Direct susceptibility testing for multi drug resistant tuberculosis: a meta-analysis

New insight in molecular detection of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis, is a pathogenic bacterium that has claimed millions of lives since the Middle Ages. According to the World Health Organization's report, tuberculosis ranks among the ten deadliest diseases worldwide. The presence of an extensive array of genes and diverse proteins within the cellular structure of this bacterium has provided us with a potent tool for diagnosis. While the culture method remains the gold standard for tuberculosis diagnosis, it is possible that molecular diagnostic methods, emphasis on the identification of mutation genes (e.g., rpoB and gyrA) and single nucleotide polymorphisms, could offer a safe and reliable alternative. Over the past few decades, as our understanding of molecular genetics has expanded, methods have been developed based on gene expansion and detection. These methods typically commence with DNA amplification through nucleic acid targeted techniques such as polymerase chain reaction. Various molecular compounds and diverse approaches have been employed in molecular assays. In this review, we endeavor to provide an overview of molecular assays for the diagnosis of tuberculosis with their properties (utilization, challenges, and functions). The ultimate goal is to explore the potential of replacing traditional bacterial methods with these advanced molecular diagnostic techniques.

Multiplex Accelerated PCR System for One-Step Helicobacter pylori cagA + Genotypes Detection: A Guide for Clinical Testing

Helicobacter pylori cagA + genotype is a leading risk factor for gastric cancer development making accurate identification and timely eradication of H. pylori critical to deadly gastric cancer prevention. Traditional clinical diagnostic methods, including conventional in vitro culture, histological examination, and (13/14)C-urea breath test methods, could only identify the presence of H. pylori, but these means are not capable of identification of cagA + strains. Herein, we firstly built a multiplex detection system based on novel accelerated PCR that could realize one-step detection of as low as 20 copies of H. pylori 16S rDNA and cagA genes within 30 min. In addition, this novel system performed strong anti-jamming capacity, and exhibited that it could specifically differentiate H. pylori cagA- and cagA + genotypes co-existence with other 4 kinds of gastrointestinal pathogens. Furthermore, this one-step system showed remarkable performance on rapid H. pylori infection diagnosis and cagA + genotypes identification in clinical gastric mucosa samples. Specifically, it outperformed histological examination in terms of accuracy and was superior to conventional PCR and DNA sequencing in terms of efficiency. This rapid, sensitive, and reliable H. pylori detection and identification system would break the limitation of traditional methods and realize H. pylori infection diagnosis and cagA + genotypes identification.

Establishment of a TaqMan-MGB probe multiplex real-time PCR system for one-step levofloxacin and clarithromycin resistant Helicobacter pylori detection

Due to the abuse of antibiotics, the prevalence of antibiotic resistant Helicobacter pylori strains continues to increase. Therefore, antibiotic resistance assessment is now essential in addition to general H. pylori diagnosis in medical institutions to fulfill clinicians administering effective antibiotic regimens. However, the conventional antibiotic resistance assessment methods, such as in vitro antibiotic susceptibility test and E-test, are skilled-staff dependent and time-consuming. The aim of this study was to establish an easy-operating TaqMan-MGB probe multiplex real-time PCR system for one-step detection of levofloxacin and clarithromycin resistance mutations with concurrent H. pylori infection diagnosis. Through the optimization of primers, probes and reaction buffers, this proposed system could accurately distinguish the recombinant plasmids with different mutation markers. More importantly, the diagnosis results of this detection system exhibited excellent consistence with the gold standard of gastric biopsy and Sanger sequencing on the detection of H. pylori infection and relevant antibiotic resistant strains, the Kappa values of which all exceeded 0.90. In addition, the results of this detection system could also be applied for the prevalence statistics of antibiotic resistance patterns for patients by age, gender and geographical location. This simple and rapid system should be beneficial for clinicians issuing personalized treatments according to the patient's H. pylori strains and avoid the abuse of antibiotics.

Automatic cough classification for tuberculosis screening in a real-world environment

Objective.The automatic discrimination between the coughing sounds produced by patients with tuberculosis (TB) and those produced by patients with other lung ailments.Approach.We present experiments based on a dataset of 1358 forced cough recordings obtained in a developing-world clinic from 16 patients with confirmed active pulmonary TB and 35 patients suffering from respiratory conditions suggestive of TB but confirmed to be TB negative. Using nested cross-validation, we have trained and evaluated five machine learning classifiers: logistic regression (LR), support vector machines, k-nearest neighbour, multilayer perceptrons and convolutional neural networks.Main Results.Although classification is possible in all cases, the best performance is achieved using LR. In combination with feature selection by sequential forward selection, our best LR system achieves an area under the ROC curve (AUC) of 0.94 using 23 features selected from a set of 78 high-resolution mel-frequency cepstral coefficients. This system achieves a sensitivity of 93% at a specificity of 95% and thus exceeds the 90% sensitivity at 70% specificity specification considered by the World Health Organisation (WHO) as a minimal requirement for a community-based TB triage test.Significance.The automatic classification of cough audio sounds, when applied to symptomatic patients requiring investigation for TB, can meet the WHO triage specifications for the identification of patients who should undergo expensive molecular downstream testing. This makes it a promising and viable means of low cost, easily deployable frontline screening for TB, which can benefit especially developing countries with a heavy TB burden.

The simple direct slide method is comparable to indirect Lowenstein Jensen proportion culture for detecting rifampicin resistant tuberculosis

Introduction. Drug resistant tuberculosis remains a worldwide problem that requires prompt diagnosis.Hypothesis/Gap statement. The WHO recommended direct, rapid Xpert MTB/RIF is prohibitively costly, therefore, there is a need to validate a rapid, affordable DST for use in low- and middle-income settings.Aim. The technical performance and time to results of a simple, direct microscopy-based slide DST (SDST) assay for diagnosis of rifampicin-resistant TB was evaluated in Uganda.Methodology. Sputum samples from 122 smear-positive re-treatment TB patients presenting to the TB treatment centre at Uganda's National Referral Hospital, Mulago, Kampala, Uganda were examined. The sputum samples were tested by the direct SDST which was compared to the indirect Lowenstein Jensen Proportion Method (LJDST) method as the gold standard. The time to results was defined as the time from DST setting to results interpretation. The results were further analysed for sensitivity and specificity as well as agreement between LJDST and SDST for rifampicin resistance determination.Results. A total of 117 smear positive sputum samples with valid results for both tests were compared. The median time to results for SDST was 14 days with an interquartile range (IQR) of 10-14 days compared to 60 days with IQR of 60-75 days for LJDST. The number for rifampicin resistance by the gold standard LJDST was 26. The SDST had a sensitivity of 96 % (95 %; CI 81-99 %) and a specificity of 97.8 % (95 %; CI 93-100 %). The Positive Predictive and Negative Predictive values for SDST were 92.3 % (95 %; CI 76.8-99 %) and 98.9 % (95 %; CI 94-100 %), respectively. The kappa agreement between SDST and LJDST was 92.3 %.Conclusion. The SDST was found to be a rapid and accurate direct test for the detection of rifampicin resistance among retreatment TB cases in low-income settings.

