Evaluation of Nanopore Sequencing for Diagnosing Pulmonary Tuberculosis Using Negative Smear Clinical Specimens

Purpose

This study aimed to evaluate the efficacy of nanopore sequencing for diagnosing pulmonary tuberculosis (PTB) using smear-negative clinical specimens.

Methods

We conducted a retrospective study based on a review of patient medical records to assess the accuracy of nanopore sequencing as a diagnostic tool for smear-negative PTB. Compared with clinical diagnosis, we determined the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of nanopore sequencing.

Results

A total of 647 patients were evaluated. Nanopore sequencing demonstrated an overall sensitivity of 91.7%, specificity of 85.3%, PPV of 95.1%, NPV of 76.4%, and AUC of 0.88. Notably, the overall diagnostic accuracy of nanopore sequencing was significantly higher than that of Mycobacterium tuberculosis (MTB) culture technique.

Conclusion

Nanopore sequencing exhibited satisfactory overall diagnostic accuracy for smear-negative PTB, regardless of MTB culture status. Therefore, if conditions permit, nanopore sequencing is recommended as a diagnostic method for smear-negative PTB.

Applicability of rpoB Gene for PCR-RFLP based Discrimination of Bifidobacterial Species Isolated from Human and Animal Sources

Bifidobacteria are widely used as probiotics for their application in the development of functional food and prophylactic therapy. This has necessitated the development of a molecular approach for the genera to be widely identified up to species and subspecies level. In the current study, PCR-RFLP of the partial RNA polymerase β-subunit (rpoB) gene fragment was evaluated for differential identification of Bifidobacterium species. The rpoB gene partial sequences of 575 bp were amplified from 93 previously identified isolates collected from various sources of human and animal origin along with 12 standard reference strains. The PCR amplified products were digested with three restriction endonucleases HhaI, HinfI and BanI separately. Dendrograms constructed from the patterns of HhaI, were found to be more discriminatory and successfully differentiated all the twelve species and also at sub-species level in between B. longum subsp. longum and B. longum subsp. infantis. However, B. adolescentis and B. pseudocatenulatum group clusters were not separated and represented by one group. The groups were further discriminated by HinfI restriction digestion. A separate combination thereof may be used for inferring the classification of bifidobacterial species targeted on rpoB PCR-RFLP analysis. To our knowledge, this work is the first report based on use of rpoB PCR-RFLP for discrimination of the isolates of genus Bifidobacterium and also provides insights into specific advantages of this method over hsp60 PCR-RFLP in differentiating B. longum subsp. longum and B. longum subsp. infantis.

Isolation of Mycobacterium avium and other nontuberculous mycobacteria in chickens and captive birds in peninsular Malaysia

Background

Mycobacterium avium complex (MAC) causes a chronic infectious in the birds known as avian mycobacteriosis. Almost all species of the birds are susceptible to MAC which consists of two closely related species of mycobacteria, that is, M. avium and M. intracellulare. This study aimed to determine the occurrence of Mycobacterium avium subsp. avium (MAA) in chickens and captive birds in selected states of Peninsular Malaysia.

Results

A 300 fecal samples were collected from village chickens (n = 100), layer chickens (n = 100) and captive birds (n = 100). Fecal samples were split into two aliquots for microbiological and molecular detection of MAA. Microbiology detection consisted of microscopy (Ziehl-Neelsen staining) and culture of samples decontaminated with 1% Cetylperidinium chloride and vancomycin, nalidixic acid and amphotericin B (VNA) antibiotic cocktail [vancomycin (VAN) 100 μg/ml, nalidixic acid (NAL) 100 μg/ml and amphotericin B (AMB) 50 μg/ml] onto Löwenstein-Jensen (L-J). Molecular detection (PCR-IS901) was performed to detect MAA DNA from the feces and PCR-16S rRNA and IS901 for identification of genus Mycobacterium and Mycobacterium avium sub species avium isolated onto L-J. All samples (296) were AFB negative smear. M. avium was isolated in 0.3% (1/296) samples by culture and detected in 2.5% (6/242) samples by PCR (IS901). Other mycobacteria were found in 1.7% (5/296) chickens. Of five isolates, two were identified as Mycobacterium terrae and M. engbaekii and remaining isolates were not sequenced. Birds positive for M. avium included White Pelican (n = 1) Black Hornbill (n = 1), Macaw (n = 2), Cockatoo (n = 2) and village chicken (n = 1).

Conclusion

It is concluded that chickens and birds were infected with M. avium in selected areas of Peninsular Malaysia. Although, PCR is rapid, reliable and cost effective method for detection of M. avium in a subclinical stage, the culture of the avian feces should still be used as a reference test for the diagnosis of avian tuberculosis.

Identification of the Mycobacterial Strains Isolated From Clinical Specimens Using hsp65 PCR-RFLP Method

Objectives

It is important to identify mycobacteria at the species level, to distinguish pathogen from non-pathogenic species, to choose the appropriate treatment regimen and to collect epidemiological data. For the identification of mycobacteria, which are time-consuming and laborious with traditional methods, faster, more sensitive and reliable methods are needed. This study aims to investigate the suitability of the hsp65 Polymerase chain reaction-restriction fragment polymorphism (PCR-RFLP) method for routine laboratory use.

Methods

In this study, 141 mycobacterial isolates were obtained from 1632 samples, which were sent to the Medical Microbiology Laboratory.

