MELDRA IVBULE1, EDVĪNS MIKLAŠEVIČS2, LIENE ČUPĀNE2, LAIMA BĒRZIŅA3, ANDRIS BĀLIŅŠ4 and ANDA VALDOVSKA5

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. K e y w o r d s: Staphylococcus aureus, antimicrobial resistance zoonosis, MRSA in pig farms Ivbule M. et al. 3 384 amount of pigs. All three farms were closed pig farms without any other commercially bred farm animals presented and were located in different areas of Latvia. These farms had farrow-to-finish pig production with size varying from 1500 to 12000. Each farmer also completed a questionnaire on farm size, internal and external biosecurity measures and antimicrobial drug use over the preceding 6 months. The characterising of each pig complex is described in Table I. The body condition of swine was scored according to Stockmanship standards (Carr, 1998). Evaluation of animal welfare, hygiene, and microclimate conditions in pig complexes were based on Council Directive 2008/120/EC of 18 December 2008 laying down minimum standards for the protection of pigs and microclimate standards according to Muirhead (Muirhead et al., 2013) suggestions. Sample collection. Pigs were divided into four groups: pre-weaned piglets with sows, 3–3.5 month old piglets, 4–4.5 month old piglets and fattening pigs (shortly before slaughter) (see Table II). There were collected nasal (n = 305) and rectal (n = 305) samples from all farms. There were taken milk samples (n = 69) and air samples (n = 22). In total amount 305 pigs and 716 microbiological samples were investigated. Samples were taken from randomly selected healthy pigs. Nasal and rectal samples were collected with sterile transport swabs (Meus, IT). Milk samples were collected in 50 ml amount sterile tubes without preservative. Air samples were collected using Baird-Parker Agar plates according to Koch’s sedimentation method (Boucher et al., 2010). The number of sampled environment, workers and pigs per age category per farm is shown in Table II. One swab from each worker was taken from both nares. Environmental samples were obtained in every compartment in. All microbiological samples were stored in 4°C and first isolation was made during 24 hours after sample collection. Microbiological examination. Microbial examination was performed in the Latvia University of Agriculture (LUA), Faculty of Veterinary Medicine. Samples from transport swabs were transferred on Baird-Parker Agar with egg yolk supplement (Becton, Dickinson, USA), and incubated in 37°C for 24 hours according to LVS EN ISO 6888-1:1999 A1:2003 ‘Microbiology S. aureus and other species – Part 1: Technique using Baird-Parker agar medium – Amendment 1: Inclusion of precision data. After incubation positive colonies were inoculated on Mannitol Salt Agar (MSA) plates (Biolife, IT) at 37°C for 24 hours and suspended in Brain Heart infusion (BHI) (Acumedia manufacturers). Staphylococcus coagulase tube test (Becton Dickinson, Number of sows 25