Molecular characterization of mutations associated with resistance to second-line tuberculosis drug among multidrug-resistant tuberculosis patients from high prevalence tuberculosis city in Morocco

Multidrug-resistant tuberculosis

One of predominant contributors to global mortality is tuberculosis (TB), an infection caused by Mycobacterium tuberculosis (MTB). Inappropriate and ineffectual treatment can lead to the development of drug-resistant TB. One of the most common forms of drug-resistant TB is multidrug-resistant tuberculosis (MDR-TB), caused by mutations in the rpoB and katG genes that lead to resistance to anti-TB drugs, rifampicin (RIF) and isoniazid (INH), respectively. Although culturing remains the gold standard, it is not rapid thereby delaying potential treatment and potentially increasing the incidence of MDR-TB. In contrast, molecular techniques provide a highly sensitive and specific alternative. This review discusses the classification of biomarkers used to detect MDR-TB, some of the commonly used anti-TB drugs, and DNA mutations in MTB that lead to anti-TB resistance. The objective of this review is to increase awareness of the need for rapid and precise detection of MDR-TB cases to decrease morbidity and mortality of this infectious disease worldwide.

Resistance Profiles to Second-Line Anti-Tuberculosis Drugs and Their Treatment Outcomes: A Three-Year Retrospective Analysis from South India

Background: Patients with first-line drug resistance (DR) to rifampicin (RIF) or isoniazid (INH) as a first-line (FL) line probe assay (LPA) were subjected to genotypic DST using second-line (SL) LPA to identify SL-DR (including pre-XDR) under the National TB Elimination Program (NTEP), India. SL-DR patients were initiated on different DR-TB treatment regimens and monitored for their outcomes. The objective of this retrospective analysis was to understand the mutation profile and treatment outcomes of SL-DR patients. Materials and Methods: A retrospective analysis of mutation profile, treatment regimen, and treatment outcome was performed for SL-DR patients who were tested at ICMR-NIRT, Supra-National Reference Laboratory, Chennai between the years 2018 and 2020. All information, including patient demographics and treatment outcomes, was extracted from the NTEP Ni-kshay database. Results: Between 2018 and 2020, 217 patients out of 2557 samples tested were identified with SL-DR by SL-LPA. Among them, 158/217 were FQ-resistant, 34/217 were SLID-resistant, and 25/217 were resistant to both. D94G (Mut3C) of gyrA and a1401g of rrs were the most predominant mutations in the FQ and SLID resistance types, respectively. Favorable (cured and treatment complete) and unfavorable outcomes (died, lost to follow up, treatment failed, and treatment regimen changed) were recorded in a total of 82/217 and 68/217 patients in the NTEP Ni-kshay database. Conclusions: As per the testing algorithm, SL- LPA is used for genotypic DST following identification of first-line resistance, for early detection of SL-DR in India. The fluoroquinolone resistance pattern seen in this study population corelates with the global trend. Early detection of fluoroquinolone resistance and monitoring of treatment outcome can help achieve better patient management.

Challenges & Solutions for Recent Advancements in Multi-Drugs Resistance Tuberculosis: A Review

In MDR-TB, mycobacterium is resistant to battlefront drugs like rifampicin and isoniazid. Now it's an urgent global challenge for treatment & diagnosis because more than 50% of drugs are resistant. Till today's information, 5 reasons are liable for MDR: (1) Errors of physicians/patients in therapy management, (2) Complexity and poor vascularization of granulomatous lesions, which obstruct drug distribution to some sites, leading to resistance development, (3) Intrinsic drug resistance of tubercle bacilli, (4) Formation of non-replicating, drug-tolerant bacilli inside the granulomas, (5) Development of mutations in Mtb genes, which are the foremost important molecular mechanisms of resistance. the most contribution of this work is a brief & clear explanation of things chargeable for resistant development, and recent diagnostic & treatment methods for MDR-TB. This study shall help researchers & scientists to develop replacement rapid diagnostic tools, drugs, and treatment protocols.

