Synergistic antibacterial activity of M. koenigii (MK) ethanol leaf extract and first-line anti-TB drugs. (A) M. smegmatis was incubated with MK extract (200 and 400 μg/ml) alone or in combination with rifampicin (RIF) (0.3 and 0.7 μg/ml) for 24 h. The number of CFUs were counted after 72 h of incubation. Data showed decreased bacterial count in presence of both MK and RIF. (B) Isobologram analysis of MK extract and RIF. The data point falls below the line indicating syngergistic activity. (C) M. smegmatis was incubated with MK extract and isoniazid (INZ) for 24 hours and numbers of CFUs were assayed. (D) M. bovis BCG was incubated with MK extract (200 μg/ml) and rifampicin (RIF) (0.3 μg/ml) for 24 hours and numbers of CFUs were assayed after 3 weeks. Media containing bacteria alone was used as control. NC means no colonies. Experiments were performed in triplicates, means ± the SD are shown. **,P ≤ 0.0005; *,P ≤ 0.01.