Combined rpoB duplex PCR and hsp65 PCR restriction fragment length polymorphism with capillary electrophoresis as an effective algorithm for identification of Mycobacterial species from clinical isolates

ABSTRACT: BACKGROUND: Mycobacteria can be quickly and simply identified by PCR restriction-enzyme analysis (PRA), but misidentification can occur because of similarities in band sizes that are critical for discriminating among species. Capillary electrophoresis can provide computer-aided band discrimination. The aim of this research was to develop an algorithm for identifying mycobacteria by combined rpoB duplex PRA (DPRA) and hsp65 PRA with capillary electrophoresis. RESULTS: Three hundred and seventy-six acid-fast bacillus smear-positive BACTEC cultures, including 200 Mycobacterium tuberculosis complexes (MTC) and 176 non-tuberculous mycobacteria (NTM) were analyzed. With combined hsp65 and rpoB DPRA, the accuracy rate was 100 % (200 isolates) for the MTC and 91.4 % (161 isolates) for the NTM. Among the discordant results (8.6 %) for the NTM, one isolate of Mycobacterial species and the an isolate of M. flavescens were found as new sub-types in hsp65 PRA. CONCLUSIONS: This effective and novel identification algorithm using combined rpoB DPRA and hsp65 PRA with capillary electrophoresis can rapidly identify mycobacteria and find new sub-types in hsp65 PRA. In addition, it is complementary to 16S rDNA sequencing.     

Distribution of non-tuberculosis mycobacteria strains from suspected tuberculosis patients by heat shock protein 65 PCR–RFLP

The genus Mycobacterium contains more than 150 species. Non-tuberculosis mycobacteria (NTM) often cause extrapulmonary and pulmonary disease. Mycobacteria detection at species level is necessary and provides useful information on epidemiology and facilitates successful treatment of patients. This retrospective study aimed to determine the incidence of the NTM isolates and Mycobacterium tuberculosis (Mtb) in clinical specimens collected from Iranian patients during February 2011–December 2013, by PCR–restriction fragment length polymorphism analysis (PRA) of the hsp65 gene. We applied conventional biochemical test and hsp65–PRA identification assay to identify species of mycobacteria in specimens from patients suspected of having mycobacterial isolates. This method was a sensitive, specific and effective assay for detecting mycobacterial species and had a 100% sensitivity and specificity for Mtb and Mycobacterium avium complex (MAC) species. Using PRA for 380 mycobacterial selected isolates, including 317 Mtb, four Mycobacterium bovis and of the 59 clinical isolates, the most commonly identified organism was Mycobacterium kansasii (35.6%), followed by Mycobacterium simiae (16.9%), Mycobacterium gordonae (16.9%), Mycobacterium fortuitum (5.1%), Mycobacterium intracellulare (5.1%), Mycobacterium avium (5.1%), Mycobacterium scrofulaceum (3.4%), Mycobacterium gastri (3.4%), Mycobacterium flavescens (3.4%), Mycobacterium chelonae (3.4%) and Mycobacterium nonchromogenicum (1.7%). PRA method, in comparison with classical methods, is rapid, useful and sensitive for the phylogenetic analysis and species detection of mycobacterial strains. Mycobacterium kansasii is the most common cause of infection by NTM in patients with non-HIV and HIV which demonstrated a high outbreak and diversity of NTM strains in our laboratory.     

Nontuberculous mycobacteria in respiratory samples from patients with pulmonary tuberculosis in the state of Rond?nia, Brazil

The main cause of pulmonary tuberculosis (TB) is infection with Mycobacterium tuberculosis (MTB). We aimed to evaluate the contribution of nontuberculous mycobacteria (NTM) to pulmonary disease in patients from the state of Rondônia using respiratory samples and epidemiological data from TB cases. Mycobacterium isolates were identified using a combination of conventional tests, polymerase chain reaction-based restriction enzyme analysis of hsp65 gene and hsp65 gene sequencing. Among the 1,812 cases suspected of having pulmonary TB, 444 yielded bacterial cultures, including 369 cases positive for MTB and 75 cases positive for NTM. Within the latter group, 14 species were identified as Mycobacterium abscessus, Mycobacterium avium, Mycobacterium fortuitum, Mycobacterium intracellulare, Mycobacterium gilvum, Mycobacterium gordonae, Mycobacterium asiaticum, Mycobacterium tusciae, Mycobacterium porcinum, Mycobacterium novocastrense, Mycobacterium simiae, Mycobacterium szulgai, Mycobacterium phlei and Mycobacterium holsaticum and 13 isolates could not be identified at the species level. The majority of NTM cases were observed in Porto Velho and the relative frequency of NTM compared with MTB was highest in Ji-Paraná. In approximately half of the TB subjects with NTM, a second sample containing NTM was obtained, confirming this as the disease-causing agent. The most frequently observed NTM species were M. abscessus and M. avium and because the former species is resistant to many antibiotics and displays unsatisfactory cure rates, the implementation of rapid identification of mycobacterium species is of considerable importance.     