Utility of line probe assay in detecting drug resistance and the associated mutations in patients with extrapulmonary tuberculosis in Addis Ababa, Ethiopia

Introduction

Molecular tests allow rapid detection of Mycobacterium tuberculosis and drug resistance in a few days. Identifying the mutations in genes associated with drug resistance may contribute to the development of appropriate interventions to improve tuberculosis control. So far, there is little information in Ethiopia about the diagnostic performance of line probe assay (LPA) and the M. tuberculosis common gene mutations associated with drug resistance in extrapulmonary tuberculosis. Thus, this study aimed to assess the frequency of drug resistance-associated mutations in patients with extrapulmonary tuberculosis (EPTB) and to compare the agreement and determine the utility of the genotypic in the detection of drug resistance in Addis Ababa, Ethiopia.

Methods

A cross-sectional study was conducted on stored M. tuberculosis isolates. The genotypic and phenotypic drug susceptibility tests were performed using LPA and BACTEC-MGIT-960, respectively. The common mutations were noted, and the agreement and the utility of the LPA were determined using the BACTEC-MGIT-960 as a gold standard.

Results

Of the 151 isolates, the sensitivity and specificity of MTBDRplus in detecting isoniazid resistance were 90.9% and 100%, respectively. While for rifampicin, it was 100% and 99.3% for sensitivity and specificity, respectively. The katG S315Tl was the most common mutation observed in 85.7% of the isoniazid-resistant isolates. In the case of rifampicin, the most common mutation (61.9%) was observed at position rpoB S531L. Mutations in the gyrA promoter region were strongly associated with Levofloxacin and Moxifloxacin resistance.

Conclusion

Line probe assay has high test performance in detecting resistance to anti-TB drugs in EPTB isolates. The MTBDRplus test was slightly less sensitive for the detection of isoniazid resistance as compared to the detection of rifampicin. The most prevalent mutations associated with isoniazid and rifampicin resistance were observed at katG S315Tl and rpoB S531L respectively. Besides, all the fluoroquinolone-resistant cases were associated with gyrA gene. Finally, a validation study with DNA sequencing is recommended.

Performance of GenoType MTBDRsl assay for detection of second-line drugs and ethambutol resistance directly from sputum specimens of MDR-TB patients in Bangladesh

Background

Rapid and early detection of drug susceptibility among multidrug-resistant tuberculosis (MDR-TB) patients could guide the timely initiation of effective treatment and reduce transmission of drug-resistant TB. In the current study, we evaluated the diagnostic performance of GenoType MTBDRsl (MTBDRsl) ver1.0 assay for detection of resistance to ofloxacin (OFL), kanamycin (KAN) and ethambutol (EMB), and additionally the XDR-TB among MDR-TB patients in Bangladesh.

Methods

The MTBDRsl assay was performed directly on 218 smear-positive sputum specimens collected from MDR-TB patients and the results were compared with the phenotypic drug susceptibility testing (DST) performed on solid Lowenstein-Jensen (L-J) media. We also analyzed the mutation patterns of gyrA, rrs, and embB genes for detection of resistance to OFL, KAN and EMB, respectively.

Results

The sensitivity and specificity of the MTBDRsl compared to phenotypic L-J DST were 81.8% (95% CI, 69.1–90.9) and 98.8% (95% CI, 95.6–99.8), respectively for OFL (PPV: 95.7% & NPV: 94.1%); 65.1% (95% CI, 57.5–72.2) and 86.7% (95% CI, 73.2–94.9), respectively for EMB (PPV: 94.9% & NPV: 39.4%); and 100% for KAN. The diagnostic accuracy of KAN, OFL and EMB were 100, 94.5 and 69.6%, respectively. Moreover, the sensitivity, specificity and diagnostic accuracy of MtBDRsl for detection of XDR-TB was 100%. The most frequently observed mutations were at codon D94G (46.8%) of gyrA gene, A1401G (83.3%) of rrs gene, and M306V (41.5%) of the embB gene.

Conclusion

Considering the excellent performance in this study we suggest that MTBDRsl assay can be used as an initial rapid test for detection of KAN and OFL susceptibility, as well as XDR-TB directly from smear-positive sputum specimens of MDR-TB patients in Bangladesh.

