Genotypes and related factors reflecting macrolide resistance in pneumococcal pneumonia infections in Japan

Although macrolide-resistant Streptococcus pneumoniae strains possessing either the ermB or mefA gene are very common in Japan, clinical and microbial factors in community-acquired pneumonia (CAP) caused by different macrolide resistance genotypes have not been evaluated. A multicenter study of CAP caused by S. pneumoniae was performed in Japan from 2003 to 2005. A total of 156 isolates were tested for susceptibility to antibiotics correlated with ermB and mefA genotyping. Independent relationships between tested variables and possession of either the ermB or the mefA gene were identified. Of 156 isolates, 127 (81.4%) were resistant to erythromycin, with the following distribution of resistance genotypes: ermB alone (50.0%), mefA alone (23.7%), and both ermB and mefA (7.1%). All isolates were susceptible to telithromycin. By multivariate analysis, oxygen saturation of <90% on admission increased the risk for ermB-positive pneumococcal pneumonia (odds ratio [OR] = 11.1; 95% confidence interval [CI] = 1.30 to 95.0; P = 0.03), but there were no associations with mefA or with ermB mefA positivity. Penicillin non-susceptibility was associated with mefA-positive and with ermB- and mefA-positive isolates (OR = 14.2; 95% CI = 4.27 to 46.9; P < 0.0001 and P < 0.0001, respectively) but not with ermB-positive isolates. The overall patient mortality was 5.1%. Mortality, the duration of hospitalization, and the resolution of several clinical markers were not associated with the different erythromycin resistance genotypes. In Japan, S. pneumoniae with erythromycin resistance or possession of ermB, mefA, or both genes was highly prevalent in patients with CAP. The risk factors for ermB-positive, mefA-positive, and double ermB-mefA-positive pneumococcal pneumonia were different, but the clinical outcomes did not differ.