• IMMUNE NETWORK
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• v.21 no.6
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• pp.40.1-40.20
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• 2021

Mycobacteroides abscessus (previously Mycobacterium abscessus; Mabc), one of rapidly growing nontuberculous mycobacteria (NTM), is an important pathogen of NTM pulmonary diseases (NTM-PDs) in both immunocompetent and immunocompromised individuals. Mabc infection is chronic and often challenging to treat due to drug resistance, motivating the development of new therapeutics. Despite this, there is a lack of understanding of the relationship between Mabc and the immune system. This review highlights recent progress in the molecular architecture of Mabc and host interactions. We discuss several microbial components that take advantage of host immune defenses, host defense pathways that can overcome Mabc pathogenesis, and how host-pathogen interactions determine the outcomes of Mabc infection. Understanding the molecular mechanisms underlying host-pathogen interactions during Mabc infection will enable the identification of biomarkers and/or drugs to control immune pathogenesis and protect against NTM infection.

• Biomedical Science Letters
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• v.18 no.3
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• pp.201-209
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• 2012

Apoptosis is a physiological programmed cell death process. Tubercle bacilli inhibit apoptosis of alveolar macrophages and phagolysosome fusion. We investigated whether the Bcl-2 family anti-apoptotic member, Bfl-1/A1, plays an important role in the anti-apoptotic process during mycobacterial infection. PMA-treated human monocytoid THP-1 cells were infected with mycobacteria (H37Rv, BCG, and K-strain) at a multiplicity of infection (MOI) of 10 for 0, 1.5, 3, 6, 9, 12, 18, 24, 48, or 72 h. In addition, PMA-treated THP-1 cells were pretreated with specific inhibitors for 45 min before stimulation with mycobacteria at an MOI of 10 for 4 h. After the indicated time, the cells were subject to reverse transcription-polymerase chain reaction (RT-PCR) analysis, and a Bfl-1/A1-specific Western blot was performed. In PMA-differentiated THP-1 cells, the expression level of Bfl-1/A1 mRNA was increased by Mycobacterium tuberculosis (MTB) H37Rv infection. The mRNA level of Bfl-1/A1 peaked 3 h after MTB infection, then declined gradually until 9 h. However, Bfl-1/A1 mRNA induction gradually re-increased from 24 h to 72 h after MTB infection. No difference in Bfl-1/A1 expression was detected following infection with MTB H37Rv, K-strain, or M. bovis BCG. These results were not dependent on mycobacterial virulence. Moreover, mRNA levels of other anti-apoptotic molecules (Mcl-1, Bcl-2, and Bcl-xL) were not increased after MTB H37Rv or K-strain infection. These results suggest that mycobacteria induce the innate immune host defense mechanisms that utilize Bfl-1/A1 molecules at early time points, regardless of virulence.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.745-752
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• 2015

Tuberculosis (TB) is the most common mycobacterial infection in developing countries, requiring a rapid, accurate, and well-differentiated detection/diagnosis. For the rapid detection and discrimination of Mycobacterium tuberculosis complex (MTC) from non-tuberculous mycobacteria (NTM), a novel, simple, and primer-combined single-step multiplex PCR using three primer pairs (6110F-6110R, 1081F-1081R, and 23SF-23SR; annealing on each of IS6110, IS1081, and 23S rDNA targets), hereafter referred to as a triplex PCR, has been developed and evaluated. The expected product for IS6110 is 416 bp, for IS1081 is 300 bp, and for 23S rDNA is 206 bp by single PCR, which was used to verify the specificity of primers and the identity of MTC using DNA extracted from the M. tuberculosis H37Rv reference strain (ATCC, USA) and other mycobacteria other than tuberculosis (MOTT) templates. The triplex PCR assay showed 100% specificity and 96% sensitivity; the limit of detection for mycobacteria was ~100 fg; and it failed to amplify any target from DNA of MOTT (50 samples tested). Of 307 blinded clinical samples, overall 205 positive M. tuberculosis samples were detected by single PCR, 142 by conventional culture, and 90 by AFB smear methods. Remarkably, the triplex PCR could subsequently detect 55 positive M. tuberculosis from 165 culture-negative and 115 from 217 AFB smear-negative samples. The triplex PCR, targeting three regions in the M. tuberculosis genome, has proved to be an efficient tool for increasing positive detection/discrimination of this bacterium from clinical samples.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.4
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• pp.313-317
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• 2015

