title: High frequency of erythromycin A resistance and distribution of mefE and ermB genes in clinical isolates of Streptococcus pneumoniae in Japan.
abstract: The ermB and mefE genes are important in terms of their responsibility for macrolide resistance in Streptococcus pneumoniae. We investigated the distribution of the ermB and mefE genes in erythromycin A-resistant S. pneumoniae isolated in our hospital during the period 1995-1998. All amoxicillin-low-susceptible isolates were considered to be resistant to erythromycin A. All isolates with resistance to erythromycin A (minimum inhibitory concentrations [MICs], > or =0.5 microg/ml) possessed ermB or mefE genes. The MICs of erythromycin A for most mefE-positive isolates ranged from 0.5 to 2 microg/ml. On the other hand, approximately 85% of ermB-positive isolates demonstrated high-level resistance to erythromycin A (MICs, > or =4 microg/ml) while the others showed low-level resistance (MICs, 0.5 to 2 microg/ml). In ermB-positive isolates with low-level resistance, high-level resistant mutants were selected with a frequency of 3.1 x 10(-6)-1.8 x 10(-3) on agar containing 4-32 MIC of erythromycin A, whereas in mefE-positive isolates, no high-level resistant mutants were detected. Mutants from ermB-positive isolates with low-level resistance showed reversibility and heterogeneity. Our data indicated a wide distribution of erythromycin A-resistant isolates with mefE or ermB genes among amoxicillin-low-susceptible S. pneumoniae in Japan. In addition, it is likely that ermB-positive isolates with low-level resistance show heterogeneous high-level resistance.
authors.affiliation: Department of Microbiology, Toho University School of Medicine, Tokyo, Japan. hiroki.okamoto@aventis.com
authors.forename: Hiroki
authors.initials: H
authors.lastname: Okamoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tateda
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ishii
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Takao
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Miyazaki
authors.forename: Keizo
authors.initials: K
authors.lastname: Yamaguchi
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D008565:Membrane Proteins; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C431304:MefE protein, Streptococcus pneumoniae; D008565:Membrane Proteins; D004917:Erythromycin; D000658:Amoxicillin; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase