Clinico-microbiological analysis of 121 patients with pulmonary Mycobacteroides abscessus complex disease in Japan - An NTM-JRC study with RIT

RATIONALE

No comprehensive analysis has previously been performed to evaluate the clinical aspects of and microbiological evidence associated with Mycobacteroides abscessus complex (MABC) infection in a region, such as Japan, with a low MABC incidence.

OBJECTIVES

This study aimed to clarify the clinicopathological characteristics of MABC, which included clinical relatedness to erm(41) sequevar, phenotype (as colony morphology and minimum inhibitory concentration), and genotype.

METHODS

A total of 121 MABC patients (68 with M. abscessus subsp. abscessus and 53 with M. abscessus subsp. massiliense) were recruited into this retrospective clinical-biological study from tertiary hospitals in Japan between 2004 and 2014.

RESULTS

Approximately 30% of MABC patients had a history of previous nontuberculous mycobacterium (NTM) disease. Furthermore, 24.8% of the patients had another concomitant NTM infection after they were diagnosed with MABC. Fewer than 10% of the patients in the M. abscessus group had T28C in erm(41). While we observed a higher conversion rate for M. massiliense than for M. abscessus (72.4% and 34.8%, respectively, p = 0.002), recurrence remained relatively common for M. massiliense (31.0%). In the M. abscessus patients, the MIC of clarithromycin (CLR) was significantly lower on day 3 in patients with a better treatment response than in refractory patients (The median MIC; 0.75 μg/ml v.s 2.0 μg/ml, p = 0.03). There was no significant relation between clinical manifestations and variable number of tandem repeat genotypes.

CONCLUSIONS

Because the history and simultaneous isolation of other NTM in MABC infection are relatively common, these information should be carefully translated into clinical actions. The evaluation of early CLR resistance in M. abscessus and the erm(41) functions should be important to improve the treatment strategy.

Mycolicibacterium smegmatis, Basonym Mycobacterium smegmatis, Expresses Morphological Phenotypes Much More Similar to Escherichia coli Than Mycobacterium tuberculosis in Quantitative Structome Analysis and CryoTEM Examination

A series of structome analyses, that is, quantitative and three-dimensional structural analysis of a whole cell at the electron microscopic level, have already been achieved individually in Exophiala dermatitidis, Saccharomyces cerevisiae, Mycobacterium tuberculosis, Myojin spiral bacteria, and Escherichia coli. In these analyses, sample cells were processed through cryo-fixation and rapid freeze-substitution, resulting in the exquisite preservation of ultrastructures on the serial ultrathin sections examined by transmission electron microscopy. In this paper, structome analysis of non pathogenic Mycolicibacterium smegmatis, basonym Mycobacterium smegmatis, was performed. As M. smegmatis has often been used in molecular biological experiments and experimental tuberculosis as a substitute of highly pathogenic M. tuberculosis, it has been a task to compare two species in the same genus, Mycobacterium, by structome analysis. Seven M. smegmatis cells cut into serial ultrathin sections, and, totally, 220 serial ultrathin sections were examined by transmission electron microscopy. Cell profiles were measured, including cell length, diameter of cell and cytoplasm, surface area of outer membrane and plasma membrane, volume of whole cell, periplasm, and cytoplasm, and total ribosome number and density per 0.1 fl cytoplasm. These data are based on direct measurement and enumeration of exquisitely preserved single cell structures in the transmission electron microscopy images, and are not based on the calculation or assumptions from biochemical or molecular biological indirect data. All measurements in M. smegmatis, except cell length, are significantly higher than those of M. tuberculosis. In addition, these data may explain the more rapid growth of M. smegmatis than M. tuberculosis and contribute to the understanding of their structural properties, which are substantially different from M. tuberculosis, relating to the expression of antigenicity, acid-fastness, and the mechanism of drug resistance in relation to the ratio of the targets to the corresponding drugs. In addition, data obtained from cryo-transmission electron microscopy examination were used to support the validity of structome analysis. Finally, our data strongly support the most recent establishment of the novel genus Mycolicibacterium, into which basonym Mycobacterium smegmatis has been classified.

