Frequency of Mycobacterium tuberculosis among Mycobacterium tuberculosis Complex Strains Isolated from Clinical Specimen

Abstract

Background: 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 specimens. Methods: 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 polymerase chain reaction (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, spacer oligonucleotide typing (spoligotyping), and exact tandem repeat D gene sequencing were performed. Results: All the 310 MTC isolates were identified to be Mtb. Two Mtb strains of the East-African-Indian 4-Vietnam genotype, which have not been reported in Korea, were also found. Conclusion: There was no zoonotic tuberculosis in this study. Since we investigated only 310 MTC isolates detected in only one medical institution, a multi-center study is needed to accurately know the prevalence of zoonotic tuberculosis in Korea.