RNA polymerase B subunit gene mutations in biofilm-embedded methicillin-resistant Staphylococcus aureus following rifampin treatment

Hung Jen Tang, Chih Cheng Lai, Po Ren Hsueh, Chi Chung Chen, Kuan Ying Wu, Yi Chung Lin, Chun Cheng Zhang, Tzu Chieh Weng, Yu Hsin Chiu, Han Siong Toh, Shyh Ren Chiang, Wen Liang Yu, Wen Chien Ko, Yin Ching Chuang

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6 Citations (Scopus)

Abstract

Background/Purpose This study was conducted to compare the mutation rates of different rpoB sites and rifampin minimum inhibitory concentration (MIC) changes prior to and after rifampin therapy for biofilm-embedded methicillin-resistant Staphylococcus aureus (MRSA) isolates. Methods The screening of rifampin-resistant MRSA isolates, from the biofilm at Day 5 with or without exposure to the susceptible breakpoint concentration of rifampin recommended by the Clinical and Laboratory Standards Institute (1 mg/L), was conducted using agar plates containing rifampin. A partial fragment of RNA polymerase B subunit gene (rpoB), including clusters I and II, was amplified and sequenced. The rifampin MIC values and mutation frequencies at different sites of rpoB were measured and evaluated in rifampicin-resistant isolates. Results Rifampin-resistant mutants could be selected from all of 39 randomly selected rifampin-susceptible MRSA isolates in the biofilm model. The spontaneous mutation frequency ranged from 1.00 × 10−4 to 3.85 × 10−7. Mutation at codon 481 was most commonly found at 35 (89.7%) of 39 MRSA isolates. Without rifampin induction, the MIC ranged between 0.125 mg/L and1024 mg/L and mutation sites included cluster I 464, 466, 468, 471, 474, 477, 481, 484, 486 and cluster II 519, 527, 529 with the percentage of 471 (35.9%), 477 (33.3%), 481 (53.8%), and 484 (35.9%). Conversely, with the induction of rifampin, the MIC value ranged ∼256–1024 mg/L. The mutation sites that were more concentrated included 468 (17.9%), 477 (30.8%), 481 (89.7%), 484 (17.9%), and 486 (33.3%). Conclusion We documented high rifampin resistance induction activity when MRSA was engaged in biofilm with rifampin exposure. Monotherapy seems to be inadequate for MRSA in biofilm. There is an urgent need for developing effective combination therapies with less rifampin resistance-inducing activities for treating MRSA in biofilms.

Original languageEnglish
Pages (from-to)394-401
Number of pages8
JournalJournal of Microbiology, Immunology and Infection
Volume49
Issue number3
DOIs
Publication statusPublished - Jun 1 2016
Externally publishedYes

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Keywords

  • biofilm-embedded MRSA
  • mutations
  • rpoB gene

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology and Microbiology(all)
  • Microbiology (medical)
  • Infectious Diseases

Cite this

Tang, H. J., Lai, C. C., Hsueh, P. R., Chen, C. C., Wu, K. Y., Lin, Y. C., Zhang, C. C., Weng, T. C., Chiu, Y. H., Toh, H. S., Chiang, S. R., Yu, W. L., Ko, W. C., & Chuang, Y. C. (2016). RNA polymerase B subunit gene mutations in biofilm-embedded methicillin-resistant Staphylococcus aureus following rifampin treatment. Journal of Microbiology, Immunology and Infection, 49(3), 394-401. https://doi.org/10.1016/j.jmii.2015.06.006