Incidence and characterisation of methicillin-resistant Staphylococcus aureus (MRSA) from nasal colonisation in participants attending a cattle veterinary conference in the UK.

Gavin K Paterson,M Estée Török,Matthew J Ellington,Julian Parkhill,Emily F Craven,Ruth N Zadoks,Anders Rhod Larsen,Ewan M Harrison,Sharon J Peacock,Mark A Holmes,Andreas Petersen

doi:10.1371/journal.pone.0068463

Abstract

We sought to determine the prevalence of nasal colonisation with methicillin-resistant Staphylococcus aureus among cattle veterinarians in the UK. There was particular interest in examining the frequency of colonisation with MRSA harbouring mecC, as strains with this mecA homologue were originally identified in bovine milk and may represent a zoonotic risk to those in contact with dairy livestock. Three hundred and seven delegates at the British Cattle Veterinarian Association (BCVA) Congress 2011 in Southport, UK were screening for nasal colonisation with MRSA. Isolates were characterised by whole genome sequencing and antimicrobial susceptibility testing. Eight out of three hundred and seven delegates (2.6%) were positive for nasal colonisation with MRSA. All strains were positive for mecA and none possessed mecC. The time since a delegate’s last visit to a farm was significantly shorter in the MRSA-positive group than in MRSA-negative counterparts. BCVA delegates have an increased risk of MRSA colonisation compared to the general population but their frequency of colonisation is lower than that reported from other types of veterinarian conference, and from that seen in human healthcare workers. The results indicate that recent visitation to a farm is a risk factor for MRSA colonisation and that mecC-MRSA are rare among BCVA delegates (<1% based on sample size). Contact with livestock, including dairy cattle, may still be a risk factor for human colonisation with mecC-MRSA but occurs at a rate below the lower limit of detection available in this study.

Highlights

Staphylococcus aureus is an important opportunistic pathogen associated with nosocomial and community-acquired infections in people, and is responsible for disease in animals where it is most economically significant as a cause of bovine mastitis [1,2].Methicillin-resistant S. aureus (MRSA) have acquired one of a number of staphylococcal cassette chromosome mec elements (SCCmec) [3], carrying a gene encoding a penicillin binding protein (PBP 2a) with low affinity for b-lactam antibiotics [4]
Since 2005 there have been a number of reports suggesting that the rate of carriage of MRSA is higher in people living or working on pig farms than in the wider community due to zoonotic acquisition of MRSA, primarily belonging to the clonal complex (CC) 398 lineage
A search of human S. aureus isolates from national collections in the UK and Denmark identified MRSA with mecC, originating from human carriage and disease as well as further bovine isolates from England

Summary

Introduction

Staphylococcus aureus is an important opportunistic pathogen associated with nosocomial and community-acquired infections in people, and is responsible for disease in animals where it is most economically significant as a cause of bovine mastitis [1,2].Methicillin-resistant S. aureus (MRSA) have acquired one of a number of staphylococcal cassette chromosome mec elements (SCCmec) [3], carrying a gene (mecA) encoding a penicillin binding protein (PBP 2a) with low affinity for b-lactam antibiotics [4]. Since 2005 there have been a number of reports suggesting that the rate of carriage of MRSA is higher in people living or working on pig farms than in the wider community due to zoonotic acquisition of MRSA, primarily belonging to the clonal complex (CC) 398 lineage. A search of human S. aureus isolates from national collections in the UK and Denmark identified MRSA with mecC, originating from human carriage and disease as well as further bovine isolates from England. Isolates with identical sequence types and spa-types were found in human and bovine isolates, suggesting transmission between the two host populations. Strengthening this supposition of interspecies transmission, work in Denmark has identified mecC MRSA human isolates from two different farms that are identical by sequence

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