Comparison of cyp141 and IS6110 for detection of Mycobacterium tuberculosis from clinical specimens by PCR

Rapid detection of Mycobacterium tuberculosis based on cyp141 via real-time fluorescence loop-mediated isothermal amplification (cyp141-RealAmp)

Background

The rapid detection of Mycobacterium tuberculosis (MTB) is essential for controlling tuberculosis. Methods We designed a portable thermocycler-based real-time fluorescence loop-mediated isothermal amplification assay (cyp141-RealAmp) using six oligonucleotide primers derived from cyp141 to detect MTB. A combined number of 213 sputum samples (169 obtained from clinically diagnosed cases of pulmonary TB and 44 from a control group without tuberculosis) underwent Acid-fast bacillus (AFB) smear, culture, Xpert MTB/RIF assays, and cyp141-RealAmp assay.

Results

By targeting MTB cyp141, this technique could detect as low as 10 copies/reaction within 30 min, and it was successfully rejected by other mycobacteria and other bacterial species tested. Of the 169 patients, there was no statistical difference between the detection rate of cyp141-RealAmp (92.90%, 95% CI: 89.03-96.07) and that of Xpert MTB/RIF (94.67%, 95% CI: 91.28-98.06) (P > 0.05), but both were statistically higher than that of culture (65.68%, 95% CI: 58.52-72.84) (P< 0.05) and AFB (57.40%, 95% CI: 49.94-64.86) (P< 0.05). Both cyp141-RealAmp and Xpert MTB/RIF had a specificity of 100%. Furthermore, a high concordance between cyp141-RealAmp and Xpert MTB/RIF was found (Kappa = 0.89).

Conclusion

The cyp141-RealAmp assay was shown to be effective, responsive, and accurate in this study. This method offers a prospective strategy for the speedy and precise detection of MTB.

Evaluating the Performance of PPE44, HSPX, ESAT-6 and CFP-10 Factors in Tuberculosis Subunit Vaccines

Mycobacterium tuberculosis (M. tuberculosis) is an intracellular pathogen causing long-term infection in humans that mainly attacks macrophages and can escape from the immune system with the various mechanisms. The only FDA-approved vaccine against M. tuberculosis (MTB) is Mycobacterium bovis bacillus Calmette-Guérin (BCG). The protection of this vaccine typically lasts 10–15 years. Due to the increasing number of people becoming ill with MTB each year worldwide, the need to develop a new effective treatment against the disease has been increased. During the past two decades, the research budget for TB vaccine has quadrupled to over half a billion dollars. Most of these research projects were based on amplifying and stimulating the response of T-cells and developing the subunit vaccines. Additionally, these studies have demonstrated that secretory and immunogenic proteins of MTB play a key role in the pathogenesis of the bacteria. Therefore, these proteins were used to develop the new subunit vaccines. In this review, based on the use of these proteins in the successful new subunit vaccines, the PPE44, HSPX, CFP-10 and ESAT-6 antigens were selected and the role of these antigens in designing and developing new subunit vaccines against TB and for the prevention of TB were investigated.

The Anti-Mycobacterial Activity Of Ag, ZnO, And Ag- ZnO Nanoparticles Against MDR- And XDR-Mycobacterium tuberculosis

Background

Nowadays, tuberculosis (TB) is one of the top ten leading causes of mortality worldwide. The emergence of multidrug-resistant (MDR) - and extensively drug-resistant (XDR) - Mycobacterium tuberculosis (M. tuberculosis) is identified as one of the most challenging threats to TB control. Thus, new and safe nano-drugs are urgently required for the elimination of TB. The aim of this study was to investigate the anti-bacterial effects of Ag, ZnO, and Ag-ZnO nanoparticles (NPs) on MDR- and XDR-M. tuberculosis.

Materials and methods

In this study, Ag, ZnO, and Ag-ZnO NPs were synthesized by the chemical reduction and chemical deposition methods. NPs were characterized using ultraviolet-visible spectroscopy, dynamic light scattering, and transmission electron microscopy. Then, various dilutions of NPs were prepared and their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined against M. tuberculosis strains using the broth microdilution and agar microdilution methods. Finally, MTT test and cell culture assay were performed.

