Recent epidemiological studies in Japan have demonstrated that the incidence of macrolide-resistant M. pneumoniae is increasing gradually in pediatric patients. The purpose of this study was to clarify the frequency and clinical characteristics of macrolide-resistant M. pneumoniae in adults.
A total of 21 children and 10 adults with M. pneumoniae infection confirmed by serology and PCR who visited to Kawasaki Medical School hospital from June 2005 to April 2008 were enrolled in this study. Primers for domain V of 23S rRNA were used as reported by Lucier et al. DNA sequences of PCR products were compared to the sequence of MP M129 (accession no. X68422).
Among 21 children, 14 children were found to be infected with macrolide-resistant M. pneumoniae. This macrolide resistance was limited to point mutations of domain V of the M. pneumoniae 23S rRNA gene, such as A2063G and A2064G. All of them were treated with macrolides initially. Fever in five children with M. pneumoniae without point mutations at 2063, 2064, or 2617 disappeared within 48 hours of treatment; however, fever persisted for more than 48 hours after treatment in 14 patients with M. pneumoniae. Minocycline was effective in these patients with macrolide-resistant M. pneumoniae. In contrast to pediatric patients, macrolide-resistant M. pneumoniae were not detected in adult patients.
Macrolide-resistance rate of M. pneumoniae may be increasing to as high as 67% in children, but macrolide-resistance was not observed in adult patients with CAP. Tetracycline was effective to these macrolide-resistant M. pneumoniae infections. Response of fever by antibiotics correlated very well to response of reduction in number of M. pneumoniae at nasopharynx.
Recently, some researchers have detected macrolide-resistant M. pneumoniae in adult patients with respiratory tract infections. Thus, medical doctors should pay attention to macrolide-resistant M. pneumoniae not only in children but also in adults.
Naoyuki Miyashita, No Financial Disclosure Information; No Product/Research Disclosure Information