Identification of Nontuberculous Mycobacteria in Patients with Pulmonary Diseases in Gyeongnam, Korea, Using Multiplex PCR and Multigene Sequence-Based Analysis

Background

Nontuberculous mycobacteria (NTM) are widely present in environments, such as soil and water, and have recently been recognized as important pathogenic bacteria. The incidence of NTM-related infections is steadily increasing. As the diagnosis and treatment of NTM infection should be distinguished from tuberculosis, and the treatment should be specific to the species of NTM acquired, accurate species identification is required.

Methods

In this study, two-step multiplex PCR (mPCR) and multigene sequence-based analysis were used to accurately identify NTM species in 320 clinical isolates from Gyeongsang National University Hospital (GNUH). In particular, major mycobacterial strains with a high isolation frequency as well as coinfections with multiple species were diagnosed through two-step mPCR. Multigene sequencing was performed to accurately identify other NTM species not detected by mPCR. Variable regions of the genes 16S rRNA, rpoB, hsp65, and 16S-23S rRNA internal transcribed spacer were included in the analysis.

Results

Two-step mPCR identified 234 (73.1%) cases of M. intracellulare, 26 (8.1%) cases of M. avium subsp. avium, and 13 (4.1%) cases of M. avium subsp. hominissuis infection. Additionally, 9 (2.8%) M. fortuitum, 9 (2.8%) M. massiliense, 2 (0.6%) M. abscessus, and 4 (1.2%) M. kansasii isolates were identified. Coinfection was identified in 7 (2.2%) samples. The sixteen samples not classified by two-step mPCR included 6 (1.9%) cases of M. chimaera, 4 (1.3%) M. gordonae, 1 (0.3%) M. colombiense, 1 (0.3%) M. mageritense, and 1 (0.3%) M. persicum identified by sequence analysis.

Conclusions

The results of this study suggest a strategy for rapid detection and accurate identification of species using two-step mPCR and multigene sequence-based analysis. To the best of our knowledge, this study is the first to report the identification of NTM species isolated from patients in Gyeongnam/Korea.

Differential diagnosis of disseminated Mycobacterium avium and Mycobacterium tuberculosis infection in HIV patients using duplex PCR

Background: Disseminated Mycobacterium avium complex (MAC) and Mycobacterium tuberculosis infections have almost similar clinical presentations but require different therapeutic management. Materials & methods: A duplex PCR was designed based on the sequence variation between the genes encoding catalase-peroxidase (KatG) of M. avium complex and M. tuberculosis, so as to discriminate MAC, M. tuberculosis and mixed mycobacterial (MAC + M. tuberculosis) infections in HIV patients. Results: An accurate, single-step differential diagnosis of disseminated mycobacterial infections in HIV patients was achieved with specific detection of a single band each for M. avium (120 bp) and M. tuberculosis (90 bp) and two bands for the mixed (120 and 90 bp) infections. Conclusion: katG gene-based duplex PCR can facilitate quick differential diagnosis of disseminated MAC and M. tuberculosis infections in HIV patients.

Exploring the advantages and limitations of sampling methods commonly used in research facilities for zebrafish health inspections

Examining zebrafish populations for the presence of disease is an integral component of managing fish health in research facilities. Currently, many different strategies are used for zebrafish fish health inspections, which is a scenario that may result in subjective and biased diagnostic evaluations. The goal of this study was to compare the success of pathogen detection between a sample size of randomly selected fish (n = 60) that provides 95% confidence in pathogen detection based on a presumed pathogen prevalence level ≥5%, and other subpopulations and sample numbers commonly submitted for diagnostic testing within a 1000 tank, 30,000 fish, recirculating research system. This included fish collected from a sump tank (n = 53), sentinel fish (n = 11), and fish that were found moribund or freshly dead (n = 18). Additionally, five fish from each subpopulation were collected for histopathologic examination. A second study used retrospective data to examine pathogen distribution between systems (n = 2-5) in multi-system facilities (n = 5) using a sample size of 60 fish per system. For the pathogens detected, results supported the use of representative sample numbers rather than smaller numbers of populations considered more at risk. The exception to this is for the moribund/mortality group, which may be a resource for targeted surveillance of select pathogens. Each system within multi-system facilities should be considered separate units in terms of fish health inspections and biosecurity. Development of these evidence-based standards for fish health inspections in zebrafish systems enhances fish welfare, provides identification of potentially zoonotic pathogens, and ensures scientific integrity and reproducibility of research results.