Results

The effects of concentrations of 1-128 µg/mL Ag NPs, ZnO NPs, 2Ag: 8ZnO, 8Ag:2ZnO, 3Ag: 7ZnO, 7Ag:3ZnO, and 5Ag:5ZnO on M. tuberculosis strains were investigated. MIC results showed the inhibitory effect of 1 µg/mL of all NPs against XDR-M. tuberculosis. In addition, the concentrations of 4 µg/mL Ag, 8 µg/mL 5Ag:5ZnO, 8 µg/mL 7Ag:3ZnO, 32 µg/mL 3Ag:7ZnO, 16 µg/mL 8Ag:2ZnO, and 64 µg/mL 2Ag:8ZnO inhibited MDR-M. tuberculosis growth. However, MBC results indicated the inability of Ag, ZnO and Ag-ZnO NPs, either in combination or alone, to kill MDR- or XDR-M. tuberculosis.

Conclusion

To the best of our knowledge, this is the first study to evaluate the effects of Ag and ZnO NPs against MDR and XDR strains of M. tuberculosis. According to the results, Ag and ZnO NPs showed bacteriostatic effects against drug-resistant strains of M. tuberculosis. Therefore, these NPs may be considered as promising anti-mycobacterial nano-drugs. However, further studies are required to affirm the bactericidal effects of these NPs against TB.

DNA markers for tuberculosis diagnosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis complex (MTBC), is an infectious disease with more than 10.4 million cases and 1.7 million deaths reported worldwide in 2016. The classical methods for detection and differentiation of mycobacteria are: acid-fast microscopy (Ziehl-Neelsen staining), culture, and biochemical methods. However, the microbial phenotypic characterization is time-consuming and laborious. Thus, fast, easy, and sensitive nucleic acid amplification tests (NAATs) have been developed based on specific DNA markers, which are commercially available for TB diagnosis. Despite these developments, the disease remains uncontrollable. The identification and differentiation among MTBC members with the use of NAATs remains challenging due, among other factors, to the high degree of homology within the members and mutations, which hinders the identification of specific target sequences in the genome with potential impact in the diagnosis and treatment outcomes. In silico methods provide predictive identification of many new target genes/fragments/regions that can specifically be used to identify species/strains, which have not been fully explored. This review focused on DNA markers useful for MTBC detection, species identification and antibiotic resistance determination. The use of DNA targets with new technological approaches will help to develop NAATs applicable to all levels of the health system, mainly in low resource areas, which urgently need customized methods to their specific conditions.

Comparison of the Purelyse® - IS6110 nested PCR with the Xpert® MTB/RIF test in clinical samples with suspected tuberculosis

Tuberculosis (TB) has a high incidence, prevalence and mortality in the world. Due to its high level of transmission and long-term pharmacological treatment, it is important to have sensitive and specific diagnostic tests. Recently, the PureLyse® system, which is a novel DNA extraction method, was proposed to be an important tool for molecular diagnosis of TB. Here, we compare the PureLyse® system followed by an IS6110 nested PCR (PureLyse® - IS6110 nested PCR) with the Xpert® MTB/RIF test for Mycobacterium tuberculosis complex (MTBC) identification in 40 clinical samples. Among the 40 samples, 26 samples were positive and 14 negative for the Xpert® MTB/RIF test as well as for the PureLyse® - IS6110 nested PCR. According to the Xpert® MTB/RIF test, positive samples presented different bacillary concentrations from "High" to "Very low" and rifampin resistance was observed in 5 samples. The concordance of both molecular methods makes the PureLyse® - IS6110 nested PCR suitable for MTBC detection in patients for low-income resources.

G allele at -924 A > G position of FoxP3 gene promoter as a risk factor for tuberculosis

BACKGROUND

Forkhead box protein 3 (FoxP3) is an important factor for development and function of Regulatory T cells (Treg). Studies have found an association between common gene polymorphisms in FoxP3 and some infectious diseases. The aim of this study was to evaluate possible associations between two Single nucleotide polymorphisms (SNPs) in the promoter of the FoxP3 gene to susceptibility to tuberculosis (TB) and the alteration of Foxp3 gene expression.

METHODS

The pattern distribution of genotype at two position, -3279 A > C (rs3761548) and -924 A > G (rs2232365) on the promoter of FoxP3 gene was evaluated using polymerase chain reaction-single specific primer (PCR-SSP) method in 183 tuberculosis patients and 183 healthy control. In addition the quantity of FoxP3 gene expression at mRNA level was identified by the real-time PCR.

