N Lounis1, L Vranckx2, T Gevers2, K Kaniga3, K Andries2. 1. Janssen Infectious Diseases BVBA, Turnhoutseweg 30, 2340 Beerse, Belgium. Electronic address: nlounis@its.jnj.com. 2. Janssen Infectious Diseases BVBA, Turnhoutseweg 30, 2340 Beerse, Belgium. 3. Janssen Research & Development, LLC, Titusville, NJ, USA.
Abstract
OBJECTIVES: In developing a standardized drug susceptibility test for bedaquiline, it is very important to know which parameters might impact its activity in vitro and result in false resistance of the bacterium to bedaquiline. We aimed to assess the impact of different in vitro conditions on the minimal inhibitory concentration (MIC) of bedaquiline against Mycobacterium tuberculosis H37Rv reference strain. METHODS: The MIC of M. tuberculosis H37Rv strain was determined under different conditions such as inoculum size, pH, temperatures, log and stationary phase cultures, protein concentration, Tween 80 concentration, and labware plastics. RESULTS: Increases in bedaquiline MIC were observed with variations in inoculum size for M. tuberculosis H37Rv on agar or in broth, in protein concentration and labware plastics on agar, and with variations in pH and Tween 80 concentrations in broth. CONCLUSIONS: In order to obtain reproducible MIC results, bedaquiline MIC should be assessed using polystyrene plates or tubes, at pH 7, with a Tween 80 concentration of 0.02%, without protein enrichment and with an inoculum size up to 10(7) colony-forming unit (CFU)/mL on 7H11 agar or with 10(5)CFU/mL in 7H9 broth.
OBJECTIVES: In developing a standardized drug susceptibility test for bedaquiline, it is very important to know which parameters might impact its activity in vitro and result in false resistance of the bacterium to bedaquiline. We aimed to assess the impact of different in vitro conditions on the minimal inhibitory concentration (MIC) of bedaquiline against Mycobacterium tuberculosis H37Rv reference strain. METHODS: The MIC of M. tuberculosis H37Rv strain was determined under different conditions such as inoculum size, pH, temperatures, log and stationary phase cultures, protein concentration, Tween 80 concentration, and labware plastics. RESULTS: Increases in bedaquiline MIC were observed with variations in inoculum size for M. tuberculosis H37Rv on agar or in broth, in protein concentration and labware plastics on agar, and with variations in pH and Tween 80 concentrations in broth. CONCLUSIONS: In order to obtain reproducible MIC results, bedaquiline MIC should be assessed using polystyrene plates or tubes, at pH 7, with a Tween 80 concentration of 0.02%, without protein enrichment and with an inoculum size up to 10(7) colony-forming unit (CFU)/mL on 7H11 agar or with 10(5)CFU/mL in 7H9 broth.
Authors: Olumide Martins; Jin Lee; Amit Kaushik; Nicole C Ammerman; Kelly E Dooley; Eric L Nuermberger Journal: Antimicrob Agents Chemother Date: 2021-09-13 Impact factor: 5.191
Authors: Erika Kapp; Hanri Visser; Samantha L Sampson; Sarel F Malan; Elizabeth M Streicher; Germaine B Foka; Digby F Warner; Sylvester I Omoruyi; Adaze B Enogieru; Okobi E Ekpo; Frank T Zindo; Jacques Joubert Journal: Molecules Date: 2017-09-30 Impact factor: 4.411