Direct-from-sputum rapid phenotypic drug susceptibility test for mycobacteria

Background

The spread of multi-drug resistant tuberculosis (MDR-TB) is a leading global public-health challenge. Because not all biological mechanisms of resistance are known, culture-based (phenotypic) drug-susceptibility testing (DST) provides important information that influences clinical decision-making. Current phenotypic tests typically require pre-culture to ensure bacterial loads are at a testable level (taking 2–4 weeks) followed by 10–14 days to confirm growth or lack thereof.

Methods and findings

We present a 2-step method to obtain DST results within 3 days of sample collection. The first involves selectively concentrating live mycobacterial cells present in relatively large volumes of sputum (~2-10mL) using commercially available magnetic-nanoparticles (MNPs) into smaller volumes, thereby bypassing the need for pre-culture. The second involves using microchannel Electrical Impedance Spectroscopy (m-EIS) to monitor multiple aliquots of small volumes (~10μL) of suspension containing mycobacterial cells, MNPs, and candidate-drugs to determine whether cells grow, die, or remain static under the conditions tested. m-EIS yields an estimate for the solution “bulk capacitance” (Cb), a parameter that is proportional to the number of live bacteria in suspension. We are thus able to detect cell death (bactericidal action of the drug) in addition to cell-growth. We demonstrate proof-of-principle using M. bovis BCG and M. smegmatis suspended in artificial sputum. Loads of ~ 2000–10,000 CFU of mycobacteria were extracted from ~5mL of artificial sputum during the decontamination process with efficiencies of 84% -100%. Subsequently, suspensions containing ~105 CFU/mL of mycobacteria with 10 mg/mL of MNPs were monitored in the presence of bacteriostatic and bactericidal drugs at concentrations below, at, and above known MIC (Minimum Inhibitory Concentration) values. m-EIS data (ΔCb) showed data consistent with growth, death or stasis as expected and/or recorded using plate counts. Electrical signals of death were visible as early as 3 hours, and growth was seen in < 3 days for all samples, allowing us to perform DST in < 3 days.

Conclusion

We demonstrated “proof of principle” that (a) live mycobacteria can be isolated from sputum using MNPs with high efficiency (almost all the bacteria that survive decontamination) and (b) that the efficacy of candidate drugs on the mycobacteria thus isolated (in suspensions containing MNPs) could be tested in real-time using m-EIS.

Genotype®MTBDRplus and Xpert®MTB/RIF in the diagnosis of tuberculosis and resistant tuberculosis: cost analysis in a tertiary referral hospital

INTRODUCTION

The present study sought to assess the mean and activity based cost (ABC) of the laboratory diagnosis for tuberculosis through the application of conventional and molecular techniques-Xpert®MTB/RIF and Genotype®MTBDRplus-in a tertiary referral hospital in Brazil.

METHODS

The mean cost and ABC formed the basis for the cost analysis of the TB laboratory diagnosis.

RESULTS

The mean cost and ABC were US$ 4.00 and US$ 3.24, respectively, for a bacilloscopy; US$ 6.73 and US$ 5.27 for a Lowenstein-Jensen (LJ) culture; US$ 105.42 and US$ 76.56 for a drug sensitivity test (DST)-proportions method (PM) in LJ; US$ 148.45 and US$ 136.80 for a DST-BACTECTM MGITTM 960 system; US$ 11.53 and US$ 9.89 for an Xpert®MTB/RIF; and US$ 84.21 and US$ 48.38 for a Genotype®MTBDRplus.

CONCLUSIONS

The mean cost and ABC proved to be good decision-making parameters in the diagnosis of TB and MDR-TB. The effective implementation of algorithms will depend on the conditions at each location.

Evaluation of GenoType MTBDRplus for the detection of drug-resistant Mycobacterium tuberculosis on isolates from Karachi, Pakistan

Objective

To compare the diagnostic performance of the GenoType MRBDRplus assay with the gold standard phenotypic drug susceptibility testing in the detection of drug resistance among culture isolates obtained from patients in Karachi, Pakistan.

Design

Mycobacterium tuberculosis isolates were obtained from 96 consecutive tuberculosis patients found to have resistance to isoniazid from two health centers in Karachi (January-November 2017). Isolates were tested for drug resistance against rifampin and isoniazid using the MTBDRplus assay. Results were compared with conventional drug-susceptibility testing and the frequency of specific mutations were reported.

Results

The MTBDRplus assay had a sensitivity for rifampin resistance of 98.8% (95% CI: 93.4–100) and for isoniazid resistance of 90.6% (95% CI: 83.0–95.6). The MTBDRplus assay showed mutations in rpoB in 81 of the 96 (84.4%) isolates. Of the 87 isolates showing resistance to isoniazid via the MTBDRplus assay, 71 (74.0%) isolates had mutations in the katG gene only, 15 (15.6%) isolates had mutations in the inhA promoter region, and 1 (1.0%) showed mutations in both genes.

Conclusion

The GenoType MTBDRplus assay in Pakistan can identify subgroups at high-risk of having isolates with mutations in the katG and/or inhA genes. Understanding the local burden of these mutations have implications for local diagnostic and treatment guidelines.

Evaluation of the GenoType MTBDRplus and MTBDRsl for the detection of drug-resistant Mycobacterium tuberculosis on isolates from Beijing, China

Background

The incidence of tuberculosis (TB), especially multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), continues to increase alarmingly worldwide. Molecular line probe assays (LPAs) are endorsed by the World Health Organization for the fast detection of MDR-TB and XDR-TB. The aim of this study was to evaluate the performance of LPAs in China.

Methods

We analyzed MDR-TB and XDR-TB in 96 isolates from Beijing by using culture-based drug susceptibility testing (DST) and LPAs to compare the detection rate of the two methods.

Results

Compared to phenotypic DST, the GenoType^® MTBDRplus and MTBDRsl, respectively, showed a sensitivity of 98.7% and a specificity of 88.9% for detection of rifampicin resistance, 82.1% and 94.4% for isoniazid, 89.7% and 94.4% for levofloxacin, 60.0% and 98.7% for amikacin/capreomycin, and 57.5% and 98.2% for ethambutol. The sensitivity and specificity of LPAs, respectively, were 80.8% and 100% for MDR-TB and 50.0% and 97.6% for XDR-TB. Mutations in codon S531L of the rpoB gene and S315T1 of the KatG gene were dominated in MDR-TB strains. The most frequently observed mutations were in codon A90V of the gyrA gene, A1401G of the rrs gene, and M306V of the embB gene, according to the MTBDRsl results.

