A case control study of environmental and occupational exposures associated with methicillin resistant Staphylococcus aureus nasal carriage in patients admitted to a rural tertiary care hospital in a high density swine region

Abstract

BackgroundDistinct strains of methicillin resistant Staphylococcus aureus (MRSA) have been identified on livestock and livestock workers. Industrial food animal production may be an important environmental reservoir for human carriage of these pathogenic bacteria. The objective of this study was to investigate environmental and occupational exposures associated with nasal carriage of MRSA in patients hospitalized at Vidant Medical Center, a tertiary hospital serving a region with intensive livestock production in eastern North Carolina.MethodsMRSA nasal carriage was identified via nasal swabs collected within 24 hours of hospital admission. MRSA carriers (cases) were gender and age matched to non-carriers (controls). Participants were interviewed about recent environmental and occupational exposures. Home addresses were geocoded and publicly available data were used to estimate the density of swine in residential census block groups of residence. Conditional logistic regression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of the scn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates was performed, and the Diversilab® system was used to match the isolates to USA pulsed field gel electrophoresis types.ResultsFrom July - December 2011, 117 cases and 119 controls were enrolled. A higher proportion of controls than cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census block groups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor from a farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, all were scn positive. Twenty-two isolates belonged to clonal complex 5.ConclusionsAbsence of livestock workers in this study precluded evaluation of occupational exposures. Higher odds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry.

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

“…Several studies revealed that the density of pigs in farms was associated with LA-MRSA acquisition [ 38 , 39 , 40 ]. The study in Denmark showed that living near pig farms was a risk factor for LA-MRSA carriage [ 41 ].…”

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization and infection isolates in a Veterans Affairs hospital

“…Specifically, we did not find any typical livestock associated spa types (CC398 or ST9), tetracycline resistance was uncommon, and few isolates were negative for the scn gene. Similarly, studies in North Carolina [ 30 ] and Pennsylvania found that proximity to livestock operations and swine manure application to crop fields is associated with increased odds for MRSA infection [ 31 ]. Yet, in those studies, no typical LA-MRSA spa types were found, and few isolates were scn -negative [ 30 , 32 ].…”

“…Similarly, studies in North Carolina [ 30 ] and Pennsylvania found that proximity to livestock operations and swine manure application to crop fields is associated with increased odds for MRSA infection [ 31 ]. Yet, in those studies, no typical LA-MRSA spa types were found, and few isolates were scn -negative [ 30 , 32 ]. Our previous results from Iowa, Ohio, and Connecticut have shown that while CC398 is the most common sequence type [ 8 , 9 , 22 ], other genetic types have also been found to colonize swine [ 22 - 24 , 33 ].…”

Antibiotic discovery throughout the Small World Initiative: A molecular strategy to identify biosynthetic gene clusters involved in antagonistic activity

“…Moreover, resistance is not confined to nosocomial settings. Environmental strains also encode resistance (Leamer, Clemmons, Jordan, & Pacha, ; Rose et al., ; Rothrock, Hiett, Guard, & Jackson, ) and contribute to life‐threatening community‐acquired infections (Furuya‐Kanamori et al., ; Leamer et al., ; McKenna, ; Schinasi et al., ). Escalating the crisis is the shift of major pharmaceutical companies away from antibiotic discovery and synthesis due to low profitability (Pammolli, Magazzini, & Riccaboni, ; Scannell, Blanckley, Boldon, & Warrington, ).…”

“…Moreover, resistance is not confined to nosocomial settings. Environmental strains also encode resistance (Leamer, Clemmons, Jordan, & Pacha, 2013;Rose et al, 2009;Rothrock, Hiett, Guard, & Jackson, 2016) and contribute to lifethreatening community-acquired infections (Furuya-Kanamori et al, 2015;Leamer et al, 2013;McKenna, 2008;Schinasi et al, 2014).…”