Enhanced In Vitro Stability of Bedaquiline with Ascorbic Acid and Pyruvate During Long-Term Incubation in <i>Mycobacterium</i> Species

Background Drug susceptibility testing in Mycobacterium species typically requires prolonged incubation periods during which the chemical integrity of antibiotics may not be maintained, potentially compromising the reliability and accuracy of minimum inhibitory concentration (MIC) determinations. Objectives This study evaluated the in vitro stability of several antibiotics, including recently introduced agents (bedaquiline [BDQ], pretomanid, delamanid and clofazimine) used for treating multidrug-resistant mycobacteriosis (linezolid and moxifloxacin), and those commonly included in combination regimens (rifampicin, isoniazid, ethambutol and clarithromycin). Methods Antibiotics were pre-incubated at 37 °C before MIC determination and those exhibiting two or more dilutions in MIC were further tested in combination with ascorbic acid (AA) and pyruvate (P). Results All antibiotics demonstrated stability except BDQ, which showed significant MIC variation after pre-incubation, which was prevented when BDQ was combined with AA and P. Conclusions These findings suggest that the combined use of AA and P may serve as an effective stabilizing strategy for BDQ during MIC determination.