Antimicrobial susceptibilities and serotypes of Streptococcus pneumoniae in southwestern Japan and correlation of penicillin-binding protein 2b and 2x mutations in susceptibilities of penicillin G and cefotaxime

Abstract

MICs of penicillin G and other drugs and serotypes were determined for 218 strains of Streptococcus pneumoniae isolated from children in southwestern Japan. Twenty-one (9.6%) and 81 (37.2%) isolates were penicillin-resistant (MIC >/=2.0 microg/ml) and intermediate (MIC 0.13-1.0 microg/ml), respectively. Panipenem was most active parenteral agent against penicillin-intermediate (MIC(90) 0.125 microg/ml) and -resistant strains (MIC(90) 0.25 microg/ml). Among oral beta-lactam agents, cefditoren had good activity against penicillin-intermediate and resistant strains (MIC(90) 0.5/1.0 microg/ml). Serogroup 6 was the most prevalent (65/218) among all strains and 19F (44 strains) was the most prevalent among penicillin-intermediate and -resistant strains. Both pbp2b resistant and susceptible genes were found in penicillin-intermediate strains. Pbp2x resistant genes were found in 33 of 80 (41.3%) cefotaxime-susceptible strains. These results suggest that possible resistance mechanisms may occur even in drug susceptible strains and that drug susceptibility survey should be updated carefully in Japan.