Bioprospecting for antituberculosis natural products – A review

There has been an increase in the reported cases of tuberculosis, a disease caused by Mycobacterium tuberculosis, which is still currently affecting most of the world’s population, especially in resource-limited countries. The search for novel antitubercular chemotherapeutics from underexplored natural sources is therefore of paramount importance. The renewed interest in studies related to natural products, driven partly by the growing incidence of MDR-TB, has increased the prospects of discovering new antitubercular drug leads. This is because most of the currently available chemotherapeutics such as rifampicin and capreomycin used in the treatment of TB were derived from natural products, which are proven to be an abundant source of novel drugs used to treat many diseases. To meet the global need for novel antibiotics from natural sources, various strategies for high-throughput screening have been designed and implemented. This review highlights the current antitubercular drug discovery strategies from natural sources.

Genotypic diversity of multi- and pre-extremely drug-resistant Mycobacterium tuberculosis isolates from Morocco

In Morocco, the prevalence of multidrug resistant tuberculosis (MDR-TB) continues to increase especially within previously treated cases; these MDR cases may evolve to extensively drug resistant tuberculosis (XDR-TB) raising major concern to TB control programs. From an epidemiological window, scarce informations are available about the genetic diversity of Mycobacterium tuberculosis (MTB) strains fueling these forms of resistance. The aim of this study was to assess to genetic diversity of MDR-MTB strains. Hence, this prospective study was conducted on patients diagnosed with MDR-TB at Pasteur Institute of Casablanca from 2010 to 2013. A total of 70 MDR-MTB isolates were genotyped by spoligotyping and 15-loci MIRU-VNTR methods. Spoligotyping generated four orphan patterns, five unique profiles whereas 61 strains were grouped in nine clusters (2 to 25 strains per cluster), the clustering rates being 87.1%. Subtyping by 15 loci MIRU-VNTR splitted all clusters already established by spoligotyping and generated 70 unique profiles not recognized in SITVIT2 database; clustering rate was equal to zero. HGDI analysis of 15 loci MIRU demonstrated that eight out of 15 loci were highly discriminant. Of note, all pre-XDR strains belongs to many clades, meaning that there no association between gyrA mutants and particular clade. Overall, the data generated by this study (i) describe the population structure of MDR MTBC in Morocco which is highly homogenous, (ii) confirm that TB in Morocco is almost exclusively transmitted by modern and evolutionary lineages with high level of biodiversity seen by MIRU, and (iii) validate the use of optimized 15-loci MIRU-VNTR format for future investigations in Morocco.

Comparative Utility of Genetic Determinants of Drug Resistance and Phenotypic Drug Susceptibility Profiling in Predicting Clinical Outcomes in Patients With Multidrug-Resistant Mycobacterium tuberculosis

Setting: Programmatic management of drug-resistant tuberculosis in Ningbo, China.

Objective: To assess whether data-driven genetic determinants of drug resistance patterns could outperform phenotypic drug susceptibility testing in predicting clinical meaningful outcomes among patients with multidrug-resistant tuberculosis (MDR-TB).

Design: We conducted a prospective cohort study of 104 MDR-TB patients. All MDR-TB isolates underwent drug susceptibility testing and genotyping for mutations that could cause drug resistance. Study outcomes were time to sputum smear conversion and probability of treatment success, as well as time to culture conversion within 6 months. Data were analyzed using latent class analysis, Kaplan–Meier curves, and Cox regression models.

Results: We report that latent class analysis of data identified two latent classes that predicted sputum smear conversion with P = 0.001 and area under receiver-operating characteristic curve of 0.73. The predicted latent class memberships were associated with superior capability in predicting sputum culture conversion at 6 months and overall treatment success compared to phenotypic drug susceptibility profiling using boosted logistic regression models.

Conclusion: These results suggest that genetic determinants of drug resistance in combination with phenotypic drug-resistant tests could serve as useful biomarkers in predicting treatment prognosis in MDR-TB.