Due to the increase in incidence of infection of Mycobacterium tuberculosis complex (MTC), it is imperative that a rapid diagnosis accompanies the handling of MTC. This is due to the three to eight weeks it takes to culture Mycobacteria, and the lack of sensitivity of microscopic examination of AFB. Recently, nested PCR has been used to detect and diagnose mycobacteria. It is especially useful in complementing diagnosis by histological extra pulmonary. After culturing all the specimens and practicing the nested PCR, we did comparison analysis between nested PCR and culture. There were 76 specimens, 31 of which were positive. Of the 31 positive specimens in culturing, only 22 were positive in nested PCR. Of the 45 negative specimens, 36 were negative in nested PCR. As a result, Sensitivity was 71% and specificity was 80%. Furthermore, the positive predictive value was 71% and negative predictive value was 80%. These results indicate that nested PCR based techniques are sensitive, specific, and rapid methods for the detection of MTC.

• Journal of Life Science
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• v.21 no.3
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• pp.473-479
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• 2011

Adenylyl cyclase (AC) catalyzes the formation of cyclic AMP (cAMP) from ATP. The cAMP produced by AC serves as a secondary messenger in a variety of signal transduction pathways, and controls various cellular functions in many organisms. ACs can be grouped into six classes based on their primary amino acid sequences. Eukaryotes and mycobacteria contain only members of class III AC. The catalytic cyclase domains of class III AC are active as dimers: mammalian ACs, which are composed of a single polypeptide with two catalytic cyclase domains, form the active site as a result of intramolecular dimerization of the catalytic cyclase domains. In contrast, mycobacterial ACs function as homodimers, since their polypeptides contain a single catalytic cyclase domain. Six amino acids are required for the catalytic activity of class III AC - two aspartate residues, a lysine-aspartate pair and an arginine-asparagine pair. 16 ACs belonging to the class III were identified in Mycobacterium tuberculosis H37Rv, and their characteristics are reviewed.

• International Journal of Advanced Culture Technology
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• v.11 no.3
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• pp.260-267
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• 2023

We aimed to investigate the proportions of MTB- and NTM-positive tests and the distribution patterns of species isolated by contracted testing agencies in South Korea. Respiratory specimens submitted to contracted testing agencies in South Korea for AFB culture from January 2014 to December 2021 were included (533,713 specimens in total). Trends based on MTB and NTM detection, patient sex and age, culture medium type, and testing year were analyzed. MTB and NTM positive detection increased in the patients. The average ages of MTB- and NTM-positive patients increased in those aged ≥61 years. For solid culture, the MTB detection rate decreased from 5.9% in 2014 to 3.3% in 2018 and increased to 4.7% in 2021; the NTM detection rate increased from 2.1% in 2014 to 3.4% in 2018 and 3.7% in 2021. For liquid culture, the MTB detection rate decreased from 8.3% in 2014 to 5.5% in 2018 and increased to 6.0% in 2021; the NTM detection rate increased from 3.5% in 2014 to 5.5% in 2018 and decreased to 5.3% in 2021. An isolation ratio reversal between MTB and NTM was observed in 2018. In this study, we provide information on mycobacterial isolation rates and species distributions using AFB culture test results from Korea's referral laboratories. Increased MTB- and NTM-isolation rates were observed in individuals aged ≥60 years, indicating the need for regular testing and focused management for them. Expanding liquid culture applications, which show higher positivity rates than solid culture methods, is necessary.

• Tuberculosis and Respiratory Diseases
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• v.86 no.1
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• pp.47-56
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• 2023

Background: There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing. Methods: NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed. Results: A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001). Conclusion: There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.

• Tuberculosis and Respiratory Diseases
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• v.53 no.6
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• pp.635-643
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• 2002

