Macrolide-Resistance Mechanisms in Streptococcus pneumoniae Isolates from Chinese Children in Association with Genes of tetM and Integrase of Conjugative Transposons 1545

摘要

This study investigated macrolide-resistant Streptococcus pneumoniae carried by Beijing children presenting withnrespiratory tract infections. Nasopharyngeal S. pneumoniae strains were tested for sensitivity with 15 antibioticsnand further analyzed for phenotypes of macrolide-resistant strains and by PCR for the macrolide-resistant genesnermB, mefA, tetM, and integrase of conjugative transposon (Tn1545) intTn. We found 185 strains of S. pneumoniaenrelatively highly resistant to erythromycin (78.9%), clindamycin (76.2%), tetracycline (86%), and SMZ-TMPn(78.7%) but with relatively low resistance to amoxicillin (2.2%), cefaclor (15.5%), ceftriaxone (2.8%), and cefuroximen(14.1%). The 146 strains of erythromycin-resistant S. pneumoniae showed extensive cross-resistance to othernmacrolides like azithromycin (100%), clarithromycin (100%), acetylspiramycin (95.2%), and clindamycin (95.9%).nGenes ermB and mefA were detected in all erythromycin-resistant strains, with ermB(+) 79.5%, ermB + mefA(+)n17.8%, and mefA(+) 2.7%. About 96.9% of tetracycline-resistant isolates were positive for tetM, compared to 26.9%nof sensitive strains. Ninety percent of tetracycline-resistant strains were also erythromycin-resistant versus 11.5%nof tetracycline-sensitive strains. The intTn gene was present in 87.6% of S. pneumoniae strains and correlated withnerythromycin and tetracycline resistance. The close relationship between the conjugative transposon Tn1545 andnthe genes ermB and tetM is probably one of the important mechanisms explaining the multiple drug resistance ofnS. pneumoniae.