Conclusion

Our study showed that, in combination with phenotypic DST, application of the LPAs might be an efficient and reliable supplementary DST assay for rapid susceptibility screening of MDR-TB and XDR-TB. Using LPAs in countries with high MDR/XDR burden allows for appropriate and timely treatment, which will reduce transmission rates and morbidity, and improve treatment outcomes in patients.

Drug resistance mechanisms and drug susceptibility testing for tuberculosis

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) is the deadliest infectious disease and the associated global threat has worsened with the emergence of drug resistance, in particular multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). Although the World Health Organization (WHO) End-TB Strategy advocates for universal access to antimicrobial susceptibility testing, this is not widely available and/or it is still underused. The majority of drug resistance in clinical MTB strains is attributed to chromosomal mutations. Resistance-related mutations could also exert certain fitness cost to the drug-resistant MTB strains and growth fitness could be restored by the presence of compensatory mutations. Understanding these underlying mechanisms could provide an important insight into TB pathogenesis and predict the future trend of MDR-TB global pandemic. This review covers the mechanisms of resistance in MTB and provides a comprehensive overview of current phenotypic and molecular approaches for drug susceptibility testing, with particular attention to the methods endorsed and recommended by the WHO.

The occurrence and frequency of genomic mutations that mediate Isoniazid and Rifampicin resistance in Mycobacterium tuberculosis isolates from untreated pulmonary Tuberculosis cases in urban Blantyre, Malawi

Background

The emergence and spread of drug-resistant Tuberculosis (TB) is a major public health threat. TB resistance originates in the course of treatment due to genomic mutations in Mycobacterium tuberculosis (MTB). An increase in new cases with drug-resistant TB could be an indicator of high levels of circulating resistant strains. This study was conducted to determine the occurrence and frequency of genomic mutations that mediate Isoniazid (INH) and Rifampicin (RIF) resistance among isolates from untreated TB cases in urban Blantyre, Malawi.

Methods

A cross-sectional retrospective study was conducted on a panel of 141(n=141) MTB clinical isolates recovered between June 2010 and January 2012 from >2+ Ziehl-Neelsen smear positive new pulmonary-TB patients with no history of treatment. Frozen isolates were revived using the BACTEC MGIT detection system. DNA was extracted using GenoLyse DNA extraction kit and detection of genomic mutations was carried out using the GenoType MTBDRplus Ver 2.0 assay.

Results

Out of the 141 isolates studied, 3 (2.1%) were found carrying mutations in the katG gene that confer resistance to Isoniazid (INH). No mutations were detected in the inhA promoter region gene that confer weak INH resistance or in the rpoB gene that confer Rifampicin resistance. All katG mutant genes had a S315T1 single point mutation, a genomic alteration that mediates high INH resistance.

Conclusion

The katG mutant gene conferring resistance to INH was the only genomic mutation observed among the isolates studied and the frequency of occurrence was low. Our findings suggest low levels of circulating drug-resistant MTB strains in urban Blantyre, Malawi.

Evaluation of Microscopic observation drug susceptibility (MODS) assay as a rapid, sensitive and inexpensive test for detection of tuberculosis and multidrug resistant tuberculosis

Background

Microscopic observation drug susceptibility (MODS) assay has been suggested as a low cost method for rapid, accurate detection of tuberculosis (TB) and multidrug resistant tuberculosis (MDR-TB).

Methods

A total of 2424 samples collected from 1063 eligible patients of suspected pulmonary or extrapulmonary TB were subjected to MODS assay. Performance of MODS was compared with culture and drug susceptibility testing (DST) by conventional solid Lowenstein-Jensen (LJ) media or liquid Mycobacteria Growth Indicator Tube (MGIT) culture.

Results

When compared to reference gold standard of positivity in either solid or liquid reference culture, the MODS assay had sensitivity, specificity, positive predictive value and negative predictive value of 91.3%, 98.2%, 96.0% and 95.9% respectively. MODS took a median time of 10.3 days to culture positivity as compared to 13.8 days using MGIT and 30.5 days using LJ culture. Culture and DST being concurrent in MODS, the median turnaround time for DST was the same as that for culture i.e. 10.3 days. The overall median turn around time for culture positivity and DST using manual MGIT and LJ medium was 23.6 days and 61.2 days respectively. The concordance between MODS culture and the reference susceptibility method was 97.7% for rifampicin, 95.6% for isoniazid, 98.5% for rifampicin and isoniazid. The cost of performing a single MODS assay was INR 200.

Conclusion

MODS is a rapid and sensitive, yet simple and inexpensive test that may be helpful to enhance diagnostic accuracy, and case detection of TB and MDR-TB in resource constrained settings.

Correlation between the BACTEC MGIT 960 culture system with Genotype MTBDRplus and TB-SPRINT in multidrug resistant Mycobacterium tuberculosis clinical isolates from Brazil

BACKGROUND

The accurate detection of multidrug-resistant tuberculosis (MDR-TB) is critical for the application of appropriate patient treatment and prevention of transmission of drug-resistant Mycobacterium tuberculosis isolates. The goal of this study was to evaluate the correlation between phenotypic and molecular techniques for drug-resistant tuberculosis diagnostics. Molecular techniques used were the line probe assay genotype MTBDRplus and the recently described tuberculosis-spoligo-rifampin-isoniazid typing (TB-SPRINT) bead-based assay. Conventional drug susceptibility testing (DST) was done on a BACTECTM MGIT 960 TB.

METHOD

We studied 80 M. tuberculosis complex (MTC) clinical isolates from Minas Gerais state, of which conventional DST had classified 60 isolates as MDR and 20 as drug susceptible.

FINDINGS

Among the 60 MDR-TB isolates with MGIT as a reference, sensitivity, specificity, accuracy, and kappa for rifampicin (RIF) resistance using TB-SPRINT and MTBDRplus, were 96.7% versus 93.3%, 100.0% versus 100.0%, 97.5% versus 95.0% and 0.94 versus 0.88, respectively. Similarly, the sensitivity, specificity, accuracy, and kappa for isoniazid (INH) resistance were 85.0% and 83.3%, 100.0% and 100.0%, 88.8% and 87.5% and 0.74 and 0.71 for both tests, respectively. Finally, the sensitivity, specificity, accuracy, and kappa for MDR-TB were 85.0% and 83.3%, 100.0% and 100.0%, 88.8% and 87.5% and 0.74 and 0.71 for both tests, respectively.