RESULTS

The frequency of G allele at -924 A > G was significantly higher was higher in TB patients (59.5%) than control group (39.5%) (P ≤ 0.05). In addition, our data viewed approximately 5- folds more FoxP3 gene expression in female patients with GG genotype in comparison to female healthy cases with the same genotype (P ≤ 0.001). There was no statistically significant differences between the distribution pattern of -3279 A > C polymorphism in patients and healthy individuals along with it effect on the FoxP3 gene expression among both groups (P > 0.05).

CONCLUSIONS

Our outcome suggests that the -924 A > G polymorphism leads to enhance FoxP3 gene expression and susceptibility to tuberculosis in the sex dependent manner. This event may rise the count of Treg cells and modulate the immune response against tuberculosis.

Molecular detection of Mycobacterium tuberculosis in cattle and buffaloes: a cause for public health concern

Tuberculosis is a re-emerging disease causing a growing public health burden. The current study was conducted to investigate the occurrence of Mycobacterium tuberculosis among cattle and buffaloes with tuberculous lesions. Typical tuberculous lesions were collected from 34 cattle and 34 buffaloes (Bubalus bubalis) through postmortem examination of slaughtered animals in abattoirs. DNAs were extracted from samples, and M. tuberculosis was identified by PCR. Positive samples were examined for resistance against rifampicin and isoniazid using GenoType MTBDRplus. Moreover, sera from 90 slaughterhouse workers, butchers, or meat inspectors were examined for the presence of M. tuberculosis antibodies using ELISA. Five cattle (14.7 %) and three buffaloes (8.8 %) tested positive. M. tuberculosis from one cattle was resistant to rifampicin and another was resistant to isoniazid. In addition, the seroprevalence of M. tuberculosis IgG among examined humans was 5.6 %. The occurrence of M. tuberculosis in cattle and buffaloes is a public health concern.

A new diagnostic tool for rapid and accurate detection of Mycobacterium tuberculosis

Mycobacterium tuberculosis, acid fast bacilli from the family of Mycobacteriaceae, is the causative agent of most cases of tuberculosis. Tuberculosis, as a communicable disease, remains a serious public health threat, killing more than one million people globally every year. Primary diagnosis of tuberculosis bacilli (TB) relies mainly on microscopic detection of acid fast bacilli (AFB), but the method suffers from low sensitivity and the results largely depend on the technician’s skill. New diagnostic tools are necessary to be introduced for rapid and accurate detection of the bacilli in sputum samples. We, in collaboration with Anda Biologicals, have developed a new platform, named as “Patho-tb”, for rapid detection of AFB with high sensitivity and with low dependence on human skills. Evaluation of Patho-tb test performance was done in two settings: (1) primary field study conducted using 38 sputa from high TB prevalence area of Iran (Zabol city near to the Afghanistan border), and (2) main study conducted using 476 sputa from Tehran, capital of Iran. Patho-tb was applied for processed sputum samples in parallel with routine diagnostic methods (including AFB microscopy, culture and PCR). All test results were compared to final clinical diagnostic state of an individual and diagnostic sensitivity (DSe), specificity, positive predictive value, negative predictive value and accuracy of each test results were calculated using standard formulations. Analytical sensitivity and specificity of the Patho-tb test were also determined. Calculated values for five above mentioned parameters are as follows: for field study: AFB (DSe: 29.6, DSp: 81.8, PPV: 80, NPV: 23.1, AC: 44.7), Patho-tb (DSe: 63, DSp: 72.7, PPV: 85, NPV: 44.4, AC: 65.8), and for main study: AFB (DSe: 86.1, DSp: 99.4, PPV: 98.5, NPV: 93.9, AC: 95.2), Patho-tb (DSe: 97.4, DSp: 92.9, PPV: 86.5, NPV: 98.7, AC: 94.3). Reproducibility of Patho-tb test results were near to 100% (Cohen’s kappa value between 0.85 and 1). The detection limit of Patho-tb test with 100% positivity rate was 3 × 10³ cells/ml of sputum. In the field study, Patho-tb test was 33.4% more sensitive than AFB microscopy, while the improvement was only 11.3% during the main study. Patho-tb results are easy to interpret and the test can be merged with other screening tests, like AFB. Totally, Patho-tb test alone or in conjunction with AFB microscopy is a useful screening tool for TB detection especially in poor geographical lab conditions.