Frequency of Mycobacterium tuberculosis Among M. tuberculosis Complex Strains Isolated from Clinical Specimen

Abstract

Rapid and accurate detection of Mycobacterium tuberculosis (MTB) is of primary importance for infection control and selection of anti-tuberculosis drugs. However, most clinical laboratories report MTB complex (MTC) without reporting MTB because MTC comprising MTB, Mycobacterium bovis, Mycobacterium africanum, Mycobacterium microti, Mycobacterium caprae and Mycobacterium pinnipedii have 99.9% similarity at the nucleotide level and identical 16S rRNA sequences. This study was conducted to analyze the species frequency of MTC isolates obtained from clinical specimen.Of 310 MTC isolates obtained from clinical samples in a tertiary care hospital from February 2017 to August 2018, MolecuTech Real TB-Taq (YD Diagnostics, Korea) real-time PCR was performed, specifically to detect MTB. For DNA showing MTB negative results by MTB-specific real-time PCR or pyrazinamide-resistant strains, PCR-based MTC typing, spoligotyping, and exact tandem repeat D gene sequencing were performed. All the 310 MTC isolates were identified to be MTB. Two MTB strains of East-African-Indian 4-Vietnam genotype, which have not been reported in Korea, were also found.There was no zoonotic tuberculosis in this study. Since we investigated only 310 MTC isolates detected in only one medical institution, multi-center study is needed to accurately know the prevalence of zoonotic tuberculosis in Korea.

Keywords

• mycobacterium tuberculosis
• complex
• sequence analysis
• spoligotyping