MAIN CONCLUSIONS

Both methods exhibited a good correlation with the conventional DST. We suggest estimating the cost-effectiveness of MTBDRplus and TB-SPRINT in Brazil.

Diagnostic accuracy of Xpert MTB/RIF assay for musculoskeletal tuberculosis: a meta-analysis

OBJECTIVES

Xpert MTB/RIF assay, a rapid and automated real-time nucleic acid amplification test, has been reported for the diagnosis of musculoskeletal tuberculosis (TB) in current years. This meta-analysis aims to determine the diagnostic accuracy of Xpert for the detection of musculoskeletal TB and rifampicin (RIF) resistance.

METHODS

We searched PubMed, Embase, China National Knowledge Infrastructure, and Wanfang for original articles published up to 1st June 2017 to identify studies in which the Xpert assay was applied to diagnose musculoskeletal TB. Pooled estimates were calculated using a random-effects model or a fixed-effects model according to heterogeneity. Summary receiver operating characteristic curves and the area under the curve (AUC) were used to summarize overall diagnostic performance. Deeks' test was performed to evaluate potential publication bias.

RESULTS

Twelve studies were identified with a pooled sensitivity and specificity of respectively 0.81 (95% confidence interval [CI] 0.78-0.83) and 0.83 (95% CI 0.80-0.86) of Xpert for the diagnosis of musculoskeletal TB. Xpert was highly sensitive (0.89, 95% CI 0.79-0.95) and highly specific (0.96, 95% CI 0.92-0.98) in detecting RIF resistance. AUC (over 0.9) suggested a relatively high level of overall diagnostic accuracy of Xpert for detecting musculoskeletal TB and RIF resistance. Prevalence and reference standard were indicated to be sources of heterogeneity between studies. No publication bias was found.

CONCLUSION

This study provides available evidence of the rapid and effective role of Xpert in diagnosing musculoskeletal TB and detecting RIF resistance.

Scaling-up the Xpert MTB/RIF assay for the detection of tuberculosis and rifampicin resistance in India: An economic analysis

BACKGROUND

India is considering the scale-up of the Xpert MTB/RIF assay for detection of tuberculosis (TB) and rifampicin resistance. We conducted an economic analysis to estimate the costs of different strategies of Xpert implementation in India.

METHODS

Using a decision analytical model, we compared four diagnostic strategies for TB patients: (i) sputum smear microscopy (SSM) only; (ii) Xpert as a replacement for the rapid diagnostic test currently used for SSM-positive patients at risk of drug resistance (i.e. line probe assay (LPA)); (iii) Upfront Xpert testing for patients at risk of drug resistance; and (iv) Xpert as a replacement for SSM for all patients.

RESULTS

The total costs associated with diagnosis for 100,000 presumptive TB cases were: (i) US$ 619,042 for SSM-only; (ii) US$ 575,377 in the LPA replacement scenario; (iii) US$ 720,523 in the SSM replacement scenario; and (iv) US$ 1,639,643 in the Xpert-for-all scenario. Total cohort costs, including treatment costs, increased by 46% from the SSM-only to the Xpert-for-all strategy, largely due to the costs associated with second-line treatment of a higher number of rifampicin-resistant patients due to increased drug-resistant TB (DR-TB) case detection. The diagnostic costs for an estimated 7.64 million presumptive TB patients would comprise (i) 19%, (ii) 17%, (iii) 22% and (iv) 50% of the annual TB control budget. Mean total costs, expressed per DR-TB case initiated on treatment, were lowest in the Xpert-for-all scenario (US$ 11,099).

CONCLUSIONS

The Xpert-for-all strategy would result in the greatest increase of TB and DR-TB case detection, but would also have the highest associated costs. The strategy of using Xpert only for patients at risk for DR-TB would be more affordable, but would miss DR-TB cases and the cost per true DR-TB case detected would be higher compared to the Xpert-for-all strategy. As such expanded Xpert strategy would require significant increased TB control budget to ensure that increased case detection is followed by appropriate care.

Evaluation of crystal violet decolorization assay for minimal inhibitory concentration detection of primary antituberculosis drugs against Mycobacterium tuberculosis isolates

In this study we evaluated the crystal violet decolorization assay (CVDA) for detection of minimum inhibitory concentration (MIC) of antituberculosis drugs. 53 isolates were tested in this study and 13 of them were multidrug resistant (MDR) isolates. The antibiotics concentrations were 2-0.06 mg/L for isoniazid (INH) and rifampicin (RIF) and were 16-0.25 mg/L for streptomycin (STM) and ethambutol (EMB). Crystal violet (CV-25 mg/L) was added into the microwells on the seventh day of incubation and incubation was continued until decolorization. Decolorization of CV was the predictor of bacterial growth. Overall agreements for four drugs were detected as 98.1%, and the average time was detected as 9.5 ± 0.89 day after inoculation. One isolate for INH and two isolates for STM were determined resistant in the reference method, but susceptible by the CVDA. One isolate was susceptible to EMB by the reference method, but resistant by the CVDA. All results were concordant for RIF. This study shows that CVDA is a rapid, reliable and suitable for determination of MIC values of Mycobacterium tuberculosis. And it can be used easily especially in countries with limited-sources.

Combination of commercially available molecular assays and culture based methods in diagnosis of tuberculosis and drug resistant tuberculosis

Early diagnosis of tuberculosis is of major clinical importance. Among 4733 clinical specimens collected from 3363 patients and subjected to Ziehl–Neelsen microscopy, 4109 were inoculated onto Löwenstein–Jensen slants and 3139 in Bactec/9000MB. Polymerase Chain Reaction (PCR) was performed in 3139 specimens, whereas, a genotypic assay was directly applied in 93 Mycobacterium tuberculosis complex PCR-positive for isoniazid and rifampicin resistance detection specimens (GenoType MTBDRplus). Recovered M. tuberculosis isolates (64) as well as, 21 more sent from Regional Hospitals were tested for antimycobacterial resistance with a phenotypic (manual MGIT-SIRE) and a genotypic assay (GenoType MTBDRplus). PCR in the clinical specimens showed excellent specificity (97.4%) and accuracy (96.8%), good sensitivity (70.4%), but low positive predictive value (40.3%). MGIT-SIRE performed to M. tuberculosis did not confer a reliable result in 16 isolates. Of the remaining 69 isolates, 15 were resistant to streptomycin, seven to isoniazid, seven to ethambutol and five to rifampicin. GenoType MTBDRplus correctly detected isoniazid (seven) and rifampicin-resistant M. tuberculosis strains (five), showing an excellent performance overall (100%). Susceptibility results by the molecular assay applied directly to clinical specimens were identical to those obtained from recovered isolates of the corresponding patients. Combining molecular and conventional methods greatly contribute to early diagnosis and accurate susceptibility testing of tuberculosis.

