title: Macrolide-resistance mechanisms in Streptococcus pneumoniae isolates from Chinese children in association with genes of tetM and integrase of conjugative transposons 1545.
abstract: This study investigated macrolide-resistant Streptococcus pneumoniae carried by Beijing children presenting with respiratory tract infections. Nasopharyngeal S. pneumoniae strains were tested for sensitivity with 15 antibiotics and further analyzed for phenotypes of macrolide-resistant strains and by PCR for the macrolide-resistant genes ermB, mefA, tetM, and integrase of conjugative transposon (Tn1545) intTn. We found 185 strains of S. pneumoniae relatively highly resistant to erythromycin (78.9%), clindamycin (76.2%), tetracycline (86%), and SMZ-TMP (78.7%) but with relatively low resistance to amoxicillin (2.2%), cefaclor (15.5%), ceftriaxone (2.8%), and cefuroxime (14.1%). The 146 strains of erythromycin-resistant S. pneumoniae showed extensive cross-resistance to other macrolides like azithromycin (100%), clarithromycin (100%), acetylspiramycin (95.2%), and clindamycin (95.9%). Genes ermB and mefA were detected in all erythromycin-resistant strains, with ermB(+) 79.5%, ermB + mefA(+) 17.8%, and mefA(+) 2.7%. About 96.9% of tetracycline-resistant isolates were positive for tetM, compared to 26.9% of sensitive strains. Ninety percent of tetracycline-resistant strains were also erythromycin-resistant versus 11.5% of tetracycline-sensitive strains. The intTn gene was present in 87.6% of S. pneumoniae strains and correlated with erythromycin and tetracycline resistance. The close relationship between the conjugative transposon Tn1545 and the genes ermB and tetM is probably one of the important mechanisms explaining the multiple drug resistance of S. pneumoniae.
authors.affiliation: Laboratory of Microbiology and Immunology, Beijing Pediatric Research Institute, Beijing Children's Hospital, Capital Medical University, Beijing, China.
authors.forename: Xuzhuang
authors.initials: X
authors.lastname: Shen
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
authors.forename: Shangjie
authors.initials: S
authors.lastname: Yu
authors.forename: Kaihu
authors.initials: K
authors.lastname: Yao
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Yuan
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Yang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D019426:Integrases / Q000235:genetics*; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000382:microbiology; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D018942:Macrolides; C083138:Tet M resistance protein, Bacteria; D019426:Integrases