title: Rifampin stability in 7H9 broth and Löwenstein-Jensen medium.
abstract: The objectives of this study were to monitor the stability of rifampin (RIF) in Löwenstein-Jensen medium (L-J medium) and 7H9 broth, which are the media commonly used for drug susceptibility testing (DST) of Mycobacterium tuberculosis. Rifampin degradation in stock solution, 7H9 broth, and L-J medium and during the inspissation process for L-J medium preparation was serially monitored by high-performance liquid chromatography (HPLC). L-J medium-based DST was conducted to examine the effect of L-J medium storage on the DST outcome. The RIF stock solution was stable for at least 3 months when kept at either 4°C or -20°C; RIF in 7H9 broth and L-J medium was almost 50% decayed after 1 week of storage at 37°C, and rifampin could not be detected in 7H9 or L-J medium after 3 weeks or 6 weeks of storage at 37°C. Approximately half of the drug was decomposed after 4 months of storage at 4°C for both media, and after 6 months of storage at 4°C, RIF in L-J medium was undetectable, while 38% of RIF remained in 7H9 medium. Approximately 21, 24, 29, and 35% RIF degradations were detected when the L-J medium was coagulated at 75°C, 80°C, 85°C, and 90°C, respectively. The DST outcomes when using L-J medium stored for different periods of time were consistent with the RIF concentration monitoring data. Rifampin in stock solution is stable for at least 3 months at a reduced storage temperature. Media containing RIF should be prepared strictly according to validated standard operating procedures. RIF degradation is a possible reason for false resistance categorizations of M. tuberculosis isolates in the clinical laboratory.
authors.affiliation: Capital Medical University Affiliated Beijing Chest Hospital, Beijing Tuberculosis and Thoracic Tumor Research Institute, 97 Beimachang, Tongzhou Qu, Beijing 101149, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Yu
authors.forename: Guanglu
authors.initials: G
authors.lastname: Jiang
authors.forename: Huiwen
authors.initials: H
authors.lastname: Li
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Hongtao
authors.initials: H
authors.lastname: Zhang
authors.forename: Liping
authors.initials: L
authors.lastname: Zhao
authors.forename: Yu
authors.initials: Y
authors.lastname: Ma
authors.forename: Christopher
authors.initials: C
authors.lastname: Coulter
authors.forename: Hairong
authors.initials: H
authors.lastname: Huang
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media / Q000737:chemistry*; D004355:Drug Stability; D006801:Humans; D012293:Rifampin / Q000032:analysis / Q000737:chemistry*; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D012293:Rifampin