The Multiple-Locus Variable Number Tandem Repeat Analysis (MLVA) of Staphylococuss aureus clinical isolates recovered from the Provincial Specialist Hospital in Lublin, Poland

Understanding the epidemiology and evolution of Staphylococcus aureus (SA) is crucial for implementing effective infection prevention and control measures. In this study, a short-term (4-month) and local molecular epidemiology of SA in the nosocomial setting was investigated using multiple-locus variable number tandem repeat (VNTR) analysis (MLVA). The study included 31 clinical SA isolates. The analysis was based on two complimentary panels encompassing 14 VNTR loci wherein a first-line assay comprised a subset of 10 loci (Panel 1), followed by a second subset of four loci (Panel 2). Thirty MLVA profiles were generated. Small amplicons were obtained for three out of the four loci included in Panel 2 for more than half of the isolates, making the calculation of the number of repeats impossible. Therefore, phylogenetic clustering was based on the analysis of basic loci included in Panel 1 (which identified two major genetic clusters). Cluster I included 26 (84%) isolates, among which 14 were classified into five sub-clusters (cutoff value ≥65%). Only one pair of the isolates shared an identical MLVA pattern. Our study indicates the usefulness of a MLVA tool comprised of a primary subset of 10 loci to track the possibility of SA intra-hospital transmission. We report a high genetic diversity of the isolates and suggest a limited degree of intra- and inter-ward SA transmission. Further genetic studies are necessary to investigate the nature of the small alleles yielded in Panel, as their subset can provide even higher resolution of the assay.