ABSTRACT
BACKGROUND: The resistance of Streptococcus pneumoniae to penicillin has been rapidly increasing during the recent three decades. In Korea, we found the incidence of penicillin resistance (PR) to pneumococci was 81% for the clinical isolates in our hospital, and 89% for the colonizing isolates of day-care center around Seoul. Alterations in penicillin-binding protein (PBP) 2B gene have been known to be associated with a resistance to penicillin. We tried to reveal the characteristics of PR of Korean pneumococcal strains through sequencing analysis of PBP 2B gene. METHODS: We determined the nucleotide sequences of 346 bp of a variable region among PBP 2B gene for 12 PR strains and 6 penicillin susceptible (PS) strains isolated in Korea. Phylogenetic tree using PAUP program was made to compare our DNA sequences with those of South African strains. RESULTS: Sequence homology of PS strains was ranged from 99.4% to 100% in Korean PS strain compared to reference strain, R6, except one strain (93.9%). PR strains showed homology of 95.1% to 100% compared to the South African 56762 strain. Phylogenetic analysis based on 346 bp of PBP 2B gene showed that Korean and South African strains formed different monophyletic groups according to the PR/PS patterns. Five specific amino acid changes compared to the PS R6 strain in the position 228, 232, 233, 244, and 261 were noted with a decreased hydrophilicity by Kyte-Doolittle assay. CONCLUSIONS: Our data suggest that the amino acid changes in the PBP 2B are associated with PR in S. pneumoniae, and that a part of Korean PR strains might be originated from a South African PR strain.