|
The 994 throat swabs obtained from 688 adults and 306 children patients with respiratory diseases were examined for Mycoplasma pneumoniae infection by culture method. Antimicrobial susceptibilities of the resulting 123 M. pneumoniae isolates were evaluated by testing minimum inhibitory concentrations (MICs) of erythromycin, minocycline, tetracycline, josamycin, sparfloxacin, ofloxacin, and ciprofloxacin by a broth micro-dilution method. The erythromycin resistant strains of M. pneumoniae was determined above 1.0 ㎍/ml of MIC for erythromycin. The erythromycin resistant strains of M. pneumoniae was confirmed resistant gene mutation of the portions of genes 23S rRNA (domain Ⅱ and Ⅴ), and ribosomal protein L4 and L22 by PCR amplified and their nucleotide sequenses were compared to those of the susceptible strain M129. The isolation rate of M. pneumoniae was 12.9% (89/688) for the adults and 11.1% (34/306) for the children. The MICs90 of the M. pneumoniae isolates were 0.12 ㎍/ml for minocycline, 0.25 ㎍/ml for sparfloxacin, 0.5 ㎍/ml for ciprofloxacin, ofloxacin, and tetracycline, respectively, and 2.0 ㎍/ml for josamycin and erythromycin, respectively. The isolation rate of erythromycin resistant M. pneumoniae from patients was 49.4% (44/89) for the adults, 47.1% (16/34) for children, and 48.8% (60/123) for the total. No mutation could be detected in the ribosomal protein L22 region, but all strains were mutated in the ribosomal protein L4 as two point mutation M144V. Two point mutations in domain V of 23S rRNA were selected in the presense of erythromycin resistant M. pneumoniae isolates, such as one strain was G2057C mutant, two strains were A2059C mutants, three strains were C2611G mutants, four strains were A2058C mutants, five strains were A2058T mutants, twenty strains were A2059G mutants, and twenty-five strains were A2058G mutants, respectively. These results show that erythromycin was not the most active compound against M. pneumoniae infection in Korea and clinical studies of macrolides in human patients are demanded.
|