High Prevalence of Macrolide Resistance in Mycoplasma pneumoniae Isolates from Adult and Adolescent Patients with Respiratory Tract Infection in China

Bin Cao 2 Chun-Jiang Zhao 0 Yu-Dong Yin 2 Fei Zhao 3 Shu-Fan Song 2 Lu Bai 2 Jian-Zhong Zhang 3 Ying-Mei Liu 2 Yu-Yu Zhang 2 Hui Wang 0 Chen Wang 1 0 Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences 1 Beijing Institute of Respiratory Medicine, Beijing Chao-Yang Hospital, Capital Medical University 2 Department of Infectious Diseases and Clinical Microbiology 3 Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China of this pathogen among adult patients with CAP. We also assessed the differences in clinical consequences between infection with macrolide-susceptible M. pneumoniae and infection with macrolide-resistant M. pneumoniae. Finally, the mechanism for resistance to macrolides in M. pneumoniae was studied. Methods. From 1 August 2008 through 30 September 2009, consecutive adults and adolescents (aged 14 years) who were seen in the fever clinic and who did not require hospitalization were prospectively enrolled in a surveillance study. None of the patients were immunocompromised; patients with human immunodeficiency virus (HIV) infection, patients with neutropenia, and patients receiving immunosuppressive chemotherapy were excluded. In addition, patients from nursing homes or patients who had been admitted to a hospital within the past 30 days were also excluded. After the first clinic encounter, all patients were followed up via telephone within 7-28 days. Symptoms and signs were recorded daily. All patients who were suspected of having CAP had a chest radiograph. When findings of the chest radiograph were normal, a chest computed tomography scan was ordered. The pneumonia severity index was used to assess the severity of illness [14]. A total of 215 and 141 throat swab specimens were collected from patients with CAP and patients with acute upper respiratory tract infection, respectively, as previously described [15]. M. pneumoniae isolates were identified by colony morphology and polymerase chain reaction (PCR) assay [15]. Minimum inhibitory concentrations (MICs) were determined by broth microdilution methods with SP4 broth (Remel) [15]. Susceptibility tests were performed in triplicate. The total length of the 23S ribosomal RNA (rRNA) gene of each M. pneumoniae strain was sequenced by the method described previously [7]. The mutations of 23S rRNA have been deposited in the GenBank sequence database and were assigned the accession numbers HM043729, HM043730, and HM043731. Amplification of ribosomal protein L4 and L22 fragments was performed with the primers described previously [6]. Sequencing results were analyzed with CLC Sequence Viewer (CLC Bio) and were compared with the M129 complete genome sequence [16]. PCR restriction fragment-length polymorphism (RFLP) typing of the P1 gene and pulsed-field gel electrophoresis (PFGE) typing were conducted for all M. pneumoniae isolates as described previously [17, 18]. Subgroup comparisons of clinical characteristics and clinical outcomes were conducted between patients infected with erythromycin-resistant strains (erythromycin MIC, 32 mg/mL) and patients infected with erythromycin-susceptible strains (eryth- - 4 ZM 32 8 .0 . 6 A 2 4 0 Mt 1 C g 5 C C C C C T 2 8 8 8 2 0 0 0 L 5 5 5 T T T T T e e e e T A 4 n n n n 9 L o o o o 0 + 2 N N N N A A 2 f e I I I I I II o n e p p p p p p u E FPG tyep I I I I I II b 8 6 2 0 2 5 3 Macrolides Erythromycin-resistant M. pneumoniae group (n p 42) Erythromycin-susceptible M. pneumoniae group (n p 17) 5 (11.9) 32 (76.2) 5 (11.9) 18 (42.9) 25.0 13.0 .138 .043a .109 .032a .523 Acknowledgments (...truncated)