CLONAL DISTRIBUTION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS INPOLAND

We report on a study of 158 methicillin-resistant Staphylococcus aureu s (MRSA) clinical isolates obtained from 1990 to 1996 in 18 different hospitals in Poland, All isolates were recovered from infection and ca rriage sites of patients, carriage sites of health care personnel, and hospital environment samples, Fifty-seven MRSA strains described here were studied previously and these were divided into two different clu sters according to the degree of heterogeneity of methicillin resistan ce expression, The aim of this study was to extend the correlation bet ween the two clusters and identify the clonal identities among all iso lates by a combination of different methodologies: (i) analysis of mec A polymorphs and Tn554 insertion patterns and (ii) determination of pu lsed-field gel electrophoresis patterns of chromosomal SmaI digests, N inety-seven of 158 strains showed a heterogeneous expression of resist ance to methicillin, Among these, 75 (77.3%) were ClaI-mecA type I, Cl aI-Tn554 type NH (NH, no homology with transposon Tn554), and pulsed-f ield gel electrophoresis (PFGE) pattern A (I::NH::A); 10 isolates were III::B::M (10.3%); and the remaining clones included a few or single isolates. The isolates with homogeneous expression of resistance to me thicillin (n = 61) were predominantly ClaI-mecA type III (49 of 61 [80 .3%]) but had great variability in their ClaI-Tn554 and PFGE patterns. This study confirmed the existence of two main clusters of MRSA in Po land.