Development of multiplex PCR assays based on the 16S-23S rRNA internal transcribed spacer for the detection of clinically relevant nontuberculous mycobacteria

Aims: To accelerate the identification and differentiation of clinically relevant nontuberculous mycobacteria (NTM) with two sets of multiplex PCR (mPCR) targeting the 16S–23S rRNA internal transcribed spacer (ITS) region for timely patient management. Methods and Results: Two mPCR assays were developed: Slow‐Growers (SG) mPCR was used for the detection of slow‐growing mycobacteria, which included Mycobacterium avium complex, Mycobacterium kansasii, Mycobacterium gordonae and Mycobacterium xenopi whilst the other mPCR assay labelled as Fast‐Growers (FG) mPCR was used for the detection of Mycobacterium fortuitum complex, Mycobacterium abscessus and Mycobacterium chelonae. In these assays, a common forward primer based on a conserved section of the 16S rRNA region was used in conjunction with species‐specific reverse primers. The mPCRs were tested against 247 clinical mycobacterial isolates and demonstrated 100% specificity and sensitivity. Identification of the mycobacterial species was also validated by DNA sequencing of the 16S–23S ITS region and when further confirmation was needed, hsp65 sequencing was performed. Conclusions: The mPCR assays could be a potentially useful diagnostic tool for the rapid and accurate identification of clinically relevant NTM. Significance and Impact of the Study: In this study, we looked at the frequency of hospital isolated NTM over the last 5 years (2005–2010), and an mPCR targeting the ITS region was developed for NTM species that appeared to be more prevalent in the context of Singapore.     

Evaluation of a Simple in-House Test to Presumptively Differentiate Mycobacterium tuberculosis Complex from Nontuberculous Mycobacteria by Detection of p-Nitrobenzoic Acid Metabolites

The timely differentiation of Mycobacterium tuberculosis complex (MTC) and non-tubercular mycobacterium (NTM) species is urgently needed in patient care since the routine laboratory method is time consuming and cumbersome. An easy and cheap method which can successfully distinguish MTC from NTM was established and evaluated. 38 mycobacterial type and reference strains and 65 clinical isolates representing 10 species of mycobacterium were included in this study. Metabolites of p-nitrobenzoic acid (PNB) reduction were identified using liquid chromatography and tandem mass spectrometry (LC/MS/MS). A spectrophotometric method was developed to detect these metabolites, which was evaluated on a number of MTC and NTM species. All of the tested NTM species and strains reduced PNB to p-aminobenzoic acid (PABA), while none of the MTC strains showed a similar activity. Spectrophotometric detection of PABA had 100% sensitivity and specificity for MTC and NTM differentiation among the type strains and the clinical isolates tested. PABA was identified as one of the metabolites of PNB reduction. All the tested NTM species metabolized PNB to PABA whereas the MTC members lacked this activity. A simple, specific and cost-effective method based on PABA production was established in order to discriminate MTC from NTM from cultured organisms.     

A comparison of mycolic acid analysis for nontuberculous mycobacteria identification by thin-layer chromatography and molecular methods