Molecular characterization of mutations associated with resistance to second line drugs in Mycobacterium tuberculosis patients from Casablanca, Morocco

The emergence and spread of extensively drug-resistant tuberculosis (XDR-TB) is a serious threat to global health. Therefore, its rapid diagnosis is crucial. The present study aimed to characterize mutations conferring resistance to second line drugs (SLDs) within multidrug Mycobacterium tuberculosis (MDR-MTB) isolates and to estimate the occurrence of XDR-TB in Casablanca, Morocco. A panel of 200 MDR-TB isolates was collected at the Pasteur Institute between 2015-2018. Samples were subjected to drug susceptibility testing to Ofloxacin (OFX), Kanamycin (KAN) and Amikacin (AMK). The mutational status of gyrA, gyrB, rrs, tlyA and eis was assessed by sequencing these target genes. Drug susceptibility testing for SLDs showed that among the 200 MDR strains, 20% were resistant to OFX, 2.5% to KAN and 1.5% to AMK. Overall, 14.5% of MDR strains harbored mutations in gyrA, gyrB, rrs and tlyA genes. From the 40 OFX^R isolates, 67.5% had mutations in QRDR of gyrA and gyrB genes, the most frequent one being Ala90Val in gyrA gene. Of note, none of the isolates harbored simultaneously mutations in gyrA and gyrB genes. In eight out of the 200 MDR-TB isolates resistant either to KAN or AMK, only 25% had A1401G or Lys89Glu change in rrs and tlyA genes respectively. This study is very informative and provides data on the alarming rate of fluoroquinolone resistance which warrants the need to implement appropriate drug regimens to prevent the emergence and spread of more severe forms of Mycobacterium tuberculosis drug resistance.

Resistance to Second-Line Anti-TB Drugs in Cambodia: A Phenotypic and Genetic Study

Background

Due to the emergence of Mycobacterium tuberculosis (M.tb) clinical isolates resistant to most potent first-line drugs (FLD), second-line drugs (SLD) are being prescribed more frequently. We explore the genetic characteristics and molecular mechanisms of M.tb isolates phenotypically resistant to SLD, including pre-extensively drug-resistant (pre-XDR) and extensively drug-resistant (XDR) isolates.

Methods

Drug-resistant (DR) M.tb isolates collected from 2012 to 2017 were tested using sequencing and phenotypic drug susceptibility testing. Genotypes were determined to explore their links with SLD resistance patterns.

Results

Of the 272 DR M.tb isolates, 6 non-multidrug resistant (non-MDR) isolates were fluoroquinolones (FQ)-resistant, 3 were XDR and 16 were pre-XDR (14 resistant to FQ and 2 to second-line injectable drugs). The most frequent mutations in FQ-resistant and second-line injectable drugs resistant isolates were gyrA D94G (15/23) and rrs a1401g (3/5), respectively. Seventy-five percent of pre-XDR isolates and 100% of XDR isolates harbored mutations conferring resistance to pyrazinamide. All XDR isolates belonged to the Beijing genotype, of which one, named XDR+, was resistant to all drugs tested. One cluster including pre-XDR and XDR isolates was observed.

Conclusion

This is the first description of SLD resistance in Cambodia. The data suggest that the proportion of XDR and pre-XDR isolates remains low but is on the rise compared to previous reports. The characterization of the XDR+ isolate in a patient who refused treatment underlines the risk of transmission in the population. In addition, genotypic results show, as expected, that the Beijing family is the main involved in pre-XDR and XDR isolates and that the spread of the Beijing pre-XDR strain is capable of evolving into XDR strain. This study strongly indicates the need for rapid interventions in terms of diagnostic and treatment to prevent the spread of the pre-XDR and XDR strains and the emergence of more resistant ones.

Genotyping and Molecular Characterization of Fluoroquinolone's Resistance Among Multidrug-Resistant Mycobacterium tuberculosis in Southwest of China

