Molecular Characteristics of Rifampin-Sensitive and -Resistant Isolates and Characteristics of rpoB Gene Mutations in Methicillin-Resistant Staphylococcus aureus
Yinjuan Guo, Bingjie Wang, Lulin Rao, Xinyi Wang, Huilin Zhao, Meilan Li, Fangyou Yu
Abstract
Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) infections have become a leading cause of severe infections in both healthcare and community settings. Mutations in the rpoB gene cause resistance to rifampin (RIF R ), a critical antibiotic for the treatment of multidrug-resistant Staphylococcus aureus . The aim of this study was to detect the molecular characteristics of RIF R MRSA and analyze the rpoB gene mutations involved in RIF resistance. Methods: A 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. Results: ST239-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 resistant 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). Conclusion: In conclusion, the predominant RIF R MRSA clones in China were ST239-III-t030. Molecular characteristics, antibiotic-resistant profiles, and rpoB mutations between RIF R MRSA and RIF S MRSA were diverse. Antibiotics for treating patients with MRSA infections can be selected based on molecular characteristics. Keywords: MRSA, rifampin, rpoB mutations, MLST, SCC mec , spa