Utility of PCR assays for rapid diagnosis of BCG infection in children

We report Mycobacterium bovis BCG infection in two children vaccinated with BCG (Tokyo strain) on the first day of life. Their diagnoses were made by biopsy of skin lesions and pus from an anterior chest wall abscess, respect ively, yielding a positive culture of mycobacteria fully susceptible to rif ampicin, isoniazid and ethambutol, but resistant to pyrazinamide. M. bovis BCG was identified by a negative niacin test, absence of nitrate reductase and resistance to pyrazinamide and cycloserine. The diagnoses were further confirmed by a combination of an allele-specific polymerase chain reaction (PCR) and a multiples PCR method. Based on the drug susceptibility results, treatment with rifampicin, isoniazid and ethambutol was instituted. One pa tient (Case 1) improved clinically and is well after treatment. However, th e other patient with severe combined immunodeficiency died of disseminated BCG infection in spite of intensive anti-tuberculosis therapy. Although BCG is considered to be a safe vaccine, it should be kept in mind that complic ations related to BCG do occur.