A performance evaluation of MTBDRplus version 2 for the diagnosis of multidrug-resistant tuberculosis

OBJECTIVE

To evaluate the performance of a recently updated rapid molecular diagnostic test, GenoType® MTBDRplus version 2, designed to detect drug resistance in both acid-fast bacilli (AFB) smear-negative and -positive specimens.

DESIGN

Sputum samples from 1128 patients at risk for multidrug-resistant tuberculosis (MDR-TB) were tested using MTBDRplus v2 and compared with reference standard MGIT™ 960™ drug susceptibility testing. The relationship of participant human immunodeficiency virus (HIV) status, diabetic status, previous treatment, and smear gradation to the likelihood of obtaining an interpretable result was assessed using logistic regression.

RESULTS

The sensitivity and specificity of MTBDRplus v2 for detecting MDR-TB, when compared to a reference standard, were respectively 96.0% (95%CI 93.5-97.6) and 99.2% (95%CI 97.0-99.9) in AFB smear-positive specimens and 82.8% (95%CI 63.5-93.5) and 98.3% (95%CI 89.9-99.9) in AFB smear-negative specimens. A dose-response relationship was observed between the proportion of interpretable test results and AFB smear bacterial load after adjusting for age, sex, body mass index, HIV status, previous treatment and diabetic status.

CONCLUSION

While MTBDRplus v2 performs well among both AFB smear-positive and -negative specimens, smear gradation appears to influence both the probability of obtaining an interpretable result and test sensitivity, indicating a significant association between bacillary load and test performance.

Redefining MTBDRplus test results: what do indeterminate results actually mean?

BACKGROUND

Although line-probe assays (LPAs) are promising, little research has been conducted to elucidate the true nature of indeterminate LPA results or assess the ability of these assays to perform on a wide range of clinical samples.

OBJECTIVE

To evaluate the performance of the commercially available GenoType(®) MTBDRplus LPA against conventional BACTEC™ MGIT™ 960 culture and drug susceptibility testing (DST) among 308 pulmonary tuberculosis (PTB) and 32 extra-pulmonary TB samples.

RESULTS

Invalid LPA results (defined as those with a missing Mycobacterium tuberculosis identification band) were obtained for 18 PTB samples, which were excluded from further analysis. The sensitivity and specificity of the MTBDRplus assay for multidrug-resistant TB, based upon the results obtained for the remaining 322 samples, was respectively 95.2% and 95.1%. Of 290 PTB samples, 40 (13.7%) were indeterminate on LPA (defined as the absence of both wild-type and corresponding mutation bands) for isoniazid (INH) and/or rifampicin (RMP), and were further evaluated by pyrosequencing (PSQ). Contrary to standard LPA interpretation, INH and RMP susceptibility were confirmed by both DST and PSQ in respectively 7.5% (3/40) and 27.5% (11/40) of indeterminate samples.

CONCLUSION

PSQ was found to be a valuable and rapid technique to resolve discrepancies in LPA test results that were not interpretable.

Tissue inhibitor of metalloproteinases 1, a novel biomarker of tuberculosis

Tuberculosis (TB) is an important infectious disease of humans and other animals. Conventional diagnostic methods, including the tuberculin skin test, chest X‑rays and bacterial culture, have certain innate disadvantages for the early, rapid and specific diagnosis of tuberculosis. The present study aimed to identify a novel diagnostic biomarker to overcome these disadvantages. The potential target identified in the present study was tissue inhibitor of metalloproteinases 1 (TIMP‑1), which has previously been demonstrated to be critical in the immune response to TB. The concentration of TIMP‑1 in the blood was determined using a commercial ELISA kit, and the relative mRNA expression levels following bacterial infection were detected by reverse transcription‑quantitative polymerase chain reaction. Based on a clinical and microbiological diagnosis, the ELISA for plasma TIMP‑1 had a sensitivity of 91.80% [95% confidence interval (CI): 85.44, 96.00] and a specificity of 91.41% (95% CI: 85.14, 95.63). In a THP‑1 cell model, Bacillus Calmette‑Guérin and Mycobacterium bovis significantly upregulated the mRNA expression levels of TIMP‑1 post infection in a time‑dependent manner (P=0.006 for BCG 24 h PI, P=3.2x10‑7 for M. bovis 24 PI). The results of the present study indicate that plasma TIMP‑1 may be a potential biomarker for the diagnosis of TB.

Multidrug-resistant tuberculosis in Lithuania - Still a long way ahead

Despite the recent advances in the diagnosis of tuberculosis, treatment of the disease, for the most part, remains the same as it was half a century ago. In recent years only two new anti-tuberculosis drugs have been approved by the European Medicines Agency and Food and Drug Administration. Though the prevalence of this disease is slowly decreasing all over Europe, new challenges appear. One of them is multidrug-resistant tuberculosis (MDR-TB). This problem is especially prominent in Lithuania, which is one of the 27 high MDR-TB burden countries in the world and falls behind neighboring countries in terms of the prevalence of the disease. The objective of this paper was to review the situation of tuberculosis and MDR-TB in Lithuania, and current available methods of treatment, control and diagnosis of this disease.

GenoType MTBDRplus Assay for Rapid Detection of Multidrug Resistance in Mycobacterium tuberculosis: A Meta-Analysis

Background

There is an urgent demand for rapid and accurate drug-susceptibility testing for the detection of multidrug-resistant tuberculosis. The GenoType MTBDRplus assay is a promising molecular kit designed for rapid identification of resistance to first-line anti-tuberculosis drugs, isoniazid and rifampicin. The aim of this meta-analysis was to evaluate the diagnostic accuracy of GenoType MTBDRplus in detecting drug resistance to isoniazid and rifampicin in comparison with the conventional drug susceptibility tests.

Methods

We searched PubMed, EMBASE, and Cochrane Library databases to identify studies according to predetermined criteria. A total of 40 studies were included in the meta-analysis. QUADAS-2 was used to assess the quality of included studies with RevMan 5.2. STATA 13.0 software was used to analyze the tests for sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the summary receiver operating characteristic curves. Heterogeneity in accuracy measures was tested with Spearman correlation coefficient and Chi-square.

