Resistance, serotype and genetic diversity of Streptococcus pneumoniae-resistant strains isolated in the West Pomerania region of Poland in the years 2001-2005.

The aim of this study was to analyse the resistance patterns, serotypes and genetic diversity of Streptococcus pneumoniae-resistant strains isolated in the West Pomerania region of Poland. They were clinical isolates obtained during a 5-year study (2001-2005) mainly from ambulatory patients with upper respiratory tract infections. The strains showed resistance to 8 out of 9 tested antibiotics (except vancomycin) and 53.8% of the strains were multidrug-resistant (MDR). The increase over time in the number of MDR strains and in resistance degrees was not statistically significant. Resistance to cotrimoxazole was the most frequent (86.7%). Penicillin nonsusceptibility was shown in 38% of the strains and resistance to macrolides in 36.7% of the strains, mainly of MLS(B) phenotype (94.1%). A significant resistance increase was only observed for beta-lactam antibiotic. The population of S. pneumoniae-resistant strains in our region presented 31 resistance patterns, 13 serotypes and a high genetic diversity-70 pulse field gel electrophoresis (PFGE) profiles have been described: 44 of them were unique and 26 clusters consisted of 2 to 30 strains similar by more than 87%. Cluster I, grouping 30 strains of similar resistant patterns (TSH: 70%, SH, TH, T, H, S) and mainly serotype 19F, isolated over the 5 years of the study, could represent a new national clone. The polysaccharide 23-valent vaccine covers 83.5%, while the conjugated 7-, 9- and 11-valent vaccines cover 79.1-79.7% of the resistant strains collected in our region. A statistically significant decrease of vaccine coverage in time has been noted.