Background : The Aim of this study was to compare the recovery of mycobacteria from sputum samples of pulmonary tuberculosis patients using the MB/BacT rapid culture system(Organon Teknika, USA) with that obtained using Lowenstein-Jensen solid medium. Methods : The two culture systems were compared using sputum samples of 99 pulmonary tuberculosis patients. Culture media were incubated at $35-37^{\circ}C$ for six weeks in the MB/BacT system and for 12 weeks in Lowenstein-Jensen solid medium. Solid media were examined macroscopically once a week, and the MB/BacT system positive vials were unloaded from the machine as soon as possible after positive signal from the connected computer was detected Confirmation of growth for mycobacteria was done by Ziehl-Neelson stained smears. Isolates were identified to differentiate Mycobacterium tuberculosis from mycobacterium other than tuberculosis(MOTT) by phenotypic and molecular methods. Results : Of the sputum samples of the 99 patients, 58 samples were smear positive and 41 in negative smear. Mycobacteria were recovered from 67(67.7%) samples by using both culture systems. The yield with MB/BacT was higher than that with Lowenstein-Jensen [67(67.7%) vs. 52(52.5%), p<0.001]. Moreover, 15(15.2%) samples were positive only in the MB/BacT, whereas none of samples was positive only in Lowenstein-Jensen. In smear-positive and smear-negative samples, the recovery rate with MB/BacT was also higher than that with Lowenstein-Jensen [sputum-positive; 56/58(96.6%) vs. 46/58(79.3%), p=0.005, sputum-negative; 6/41(14.6%) vs. 5/41(12.2%), p<0.001]. The mean times to detection of Mycobacteria were 13.3 and 27.2 days with MB/BacT and Lowenstein-Jensen respectively(p<0.001). Conclusion : This results indicate that the the MB/BacT is more efficient and faster than Lowenstein-Jensen for the recovery of mycobacteria.

• The Journal of the Korean Society for Microbiology
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• v.15 no.1
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• pp.9-17
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• 1980

In the ecology and epidemiologic studies on various serotypes of atypical mycobacteria(AM), Schaefer's bacterial agglutination test(BA) provided the basis of the serologic procedures. Recently, attempts have been made to modify and to simplify the Schaefer's BA such as a slide agglutination test(Engel & Beerwald, 1970), a "simplified" BA(Reznikov & Leggo, 1972), an agglutination inhibition test(Richards & Eacret, 1972) and "micromethod"(Thoen et al., 1975). The BA, however, was not widely applied as a routine laboratory test mainly because it requires much times and labors to perform and partley because it is not applicable to hydrophobic strains either often encountered in the isolation of AM in the clinical bacteriology or stock strains maintained in the laboratory. On the contrary, fluorescent antibody technique with mycobacteria may have advantages over the BA because it is far more simpler in serologic procedures and is applicable to all strains of mycobacteria regardless of smooth or rough types of cultures. At the present, it is well known that the type-specific antigens are lacking on the surface of rough type of AM compared to that on smooth type of strain, but the antigenicity on the surface of the hydrophobic strains of AM which resulted from a series of subculture and the strain in the laboratory for 3 to 6 months has not been clarified. In this study, an attempt to serotype the hydrophobic strains of M. scrofulaceum serotype 41, 42 and 43 by fluorescent anti-complement(FAC) technique was made. The FAC technique with mycobacteria was also described in detail. In the summary, the complement fixing antibody titres of reference sera to smooth types of homologous serotype was highest, but the antibody titres of reference sera to hydrophobic strains of serotypes, 41, 42 and 43 gave two-to 8-folds lower than those to smooth type of strains. Although the sensitivity of type-specific antigens on the hydrophobic strains to reference sera was much lower, using the two units of reference sera determined by titration with hydrophobic strains, three serotypes, i. e., 41, 42 and 43 were specifically differentiated one another by FAC technique. This result indicated that the hydrophobic strains which were maintained in the laboratory at least for 6 months still retain type-specific antigen detectable by FAC technique.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.4
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• pp.435-438
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• 2017

Nontuberculous mycobacteria (NTM) contains M. avium-intracellular complex (MAC), M. fortuitum, M. chelonae, M. abscessus, M. kansasii, etc., which causes infections in swine, poultry, and other animals. These bacteria are opportunistic pathogens that can contaminate people, and in doing so, cause various social economic problems. This study proved that NTM are also present in air conditioners of multiuse facilities in frequently visited populated areas. The results of this study are meaningful because they showed that pathogenic microbes can live in the surroundings and cause diseases to people with impaired immunity. This study used the AFB stain, L-J medium culture, and PCR method for the detection of MTB and NTM in air conditioner dust. MTB was not detected in any of the collected samples, while NTM was detected in 2 out of 40 samples (5%). Most people living in the modern environment cannot avoid being exposed to air conditioners so special attention is needed for sanitary inspections and the management of air conditioners. Moreover, it is important to study NTM through various individuals, accumulate the related data and establish the methods and standards of hygiene management system to reduce NTM infections in public areas. Moreover, it would be necessary to identify the precise species of NTM through DNA sequencing and evaluate the effects of NTM on the pulmonary tuberculosis in immunodeficiency patients.