Background and objective: Since 2000, the prevalence of macrolide-resistant (MR) Mycoplasma pneumoniae has increased among paediatric patients in Japan. To determine the efficacy of macrolides against MR M. pneumoniae pneumonia, microbiological and clinical efficacies were compared during the antibiotic treatment.
Methods: Samples from a total of 30 children with M. pneumoniae pneumonia, as confirmed by PCR and serology, were analyzed. Primers for domain V of 23S rRNA were used, and DNA sequences of the PCR products were compared with the sequence of an M. pneumoniae reference strain.
Results: Isolates from 21 patients demonstrated point mutations, and these patients were defined as MR. The remaining nine patients, whose isolates showed no point mutations, were categorized as control (macrolide-sensitive) patients. The number of M. pneumoniae in nasopharyngeal samples from the control group decreased rapidly 48 h after initiation of macrolide treatment and showed a close relationship with clinical outcome. In contrast, the number of M. pneumoniae 48 h after initiation of macrolide treatment were significantly higher in samples from MR patients than in samples from macrolide-sensitive patients. In 15 of 21 MR patients, fever persisted for more than 48 h after the initiation of macrolide treatment. When treatment was changed to minocycline, fever disappeared within 48 h in all these MR patients. There were no differences between MR patients who demonstrated a reduction in fever and those in whom fever persisted after 48 h of macrolide treatment.
Conclusions: The microbiological and clinical efficacies of macrolides for treating patients with MR M. pneumoniae pneumonia were low. These results show that macrolides are clearly less effective in patients with MR M. pneumoniae pneumonia.