LAUSR

BACKGROUND To investigate the biological characteristics and antibiotic treatment effect of different Mycoplasma pneumoniae isolates co-infection in the same patient. METHODS Two throat swab specimens from one patient, on the day of admission (Sp01) and of discharge (Sp13), were liquid culture and subcultured in agar media to obtain M. pneumoniae monoclones. The 23S rRNA gene of fifty monoclones from specimens Sp01 and Sp13 were analyzed. Real-time PCR assay was used for the mutation detection and genotyping. Two typical monoclones were isolated for antimicrobial susceptibility testing. RESULTS The proportion of genotype 1 monoclones accounted for 70.8% (34/48) in Sp01, while accounted for 95.7% (44/46) in Sp13. All genotype 1 monoclones were of the 4-5-7-2 MLVA type, while all genotype 2 monoclones were 3-5-6-2 MLVA type. Each genotype 1 monoclone which harbored the A2063 G mutation in 23S rRNA gene, was resistant to erythromycin and azithromycin in vitro, while the genotype 2 which did not carry the mutation in the 23S rRNA gene, was susceptible to macrolide (ML). The proportion of ML resistant M. pneumoniae monoclones in the specimens culture collected at the time of discharge raised from 70.8%to 95.7%. CONCLUSION This is the first report on the isolation of ML resistant and ML susceptible strains of M. pnuemoniae from the same patient. After treatment, the proportion of ML resistant M. pnuemoniae increased, but the patient still carried the active ML susceptible strains. It means the ML-sensitive strains did not disappear completely.