Phenotypic and Genotypic Drug Susceptibility Assessment of Mycobacterium bovis Bacillus Calmette-Guérin Clinical Strains

Abstract

Purpose

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) is the only vaccine licensed against tuberculosis. Despite the protection offered by the vaccine, in some circumstances children and immunocompromised individuals can develop associated infections, known as BCGitis. Drug susceptibility patterns of BCG clinical strains have rarely been described. We aimed to describe the susceptibility pattern of BCG clinical strains isolated in two different countries.

Methods

We performed culture-based drug susceptibility testing of thirty one BCG strains isolated from patients in Brazil (n=5, 16%) and Argentina (n=26, 84%) using the broth micro-dilution method (phenotypic method). Final antibiotic concentrations for susceptibility testing ranged from 0.5 to 16 mg/L for amikacin, 0.3125 to 10 mg/L for ethambutol, 0.05 to 1.6 mg/L for isoniazid and 0.25 to 8 mg/L for rifampicin, streptomycin and ofloxacin. Additionally, we compared the results with genetic data obtained by whole genome sequencing.

Results

By using the phenotypic method we detected one strain resistant to ethambutol, three strains resistant to rifampicin and one resistant to isoniazid. Additionally, two strains that were phenotypically resistant to both isoniazid and rifampicin carried mutations in the katG and rpoB genes simultaneously.

Conclusion

There is evidence of the emergence of BCG-resistant strains isolated from vaccine-related complications. We recommend drug susceptibility testing of the BCG strain causing the infection in order to prevent treatment failure.

Keywords:

• BCG
• mycobacteria
• resistance
• vaccine

Acknowledgments

We thank Dr. Leila Mendonça-Lima for supplying the DNA of the vaccine BCG Moreau. We also acknowledge the sequencing platform of Fiocruz (RPT01J) and Ricardo Junqueira for assistance in the preparation of libraries, Kamila Chagas Peronni from the Laboratory of Molecular Genetics and Bioinformatics from the Regional Center of Haemotherapy and Professor Valdes Bollela from the School of Medicine, São Paulo University in Ribeirão Preto.

Sponsorships

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) - Finance Code 001. The authors also acknowledge the support of Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ). PNS was supported by CNPq grant PQ 310,418/2016-0.

Disclosure

Dr Maria Carolina Sisco report grants from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES), grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq, during the conduct of the study. The authors report no other conflicts of interest in this work.