Six species of nontuberculous mycobacteria carry non-identical 16S rRNA gene copies

Nontuberculous mycobacteria (NTM) can carry two or more 16S rRNA gene copies that are, in some instances, non-identical. In this study, we used a combined cloning and sequencing approach to analyze 16S rRNA gene sequences of six NTM species, Mycobacterium cosmeticum, M. pallens, M. hodleri, M. crocinum, M. flavescens, and M. xenopi. Our approach facilitated the identification of two distinct gene copies in each species. The two M. cosmeticum genes had a single nucleotide difference, whereas two nucleotide polymorphisms were identified in M. hodleri, M. flavescens, and M. xenopi. M. pallens had a difference in four nucleotides and M. crocinum - in 23 nucleotides. Thus, we showed that the six NTM species possess at least two non-identical 16S rRNA gene copies. The full-length sequences of the intraspecies 16S rRNA variants will facilitate NTM identification and sequence analysis of specimens or other samples.

Prevention of aerosol isolation of nontuberculous mycobacterium from the patient's bathroom

Recent clinical studies have revealed that reappearance of the same nontuberculous mycobacterium (NTM) infection is common after successful standard treatment [1, 2]. Using pulsed-field gel electrophoresis analysis, Wallaceet al. [1] found that ∼75% of Mycobacterium avium-intracellulare complex (MAC) isolates identified after successful treatment are the result of reinfection. According to a recent study conducted by Kohet al. [2] using repetitive sequence-based PCR analysis, all re-identified M. abscessus subsp. abscessus isolates had a unique genotype. Therefore, patients with NTM are exposed to large amounts of microbes in their daily lives, particularly in cases of reinfection.

Reinfection of nontuberculous mycobacterium pulmonary disease may be caused by identical and not different genotypeshttp://ow.ly/62cH30krdpa

Evaluation of PyroMark Q24 pyrosequencing as a method for the identification of mycobacteria

We evaluated PyroMark Q24 (QIAGEN) pyrosequencing as a method for the identification of mycobacteria, with potential application in clinical practice. Sequence data from the hypervariable region A of the 16S rRNA gene (43 and 35bp sequences) were obtained using PyroMark Q24, and a similarity search was performed automatically with PyroMark IdentiFire software. Of the 148 mycobacterial type strains tested, 138 (93.2%) were accurately identified to single or clade species level, including complex level. From the remaining 10 strains, 3 (Mycobacterium gilvum, Mycobacterium goodi, and Mycobacterium thermoresistible) showed poor sequencing quality of homopolymers. For 6 other strains (Mycobacterium cosmeticum, Mycobacterium flavescens, Mycobacterium pallens, Mycobacterium hodleri, Mycobacterium xenopi, and Mycobacterium crocinum), the sequences were unreadable from the middle, and Sanger sequencing indicated biallelic site. Finally, a 40bp sequence for Mycobacterium gordonae could not be obtained despite repeated attempts. PyroMark Q24 provided accurate identification of multiple mycobacterial strains isolated from common clinical settings, but additional gene sequencing is required to distinguish species identified as a group or complex.

Laboratory evaluation of the Anyplex™ II MTB/MDR and MTB/XDR tests based on multiplex real-time PCR and melting-temperature analysis to identify Mycobacterium tuberculosis and drug resistance

We evaluated the performance of two multiplex, real-time PCR tests (Anyplex II MTB/MDR and MTB/XDR; Seegene, Seoul, Korea), designed to detect the Mycobacterium tuberculosis complex (MTC) and drug-resistance mutations associated with isoniazid, rifampicin, fluoroquinolones, and second-line injectable drugs. We analyzed 122 clinical isolates with the Anyplex II MTB/MDR test, 68 of which were also tested with the Anyplex II MTB/XDR test. The Anyplex II MTB/MDR and MTB/XDR tests showed the following respective sensitivities and specificities: 68.8% and 100% for detecting isoniazid resistance, 93.8% and 100% for rifampicin, 82.8% and 100% for levofloxacin, 75.0% and 100% for kanamycin, and 92.6% and 100% for MTC identification. These kits correctly identified 61.8% of multi-drug resistant M. tuberculosis isolates and 64.7% of extensively drug-resistant M. tuberculosis isolates, and enabled semi-automatic detection of drug-resistant MTC in 3 hours. The Anyplex II kits could be useful as rule-in tests for detecting MTC and drug resistance.

