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 MLSB 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.