Susceptibility Pattern of Bacille Calmette-Guerin Strains Against Pyrazinamide and Other Major Anti-Mycobacterial Drugs

BCG (Bacille Calmette-Guerin) vaccine is an attenuated live vaccine administered to prevent Tuberculosis. Disseminated infection due to BCG is a rare life threatening complication of this vaccine, especially in immunocompromised patients. The current study evaluated the sensitivity pattern of the BCG strain supplied by the Institute de Pasteur, Iran against anti-mycobacterial drugs used to treat disseminated infection caused by the vaccine. Bacille Calmette-Guerin strain ATCC 1173 P was purchased from the Pasteur Institute in Tehran and three samples of Mycobacterium bovis isolated from subaxillary adenitis of three patients were tested for susceptibility to major anti-mycobacterial drugs by MODS (microscopic observation drug sensitivity) method. All samples of BCG strain were resistant to most of the anti-mycobacterial drugs used separately except for concentrations of isoniazid 1 µg/mL, ethambutol 3 µg/mL, ciprofloxacin 4 µg/mL and clarithromycin 2 µg/mL. Addition of pyrazinamide (PZA) 25 µg/mL, the susceptibility pattern did not change to any drug , but increasing PZA concentration to 50 µg/ml and combining it with ethionamide 2 µg/mL, isoniazid 0.2 µg/mL, streptomycin 2 µg/mL, rifampin 0.5 µg/mL or ciprofloxacin 0.2 µg/mL, made the Mycobacterium strains susceptible. The current study findings revealed that Mycobacterium bovis resistance to pyrazinamide is resolved by increasing the concentration of the drug and combining PZA with other anti-mycobacterial agents