Continued Upward Trend in Non-Tuberculous Mycobacteria Isolation over 13 Years in a Tertiary Care Hospital in Korea

Purpose@#Despite decreased prevalence of tuberculosis, the incidence of the diseases associated with nontuberculous mycobacteria (NTM) has been increasing in South Korea and around the world. The present retrospective study was conducted to determine longitudinal changes in the epidemiology and distribution of NTM over 13 years at a tertiary care hospital in Korea. @*Materials and Methods@#We retrospectively analyzed data on Mycobacterium species over 13 years (January 2007 to December 2019) by utilizing the laboratory information system. Mycobacterium species were identified using biochemical tests and PCR-restriction fragment length polymorphism and Mycobacteria GenoBlot assays. @*Results@#After excluding duplicates from the initial pool of 17996 mycobacterial isolates, 7674 strains were analyzed and 2984 (38.9%) NTM were isolated. The proportion of NTM continuously increased over the 13-year period, from 17.0% in 2007 to 57.5% in 2019. Among the NTM isolates, the most common species were Mycobacterium intracellulare (50.6%), M. avium (18.3%), M. fortuitum complex (4.9%), M. abscessus (4.5%), M. gordonae (3.3%), M. kansasii (1.1%), M. chelonae (1.0%), and M. massiliense (0.9%).In patients over the age of 70 years, the proportion of NTM among the isolates increased from 26.6% in 2007 to 62.0% in 2019, and that of M. intracellulare isolates among the NTM increased from 13.9% (11/79) in 2007 to 37.4% (175/468) in 2019. @*Conclusion@#The number of NTM isolates continuously increased over the study period, and the increase in the proportion of M. intracellulare in patients aged over 70 years was notable.

Continued Upward Trend in Non-Tuberculous Mycobacteria Isolation over 13 Years in a Tertiary Care Hospital in Korea

Purpose@#Despite decreased prevalence of tuberculosis, the incidence of the diseases associated with nontuberculous mycobacteria (NTM) has been increasing in South Korea and around the world. The present retrospective study was conducted to determine longitudinal changes in the epidemiology and distribution of NTM over 13 years at a tertiary care hospital in Korea. @*Materials and Methods@#We retrospectively analyzed data on Mycobacterium species over 13 years (January 2007 to December 2019) by utilizing the laboratory information system. Mycobacterium species were identified using biochemical tests and PCR-restriction fragment length polymorphism and Mycobacteria GenoBlot assays. @*Results@#After excluding duplicates from the initial pool of 17996 mycobacterial isolates, 7674 strains were analyzed and 2984 (38.9%) NTM were isolated. The proportion of NTM continuously increased over the 13-year period, from 17.0% in 2007 to 57.5% in 2019. Among the NTM isolates, the most common species were Mycobacterium intracellulare (50.6%), M. avium (18.3%), M. fortuitum complex (4.9%), M. abscessus (4.5%), M. gordonae (3.3%), M. kansasii (1.1%), M. chelonae (1.0%), and M. massiliense (0.9%).In patients over the age of 70 years, the proportion of NTM among the isolates increased from 26.6% in 2007 to 62.0% in 2019, and that of M. intracellulare isolates among the NTM increased from 13.9% (11/79) in 2007 to 37.4% (175/468) in 2019. @*Conclusion@#The number of NTM isolates continuously increased over the study period, and the increase in the proportion of M. intracellulare in patients aged over 70 years was notable.

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

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 specimen.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 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.RESULTS: 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.CONCLUSION: 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.

Detection of Bacterial and Viral Pathogens in Stool Specimens Using Multiplex PCR

BACKGROUND: The rapid and accurate detection of diarrheal pathogens is essential to prevent the spread of diarrheal diseases. Recently, a multiplex PCR assay was developed to simultaneously detect various bacterial and viral diarrheal pathogens. In this study, we investigated the frequency of detection of various potential pathogens causing diarrhea by using multiplex PCR and compared the results to the results of stool culture tests for bacteria and enzyme immunoassays (EIAs) for rotaviruses and Clostridium difficile toxin B (CDTB). METHODS: We retrospectively analysed the results for multiplex PCR, culture tests, and EIA obtained from stool specimens submitted to the laboratory from May 2013 to September 2014. Multiplex PCR was performed using the Seeplex diarrhea ACE detection kit (Seegene, Korea), which detects five viruses and eight bacteria. RESULTS: Among 890 stool specimens, 408 (45.8%) were found to be positive by PCR. The PCR positivity rate for bacteria and viruses was 31.1% (277/890) and 18.9% (161/890), respectively. The relative frequencies of microorganisms or toxins detected by PCR were, in decreasing order, CDTB 24.0%, Clostridium perfringens 20.6%, norovirus-GII 15.8%, rotavirus 11.3%, Campylobacter spp. 7.5%, enteric adenovirus 5.7%, and Salmonella spp. 5.1%. The concordance rate of the results obtained using the PCR and culture tests was 99.2% for Salmonella spp., 95.7% for Campylobacter spp., and. 79.8% for C. difficile . The concordance rates for rotaviruses and CDTB were 99.7% and 83.6%, respectively. CONCLUSIONS: The multiplex PCR method showed a high detection rate and is useful for the simultaneous detection of various diarrheal pathogens.