Although fluoroquinolones (FQs) are the backbone drugs for the treatment of multidrug-resistant tuberculosis (MDR-TB), the knowledge about the resistance pattern and molecular characterization of new-generation FQs in Chongqing is limited. This study aimed to investigate the resistance rate and mutation types of later-generation FQs against MDR-TB in Chongqing, and further to explore the relationship between different genotypes and phenotypes. A total of 967 clinical strains were characterized using multilocus sequence typing and drug susceptibility testing, followed by analysis of genotype/phenotype association. The 229 (23.7%, 229/967) isolates were identified as MDR-TB. The most effective agent against MDR-TB was gatifloxacin (GFX) (20.1%, 46/229), and the highest resistant rate was observed in ofloxacin (OFX) (41.0%, 94/229). Of the 190 strains (83.0%) identified as Beijing genotype, 111 isolates were modern Beijing genotype (58.4%) and 79 isolates were ancient Beijing genotype (41.6%). By analyzing 94 OFX-resistant isolates, 13 isolates were clustered with the cumulative clustering rate of 13.8% (13/94). Of the 91 isolates (39.7%, 91/229) with a mutation in gyrA gene, mutation in codon 94 was the most prevalent. Only 15 isolates (6.6%, 15/229) harbored a mutation in gyrB gene. There was no significant difference in the mutation rate of gyrA gene between Beijing and non-Beijing genotype, clustered isolates, and nonclustered isolates (p > 0.05).

Frequency and patterns of first- and second-line drug resistance-conferring mutations in Mycobacterium tuberculosis isolated from pulmonary tuberculosis patients in a cross-sectional study in Tigray Region, Ethiopia

OBJECTIVES

Tuberculosis (TB) is a preventable and treatable infectious disease, but the continuing emergence and spread of multidrug-resistant TB is threatening global TB control efforts. This study aimed to describe the frequency and patterns of drug resistance-conferring mutations of Mycobacterium tuberculosis (MTB) isolates detected from pulmonary TB patients in Tigray Region, Ethiopia.

METHODS

A cross-sectional study design was employed to collect sputum samples from pulmonary TB patients between July 2018 to August 2019. Culture and identification tests were done at Tigray Health Research Institute (THRI). Mutations conferring rifampicin (RIF), isoniazid (INH) and fluoroquinolone (FQ) resistance were determined in 227 MTB isolates using GenoType MTBDRplus and GenoType MTBDRsl.

RESULTS

Mutations conferring resistance to RIF, INH and FQs were detected in 40/227 (17.6%), 41/227 (18.1%) and 2/38 (5.3%) MTB isolates, respectively. The majority of mutations for RIF, INH and FQs occurred at codons rpoB S531L (70%), katG S315T (78%) and gyrA D94Y/N (100%), respectively. This study revealed a significant number of unknown mutations in the rpoB, katG and inhA genes.

CONCLUSION

High rates of mutations conferring resistance to RIF, INH and FQs were observed in this study. A large number of isolates showed unknown mutations, which require further DNA sequencing analysis. Periodic drug resistance surveillance and scaling-up of drug resistance testing facilities are imperative to prevent the transmission of drug-resistant TB in the community.

Mutations Associated with Rifampicin Resistance in Mycobacterium tuberculosis Isolates from Moroccan Patients: Systematic Review

Background

In recent years, the treatment of tuberculosis has been threatened by the increasing number of patients with drug resistance, especially rifampicin resistance, which is the most effective first-line antibiotic against Mycobacterium tuberculosis.

Methods

We performed a systematic review of the literature by searching the PubMed database for studies of rifampicin-resistant Mycobacterium tuberculosis (MTB) isolates from Moroccan patients, published between 2010 and 2020. The aim of this review was to quantify the frequency of the most common mutations associated with rifampicin resistance, to describe the frequency at which these mutations co-occur. Identified studies were critically appraised according to the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool.

Results

6 studies met our inclusion criteria. Results show that 99.36% of MTB isolates had a single-point mutation, and the most commonly mutated codon of rpoB gene is 531 with 70.33% of phenotypically resistant strains. However, 10.38% of MTB strains phenotypically resistant to RIF did not exhibit any mutation in the rpoB gene.

Conclusion

Identification of a resistance-associated mutation to rifampicin can be a good marker of drug-resistant TB, but lack of a mutation in the target sequence must be interpreted with caution.

