[Molecular biological analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates of human and animal origin].

Abstract

Objectives: The aim of this study was to compare methicillin-resistant Staphylococcus aureus (MRSA) isolates originating from the human population (hospitalized patients) with those from the animal sector (livestock and companion animals).

Material and methods: Over an 11-month period from 2023 to 2024, MRSA isolates were obtained from both human and animal sources. The collected bacterial strains underwent antimicrobial susceptibility testing using the standard microdilution method according to EUCAST criteria. Additionally, a molecular biological analysis was performed to detect the presence of the mecA/C genes, selected virulence factors (PVL, TSST-1, enterotoxins, and exfoliatins), and spa type classification.

Results: From clinical samples obtained from patients at the University Hospital Olomouc and the Military Hospital in Olomouc, 3 189 Staphylococcus aureus (SA) isolates were detected. Of these, 60 were identified as MRSA using standard laboratory methods (2 % prevalence). These isolates were most frequently classified as spa type t003 (45 %), with 89 % of the identified MRSA isolates possessing at least one of the selected virulence genes. In 19 % of the isolates, genes for Panton-Valentine leukocidin (PVL) were identified. In animal samples (a total of 113 SA isolates), the MRSA prevalence was 17 %, with the most common spa type being t034 (53 %). The MRSA isolates of animal origin did not possess any of the tested virulence factors.

Conclusions: The low observed prevalence of MRSA in humans indicates effective adherence to hygiene standards in healthcare facilities. Conversely, the high carriage rate of MRSA in the animal population should not be overlooked. Companion animals colonized by MRSA may pose a risk to themselves and their owners. Livestock colonized by MRSA strains may present a potential risk to personnel handling them and could also serve as a source of contaminated food products.