TDK conference 2019

Methicillin-resistant Staphylococcus aureus (MRSA) is a major concern for both public and veterinary medicine. The livestock-associated (LA-)MRSA lineage CC398 has been recognised as an occupational hazard for people in contact with pigs and it can occasionally be introduced into hospitals. After its first report from swine and swine farmers in 2005, a Europe-wide baseline study was conducted on MRSA prevalence in 2008. With the participation of more than 5000 holdings (breeding and production holdings) from 26 countries, the prevalence of MRSA-positive production and breeding holdings was 14.0%, and 26.9%, respectively. Hungary reported 0% and 2,1% MRSA prevalence for 40 breeding and 141 production farms surveyed, respectively. Data on the matter lack from the past 10 years in Hungary. Between April 2019 and August 2019, pooled dust samples were collected randomly from Hungarian wide-scale swine farms and were tested for MRSA. Nasal swabs of veterinarians related to the holdings were also analysed. A questionnaire about basic farm data and MRSA-status was also enclosed. All MRSA isolates were characterised by molecular methods (spa-typing, SCCmec-typing) and by phenotypic antimicrobial susceptibility testing. Strains of human and environmental origin were compared to unravel possible occupational hazard. Results were evaluated regarding the data of the questionnaires.

A total of 21 unrelated Hungarian production holdings were tested and revealed 90,5% (2/21) MRSA prevalence. From the 19 MRSA-positive samples, 21 different strains were isolated. All strains could be assigned to the clonal complex 398 according to their spa-type, while SCCmecV predominated amongst the isolates (20/21). From the 21 farms, 11 human samples arrived and 8 resulted in MRSA-positivity (72,7%). In two cases, the farms were MRSA-negative. In three cases, strains of the same genotype were isolated both from the environmental and the nasal sample, while in three cases they differed by their spa-type. All but one human derived MRSA strains were also classified as livestock-associated CC398. Most of the strains showed resistance to at least 5 antimicrobial agents, including beta-lactams, tetracyclines, clindamycin, sulphonamides and pleuromutilins.

This is the first prevalence study on MRSA of swine origin in Hungary after 10 years. Despite the limited size of our sample, it seems that the proportion of positive farms has increased dramatically. The results of the simultaneous sampling of swine veterinarians call attention to the occupational hazard meant by the environmental burden of MRSA on swine farms and poses the risk of mutual exchange of clinically important resistance genes from livestock environment to microbiome of human medical interest.