Whole-genome sequencing analysis of multidrug-resistant Mycobacterium tuberculosis from Java, Indonesia

Introduction. Multidrug-resistant tuberculosis (MDR-TB) is a major public health problem globally, including in Indonesia. Whole-genome sequencing (WGS) analysis has rarely been used for the study of TB and MDR-TB in Indonesia.Aim. We evaluated the use of WGS for drug-susceptibility testing (DST) and to investigate the population structure of drug-resistant Mycobacterium tuberculosis in Java, Indonesia.Methodology. Thirty suspected MDR-TB isolates were subjected to MGIT 960 system (MGIT)-based DST and to WGS. Phylogenetic analysis was done using the WGS data. Results obtained using MGIT-based DST and WGS-based DST were compared.Results. Agreement between WGS and MGIT was 93.33 % for rifampicin, 83.33 % for isoniazid and 76.67 % for streptomycin but only 63.33 % for ethambutol. Moderate WGS-MGIT agreement was found for second-line drugs including amikacin, kanamycin and fluoroquinolone (73.33-76.67 %). MDR-TB was more common in isolates of the East Asian Lineage (63.3%). No evidence of clonal transmission of DR-TB was found among members of the tested population.Conclusion. Our study demonstrated the applicability of WGS for DST and molecular epidemiology of DR-TB in Java, Indonesia. We found no transmission of DR-TB in Indonesia.

Characteristics of pulmonary multidrug-resistant tuberculosis patients in Tigray Region, Ethiopia: A cross-sectional study

BACKGROUND

Tuberculosis (TB) is among the top 10 causes of mortality and the first killer among infectious diseases worldwide. One of the factors fuelling the TB epidemic is the global rise of multidrug resistant TB (MDR-TB). The aim of this study was to determine the magnitude and factors associated with MDR-TB in the Tigray Region, Ethiopia.

METHOD

This study employed a facility-based cross-sectional study design, which was conducted between July 2018 and August 2019. The inclusion criteria for the study participants were GeneXpert-positive who were not under treatment for TB, PTB patients' ≥15 years of age and who provided written informed consent. A total of 300 participants were enrolled in the study, with a structured questionnaire used to collect data on clinical, sociodemographic and behavioral factors. Sputum samples were collected and processed for acid-fast bacilli staining, culture and drug susceptibility testing. Drug susceptibility testing was performed using a line probe assay. Logistic regression was used to analyze associations between outcome and predictor variables.

RESULTS

The overall proportion of MDR-TB was 16.7% (11.6% and 32.7% for new and previously treated patients, respectively). Of the total MDR-TB isolates, 5.3% were pre-XDR-TB. The proportion of MDR-TB/HIV co-infection was 21.1%. A previous history of TB treatment AOR 3.75; 95% CI (0.7-2.24), cigarette smoking AOR 6.09; CI (1.65-2.50) and patients who had an intermittent fever (AOR = 2.54, 95% CI = 1.21-5.4) were strongly associated with MDR-TB development.

CONCLUSIONS

The magnitude of MDR-TB observed among new and previously treated patients is very alarming, which calls for an urgent need for intervention. The high proportion of MDR-TB among newly diagnosed cases indicates ongoing transmission, which suggests the need for enhanced TB control program performance to interrupt transmission. The increased proportion of MDR-TB among previously treated cases indicates a need for better patient management to prevent the evolution of drug resistance. Assessing the TB control program performance gaps and an optimal implementation of the WHO recommended priority actions for the management of drug-resistant TB, is imperative to help reduce the current high MDR-TB burden in the study region.

Performance of Genotype MTBDRsl V2.0 over the Genotype MTBDRsl V1 for detection of second line drug resistance: An Indian perspective

Genotype MTBDRsl Version 1 (V1.0) was recommended as an initial test for rapid detection of pre-extensively drug resistant (pre-XDR) and extensively drug resistant tuberculosis (XDR-TB). However, in recent years a number of novel mutations are identified that confer resistance. Thus, Genotype MTBDRsl V2.0 was endorsed by WHO. Though, Genotype MTBDRsl V2.0 has been rolled out in national TB programme in 2018, there is dearth of data from India on its performance for second line drug susceptibility testing (DST). For this, performance of new version was evaluated on 113 MDR-TB isolates. The results showed that 39 (34.5%) of these isolates were resistant to FQ and 7 (6.2%) were XDR by Genotype MTBDRsl V2.0. Amongst the FQ resistant isolates most prevalent mutation was ΔWT3-D94G (17; 38.6%) and N538D (12; 85.7%). Among the AG/CP and KAN resistant isolates most common mutation in the rrs region was ΔWT1-A1401G (5; 71.4%) and C-14T (2; 28.5%) in eis gene. Second line Bactec MGIT-960 detected 40 (35.4%) isolates as resistant to FQ and 6 (5.3%) as XDR isolates, whereas Genotype MTBDRsl V1.0 also detected 39 (34.5%) as resistant to FQ but missed 2 isolates in correctly identifying as XDR (5; 4.4%). Thus, concordance of second line Bactec MGIT-960 with Genotype MTBDRsl V2.0 was similar (100%) for FQ detection but it has improvised the diagnostic sensitivity for correctly identifying XDR isolates. Nevertheless, the cost of Genotype MTBDRsl V2.0 remains an issue for screening of second line drug (SLDs) resistance from countries with high burden of MDR-TB.

