• Tuberculosis and Respiratory Diseases
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• 제85권3호
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• pp.264-272
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• 2022

Background: The current conventional drug susceptibility test (DST) for Mycobacterium tuberculosis (Mtb) takes several weeks of incubation to obtain results. As a rapid method, molecular DST requires only a few days to get the results but does not fully cover the phenotypic resistance. A new rapid method based on the ability of viable Mtb bacilli to hydrolyze fluorescein diacetate to free fluorescein with detection of fluorescent mycobacteria by flow cytometric analysis, was recently developed. Methods: To evaluate this cytometric method, we tested 39 clinical isolates which were susceptible or resistant to isoniazid (INH) or rifampin (RIF), or ethambutol (EMB) by phenotypic or molecular DST methods and compared the results. Results: The susceptibility was determined by measuring the viability rate of Mtb and all the isolates which were tested with INH, RIF, and EMB showed susceptibility results concordant with those by the phenotypic solid and liquid media methods. The isolates having no mutations in the molecular DST but resistance in the conventional phenotypic DST were also resistant in this cytometric method. These results suggest that the flow cytometric DST method is faster than conventional agar phenotypic DST and may complement the results of molecular DST. Conclusion: In conclusion, the cytometric method could provide quick and more accurate information that would help clinicians to choose more effective drugs.

• Tuberculosis and Respiratory Diseases
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• 제85권3호
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• pp.256-263
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• 2022

Background: Mycobacterium tuberculosis (Mtb) is resistant to the β-lactam antibiotics due to a non-classical transpeptidase in the cell wall with β-lactamase activity. A recent study showed that meropenem combined with clavulanate, a β-lactamase inhibitor, was effective in multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB). However, in Korea, clavulanate can only be used as drugs containing amoxicillin. In this study, we investigated the susceptibility and genetic mutations of drug-resistant Mtb isolates to amoxicillin-clavulanate and meropenem-clavulanate to improve the diagnosis and treatment of drug-resistant TB patients. Methods: The minimum inhibitory concentration (MIC) of amoxicillin-clavulanate and meropenem-clavulanate was examined by resazurin microtiter assay. We used 82 MDR and 40 XDR strains isolated in Korea and two reference laboratory strains. Mutations of drug targets blaC, blaI, ldtA, ldtB, dacB2, and crfA were analyzed by polymerase chain reaction and DNA sequencing. Results: The MIC₉₀ values of amoxicillin/clavulanate and meropenem/clavulanate in drug-resistant Mtb isolates were 64/2.5 and 16/2.5 mg/L, respectively. Gene mutations related to amoxicillin/clavulanate and meropenem/clavulanate resistance could not be identified, but T448G mutation was found in the blaC gene related to β-lactam antibiotics' high susceptibility. Conclusion: Our results provide clinical consideration of β-lactams in treating drug-resistant TB and potential molecular markers of amoxicillin-clavulanate and meropenem-clavulanate susceptibility.

• 한국동물위생학회지
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• 제46권1호
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• pp.29-34
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• 2023

Mycobacterium tuberculosis complex (M. tuberculosis complex) is a causative agent of contagious chronic disease in a wide range of mammalian hosts, mainly cattle, goat, pigs, wildlife, and humans. The definite diagnosis of tuberculosis is made based on culture of M. tuberculosis, but it takes a long time. In the present study, we analyzed whether the detection time of M. tuberculosis could be reduced when cultured in the medium containing the culture-promoting ingredients-107 (CPI-107) using the BacT/Alert 3D system, an automatic culture system. The time to detection (TTD) tended to decrease as the added concentration of CPI-107 increase. In the case of low numbers of M. tuberculosis, it decreased by 21.0% at 1.2 mg/mL of CPI-107 and by 15.9% in the case of high numbers of M. tuberculosis. In the culture using clinically isolated M. tuberculosis strains, the shortening of the culture time by CPI was more evident. In conclusion, the detection time of M. tuberculosis was shortened in the medium added with CPI-107, and this could be used for isolation, culture and drug susceptibility test of M. tuberculosis.

• Genomics & Informatics
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• 제21권3호
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• pp.32.1-32.11
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• 2023

Resistance to anti-tuberculosis drugs, especially ethambutol (EMB), has been widely reported worldwide. EMB resistance is caused by mutations in the embB gene, which encodes the arabinosyl transferase enzyme. This study aimed to detect mutations in the embB gene of Mycobacterium tuberculosis from Papua and to evaluate their impact on the effectiveness of EMB. We analyzed 20 samples of M. tuberculosis culture that had undergone whole-genome sequencing, of which 19 samples were of sufficient quality for further bioinformatics analysis. Mutation analysis was performed using TBProfiler, which identified M306L, M306V, D1024N, and E378A mutations. In sample TB035, the M306L mutation was present along with E378A. The binding affinity of EMB to arabinosyl transferase was calculated using AutoDock Vina. The molecular docking results revealed that all mutants demonstrated an increased binding affinity to EMB compared to the native protein (-0.948 kcal/mol). The presence of the M306L mutation, when coexisting with E378A, resulted in a slight increase in binding affinity compared to the M306L mutation alone. The molecular dynamics simulation results indicated that the M306L, M306L + E378A, M306V, and E378A mutants decreased protein stability. Conversely, the D1024N mutant exhibited stability comparable to the native protein. In conclusion, this study suggests that the M306L, M306L + E378A, M306V, and E378A mutations may contribute to EMB resistance, while the D1024N mutation may be consistent with continued susceptibility to EMB.