The development of fast, inexpensive, and reliable tests to identify nontuberculous mycobacteria (NTM) is needed. Studies have indicated that the conventional identification procedures, including biochemical assays, are imprecise. This study evaluated a proposed alternative identification method in which 83 NTM isolates, previously identified by conventional biochemical testing and in-house M. avium IS1245-PCR amplification, were submitted to the following tests: thin-layer chromatography (TLC) of mycolic acids and PCR-restriction enzyme analysis of hsp65(PRA). High-performance liquid chromatography (HPLC) analysis of mycolic acids and Southern blot analysis for M. avium IS1245 were performed on the strains that evidenced discrepancies on either of the above tests. Sixty-eight out of 83 (82%) isolates were concordantly identified by the presence of IS1245 and PRA and by TLC mycolic acid analysis. Discrepant results were found between the phenotypic and molecular tests in 12/83 (14.4%) isolates. Most of these strains were isolated from non-sterile body sites and were most probably colonizing in the host tissue. While TLC patterns suggested the presence of polymycobacterial infection in 3/83 (3.6%) cultures, this was the case in only one HPLC-tested culture and in none of those tested by PRA. The results of this study indicated that, as a phenotypic identification procedure, TLC mycolic acid determination could be considered a relatively simple and cost-effective method for routine screening of NTM isolates in mycobacteriology laboratory practice with a potential for use in developing countries. Further positive evidence was that this method demonstrated general agreement on MAC and M. simiae identification, including in the mixed cultures that predominated in the isolates of the disseminated infections in the AIDS patients under study. In view of the fact that the same treatment regimen is recommended for infections caused by these two species, TLC mycolic acid analysis may be a useful identification tool wherever molecular methods are unaffordable.     

Comparison of repetitive-sequence-based polymerase chain reaction with random amplified polymorphic DNA analysis for rapid genotyping of nontuberculosis mycobacteria

Nontuberculosis mycobacteria (NTM) are an important cause of human disease and infections. Though less notorious than tuberculosis, these infections are clinically significant and have been associated with outbreaks in various settings. To accommodate outbreak investigations for the numerous species of NTM, we evaluated a DiversiLab repetitive-sequence-based PCR (rep-PCR) kit for genotyping of mycobacteria. This kit was used to genotype both rapidly and slowly growing mycobacteria and was compared with other PCR-based genotyping methods, including random amplified polymorphic DNA (RAPD) analysis, hsp65 gene sequencing, and mycobacterial interspersed repetitive unit?- variable number of tandem repeat (MIRU-VNTR) analysis. Compared with RAPD analysis, rep-PCR achieved better reproducibility in testing. When compared with hsp65 gene sequencing and MIRU-VNTR for Mycobacterium avium , rep-PCR provided results that agreed with these less discriminatory genotyping methods but provided a higher level of discrimination for situations such as outbreak investigations. We also evaluated the kit for its ability to identify closely related rapidly growing NTM. While rep-PCR was informative in some cases, a much larger library of isolates would be necessary to truly evaluate it as an identification tool. Overall, rep-PCR was able to provide improved reproducibility over RAPD and a discriminatory genotyping method for the isolates evaluated in this study.     

Pyrosequence Analysis of the hsp65 Genes of Nontuberculous Mycobacterium Communities in Unchlorinated Drinking Water in the Netherlands

Studies have shown that certain opportunistic pathogenic species of nontuberculous mycobacteria (NTM) can be present in distributed drinking water. However, detailed information about NTM population composition in drinking water is lacking. Therefore, NTM communities in unchlorinated drinking water from the distribution system of five treatment plants in the Netherlands were characterized using 454 pyrosequencing of the hsp65 gene. Results showed high diversities in unchlorinated drinking water, with up to 28 different NTM operational taxonomic units (OTUs) in a single sample. Each drinking water sample had a unique NTM community, and most (81.1%) OTUs were observed only once. One OTU was observed in 14 of 16 drinking water samples, indicating that this NTM species is well adapted to unchlorinated drinking water conditions. A clear influence of season, source type (groundwater, surface water), easily assimilable organic carbon (AOC) concentration, biofilm formation rate, and active biomass in treated water on the establishment of an NTM community in drinking water was not observed. Apparently, local conditions are more important for the development of a specific NTM community in the drinking water distribution system. A low (4.2%) number of hsp65 gene sequences showed more than 97% similarity to sequences of the opportunistic pathogens M. avium, M. genavense, and M. gordonae. However, most (95.8%) NTM hsp65 gene sequences were related to not-yet-described NTM species that have not been linked to disease, indicating that most NTM species in unchlorinated drinking water from distribution systems in the Netherlands have a low public health significance.     

