No abstract

Among 380 Mycoplasma pneumoniae isolates from 3,678 pediatric patients with community-acquired pneumonia, 50 macrolide-resistant strains had an A2063G transition in domain V of the 23S rRNA, whereas 5 had an A2064G transition. These resistant strains increased rapidly from April 2002 to December 2006.For Mycoplasma pneumoniae, a major etiologic agent of lower respiratory tract infections acquired in the community, 14-membered ring macrolides (ML) generally are recognized as first-choice agents. In Japan, ML-resistant (ML r ) M. pneumoniae possessing a 23S rRNA mutation first was isolated from pediatric patients with community-acquired pneumonia (CAP) and bronchitis as reported in 2001 by Okazaki et al. (4). Patient symptoms appeared to be prolonged when isolates showed ML resistance (5).We subjected M. pneumoniae isolated from pediatric patients with CAP between 2002 and 2006 to susceptibility evaluation for eight agents, including ML. In strains showing ML resistance, the 23S rRNA gene was analyzed.Between April 2002 and December 2006, 3,678 clinical samples were sent to our laboratory from pediatricians affiliated with 10 institutions participating in the Acute Respiratory Diseases Study Group. All samples originating from pediatric patients diagnosed with pneumonia according to clinical symptoms and chest X-ray images were collected after informed consent was given by the patients and/or their parents or guardians.Immediately after receipt, the samples were suspended in 1.5 ml of pleuropneumonia-like organism (PPLO) broth (Difco, Detroit, MI). DNA then was extracted by using Extragen II (Tosoh, Tokyo, Japan) according to the manufacturer's protocol. Real-time PCR to detect M. pneumoniae was performed as described previously (2) using the extracted DNA. Culture of M. pneumoniae was carried out for PCR-positive samples using PPLO broth according to previously described methods (6).The MICs of eight agents for M. pneumoniae isolates were determined with microdilution methods using PPLO broth.These agents were erythromycin, clarithromycin, azithromycin, josamycin, rokitamycin, telithromycin, minocycline, and levofloxacin. M. pneumoniae M129 strain was used as a control.The full length of the 23S rRNA gene was sequenced by methods described previously (3) in 55 M. pneumoniae strains showing ML resistance.For patients with adequate clinical information, clinical courses of CAP caused by ML r M. pneumoniae (n ϭ 53) were compared to those of CAP with ML-susceptible (ML s ) M. pneumoniae (n ϭ 58). Variables compared included (i) the number of days from initiation of ML treatment until defervescence to 37°C and (ii) whether or not initial treatment with ML was changed later to another agent. Body temperature that exceeded 38°C at least once daily was defined as ongoing fever. Table 1 Table 2 shows the MIC range, MIC 50 , and MIC 90 for eight agents according to the presence or absence of a mutation of the 23S rRNA gene in the 380 M. pneumoniae isolates; 50 strains had an A2063G transition in domain V, and 5 strains had...

Macrolides are inappropriate as first-choice agents against MRMP in terms of shortening the clinical course and decreasing M. pneumoniae. Control and prevention of MRMP outbreaks in children require early decreases in M. pneumoniae as well as improvement of clinical findings.