In vitro activity of sitafloxacin against Mycobacterium tuberculosis with gyrA/B mutations isolated in Japan

Purpose. Sitafloxacin (SFX) is a new fluoroquinolone (FQ) that has shown a strong bactericidal effect against Mycobacterium tuberculosis (Mtb) in vitro. However, data on SFX efficacy against Mtb with gyrA/B mutations and its epidemiological cut-off (ECOFF) value remain limited. Therefore, we evaluated and compared the in vitro activity of SFX against gyrA/B-mutant Mtb to that of moxifloxacin (MFX), levofloxacin (LFX) and ciprofloxacin (CFX), and determined the ECOFF for SFX.Methodology. A total of 109 clinical Mtb isolates, including 73 multidrug-resistant (MDR) isolates, were subjected to minimum inhibitory concentration (MIC) analysis in oleic-albumin-dextrose-catalase (OADC)-supplemented Middlebrook 7H9 medium. Our results showed that SFX had lower cumulative MIC than MFX, LFX and CFX. Furthermore, we performed direct DNA sequencing of the quinolone-resistance-determining regions (QRDRs).Results. We identified the following mutations: D94G, D94A, A90V, D94H, D94N and G88A in gyrA; and A543V, A543T, E540D, R485C, D500A, I552S and D577A in gyrB. Based on our results, an ECOFF of 0.125 µg ml^-1 was proposed for SFX. With this ECOFF, 15 % of LFX-resistant isolates with MIC ≥2 µg ml^-1 were susceptible to SFX.Conclusion. SFX had the lowest cumulative MIC and a relatively low ECOFF value against Mtb, indicating that SFX was not only more effective against gyrA-mutant isolates, but also MDR isolates in Japan.

[EXTERNAL QUALITY ASSESSMENT OF ANTI-TUBERCULOSIS DRUG SUSCEPTIBILITY TESTING FOR DIAGNOSING EXTENSIVELY DRUG-RESISTANT MYCOBACTERIUM TUBERCULOSIS]

[Objective] The infectious disease control law has been amended in May 2015, and the category definition of Mycobacterium tuberculosis as infectious pathogen has been changed, following the definition of extensively drug-resistant M.tuberculosis (XDR-TB) by World Health Organization. To assess the diagnostic capacity of XDR-TB, we conducted an external quality assessment (EQA) for the anti-tuberculosis drug susceptibility testing (DST). [Method] A total of 10 M.tuberculosis strains with known drug susceptibility were sent to each participating laboratory. The drugs assessed were isoniazid (INH), rifampicin (RFP), streptomycin (SM), ethambutol (EB), levofloxacin (LVFX), and kanamycin (KM). DST was performed using each routine method(s), and the results were compared with the judicial diagnoses. The sensitivity, specificity, overall agreement (effi- ciency) and kappa coefficient were calculated for each drug tested. In addition, the diagnostic accuracy of multidrug-resis- tant M. tuberculosis (MDR-TB) and XDR-TB was assessed. [Results] A total of 88 institutes including 67 hospitals, 16 commercial laboratories, and 5 public health laboratories par- ticipated in the EQA. With 2 laboratories submitting 2 sets of results, a total of 90 independent data sets were analyzed. As for INH, RFP and LVFX, the efficiency was over 95%, but we found two strains each for SM, EB and KM with the efficiency less than 95%. Especially, strain 1 and strain 2 showed efficiency of 72.2% and 71.1% to SM, respectively. This error was mainly found in a certain test kit. If we consider the passing score as showing ≥95 % sensitivity and specificity both to INH and RFP, the diagnostic accuracy of MDR-TB was 92.2% (83/90) in this study. With the same criteria to INH, RFP, LVFX and KM, that of XDR-TB was 79.7% (63/79). [Discussion] The diagnostic capacity of XDR-TB was not sufficient in the current study. Good case management and pathogen control requires higher accuracy. The government may need to conduct a constant EQA and relevant remedial actions.