Isolation and identification of mycobacteria from soils at an illegal dumping site and landfills in Japan

In order to study the diversity and community of genus Mycobacterium in polluted soils, we tried to isolate mycobacteria from 11 soil samples collected from an illegal dumping site and 3 landfills in Japan. Using culture methods with or without Acanthamoeba culbertsoni, a total of 19 isolates of mycobacteria were obtained from 5 soil samples and 3 of them were isolated only by the co-culture method with the amoeba. Conventional biochemical tests and sequencing of the hsp65, rpoB, and 16S rRNA genes were performed for species identification of 17 of the 19 isolates. Among the 17 isolates, there was one isolate each of Mycobacterium vanbaalenii, Mycobacterium mageritense, Mycobacterium frederiksbergense, M. vanbaalenii or Mycobacterium austroafricanum, and Mycobacterium chubuense or Mycobacterium chlorophenolicum. The remaining 12 isolates could not be precisely identified at the species level. A phylogenic tree based on the hsp65 sequences indicated that 2 of the 12 isolates were novel species. In addition, 4 isolates were phylogenically close to species that degrade polycyclic aromatic hydrocarbons, which induce some cancers in humans. These results demonstrated that there were many hitherto-unreported mycobacteria in the polluted soils, and suggested that some mycobacteria might play roles in the natural attenuation and engineered bioremediation of contaminated sites with other microorganisms.     

Isolation of novel mycobacteria contaminating an aquarium fish tank in a Japanese university hospital

Aims: To better understand nontuberculous mycobacteria (NTM) contamination in a hospital setting, six freshwater fish gut homogenates and water in an aquarium fish tank placed on the reception counter of a nursing station were cultured for mycobacteria. Methods and Results: By direct sequencing of 16s rRNA, rpoB and hsp65, scotochromogenic and nonchromogenic Mycobacterium szulgai isolates containing hsp65 type II (GenBank accession nos. FJ384762 and FJ384764 , respectively), Mycobacterium gordonae isolates containing rpoB clusters B and E (GenBank accession no. FJ384766 ), and Mycobacterium kansasii isolates containing hsp65 type VI were collected from the gut homogenates and water from the fish tank. However, no isolates were obtained from the tap water used to refill the fish tank. A randomly amplified polymorphic DNA (RAPD) analysis using a 10‐mer primer (5′‐TGGTCGCGGC) showed that some NTM from the fish tank water were identical to those obtained from the gut homogenates. Conclusions: Fish and water in the tank were contaminated by the novel NTM. Significance and Impact of the Study: These findings could help to elucidate infection routes and contamination sources of novel NTM from water sources.     

Comparative evaluation of Polymerase Chain Reaction-Restriction Enzyme Analysis (PRA) and sequencing of heat shock protein 65 (hsp65) gene for identification of aquatic mycobacteria

Traditional identification of mycobacteria based on cultural and biochemical tests can take several weeks and may fail to provide a precise identification. Polymerase Chain Reaction-Restriction Enzyme Analysis (PRA) of the gene encoding heat shock protein 65 kDa (hsp65) gene has been proposed as a rapid and inexpensive alternative approach. Despite being widely used for differentiation of mammalian mycobacteria, this method has only been applied in the identification of a small number of aquatic mycobacteria. The present study aimed to evaluate the potential use of PRA of hsp65 for the identification of aquatic mycobacteria compared with sequence analysis. Seventy one mycobacterial isolates including, 10 type/reference strains and the remainder field isolates, were subjected to PRA of a 441 bp fragment of this gene. For 68 representative isolates, sequence analysis was performed. All rapidly and slowly growing mycobacteria had best matches with 99.3% to 100% similarity with their corresponding species in the databanks. PRA proved to be a simple and rapid method for identifying aquatic mycobacteria. However, the incidence of similar or identical restriction patterns for some species of mycobacteria, and in particular, identification of new species of mycobacteria is a major problem using such a method. In contrast, the nucleic acid sequencing of the hsp65 gene yielded unambiguous results.     

Selecting criteria for improving results of an immunochromatographic assay for Mycobacterium tuberculosis complex identification from BacT/ALERT cultures

We describe a combined macro and microscopic criteria for rapid presumptive differentiation between Mycobacterium tuberculosis complex (MTC) and nontuberculous mycobacteria (NTM) evaluated by two independent observers. This strategy achieved rapid MTC identification in most cases (95.8% expert observer and 91.6% novice observer) with significant savings compared to more expensive and unnecessary tests.     