Results

In the culture, mycobacteria were identified as 138 M. tuberculosis complex (MTBC) and three non-tuberculosis mycobacteria (NTM) by conventional methods. Using the hsp65 PCR-RFLP method, 137 isolates were identified as MTBC, four isolates as NTM. An isolate that was evaluated as MTBC because it was PNB sensitive by the conventional method was determined as NTM with the hsp65 method. In the identification of non-tuberculosis mycobacteria with the hsp65 PCR-RFLP method, one isolate was identified as M. abcessus and three isolates were identified as M. avium complex.

Conclusion

In our study, it was concluded that the hsp65 PCR-RFLP method, which allows identification of mycobacteria, including NTMs, is a method that is cheap, easy and suitable for routine use to provide rapid information to the clinic. The scope of the agar and database used in the method is effective in the definition of the correct species.

Methodological and Clinical Aspects of the Molecular Epidemiology of Mycobacterium tuberculosis and Other Mycobacteria

Molecular typing has revolutionized epidemiological studies of infectious diseases, including those of a mycobacterial etiology. With the advent of fingerprinting techniques, many traditional concepts regarding transmission, infectivity, or pathogenicity of mycobacterial bacilli have been revisited, and their conventional interpretations have been challenged. Since the mid-1990s, when the first typing methods were introduced, a plethora of other modalities have been proposed. So-called molecular epidemiology has become an essential subdiscipline of modern mycobacteriology. It serves as a resource for understanding the key issues in the epidemiology of tuberculosis and other mycobacterial diseases. Among these issues are disclosing sources of infection, quantifying recent transmission, identifying transmission links, discerning reinfection from relapse, tracking the geographic distribution and clonal expansion of specific strains, and exploring the genetic mechanisms underlying specific phenotypic traits, including virulence, organ tropism, transmissibility, or drug resistance. Since genotyping continues to unravel the biology of mycobacteria, it offers enormous promise in the fight against and prevention of the diseases caused by these pathogens. In this review, molecular typing methods for Mycobacterium tuberculosis and nontuberculous mycobacteria elaborated over the last 2 decades are summarized. The relevance of these methods to the epidemiological investigation, diagnosis, evolution, and control of mycobacterial diseases is discussed.

Molecular typing of Iranian mycobacteria isolates by polymerase chain reaction-restriction fragment length polymorphism analysis of 360-bp rpoB gene

Background:

Diagnosis and typing of Mycobacterium genus provides basic tools for investigating the epidemiology and pathogenesis of this group of bacteria. Polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis (PRA) is an accurate method providing diagnosis and typing of species of mycobacteria. The present study is conducted by the purpose of determining restriction fragment profiles of common types of mycobacteria by PRA method of rpoB gene in this geographical region.

Materials and Methods:

Totally 60 clinical and environmental isolates from February to October, 2013 were collected and subcultured and identified by phenotypic methods. A 360 bp fragment of the rpoB gene amplified by PCR and products were digested by MspI and HaeIII enzymes.

Results:

In the present study, of all mycobacteria isolates identified by PRA method, 13 isolates (21.66%) were Mycobacterium tuberculosis, 34 isolates (56.66%) were rapidly growing Nontuberculosis Mycobacteria (NTM) that including 26 clinical isolates (43.33%) and 8 environmental isolates (13.33%), 11 isolates (18.33%) were clinical slowly growing NTM. among the clinical NTM isolates, Mycobacterium fortuitum Type I with the frequency of 57.77% was the most prevalent type isolates. Furthermore, an unrecorded of the PRA pattern of Mycobacterium conceptionense (HeaIII: 120/90/80, MspI: 120/105/80) was found. This study demonstrated that the PRA method was high discriminatory power for identification and typing of mycobacteria species and was able to identify 96.6% of all isolates.

Conclusion:

Based on the result of this study, rpoB gene could be a potentially useful tool for identification and investigation of molecular epidemiology of mycobacterial species.

Development of a novel PCR restriction analysis of the hsp65 gene as a rapid method to screen for the Mycobacterium tuberculosis complex and nontuberculous mycobacteria in high-burden countries

The limitations of conventional methods of identification of Mycobacterium tuberculosis have led to the development of several nucleic acid amplification techniques which have the advantage of being rapid, sensitive, and specific. However, their expense or the need for technical expertise makes it difficult to use them in regions in which tuberculosis is endemic. A novel PCR restriction analysis (PRA) of the hsp65 gene was therefore developed for rapid screening of clinical isolates to identify Mycobacterium spp. The restriction enzymes NruI and BamHI were selected to obtain a limited number of restriction patterns to further differentiate between Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM). Three hundred ten isolates from clinical specimens and 24 reference strains were tested. The assay correctly identified 295 of the 310 culture isolates as MTBC, while the remaining 15 isolates were identified as NTM. Of the isolates tested, 135 MTBC strains and all 15 NTM were also confirmed by PRA using Sau96I and CfoI. Thirty-eight randomly selected MTBC strains and all 15 NTM were further confirmed by sequencing. The NruI/BamHI PRA was simple, as it did not require any elaborate analyses. It was cost-effective, rapid, highly sensitive, and specific and did not require technical expertise. The assay can, therefore, be used as a simple screening test not only to detect Mycobacterium spp. but also to differentiate MTBC from NTM in peripheral laboratories with minimal availability of funds.