Systemic Mycobacterium kansasii Infection in a Domestic Shorthair Cat

A 1-year-old, female domestic shorthair cat was presented with anorexia, depression and weight loss, accompanied by multifocal nodules affecting the face, pinnae and periarticular tissue. Routine medical treatments were ineffective. The animal's physical condition continued to deteriorate and it finally died. Post-mortem examination revealed multifocal to coalescing firm nodules with occasional ulceration affecting the ears, peri-ocular areas, nasal planum, oral cavity and laryngopharyngeal region. Tan-coloured, firm, nodular lesions were also observed in the periarticular tissue, lungs and tracheobronchial and mediastinal lymph nodes. Impression smears of several of these lesions revealed a myriad of slender rod-shaped organisms, mainly in the cytoplasm of macrophages. Histopathological examination showed severe pyogranulomatous inflammation with or without necrosis in the nodules. Acid-fast staining revealed large numbers of acid-fast bacilli. Mycobacterium kansasii was detected in the tissues using multiplex polymerase chain reaction and DNA sequencing. No protozoal or fungal organisms were detected using special stains. On the basis of these results, the cat was diagnosed with systemic M. kansasii infection. To our knowledge, there have been few reports of M. kansasii infection, especially with systemic spread, in cats.

Clinical characteristics and treatment outcomes of tuberculosis in the elderly: a case control study

Background

The purpose of this study was to evaluate the differences in clinical characteristics and treatment outcomes between older and younger tuberculosis (TB) patients in Korea.

Methods

We retrospectively analyzed the medical records of 271 younger (20–64 years old at diagnosis) and 199 older (≥65 years) TB patients who had been newly diagnosed and treated at Chonnam National University Hospital from May 2008 to August 2010.

Results

Dyspnea and comorbid medical conditions were more frequent and positive TB culture rates were higher in older TB patients. In chest computed tomography (CT) scans of pulmonary TB patients, older patients were less likely to have micronodules (<7 mm in diameter), nodules (<30 mm in diameter), masses (>30 mm in diameter), and cavities compared with younger patients, but were more likely to have consolidations. Incidence of adverse drug reactions did not differ between the two groups, except for severe gastrointestinal disorders. There were no significant differences in favorable treatment outcomes between younger and older TB patients (97% vs. 94%, respectively; p = 0.251).

Conclusions

Older TB patients had more frequent dyspnea and less frequent active TB findings on chest CT. Treatment success and adverse drug reaction rates were similar in older and younger TB patients.

Incidence of tuberculous and non-tuberculous mycobacteria, differentiated by multiplex PCR, in clinical specimens of a large general hospital

OBJECTIVE

To determine the incidence of Mycobacterium tuberculosis complex and non-tuberculous mycobacterial isolates in the routine setting of a large general hospital using an "in-house" multiplex polymerase chain reaction method and to establish a paradigm for the definitive identification of mycobacteria isolated using semi-automated equipment.

METHODS

Established tests, including polymerase chain reaction restriction enzyme analysis, PNB, and NAP inhibition tests as the gold standard, showed 100% agreement with an IS6110/hsp65 multiplex polymerase chain reaction when used to identify stock strains (n = 117).

