Molecular characteristic of rifampin-sensitive and resistant isolates and characteristics of rpoB gene mutations in MRSA

Abstract BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) infections have become a leading cause of bacterial infections in both healthcare and community settings. Mutations in the rpoB gene cause resistance to rifampin (RIF R ), a critical antibiotic for treatment of multidrug-resistant S. aureus . The aim of this study was to detect the molecular characteristics of RIF R MRSA and analysis the rpoB gene mutations involved in RIF resistance. MethodsA total of 49 RIF R MRSA and 38 RIF S MRSA isolates collected from seven cities in China were analyzed by multilocus sequence typing, staphylococcus chromosomal cassette mec (SCC mec ) typing, spa typing, and rpoB gene mutations. ResultsST239-III-t030 (35/49, 71.4%), the major clone in RIF R MRSA isolates; ST45-IV-t116 (16/38, 42.1%), the major clone in RIF S MRSA isolates with rpoB mutations. RIF R MRSA isolates were resistance to erythromycin, ciprofloxacin, tetracycline, gentamicin, and clindamycin. By contrast, RIF S MRSA isolates with rpoB mutation were more susceptible to ciprofloxacin, tetracycline, and gentamicin. Forty-three (87.8%) isolates present the mutational change H481N and L466S, conferring 128-512 μg/ml RIF resistance. The four isolates with RIF MIC > 1024 μg/ml had additional amino acid substitution: H481N, L466S, A473T (n=2); H481Y (n=2), associated with a high-level RIF resistance. Of 38 RIF S MRSA isolates, two mutations were observed, including H481N (n=37) and A477D (n=1). ConclusionThe predominant RIF R MRSA clones in China were ST239III-t030. Molecular character, antibiotic resistant profiles, and rpoB mutations between RIF R MRSA and RIFS MRSA were diverse. Antibiotics for treating patients with MRSA infections can be selected based on molecular characteristics.