Results

Patient selection bias was observed in most studies. The pooled sensitivity (95% confidence intervals were 0.91 (0.88–0.94) for isoniazid, 0.96 (0.95–0.97) for rifampicin, and 0.91(0.86–0.94) for multidrug-resistance. The pooled specificity (95% CI) was 0.99 (0.98–0.99) for isoniazid, 0.98 (0.97–0.99) for rifampicin and 0.99 (0.99–1.00) for multidrug-resistance, respectively. The area under the summary receiver operating characteristic curves ranged from 0.99 to 1.00.

Conclusion

This meta-analysis determined that GenoType MTBDRplus had good accuracy for rapid detection of drug resistance to isoniazid and/or rifampicin of M. tuberculosis. MTBDRplus method might be a good alternative to conventional drug susceptibility tests in clinical practice.

Evaluation of GenoFlow DR-MTB Array Test for Detection of Rifampin and Isoniazid Resistance in Mycobacterium tuberculosis

The aim of this study was to evaluate the GenoFlow DR-MTB array test (DiagCor Bioscience, Hong Kong) on 70 cultured isolates and 50 sputum specimens. The GenoFlow array test showed good sensitivity and specificity compared to the phenotypic Bactec 460TB. This array accurately detected mutations inrpoB,katG, andinhAassociated with resistance to rifampin and isoniazid.

A molecular platform for the diagnosis of multidrug-resistant and pre-extensively drug-resistant tuberculosis based on single nucleotide polymorphism mutations present in Colombian isolates of Mycobacterium tuberculosis

Developing a fast, inexpensive, and specific test that reflects the mutations present in Mycobacterium tuberculosis isolates according to geographic region is the main challenge for drug-resistant tuberculosis (TB) control. The objective of this study was to develop a molecular platform to make a rapid diagnosis of multidrug-resistant (MDR) and extensively drug-resistant TB based on single nucleotide polymorphism (SNP) mutations present in therpoB, katG, inhA,ahpC, and gyrA genes from Colombian M. tuberculosis isolates. The amplification and sequencing of each target gene was performed. Capture oligonucleotides, which were tested before being used with isolates to assess the performance, were designed for wild type and mutated codons, and the platform was standardised based on the reverse hybridisation principle. This method was tested on DNA samples extracted from clinical isolates from 160 Colombian patients who were previously phenotypically and genotypically characterised as having susceptible or MDR M. tuberculosis. For our method, the kappa index of the sequencing results was 0,966, 0,825, 0,766, 0,740, and 0,625 forrpoB, katG, inhA,ahpC, and gyrA, respectively. Sensitivity and specificity were ranked between 90-100% compared with those of phenotypic drug susceptibility testing. Our assay helps to pave the way for implementation locally and for specifically adapted methods that can simultaneously detect drug resistance mutations to first and second-line drugs within a few hours.

MTBDRplus and MTBDRsl Assays: Absence of Wild-Type Probe Hybridization and Implications for Detection of Drug-Resistant Tuberculosis

Accurate identification of drug-resistantMycobacterium tuberculosisis imperative for effective treatment and subsequent reduction in disease transmission. Line probe assays rapidly detect mutations associated with resistance and wild-type sequences associated with susceptibility. Examination of molecular-level performance is necessary for improved assay result interpretation and for continued diagnostic development. Using data collected from a large, multisite diagnostic study, probe hybridization results from line probe assays, MTBDRplusand MTBDRsl, were compared to those of sequencing, and the diagnostic performance of each individual mutation and wild-type probe was assessed. Line probe assay results classified as resistant due to the absence of wild-type probe hybridization were compared to those of sequencing to determine if novel mutations were inhibiting wild-type probe hybridization. The contribution of absent wild-type probe hybridization to the detection of drug resistance was assessed via comparison to a phenotypic reference standard. In our study, mutation probes demonstrated significantly higher specificities than wild-type probes and wild-type probes demonstrated marginally higher sensitivities than mutation probes, an ideal combination for detecting the presence of resistance conferring mutations while yielding the fewest number of false-positive results. The absence of wild-type probe hybridization without mutation probe hybridization was determined to be primarily the result of failure of mutation probe hybridization and not the result of novel or rare mutations. Compared to phenotypic culture-based drug susceptibility testing, the absence of wild-type probe hybridization without mutation probe hybridization significantly contributed to the detection of phenotypic rifampin and fluoroquinolone resistance with negligible increases in false-positive results.

Microscopic Observation Drug Susceptibility Assay for Rapid Diagnosis of Lymph Node Tuberculosis and Detection of Drug Resistance

In this study, 132 patients with lymphadenopathy were investigated. Fifty-two (39.4%) were diagnosed with tuberculosis (TB). The microscopic observation drug susceptibility (MODS) assay provided rapid (13 days), accurate diagnosis (sensitivity, 65.4%) and reliable drug susceptibility testing (DST). Despite its lower sensitivity than that of other methods, its faster results and simultaneous DST are advantageous in resource-poor settings, supporting the incorporation of MODS into diagnostic algorithms for extrapulmonary TB.

Isoniazid and rifampin drug susceptibility testing: application of 2,3,5-triphenyl tetrazolium chloride assay and microscopic-observation drug-susceptibility assay directly on Ziehl-Neelsen smear positive sputum specimens

The current study was aimed to evaluate the performance of direct 2,3,5-triphenyl tetrazolium chloride assay and direct microscopic observation drug susceptibility assay with indirect Löwenstein-Jensen proportion method directly on Ziehl-Neelsen smear positive sputum specimens.

Methods

Direct acid fast bacilli smear positive sputum specimens (n = 264) were subjected to isoniazid and rifampicin drug susceptibility testing by direct 2,3,5-triphenyl tetrazolium chloride assay, direct microscopic observation drug susceptibility assay, and the performances were compared with indirect Löwenstein-Jensen proportion method.

Results

The direct 2,3,5-triphenyl tetrazolium chloride assay demonstrated an overall sensitivity, specificity, positive predictive value, and negative predictive value of 99.2%, 82.4%, 99.2%, and 88.5%, respectively, for the detection of isoniazid and rifampicin resistant Mycobacterium tuberculosis isolates when compared to indirect Löwenstein-Jensen proportion method. Likewise, the overall sensitivity, specificity, positive predictive value and negative predictive value of direct microscopic observation drug susceptibility assay were 98.8%, 82.4%, 99.2%, and 78.2%, respectively.

Conclusion

The direct 2,3,5-triphenyl tetrazolium chloride assay was found to be an economical alternative method for the rapid and accurate detection of isoniazid and rifampicin resistance from direct acid fast bacilli smear positive sputum specimens.