[SPECIFICITY EVALUATION OF TRCReady® MTB AND TRCReady® MAC FOR IDENTIFYING MYCOBACTERIUM TUBERCULOSIS COMPLEX, MYCOBACTERIUM AVIUM AND MYCOBACTERIUM INTRACELLULARE]

[Objective] To evaluate the specificity of TRC- Ready® MTB and TRCReady® MAC (Tosoh Bioscience, Japan) for identifying M.tubercidosis complex (MTC), M.avium and M. intracellulare. [Method] We tested TRCReady® MTB and TRCReady® MAC using TRCReady®-80 (Tosoh Bioscience, Japan), which is an automated nucleic amplification test instrument, with 151 Mycobacterium species (4 MTC and 147 Non-tuberculosis Mycobacterium (NTM) type strains). [Results] The specificity of TRCReady® MTB was 100%, however, TkCReady® MAC misidentified a total of six NTMs, M.arosiense, M.chimaera, M.colombiense, M.marseillense, M. vulneris and M.yongonense, as M. intracellulare. Then, the specificity for TRCReady® MAC was 96.0% (145/151). [Discussion] TRCReady® MTB and TRCReady® MAC are highly specific for identifying MTC, M.avium and M. intracellulare. Six NTM species which have been rarely isolated in Japan showed false-positive results as M.intra- celludare. However, when a sample was identified as M.in- tracellulare, the phenotypic characteristics like colony mor- phology would be carefully examined.

Evaluation of QuantiFERON-TB Gold Plus for Detection of Mycobacterium tuberculosis infection in Japan

Performance of interferon-γ (IFN-γ) release assays still needs to be improved. The data on the performance of QuantiFERON-TB Gold Plus (QFT-Plus), a new-generation of QFT assay are limited. This study evaluated the diagnostic performance of QFT-Plus, and compared to that of QuantiFERON-TB Gold In-Tube (QFT-GIT). Blood samples were collected from 162 bacteriologically confirmed tuberculosis (TB) patients and 212 Mycobacterium tuberculosis-uninfected volunteers; these samples were then tested with QFT-GIT and QFT-Plus. The IFN-γ concentration of QFT-Plus was lower than that of QFT-GIT in TB patients (p < 0.001). Receiver operating characteristic curves were compared between QFT-GIT and QFT-Plus. Both assays showed area under the curve values over 0.99 without significant difference. Using the conventional cut-off (0.35 IU/mL) for QFT-GIT, QFT-Plus had a lower sensitivity of 91.1% compared to 96.2% (p = 0.008) at its optimum cut-off (0.168 IU/mL) with the same specificity. Moreover, IFN-γ values were significantly reduced with age in QFT-GIT (p = 0.035) but not in QFT-Plus. The diagnostic performance of QFT-Plus was as accurate as that of QFT-GIT despite a lack of TB7.7 antigen and despite the decrease in quantitative values. However, the cut-off value for QFT-Plus should be considered independently from that of QFT-GIT to obtain the best sensitivity without compromising specificity.

Successful Treatment of Peritoneal Dialysis-related Peritonitis due to Mycobacterium iranicum

A 68-year-old man on peritoneal dialysis (PD) was hospitalized with the clinical picture of peritonitis. The patient was diagnosed with peritonitis caused by nontuberculous mycobacteria (NTM) according to positive Ziehl-Neelsen staining and negative Mycobacterium tuberculosis polymerase chain reaction results. Oral levofloxacin and clarithromycin, and later intraperitoneal imipenem were started. According to the anti-NTM susceptibility test results, oral minocycline was administered. The patient was treated for 6 months. He recovered without PD catheter removal; thus, PD was successfully continued. A genetic analysis identified the isolate as Mycobacterium iranicum. This is the first report of PD-related peritonitis caused by M. iranicum.