Isolation and Identification of Environmental Mycobacteria in the Waters of a Hemodialysis Center

The use of poorly treated water during hemodialysis may lead to contamination with nontuberculous mycobacteria (NTM). This study aimed to isolate and identify NTM species in the water of a Brazilian hemodialysis center. We collected 210 samples of water from the hydric system of the unit (post-osmosis system, hemodialysis rooms, reuse system, and hemodialysis equipment) and from the municipal supply network; we isolated the NTM by a classic microbiological technique and identified them by the PCR restriction enzyme pattern of the hsp65 gene (PRA). Fifty-one (24.3 %) of the collected samples tested positive for NTM; both the municipal supply network (2 samples, 3.2 %) and the hydric system of the hemodialysis center (49 samples, 96.1 %) contained NTM. We isolated and identified potentially pathogenic bacteria such as Mycobacterium lentiflavum (59.0 %) and M. kansasii (5.0 %), as well as rarely pathogenic bacteria like M. gordonae (24.0 %), M. gastri (8.0 %), and M. szulgai (4.0 %). The ability of NTM to cause diseases is well documented in the literature. Therefore, the identification of NTM in the water of a Brazilian hemodialysis center calls for more effective water disinfection procedures in this unit.     

Raman spectroscopic identification of Mycobacterium tuberculosis

In this study, Raman microspectroscopy has been utilized to identify mycobacteria to the species level. Because of the slow growth of mycobacteria, the per se cultivation‐independent Raman microspectroscopy emerges as a perfect tool for a rapid on‐the‐spot mycobacterial diagnostic test. Special focus was laid upon the identification of Mycobacterium tuberculosis complex (MTC) strains, as the main causative agent of pulmonary tuberculosis worldwide, and the differentiation between pathogenic and commensal nontuberculous mycobacteria (NTM). Overall the proposed model considers 26 different mycobacteria species as well as antibiotic susceptible and resistant strains. More than 8800 Raman spectra of single bacterial cells constituted a spectral library, which was the foundation for a two‐level classification system including three support vector machines. Our model allowed the discrimination of MTC samples in an independent validation dataset with an accuracy of 94% and could serve as a basis to further improve Raman microscopy as a first‐line diagnostic point‐of‐care tool for the confirmation of tuberculosis disease.

     

Species Spectrum of Nontuberculous Mycobacteria Isolated from Clinical Specimens in Kuwait

Specific identification of mycobacteria is of clinical relevance since treatment varies according to the Mycobacterium species causing infection. All mycobacterial isolates are currently identified as M. tuberculosis (MTB) or nontuberculous mycobacteria (NTM) based on p-nitro-α-acetylamino-β-hydroxypropiophenone (NAP) test, and the species spectrum of NTM-causing infections in Kuwait remains unknown. This study identified all NTM strains isolated in Kuwait from 1 October 2003 to 31 March 2004 to the species level. The mycobacteria were cultured from various clinical specimens using the BACTEC 460 TB system and NAP test was performed to differentiate MTB from NTM strains. The INNO-LiPA MYCOBACTERIA v2 assay (LiPA) was used for species-specific identification of NTM strains and some randomly selected MTB strains. The LiPA results for selected isolates were confirmed by DNA sequencing of the 16S-23S internal transcribed spacer region. A total of 325 isolates of Mycobacterium species originating from 305 individual patients were recovered during the study period, with 307 and 18 isolates identified as MTB and NTM, respectively. The LiPA correctly identified all 18 MTB isolates analyzed. Seven different NTM species were identified among 18 NTM isolates originating from 14 patients, with M. fortuitum causing the majority of NTM infections in Kuwait. One patient was infected with two NTM species. Rapid species-specific identification of NTM may help with appropriate treatment regimens for proper patient management. The DNA sequencing data reported in this study are deposited in EMBL under accession numbers AM709724 to AM709731.     

A single-step sequencing method for the identification of Mycobacterium tuberculosis complex species

Background

The Mycobacterium tuberculosis complex (MTC) comprises closely related species responsible for strictly human and zoonotic tuberculosis. Accurate species determination is useful for the identification of outbreaks and epidemiological links. Mycobacterium africanum and Mycobacterium canettii are typically restricted to Africa and M. bovis is a re-emerging pathogen. Identification of these species is difficult and expensive.

Methodology/Principal Findings

The Exact Tandem Repeat D (ETR-D; alias Mycobacterial Interspersed Repetitive Unit 4) was sequenced in MTC species type strains and 110 clinical isolates, in parallel to reference polyphasic identification based on phenotype profiling and sequencing of pncA, oxyR, hsp65, gyrB genes and the major polymorphism tandem repeat. Inclusion of M. tuberculosis isolates in the expanding, antibiotic-resistant Beijing clone was determined by Rv0927c gene sequencing. The ETR-D (780-bp) sequence unambiguously identified MTC species type strain except M. pinnipedii and M. microti thanks to six single nucleotide polymorphisms, variable numbers (1–7 copies) of the tandem repeat and two deletions/insertions. The ETR-D sequencing agreed with phenotypic identification in 107/110 clinical isolates and with reference polyphasic molecular identification in all isolates, comprising 98 M. tuberculosis, 5 M. bovis BCG type, 5 M. canettii, and 2 M. africanum. For M. tuberculosis isolates, the ETR-D sequence was not significantly associated with the Beijing clone.