• Genomics & Informatics
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• 제21권3호
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• pp.42.1-42.23
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• 2023

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, one of the most deadly infections in humans. The emergence of multidrug-resistant and extensively drug-resistant Mtb strains presents a global challenge. Mtb has shown resistance to many frontline antibiotics, including rifampicin, kanamycin, isoniazid, and capreomycin. The only licensed vaccine, Bacille Calmette-Guerin, does not efficiently protect against adult pulmonary tuberculosis. Therefore, it is urgently necessary to develop new vaccines to prevent infections caused by these strains. We used a subtractive proteomics approach on 23 virulent Mtb strains and identified a conserved membrane protein (MmpL4, NP_214964.1) as both a potential drug target and vaccine candidate. MmpL4 is a non-homologous essential protein in the host and is involved in the pathogen-specific pathway. Furthermore, MmpL4 shows no homology with anti-targets and has limited homology to human gut microflora, potentially reducing the likelihood of adverse effects and cross-reactivity if therapeutics specific to this protein are developed. Subsequently, we constructed a highly soluble, safe, antigenic, and stable multi-subunit vaccine from the MmpL4 protein using immunoinformatics. Molecular dynamics simulations revealed the stability of the vaccine-bound Tolllike receptor-4 complex on a nanosecond scale, and immune simulations indicated strong primary and secondary immune responses in the host. Therefore, our study identifies a new target that could expedite the design of effective therapeutics, and the designed vaccine should be validated. Future directions include an extensive molecular interaction analysis, in silico cloning, wet-lab experiments, and evaluation and comparison of the designed candidate as both a DNA vaccine and protein vaccine.

• IMMUNE NETWORK
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• 제23권2호
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• pp.16.1-16.19
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• 2023

Bacillus Calmette-Guerin (BCG) vaccine is the only licensed vaccine for tuberculosis (TB) prevention. Previously, our group demonstrated the vaccine potential of Rv0351 and Rv3628 against Mycobacterium tuberculosis (Mtb) infection by directing Th1-biased CD4⁺ T cells co-expressing IFN-γ, TNF-α, and IL-2 in the lungs. Here, we assessed immunogenicity and vaccine potential of the combined Ags (Rv0351/Rv3628) formulated in different adjuvants as subunit booster in BCG-primed mice against hypervirulent clinical Mtb strain K (Mtb K). Compared to BCG-only or subunit-only vaccine, BCG prime and subunit boost regimen exhibited significantly enhanced Th1 response. Next, we evaluated the immunogenicity to the combined Ags when formulated with four different types of monophosphoryl lipid A (MPL)-based adjuvants: 1) dimethyldioctadecylammonium bromide (DDA), MPL, and trehalose dicorynomycolate (TDM) in liposome form (DMT), 2) MPL and Poly I:C in liposome form (MP), 3) MPL, Poly I:C, and QS21 in liposome form (MPQ), and 4) MPL and Poly I:C in squalene emulsion form (MPS). MPQ and MPS displayed greater adjuvancity in Th1 induction than DMT or MP did. Especially, BCG prime and subunit-MPS boost regimen significantly reduced the bacterial loads and pulmonary inflammation against Mtb K infection when compared to BCG-only vaccine at a chronic stage of TB disease. Collectively, our findings highlighted the importance of adjuvant components and formulation to induce the enhanced protection with an optimal Th1 response.

• Tuberculosis and Respiratory Diseases
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• 제87권3호
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• pp.386-397
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• 2024

