Genetic characterization of methicillin-resistant Staphylococcus aureus (MRSA) stains through spa-typing in a tertiary Greek hospital

The aim of the present study was to investigate the MRSA spa types in a tertiary hospital in northern Greece and focusing on the WGS analysis of two specific MRSA isolates. Methods: All MRSA strains isolated from July 2019 until June 2020 in “Georgios Gennimatas” General Hospital of Thessaloniki, Greece were included in the study. Identification and antimicrobial susceptibility testing were performed using VITEK II automated system. Spa typing was conducted in all strains. A minimum spanning tree (MST) was used to display the spa-type frequencies and the genetic distance between them. MLST assignment was also performed using the online MLST-DTU tool. Two t127-MRSA isolates (IM-MRSA and PD-MRSA) were selected for whole-genome sequencing (WGS) analysis.Results: A total of 39 MRSA isolates from an equal number of patients were included in the study. Twenty-two different spa types were detected, with t002, t003, and t422 being the most frequent (5/39, 12.8% each), followed by t1994 (4/39, 10.3%), t127, and t328 (2/39, 5.1%, each). The isolates showed genetic diversity between them, according to the MST. IM-MRSA and PD-MRSA were assigned to ST9-XII-t127 and ST1-IVa-t127, respectively. In addition, they carried different combinations of antimicrobial resistance genes and plasmids.