Antimicrobial resistance of Haemophilus influenzae isolated from the nasopharynx of Japanese children with acute otitis media

Abstract

Beta-lactamase-producing (BLP) strains having the bla gene were identified in 16 isolates (2.5%). PGM strains were identified in 279 isolates (43.3%). There were 242 PGM1-non-BLP strains (37.6%) with mutations in the variable mutated locus of ftsI, 35 PGM2-non-BLP strains (5.4%) with mutations in the highly mutated locus of ftsI and 2 BLP-PGM strains (0.3%) with mutations in ftsI that produced beta-lactamase. BLP-non-PGM strains producing beta-lactamase without mutations in ftsI were identified in 14 isolates (2.2%). MICs of PGM1-non-BLP strains to AMP were 0.5-2.0 microg/ml. The MIC90 of CDN to the PGM1-non-BLP strains was the lowest (0.06 microg/ml). The proportion of PGM1-non-BLP strains increased rapidly during 1999-2002 and then decreased in 2003. In contrast, the proportion of PGM2-non-BLP strains increased in 2003.