Conclusions/Significance

ETR-D sequencing allowed accurate, single-step identification of the MTC at the species level. It circumvented the current expensive, time-consuming polyphasic approach. It could be used to depict epidemiology of zoonotic and human tuberculosis, especially in African countries where several MTC species are emerging.     

Non‐Tuberculosis mycobacterium speciation using HPLC under Revised National TB Control Programme (RNTCP) in India

Aims

Non‐Tuberculous Mycobacteria (NTM) are ubiquitous in nature. The data on prevalence of NTM under the RNTCP is scarce. Many NTM species have clinical significance, and hence their identification and speciation are important.

Methods and Results

It is a cross‐sectional study conducted at the five RNTCP accredited culture and drug susceptibility testing (CDST) laboratory. The culture isolates from AFB positive but Immunochromatographic test negative samples were taken for identification and speciation using HPLC. Of the total 266 isolates only 164 isolates had a second sample received at the laboratory. The speciation was done using HPLC for those isolates. The type of species identified are: 26·8% (44) were Mycobacterium chelonae, 12·8% (21) were Mycobacterium fortuitum, 9% (15) were Mycobacterium gordonae, 9% (15) were Mycobacterium tuberculosis complex, 6·1% (10) were Mycobacterium kansasii, 4·9% (8) were Mycobacterium simiae, 2·4% (4) were Mycobacterium thermophile, 1·2% (2) were Mycobacterium gastri, 0·6% (1) were Mycobacterium scrofulaceum, 0·6% (1) were Mycobacterium avium and 4·9% (8) isolates had chromatogram which was un‐interpretable.

Conclusion

Identification and its speciation of NTM are not routinely done under TB control programme. Since HPLC could identify 95% of isolates belonging to 10 species, the speciation of NTM using HPLC should gain importance in the diagnosis of disease caused by NTM.

Significance and Impact of Study

NTM are emerging as important causative agents of pulmonary and extra pulmonary disease, the ability to recognize disease caused by NTM and subsequently treat such disease has become increasingly important. The identification of NTM up to its species level should gain importance in all TB reference Laboratories.     

Antimicrobial Susceptibility of Standard Strains of Nontuberculous Mycobacteria by Microplate Alamar Blue Assay

In this study, 24 standard nontuberculous mycobacteria (NTM) species strains including 12 slowly growing mycobacteria strains and 12 rapidly growing mycobacteria strains were subjected to drug susceptibility testing using microplate Alamar Blue assay-based 7H9 broth. The most active antimicrobial agents against the 24 NTM strains were streptomycin, amikacin, the fluoroquinolones, and the tetracyclines. Mycobacterium chelonae, Mycobacterium abscessus, Mycobacterium bolletii, and Mycobacterium simiae are resistant to most antimicrobial agents. The susceptibility results of this study from 24 NTM standard strains can be referenced by clinicians before susceptibility testing for clinical isolates is performed or when conditions do not allow for susceptibility testing. The application of broth-based methods is recommended by the Clinical and Laboratory Standards Institute, and the documentation of the susceptibility patterns of standard strains of mycobacteria can improve the international standardization of susceptibility testing methods.     

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.     

PCR restriction fragment length polymorphism analysis (PRA)-algorithm targeting 644 bp Heat Shock Protein 65 (hsp65) gene for differentiation of Mycobacterium spp

A method based on PCR-restriction fragment length polymorphism analysis (PRA) using a novel region of the hsp65 gene was developed for the rapid and exact identification of mycobacteria to the species level. A 644 bp region of hsp65 in 62 mycobacteria reference strains, and 4 related bacterial strains were amplified, and the amplified DNAs were subsequently digested with restriction enzymes, namely, AvaII, HphI, and HpaII. Most of the mycobacteria species were easily differentiated at the species level by the developed method. In particular, the method enabled the separation of M. avium, M. intracellulare and M. tuberculosis to the species level by AvaII digestion alone. An algorithm was constructed based on the results and a blind test was successfully performed on 251 clinical isolates, which had been characterized by conventional biochemical testing. Our results suggest that this novel PRA offers a simple, rapid, and accurate method for the identification of mycobacteria culture isolates at the species level.