Prevalence and molecular characterization of amikacin resistance among Mycobacterium tuberculosis clinical isolates from southern China

OBJECTIVES

Amikacin is the only second-line injectable antituberculosis (anti-TB) drug still recommended for multidrug-resistant tuberculosis (MDR-TB) treatment when a short MDR-TB regimen is designed. Mutations in rrs and eis are reported to be associated with resistance to amikacin. In this study, we investigated the incidence of rrs, eis, tap and whiB7 mutations in amikacin-resistant Mycobacterium tuberculosis clinical isolates to find the proportion of different mutations related to amikacin resistance.

METHODS

A total of 395 clinical isolates of M. tuberculosis were used for phenotypic drug susceptibility testing (DST) to 10 drugs with the Löwenstein-Jensen (L-J) method. We sequenced rrs, eis, tap and whiB7 genes in 178 M. tuberculosis clinical isolates (89 amikacin-resistant isolates and 89 of 306 amikacin-susceptible isolates).

RESULTS

Our data showed that 22.53% (89/395) M. tuberculosis clinical isolates were resistant to amikacin. Of the 89 amikacin-resistant isolates, 89.89% (80/89) were MDR-TB, of which 12.36% (11/89) were pre-extensively drug-resistant TB (pre-XDR-TB) and 77.53% (69/89) were XDR-TB. The rrs mutations were found in 82% (73/89) in amikacin-resistant M. tuberculosis clinical isolates. The A1401G alteration in the rrs gene was the most dominant mutation (80.90%; 72/89). Five mutations were detected as new in rrs, tap and whiB7. Notably, 13.48% (12/89) amikacin-resistant isolates had no known mutation in these genes.

CONCLUSIONS

Our data reveal that the rrs mutation is a predominant molecular marker of amikacin resistance in southern China. Analysis of the rrs gene mutations will significantly reduce the time and cost to diagnose amikacin resistance in TB patients. Other unknown amikacin resistance mechanism(s) exist.

Phenotypic and Genotypic Characterization of Streptomycin-Resistant Multidrug-Resistant Mycobacterium tuberculosis Clinical Isolates in Southern China

Streptomycin (STR) is the first antibiotic used in the treatment of tuberculosis (TB) and the earliest antituberculosis drug with acquired resistance developed by Mycobacterium tuberculosis. The high prevalence of such resistance in many parts of the world limits its use for treating multidrug-resistant (MDR) TB. The aims of this study are to characterize of mutations in rpsL, rrs, and gidB genes in MDR M. tuberculosis isolates originating from southern China and to investigate possible relationship between mutations and strain genotypes for precise diagnosis and treatment. Sequences of rpsL, rrs, and gidB genes and the resistance profiles were analyzed for 218 MDR M. tuberculosis isolates. Our study showed that 68.35% of MDR M. tuberculosis isolates were resistant to STR and 89.91% of STR-resistant (STR^R) isolates were Beijing lineage strains. Mutations were observed in STR^R MDR M. tuberculosis isolates at the following rates: 72.48% in rpsL, 36.91% in rrs, and 15.44% in gidB. Compared with the phenotypic data, the combination of mutations in rpsL, rrs, and gidB has sensitivity and specificity of 96.64% and 100.00%, respectively. The most common mutations in STR^R isolates were rpsL128,263 and rrs514,1401, of which rpsL128 showed association with Beijing lineage (p < 0.001). It is noteworthy that a1401g mutation was present in rrs, while MDR M. tuberculosis isolates were resistant to both STR and amikacin. Twenty two novel mutations were found in STR^R isolates. These findings could be helpful to develop rapid molecular diagnostic methods and understand STR resistance in China for developing TB precision medicine and disturbance of drug-resistant TB transmission.