The potential of a multiplex high-throughput molecular assay for early detection of first and second line tuberculosis drug resistance mutations to improve infection control and reduce costs: a decision analytical modeling study

Background

Molecular resistance detection (MRD) of resistance to second-line anti-tuberculous drugs provides faster results than phenotypic tests, may shorten treatment and allow earlier separation among patients with and without second-line drug resistance.

Methods

In a decision-analytical model we simulated a cohort of patients diagnosed with TB in a setting where drug resistant TB is highly prevalent and requires initial hospitalization, to explore the potential benefits of a high-throughput MRD-assay for reducing potential nosocomial transmission of highly resistant strains, and total costs for diagnosis of drug resistance, treatment and hospitalization. In the base case scenario first-line drug resistance was diagnosed with WHO-endorsed molecular tests, and second-line drug resistance with culture and phenotypic methods. Three alternative scenarios were explored, each deploying high-throughput MRD allowing either detection of second-line mutations in cultured isolates, directly on sputum, or MRD with optimized markers.

Results

Compared to a base case scenario, deployment of high-throughput MRD reduced total costs by 17-21 %. The period during which nosocomial transmission may take place increased by 15 % compared to the base case if MRD had currently reported suboptimal sensitivity and required cultured isolates; increased by 7 % if direct sputum analysis were possible including in patients with smear-negative TB, and reduced by 24 % if the assay had improved markers, but was still performed on cultured isolates. Improved clinical sensitivity of the assay (additional markers) by more than 35 % would be needed to avoid compromising infection control.

Conclusions

Further development of rapid second-line resistance testing should prioritize investment in optimizing markers above investments in a platform for direct analysis of sputum.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1205-4) contains supplementary material, which is available to authorized users.

Nested reverse transcriptase-polymerase chain reactions targeting the messenger RNA of icl2, hspx, and rRNAP1 genes to detect viable Mycobacterium tuberculosis directly from clinical specimens

There is an urgent need for a rapid and reliable test to detect actively multiplying Mycobacterium tuberculosis directly from clinical specimens for an early initiation of the appropriate antituberculous treatment. This study was aimed at the optimization and application of nested reverse transcriptase-PCR (nRT-PCR) targeting the messenger RNA of the icl2, hspx, and rRNAP1 genes directly from sputum specimens, and their evaluation against the culture by the BACTEC MicroMGIT mycobacterial culture system. 203 Sputum samples from clinically suspected tuberculosis patients and 30 control specimens (clinically proven viral or bacterial infections other than tuberculosis) were included in this study. The mycobacterial culture was performed by the BACTEC MicroMGIT system following the manufacturer's instructions. The primers for nRT-PCRs targeting icl2, hspx, and rRNAP1 genes were indigenously designed using the Primer-BLAST software, and optimized for sensitivity and specificity. The icl2, hspx, and rRNAP1 genes were able to pick up 63.9%, 67.2%, and 58.75%, respectively, of culture-negative sputum specimens collected from clinically suspected tuberculosis patients. However, three (1.4%) were negative for nRT-PCR, but M. tuberculosis culture positive. All the 30 controls were negative for culture by the BACTEC MicroMGIT method and all three nRT-PCR. The novel nRT-PCRs targeting icl2, hspx, and rRNAP1 genes developed in this study are rapid and reliable diagnostic tools to detect viable M. tuberculosis directly from sputum specimens. However, further study by including a larger number of sputum specimens needs to be carried out to ascertain the diagnostic utility of the novel nRT-PCRs optimized in the study.

Lab-on-Chip-Based Platform for Fast Molecular Diagnosis of Multidrug-Resistant Tuberculosis

We evaluated the performance of the molecular lab-on-chip-based VerePLEX Biosystem for detection of multidrug-resistant tuberculosis (MDR-TB), obtaining a diagnostic accuracy of more than 97.8% compared to sequencing and MTBDRplus assay for Mycobacterium tuberculosis complex and rifampin and isoniazid resistance detection on clinical isolates and smear-positive specimens. The speed, user-friendly interface, and versatility make it suitable for routine laboratory use.

Evaluation of four colourimetric susceptibility tests for the rapid detection of multidrug-resistant Mycobacterium tuberculosis isolates

The purpose of this study is to evaluate four rapid colourimetric methods, including the resazurin microtitre assay (REMA), malachite green decolourisation assay (MGDA), microplate nitrate reductase assay (MNRA) and crystal violet decolourisation assay (CVDA), for the rapid detection of multidrug-resistant (MDR) tuberculosis. Fifty Mycobacterium tuberculosis isolates were used in this study. Eighteen isolates were MDR, two isolates were only resistant to isoniazid (INH) and the remaining isolates were susceptible to both INH and rifampicin (RIF). INH and RIF were tested in 0.25 µg/mL and 0.5 µg/mL, respectively. The agar proportion method was used as a reference method. MNRA and REMA were performed with some modifications. MGDA and CVDA were performed as defined in the literature. The agreements of the MNRA for INH and RIF were 96% and 94%, respectively, while the agreement of the other assays for INH and RIF were 98%. In this study, while the specificities of the REMA, MGDA and CVDA were 100%, the specificity of the MNRA was lower than the others (93.3% for INH and 90.9% for RIF). In addition, while the sensitivity of the MNRA was 100%, the sensitivities of the others were lower than that of the MNRA (from 94.1-95%). The results were reported on the seventh-10th day of the incubation. All methods are reliable, easy to perform, inexpensive and easy to evaluate and do not require special equipment.

Xpert MTB/RIF and GenoType MTBDRplus assays for the rapid diagnosis of bone and joint tuberculosis

BACKGROUND

Bone and joint tuberculosis (BJTB) constitutes about 10-20% of the extrapulmonary tuberculosis (EPTB) cases in China. The GenoType MTBDRplus assay (MTBDR) has been endorsed by the World Health Organization (WHO) for the diagnosis of pulmonary TB (PTB), while the Xpert MTB/RIF assay (Xpert) has also been endorsed by the WHO for the diagnosis of both PTB and EPTB. The diagnostic utility of these two techniques for BJTB was investigated prospectively.

METHODS

Sixty pus specimens were obtained from orthopedic patients. Smear, culture, Xpert, and MTBDR assays were performed for each specimen, and MGIT 960-based drug susceptibility testing (DST) was conducted for all of the isolates recovered. The diagnostic efficiency of Xpert and MTBDR was evaluated on the basis of bacteriological examination and the composite reference standard (CRS).

RESULTS

Fifty of the 60 patients were considered to have BJTB according to the CRS. The sensitivities of smear, culture, Xpert, and MTBDR were 26% (13/50), 48% (24/50), 82% (41/50), and 72% (36/50) respectively, while the specificities of all of the tests were 100% (10/10). Xpert was 100% concordant with MGIT 960-based DST for the detection of rifampicin resistance. MTBDR had a sensitivity of 83.3% and a specificity of 100% for the detection of rifampicin resistance and a sensitivity of 85.7% and specificity of 100% for the detection of isoniazid resistance.

