSA) in these settings remains unclear. Additionally, little evidence exists comparing MDRSA nasal carriage among workers raising livestock with versus without antimicrobial selective pressure. Aims: To summarize evidence from recent studies of MDRSA occurrence in surface waters proximal to industrial hog operation fecal waste sprayfields and MDRSA nasal carriage prevalence among industrial compared with antibiotic-free livestock operation workers. Methods: Surface water samples from sites proximal to industrial hog operation fecal waste sprayfields and nasal swabs from workers at industrial and antibiotic-free livestock operations were collected. Antimicrobial susceptibility to 15 drugs and the molecular characteristics of S. aureus isolates was determined, including markers of livestock-association (tet-resistant, ST398, scn negative). MDRSA was defined as resistance to three or more classes of antimicrobials. Results: MRSA, MDRSA, and tet-resistant S. aureus isolates were detected in surface waters proximal to industrial hog operation fecal waste sprayfields. Industrial livestock operation workers carried MRSA and MDRSA that tended to be tet-resistant, ST398, and lacking the human-adapted scn gene, whereas MRSA and MDRSA isolates possessing all three of these livestock-associated characteristics were not observed among antibiotic-free livestock operation workers. Conclusions: The observed environmental and occupational occurrence of MRSA and MDRSA raises important questions about the safety of fecal waste management and antimicrobials uses in livestock production.