Six Cases of Pulmonary Mycobacterium shinjukuense Infection at a Single Hospital

Mycobacterium shinjukuense lung disease was diagnosed in 3 men and 3 women [mean age: 77.0±12.2 (57-93) years]. On imaging, 3 patients with previous pulmonary tuberculosis exhibited a fibrocavitary pattern, while the other 3 patients showed nodular bronchiectasis. A test with a tuberculosis rRNA identification kit (TRC Rapid(®) M. TB) was falsely positive for M. tuberculosis due to DNA sequence similarity in 16SrRNA. M. shinjukuense was identified by the gene sequences of rpoB, 16S rRNA, and hsp65. The symptoms and imaging findings of most of the patients have improved with chemotherapy with low minimum inhibitory concentrations of anti-tuberculosis drugs.

COBAS® TaqMan® MTB, smear positivity grade and MGIT culture; correlation analyses of three methods for bacillary quantification

We investigated the correlation between the cycle threshold (Ct) value of the COBAS(®) TaqMan(®) MTB (TaqMan MTB), the mycobacterial smear positivity grade, and the time to detection (TTD) in the Mycobacteria Growth Indicator Tube (MGIT) for quantification of Mycobacterium tuberculosis (MTB). For 57 sputum samples, significant correlations were observed between the Ct value, the smear positivity grade, and the MGIT TTD (Spearman's rank correlation coefficient: r(s) = -0.940, P < 0.001 and Pearson's correlation coefficient: r(p) = 0.737, P < 0.001). In addition, a correlation was observed between the number of bacteria estimated based on the smear positivity grade and the number of MTB bacilli calculated by the Ct value (r(s) = 0.930, P < 0.001). This study has demonstrated the possible estimation of the smear positivity grade and MGIT TTD using the Ct value of TaqMan MTB, which is based on a real-time PCR system, for diagnostic samples.

Factors contribute to efficiency of specimen concentration of Mycobacterium tuberculosis by centrifugation and magnetic beads

BACKGROUND

A concentration of specimen is recommended for the effective recovery of Mycobacterium tuberculosis (MTB), but the bacteriological efficiency is not well evaluated. The present study evaluated the factors contributing to concentration efficiency of centrifugation and bead-based technique (TB-Beads; Microsens, UK) to recover MTB by using simple in vitro specimens.

METHODS

Four specimens were prepared (6.5×10(3); 8.1×10(4); 7.9×10(5); and 6.4×10(6)cfu/mL) of different concentrations with or without 5×10(4) of THP-1 cells (RIKEN BRC, Japan). Specimens were subjected to centrifugation at 2000, 3000, and 4000g for 15min, and to TB-Beads. The concentration and recovery rate were calculated to evaluate the efficiency of each method.

RESULTS

The specimens containing a higher number of bacteria and THP-1 cells had a tendency to yield a higher concentration and recovery rate (p=0.001-0.083). MTB was recovered more efficiently with THP-1 cells from the 6.5×10(3)cfu/mL specimen by centrifugation (p⩽0.001) than without them; 24.7-54.4% of MTB were recovered with THP-1 cells by centrifugation at 3000g for 15min, while the recovery using TB-Beads was a maximum of 12.7%.

CONCLUSIONS

The efficiency of centrifugation depends on the bacterial density and the co-existence of THP-1 cells. The efficiency of TB-Beads was not as high as centrifugation.

