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

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Background: 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. Objectives: 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. Patients and Materials: 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. Results: 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. Conclusions: 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.