Research in Medicine

Background and Aim: In Iran vaccination with Bacillus Calmette-Guérin (BCG) is performed on all newborns within the first days of life for prevention of tuberculosis. It is a live attenuated vaccine and produced from genetically different vaccine strains of Mycobacterium bovis. This vaccine is safe but local adverse reactions such as administration site abscess and lymphadenitis occur in some healthy children vaccinated with this vaccine as the most common side effect of BCG vaccination. Disseminated BCG infections are very rare in immunocompetent children but lymphadenitis is very common in Iran and other countries. It is indicated that the vaccine strain and it’s genetically variations are correlated with these side effects. Therefore, in this study we aimed to analyze the genetic characterizations of vaccine strains used in Iran.

Materials and Methods: Thirty infants showing lymphadenitis induced by BCG vaccination were chosen for this study. After aspiration from the lesions, they were subjected to acid fast staining and culture on Lowenstein Jensen medium.  Subsequently, DNA was extracted from samples using Phenol–chloroform method.  The genus of the isolates was characterized by primer for 16sRNA gene. Then using RD1, RD14 and DU1 primers and in the next step RD9, RD4Deleted, RD4Present and RD1Deleted primers the species and strains of the isolates were characterized.

Results: Performing 16sRNA PCR, all 30 samples of acid fast bacilli were confirmed as Mycobacterium genus. Then using RD1, RD14, DU1, RD9, RD4 Deleted, RD4 Present and RD1 Deleted primers all isolates were detected as Mycobacterium bovis BCG strain Pasteur.

Conclusion: In this study all of the strains isolated from the patients were detected as Mycobacterium bovis BCG strain Pasteur. Therefore, the other possible factors causing BCG complications including BCG overdose, faulty intradermal technique, and disturbance of cellular immunity should be considered as the other risk factors of causing lesions.