Disseminated Mycobacterium abscessus Infection Following Septic Arthritis: A Case Report and Review of the Literature

Mycobacterium abscessus is a rapidly growing mycobacterium found mainly in patients with respiratory or cutaneous infections, but it rarely causes disseminated infections. Little is known about the clinical characteristics, treatment, and prognosis of disseminated M abscessus infection. A 75-year-old Japanese woman who had been treated for 17 years with a corticosteroid for antisynthetase syndrome with antithreonyl-tRNA synthetase antibody developed swelling of her right elbow. X-ray of her right elbow joint showed osteolysis, and magnetic resonance imaging revealed fluid in her right elbow joint. M abscessus grew in joint fluid and blood cultures. She was diagnosed with a disseminated M abscessus infection following septic arthritis. Antimicrobial treatment by clarithromycin, amikacin, and imipenem/cilastatin combined with surgical debridement was administered. Although blood and joint fluid cultures became negative 1 week later, the patient died at 6 weeks from starting antimicrobial treatment. We reviewed 34 cases of disseminated M abscessus infections from the literature. Most of the patients had immunosuppressive backgrounds such as transplantation, use of immunosuppressive agents, hematological malignancy, and end stage renal disease. The duration from onset of symptoms to diagnosis was over 3 months in half of the cases. All fatal cases had positive blood cultures or use of immunosuppressive agents. Clinicians should bear in mind that mycobacterial infections including M abscessus are one of the differential diagnoses in patients with subacute arthritis and soft tissue infections.

Structome analysis of virulent Mycobacterium tuberculosis, which survives with only 700 ribosomes per 0.1 fl of cytoplasm

We previously reported the exquisite preservation of the ultrastructures of virulent Mycobacterium tuberculosis cells processed through cryofixation and rapid freeze substitution. Here, we report the “structome” analysis (i.e., the quantitative three-dimensional structural analysis of a whole cell at the electron microscopic level) of virulent M. tuberculosis using serial ultrathin sections prepared after cryofixation and rapid freeze substitution and analyzed by transmission electron microscopy. Five M. tuberculosis cells, which were contained in the serial ultrathin cross sections encompassing from one end to the other, were cut into 24, 36, 69, 55, and 63 serial ultrathin sections, respectively. On average, the cells were 2.71 ± 1.05 μm in length, and the average diameter of the cell was 0.345 ± 0.029 μm. The outer membrane and plasma membrane surface areas were 3.04 ± 1.33 μm² and 2.67 ± 1.19 μm², respectively. The cell, outer membrane, periplasm, plasma membrane, and cytoplasm volumes were 0.293 ± 0.113 fl (= μm³), 0.006 ± 0.003 fl, 0.060 ± 0.021 fl, 0.019 ± 0.008 fl, and 0.210 ± 0.091 fl, respectively. The average total ribosome number was 1,672 ± 568, and the ribosome density was 716.5 ± 171.4/0.1 fl. This is the first report of a structome analysis of M. tuberculosis cells prepared as serial ultrathin sections following cryofixation and rapid freeze substitution and examined by transmission electron microscopy. These data are based on the direct measurement and enumeration of exquisitely preserved single-cell structures in transmission electron microscopy images rather than calculations or assumptions from indirect biochemical or molecular biological data. In addition, these data may explain the slow growth of M. tuberculosis and enhance understanding of the structural properties related to the expression of antigenicity, acid-fastness, and the mechanism of drug resistance, particularly in regard to the ratio of target to drug concentrations.

Optimization of the microscopic observation drug susceptibility assay for four first-line drugs using Mycobacterium tuberculosis reference strains and clinical isolates

OBJECTIVE

The aim of this study is to determine the appropriate cut-off value and turnaround time of the microscopic observation drug susceptibility assay (MODS) for isoniazid (INH), rifampicin (RMP), streptomycin (STR), and ethambutol (EMB).

DESIGN

A total of 39 Mycobacterium tuberculosis strains with confirmed drug susceptibility (reference strains) were tested with a range of drug concentrations to determine the optimal cut-off values for INH, RMP, STR, and EMB by MODS. Standard drug susceptibility testing (DST) results were evaluated relative to the Löwenstein-Jensen (L-J) proportion method. Following which, the performance of MODS was evaluated again using 36 sputum samples from patients with tuberculosis (TB) using the cut-off values determined in the aforementioned process.

