CHARACTERIZATION OF 2 DIFFERENT CLUSTERS OF CLONALLY RELATED METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS STRAINS BY CONVENTIONAL AND MOLECULAR TYPING

The DNA fragments of 28 distinct isolates of methicillin-resistant Sta phylococcus aureus (MRSA) originating from different hospitals in Wars aw and Lodz, were studied. They were obtained by cleavage with restric tion endonuclease SmaI and subsequently analysed by pulsed-field elect rophoresis. Sixteen different patterns were seen and clusters of relat ed strains were clearly distinguishable. Minor differences in fragment patterns within these clusters and among epidemiologically related st rains, revealed genomic rearrangements in the course of clonal dissemi nation of particular strains. The isolates were also checked for the e xpression of methicillin resistance. Isolates with heterogenous and ho mogenous phenotypes, fell into clearly distinct clusters and thus form ed two clonally related MRSA strains. Differences were also seen with phage and biochemical typing, and anti-microbial resistance patterns.