Background: Despite the global increase in nontuberculous mycobacterial pulmonary disease (NTM-PD), clinical characteristics show geographical variations. We investigated the clinical characteristics of patients with NTM-PD in South Korea. Methods: We systematically reviewed articles concerning patients with NTM-PD in South Korea until February 2022. Individual participant data, regardless of treatment, were collected using a standard case report form. Results: Data of 6,489 patients from 11 hospitals between 2002 and 2019 were analyzed. The mean age was 61.5±11.7 years, of whom 57.7% were women. Mycobacterium avium (41.4%) and Mycobacterium intracellulare (38.4%) comprised most of the causative species, followed by Mycobacterium abscessus subspecies abscessus (8.6%) and M. abscessus subspecies massiliense (7.8%). Bronchiectasis (59.4%) was the most common pulmonary comorbidity. Although reported cases of NTM-PD increased over the years, the proportions of causative species and radiologic forms remained similar. Distinct clinical characteristics were observed according to age and sex. Men were older at the time of diagnosis (median 63.8 years vs. 59.9 years, p<0.001), and had more cavitary lesions than women (38.8% vs. 21.0%, p<0.001). The older group (≥65 years) had higher proportions of patients with body mass index <18.5 kg/m² (27.4% vs. 18.6%, p<0.001) and cavitary lesions (29.9% vs. 27.6%, p=0.009) than the younger group. Conclusion: We conducted a meta-analysis of the clinical characteristics of patients with NTM-PD in South Korea, and found age- and sex-related differences in disease-specific severity. Further investigation would enhance our comprehension of the nature of the disease, and inherited and acquired host factors.

• 대한화학회지
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• 제52권3호
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• pp.273-280
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• 2008

결핵은 전 세계적으로 심각한 공중보건문제로 남아있다. 최근에는 결핵의 발병률이 증가하고 있는 추세이며 이에 따른 결핵의 정확한 조기치료와 심각한 부작용, 그리고 전염을 방지하기 위해서는 신속하고 정확한 결핵의 진단이 절실하게 필요하다. 본 연구에서는 결핵유전자를 빠르게 검출하는데 있어서 등온증폭법이 가지고 있는 높은 특이성과 신속성에 대하여 평가하였다. 결핵 DNA의 순차적 10배위 정량희석 DNA를 사용하였으며 일반PCR 방법과 등온증폭법의 실험방법의 검출한계, 민감성, 특이성, 재현성을 비교하였다. 그 결과 등온 증폭법은 빠른 증폭 시간과 높은 민감성, 높은 특이성을 가지고 있었으며 병원이나 연구실, 진단 검사실 등에서 결핵유전자를 빠르고 정확하게 진단할 수 있는 유용한 방법이 될 수 있을 것이다.

• Tuberculosis and Respiratory Diseases
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• 제58권2호
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• pp.142-152
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• 2005

배 경 : 최근 결핵에 대한 새로운 백신 개발은 초회 면역 방법 및 추가 면역 방법을 이용하는 방향으로 연구되고 있다. 본 실험은 새로운 백신 후보 물질로서의 가능성을 알아보기 위하여 결핵균 adenylate kinase (AK), nucleoside diphosphate (NdK) 및 heat shock protein 70(Hsp70)의 결핵균에 대한 방어면역효능을 측정하였다. 방 법 : 재조합 단백질들을 정제하기 위하여 중합효소 연쇄반응으로 증폭한 결핵균 유전자 단편들을 E.coli expression vector, pQE30에 클로닝한 후, Ni-NTA resin을 이용하여 정제하였다. DDA와 재조합 단백질들을 마우스에 면역주사하고 면역반응 생성 유무를 확인하기 위하여 항체와 $IFN-{\gamma}$ 생성능을 측정하였다. 면역주사 한 마우스에 결핵균을 공기 감염시킨 후, 폐와 비장을 분리하여 결핵균 생균수 실험을 하였다. 결 과 : 재조합 단백질 AK, NdK 와 Hsp70을 면역보강제인 DDA를 이용하여 면역주사 한 결과에서, 생리식염수 혹은 DDA를 면역주사 한 마우스에 비교하여 재조합 단백질을 면역주사 한 마우스에서는 각 항원에 대해 항체와 $IFN-{\gamma}$ 생성능이 높게 나타났으나 결핵균에 대한 효과적인 방어면역효능은 나타나지 않았다. 결 론 : 마우스를 모델로 한 결핵균에 대한 방어면역효능 실험에서, 면역보강제 DDA를 이용한 재조합 단백질 AK, NdK 및 Hsp70을 면역주사 한 경우에는 결핵균의 성장을 효과적으로 조절하지 못하였다. 혼합 단백질 혹은 다른 T세포 면역보강제의 사용에 의한 추시가 필요하다.

• 대한미생물학회지
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• 제34권5호
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• pp.491-500
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• 1999

A recent study showed that comparative sequence analysis of rpoB DNAs could reveal natural relationships in genus Mycobacterium [J Clin Microbial. 37 (6). 1999]. rpoB DNAs showed interspecies variation and intraspecies conservation. Based on these data, we developed polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) protocols which enable species differentiation in genus Mycobacterium. When this assay was applied to 24 clinical isolates identified as M. avium complex (MAC) by biochemical test, these were successfully differentiated into M. avium and M. intracellulare. These results were concordant with those obtained by 16s rDNA analysis. It is the first report that PCR-SSCP analysis of rpoB DNA could be used for species differentiation of MAC strains.