RESULTS

With 39 reference strains, DST identified the following cut-off values: 0.8μg/ml INH (sensitivity, 96.0%; specificity, 92.9%), 2.0μg/ml RMP (sensitivity, 100%; specificity, 95.5%), 4.0μg/ml STR (sensitivity, 90.5%; specificity, 93.8%), and 4.0μg/ml EMB (sensitivity, 100%; specificity, 91.7%). When these cut-off values were used to analyze the 36 clinical isolates, the sensitivity and specificity of MODS were 100% and 93.1% for INH, 100% and 93.8% for RMP, 87.5% and 96.4% for STR, and 100% and 88.2% for EMB, respectively. The turnaround time for these clinical specimens was 9.0days by MODS (95% CI: 5.3-12.7), compared with 11.7days (95% CI: 9.5-13.9) for smear negative specimens.

CONCLUSION

Our study identified the optimal cut-off values of the four first-line drugs for MODS based on a wide concentration range. With the optimal cut-off values determined in this study, MODS showed high discriminatory efficiency for DST. This study also demonstrated that MODS is useful for rapid diagnosis of drug-resistant TB even for a smear negative specimen, despite the fact that it generally uses smear positive specimens as direct DST.

Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex

BACKGROUND

The rapid identification of acid-fast bacilli recovered from patient specimens as Mycobacterium tuberculosis complex (MTC) is critically important for accurate diagnosis and treatment. A thin-layer immunochromatographic (TLC) assay using anti-MPB64 or anti-MPT64 monoclonal antibodies was developed to discriminate between MTC and non-tuberculosis mycobacteria (NTM). Capilia TB-Neo, which is the improved version of Capilia TB, is recently developed and needs to be evaluated.

METHODS

Capilia TB-Neo was evaluated by using reference strains including 96 Mycobacterium species (4 MTC and 92 NTM) and 3 other bacterial genera, and clinical isolates (500 MTC and 90 NTM isolates). M. tuberculosis isolates tested negative by Capilia TB-Neo were sequenced for mpt64 gene.

RESULTS

Capilia TB-Neo showed 100% agreement to a subset of reference strains. Non-specific reaction to M. marinum was not observed. The sensitivity and specificity of Capilia TB-Neo to the clinical isolates were 99.4% (99.6% for M. tuberculosis, excluding M. bovis BCG) for clinical MTC isolates and 100% for NTM isolates tested, respectively. Two M. tuberculosis isolates tested negative by Capilia TB-Neo: one harbored a 63-bp deletion in the mpt64 gene and the other possessed a 3,659-bp deletion from Rv1977 to Rv1981c, a region including the entire mpt64 gene.

CONCLUSIONS

Capilia TB-Neo is a simple, rapid and highly sensitive test for identifying MTC, and showed better specificity than Capilia TB. However, Capilia TB-Neo still showed false-negative results with mpt64 mutations. The limitation should be recognized for clinical use.

[Evaluation of the use of SPEED-OLIGO Mycobacteria for identification of Mycobacterium species]

OBJECTIVE

To evaluate the use of SPEED-OLIGO MYCOBACTERIA (Vircell, Spain) in identifying Mycobacterium species.

METHOD

We examined 15 type or reference strains of mycobacteria (M. tuberculosis H37Rv and 14 non-tuberculosis mycobacteria), 48 clinical isolates, and 17 AFB-positive sputa by using SPEED-OLIGO MYCOBACTERIA, and compared the results with those obtained using other referral methods available for species identification.

RESULT

SPEED-OLIGO MYCOBACTERIA yielded favorable results in 80.0%, 91.7%, and 88.2% of the cases of the tested type/reference strains, clinical isolates, and clinical samples, respectively. However, the type/reference strains M. celatum, M. fortuitum subsp. fortuitum, and M. marinum, and the clinical isolates M. intermedium, M. marinum, and M. szulgai were misidentified when SPEED-OLIGO MYCOBACTERIA was used.

DISCUSSION

SPEED-OLIGO MYCOBACTERIA can facilitate the rapid identification of Mycobacterium species mainly because of its short turn-around time and simple procedures. However, the accuracy of this method remains unsatisfactory.