CONCLUSION

With their high sensitivities, short turnaround times, and ability to diagnose TB and detect drug resistance simultaneously, both Xpert and MTBDR are feasible as diagnostic tools for BJTB in clinical practice.

Rapid detection of multidrug-resistant Mycobacterium tuberculosis using the malachite green decolourisation assay

Early detection of drug resistance in Mycobacterium tuberculosis isolates allows for earlier and more effective treatment of patients. The aim of this study was to investigate the performance of the malachite green decolourisation assay (MGDA) in detecting isoniazid (INH) and rifampicin (RIF) resistance in M. tuberculosis clinical isolates. Fifty M. tuberculosis isolates, including 19 multidrug-resistant, eight INH-resistant and 23 INH and RIF-susceptible samples, were tested. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and agreement of the assay for INH were 92.5%, 91.3%, 92.5%, 91.3% and 92%, respectively. Similarly, the sensitivity, specificity, PPV, NPV and agreement of the assay for RIF were 94.7%, 100%, 100%, 96.8% and 98%, respectively. There was a major discrepancy in the tests of two isolates, as they were sensitive to INH by the MGDA test, but resistant by the reference method. There was a minor discrepancy in the tests of two additional isolates, as they were sensitive to INH by the reference method, but resistant by the MGDA test. The drug susceptibility test results were obtained within eight-nine days. In conclusion, the MGDA test is a reliable and accurate method for the rapid detection of INH and RIF resistance compared with the reference method and the MGDA test additionally requires less time to obtain results.

Rapid Detection of Rifampicin and Isoniazid Resistant Mycobacterium tuberculosis Using Genotype MTBDRplus Assay in Nepal

Rapid line probe assay (LPA) can be a practical and rapid alternative to the slow conventional phenotypic drug susceptibility testing (DST) for detection of drug resistant tuberculosis (TB). The purpose of this study is to determine the diagnostic accuracy of Genotype MTBDRplus, LPA for TB, and compare its performance with conventional DST. A total of 54 culture samples were analyzed for DST using both conventional proportion method and MTBDRplus, where conventional DST identified 43 isolates (79.6%) as drug resistant. Among these 43 drug resistant isolates, 30 isolates (69.7%) were found to be multidrug resistant (MDR). Of all observed mutations using MTBDRplus, codon 531 of rpoB gene and codon 315 of katG gene were found to have highest mutational frequency for RIF resistance (64.7%) and INH resistance (96.8%), respectively. In the present study, MTBDRplus assay was shown to have excellent specificity (100%) for both RIF and INH resistance while sensitivity of the assay was little lower with value of 89.4% for RIF resistance and 91.4% for INH resistance. Therefore, the assay can be a rapid, reliable, and promising molecular test for early detection of MDR-TB in Nepal.

AID TB resistance line probe assay for rapid detection of resistant Mycobacterium tuberculosis in clinical samples

OBJECTIVES

To determine the sensitivity and specificity of AID TB Resistance line probe assay (AID Diagnostika, Germany) to detect Mycobacterium tuberculosis and its resistance to first- and second-line drugs in clinical samples using BACTEC 460TB as the reference standard.

METHODS

The test consists on three strips to detect resistance to isoniazid/rifampicin, fluoroquinolones/ethambutol, and kanamycin/amikacin/capreomycin/streptomycin, respectively. This test was performed on 65 retrospectively selected clinical samples corresponding to 32 patients.

RESULTS

A valid result was obtained for 92.3% (60/65), 90.8% (59/65) and 78.5% (51/65) of the samples tested, considering the three strips, respectively. Global concordance rates between AID and BACTEC for detecting resistance to isoniazid, rifampicin, fluoroquinolones, ethambutol, kanamycin/capreomycin and streptomycin were 98.3% (59/60), 100% (60/60), 91.5% (54/59), 72.9% (43/59), 100% (51/51) and 98.0% (50/51), respectively. Regarding the discordant results obtained between AID and BACTEC, the alternative molecular methods performed (GenoType MTBDRplus, GenoType MTBDRsl [Hain Lifescience, Germany] and/or pyrosequencing) confirmed the genotypic result in 90.9% (20/22) of the cases.

CONCLUSIONS

AID line probe assay is a useful tool for the rapid detection of drug resistance in clinical samples enabling an initial therapeutic approach. Nevertheless, for a correct management of drug resistant tuberculosis patients, molecular results should be confirmed by a phenotypic method.

Multidrug-resistant tuberculosis in Ethiopia: efforts to expand diagnostic services, treatment and care

The emergence of drug-resistant tuberculosis (TB), particularly multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB, is a major public health problem. The purpose of this review is to describe the current status of MDR-TB and factors that increase the risk of this infection. We conducted a systematic review of the literature on MDR-TB in Ethiopia. Out of 766 articles, 23 were found to meet eligibility criteria and included in this review. Among the 23 papers, six of them reported high prevalence of MDR-TB in the range of 3.3%-46.3%. Likewise, two studies reported XDR-TB in the range of 1% - 4.4% in Ethiopia. The most powerful predictor of the emergence of MDR-TB reported in Ethiopia is previous exposure to anti-TB drug treatment. This review indicated that MDR-TB in Ethiopia is a serious public health problem that needs to be addressed urgently. Strengthening early case detection and proper treatment of drug-susceptible TB in accordance with World Health Organization (WHO) treatment guidelines to ensure adequate treatment success rates is critical. Consequently, efforts have been made to a rapidly increase MDR-TB diagnosis as well as the number of treatment sites to implement a directly observed treatment, short-course (DOTS) plus strategy to interrupt transmission of MDR-TB.

Enhanced recovery, enrichment and detection of Mycobacterium marinum with the Portable Microbe Enrichment Unit (PMEU)

The use of PMEU significantly accelerated the growth of otherwise slowly growing Mycobacterium sp. Compared to the static reference cultures, M. marinum was detected after 24-48h of cultivation in the PMEU Spectrion(®) equipped with infrared (IR) sensors. Parallel static cultures did not exhibit or indicate mycobacterial growth within these time limits, and essentially no growth was found in them. The PMEU approach could provide a powerful tool for the rapid diagnosis and determination of environmental and clinical isolates of slow-growing species of mycobacteria. This approach also provides a method for improving diagnostics for M. tuberculosis and other pathogenic mycobacteria, including their antibiotic resistant forms, which represents a significant health problem worldwide and in Africa in particular.