IntroductionMethicillin-resistant Staphylococcus aureus (MRSA) is a highly resistant and difficult to cure zoonotic microorganism, which makes up a large part of food toxic infections and has shown high prevalence among pig population all over the world. The aim of the study was to establish the occurrence of MRSA in slaughterhouses, evaluate its antimicrobial resistance, and verify whether there are any differences or similarities with reference to other European countries.Material and MethodsA total of 100 pigs, 105 carcasses, 19 workers, and 24 samples from the environment of several slaughterhouses were examined by conventional microbial and molecular methods.ResultsIn total, 78 MRSA isolates were found. MRSA prevalence in slaughtered pigs varied from 8.0% to 88.6% depending on the slaughterhouse, reaching higher prevalence in slaughterhouses with higher slaughter capacity. In total, 21.1% of all workers were carriers of MRSA and 6.7% of carcasses were contaminated with MRSA. The 98.2% of MRSA isolates were resistant to penicillin, 89.1% to tetracycline, 60.1% to erythromycin, 65.5% to gentamycin, and 15 different spa types were found, among which spa type t01333 was most widespread.ConclusionThe study indicated that MRSA prevalence and spa types differed according to slaughterhouse slaughter capacity and good hygiene practices. Quite high MRSA occurrence among slaughterhouse workers is one of the main factors which increase pork contamination risk.

Methicillin resistant Staphylococcus aureus (MRSA) is widespread worldwide in different types of animal species and as a zoonosis takes a great risk for human health not only as a food toxicoinfection, but also as a highly resistant pathogen causing serious soft tissue infectious, septicaemia and even death. One of the most affected food-producing animal species is swine in the production of which new antibiotics in big amounts are used more and more continuously, increasing antimicrobial resistance. In this study several commercial pig farms and pigs with different age groups as well as farm workers and samples from environment were examined with the purpose of detecting MRSA prevalence and evaluating antimicrobial resistance. A total of 85 isolated MRSA strains were characterised by conventional microbial and molecular methods. MRSA was found in all farms. MRSA prevalence in different pig age groups and farms varied from none to 79.2% reaching higher values among 3-3.5 (26.6%) and 4-4.5 (31.9%) old pigs. The 98.7% of 74 further investigated MRSA isolates were resistant to penicillin, 94.9% to tetracycline, 45.6% to cephalexin and 10 different spa types were found among which spa type t011 was the most widespread. To the best of our knowledge, this is the first time MRSA was researched in sow milk and the first description of the presence of MRSA in several age groups of pigs in Latvia.

Promocijas darbs izstrādāts Latvijas Lauksaimniecības universitātes Veterinārmedicīnas fakultātes Pārtikas un vides higiēnas institūta mikrobioloģijas laboratorijā;  Latvijas Lauksaimniecības universitātes Biotehnoloģiju zinātniskajā laboratorijā;  Rīgas Stradiņa universitātes Onkoloģijas institūtā.