Tsi-Shu Huang1, Calvin M Kunin2, Hui-Min Wang3, Bo-Shiun Yan4, Shiao-Ping Huang5, Yao-Shen Chen6, Susan Shin-Jung Lee7, Wan-Jr Syu8. 1. Section of Microbiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Department of Medical Technology, Fooyin University, Ta-Liao Hsiang, Kaohsiung Hsien, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan. 2. Department of Internal Medicine, Ohio State University, Columbus, Ohio, USA. 3. Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung, Taiwan. 4. Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan. 5. Department of Medical Technology, Fooyin University, Ta-Liao Hsiang, Kaohsiung Hsien, Taiwan. 6. Section of Microbiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Infectious Diseases, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan; Graduate Institute of Environmental Education, National Kaohsiung Normal University, Kaohsiung, Taiwan. 7. Infectious Diseases, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan. 8. Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan. Electronic address: wjsyu@ym.edu.tw.
Abstract
BACKGROUND/ PURPOSE: Active efflux is known to play a major role in the resistance of many bacteria to antibiotics. To evaluate the possibility of overcoming resistance by suppressing the efflux, we determined the effect of reserpine, an efflux pump inhibitor. METHODS: Intracellular accumulations and the minimal inhibitory concentrations (MICs) of ciprofloxacin in M. tuberculosis H37Rv and 16 clinical isolates were determined, compared, and analyzed. Nine of the clinical isolates were resistant to isoniazid and rifampin (multiple-drug resistant MDR). Five of these were resistant to ciprofloxacin. RESULTS: A reserpine-inhibited efflux system was identified in the H37Rv control and 10:1 (90.9%) of ciprofloxacin-susceptible and 4:1 (80%) of ciprofloxacin-resistant clinical isolates. The MIC of ciprofloxacin decreased in the presence of reserpine in 3/10 (30%) of the ciprofloxacin-susceptible and 2/4 (50%) of the MDR ciprofloxacin-resistant strains that expressed efflux pumps. Two of the efflux-positive, ciprofloxacin-resistant strains in which the MIC of ciprofloxacin was not decreased by reserpine were found to carry a D94A gyrA mutation. In contrast, two strains with the D94G gyrA mutation were susceptible to ciprofloxacin in the presence of reserpine. An efflux-negative strain, highly resistant to multiple antibiotics, was found to have a novel G247S mutation that differs from known mutations in the QRDR region of the gyrA gene. CONCLUSION: These findings indicate t hat reserpine can increase intracellular concentrations of ciprofloxacin, but is unable to overcome other mechanisms of resistance in clinical isolates.
BACKGROUND/ PURPOSE: Active efflux is known to play a major role in the resistance of many bacteria to antibiotics. To evaluate the possibility of overcoming resistance by suppressing the efflux, we determined the effect of reserpine, an efflux pump inhibitor. METHODS: Intracellular accumulations and the minimal inhibitory concentrations (MICs) of ciprofloxacin in M. tuberculosis H37Rv and 16 clinical isolates were determined, compared, and analyzed. Nine of the clinical isolates were resistant to isoniazid and rifampin (multiple-drug resistant MDR). Five of these were resistant to ciprofloxacin. RESULTS: A reserpine-inhibited efflux system was identified in the H37Rv control and 10:1 (90.9%) of ciprofloxacin-susceptible and 4:1 (80%) of ciprofloxacin-resistant clinical isolates. The MIC of ciprofloxacin decreased in the presence of reserpine in 3/10 (30%) of the ciprofloxacin-susceptible and 2/4 (50%) of the MDR ciprofloxacin-resistant strains that expressed efflux pumps. Two of the efflux-positive, ciprofloxacin-resistant strains in which the MIC of ciprofloxacin was not decreased by reserpine were found to carry a D94A gyrA mutation. In contrast, two strains with the D94G gyrA mutation were susceptible to ciprofloxacin in the presence of reserpine. An efflux-negative strain, highly resistant to multiple antibiotics, was found to have a novel G247S mutation that differs from known mutations in the QRDR region of the gyrA gene. CONCLUSION: These findings indicate t hat reserpine can increase intracellular concentrations of ciprofloxacin, but is unable to overcome other mechanisms of resistance in clinical isolates.
Authors: Shashank Gupta; Sandeep Tyagi; Deepak V Almeida; Mariama C Maiga; Nicole C Ammerman; William R Bishai Journal: Am J Respir Crit Care Med Date: 2013-09-01 Impact factor: 21.405