RESULTS

In a subsequent study, 8,790 clinical specimens producing 476 isolates were evaluated with multiplex PCR and also showed 100% agreement in identification using PRA-polymerase chain reaction as the gold standard. The application of this technique to routine analysis was demonstrated in this study. A method was established with the initial application of multiplex PCR for all positive liquid cultures and the subsequent identification of non-tuberculous mycobacteria by polymerase chain reaction restriction enzyme analysis. In total, 77% of isolates belonged to the Mycobacterium tuberculosis complex, and 23% were non-tuberculous mycobacteria.

CONCLUSIONS

Several non-tuberculous mycobacterial species were identified, primarily M. avium, but other potentially pathogenic species were also frequently observed, including M. fortuitum, M. abscessus, and M. kansasii. The expeditious communication of these data to the clinical staff was fundamental for the diagnosis of clinical cases. Even in settings where tuberculosis is of major importance, the incidence of non-tuberculous mycobacteria infection is substantial.

Rapid and accurate identification of Mycobacterium tuberculosis complex and common non-tuberculous mycobacteria by multiplex real-time PCR targeting different housekeeping genes

Rapid and accurate identification of mycobacteria isolates from primary culture is important due to timely and appropriate antibiotic therapy. Conventional methods for identification of Mycobacterium species based on biochemical tests needs several weeks and may remain inconclusive. In this study, a novel multiplex real-time PCR was developed for rapid identification of Mycobacterium genus, Mycobacterium tuberculosis complex (MTC) and the most common non-tuberculosis mycobacteria species including M. abscessus, M. fortuitum, M. avium complex, M. kansasii, and the M. gordonae in three reaction tubes but under same PCR condition. Genetic targets for primer designing included the 16S rDNA gene, the dnaJ gene, the gyrB gene and internal transcribed spacer (ITS). Multiplex real-time PCR was setup with reference Mycobacterium strains and was subsequently tested with 66 clinical isolates. Results of multiplex real-time PCR were analyzed with melting curves and melting temperature (T (m)) of Mycobacterium genus, MTC, and each of non-tuberculosis Mycobacterium species were determined. Multiplex real-time PCR results were compared with amplification and sequencing of 16S-23S rDNA ITS for identification of Mycobacterium species. Sensitivity and specificity of designed primers were each 100 % for MTC, M. abscessus, M. fortuitum, M. avium complex, M. kansasii, and M. gordonae. Sensitivity and specificity of designed primer for genus Mycobacterium was 96 and 100 %, respectively. According to the obtained results, we conclude that this multiplex real-time PCR with melting curve analysis and these novel primers can be used for rapid and accurate identification of genus Mycobacterium, MTC, and the most common non-tuberculosis Mycobacterium species.

Treatment outcome of combination therapy including clarithromycin for Mycobacterium avium complex pulmonary disease

BACKGROUND/AIMS

The frequency of nontuberculous mycobacteria pulmonary disease in HIV-negative patients is increasing; the most common pathogen in Korea is the Mycobacterium avium complex (MAC). However, few studies have evaluated the treatment outcome of MAC pulmonary disease in Korea.

METHODS

The efficacy of a clarithromycin-containing regimen for MAC pulmonary disease was studied in 42 patients treated for more than 6 months between January 2005 and December 2008. All patients were treated with a regimen consisting of clarithromycin, rifampin, and ethambutol. Streptomycin was added in 10 patients.

RESULTS

Among the 42 patients, a negative culture conversion was achieved in 33 (78.6%), and the median duration of treatment in these patients was 19 months (interquartile range [IQR], 16 to 22). Of the 33 patients with a negative culture conversion, 14 completed treatment. During the follow-up period (median, 10 months; IQR, 4 to 20) for the 14 patients, one relapsed at 24 months after treatment completion. The culture conversion rate was significantly higher in patients who were treated with more than 500 mg/day clarithromycin (87.1% vs. 54.5%, p = 0.038).

CONCLUSIONS

The combined regimen including clarithromycin was effective against MAC pulmonary disease. High-dose clarithromycin of more than 500 mg/day may improve the outcome of patients with MAC pulmonary disease.