Detection of Second Line Drug Resistance among Drug Resistant Mycobacterium Tuberculosis Isolates in Botswana

The emergence and transmission of multidrug resistant (MDR) and extensively drug resistant (XDR) Mycobacterium tuberculosis (M.tb) strains is a threat to global tuberculosis (TB) control. The early detection of drug resistance is critical for patient management. The aim of this study was to determine the proportion of isolates with additional second-line resistance among rifampicin and isoniazid resistant and MDR-TB isolates. A total of 66 M.tb isolates received at the National Tuberculosis Reference Laboratory between March 2012 and October 2013 with resistance to isoniazid, rifampicin or both were analyzed in this study. The genotypes of the M.tb isolates were determined by spoligotyping and second-line drug susceptibility testing was done using the Hain Genotype MTBDRsl line probe assay version 2.0. The treatment outcomes were defined according to the Botswana national and World Health Organization (WHO) guidelines. Of the 57 isolates analyzed, 33 (58%) were MDR-TB, 4 (7%) were additionally resistant to flouroquinolones and 3 (5%) were resistant to both fluoroquinolones and second-line injectable drugs. The most common fluoroquinolone resistance-conferring mutation detected was gyrA A90V. All XDR-TB cases remained smear or culture positive throughout the treatment. Our study findings indicate the importance of monitoring drug resistant TB cases to ensure rapid detection of second-line drug resistance.

Mutation and Transmission Profiles of Second-Line Drug Resistance in Clinical Isolates of Drug-Resistant Mycobacterium tuberculosis From Hebei Province, China

The emergence of drug-resistant tuberculosis (TB) is involved in ineffective treatment of TB, especially multidrug resistant/extensively resistant TB (MDR/XDR-TB), leading to acquired resistance and transmission of drug-resistant strains. Second-line drugs (SLD), including both fluoroquinolones and injectable drugs, were commonly proved to be the effective drugs for treatment of drug-resistant TB. The purpose of this study was to investigate the prevalence of SLD-resistant strains and its specific mutations in drug-resistant Mycobacterium tuberculosis clinical isolates, and to acknowledge the transmission pattern of SLD resistance strains in Hebei. The genes gyrA, gyrB, rrs, eis promoter and tlyA of 257 drug-resistant clinical isolates were sequenced to identify mutations that could be responsible for resistance against fluoroquinolones and second-line injectable drugs. Each isolate was genotyped by Spoligotyping and 15-loci MIRU-VNTR. Our results indicated that 48.2% isolates were resistant to at least one of five SLD. Of them, 37.7% isolates were resistant to fluoroquinolones and 24.5% isolates were resistant to second-line injectable drugs. Mutations in genes gyrA, gyrB, rrs, eis promoter and tlyA were detected in 73 (75.3%), 7 (7.2%), 24 (38.1%), 5 (7.9%), and 3 (4.8%) isolates, respectively. The most prevalent mutations were the D94G (23.7%) in gyrA gene and the A1401G (33.3%) in rrs gene. A combination of gyrA, rrs and eis promoter can act as a valuable predicator for predicting XDR phenotype. These results highlight the development of rapid diagnosis are the effective manners for the control of SLD-TB or XDR-TB.

Surveillance of Rifampicin Resistance With GeneXpert MTB/RIF in the National Reference Laboratory for Tuberculosis at the Institut Pasteur in Bangui, 2015-2017

Background

The Central African Republic (CAR) has one of the heaviest burdens of tuberculosis (TB) in the world, with an incidence of 423 cases per 100 000 population. Surveillance of resistance to rifampicin with GeneXpert MTB/RIF was instituted in the National TB Reference Laboratory in 2015. The aim of this study was to evaluate, after 3 years, resistance to rifampicin, the most effective firstline drug against TB.

Methods

The surveillance database on cases of rifampicin resistance was retrospectively analyzed. The populations targeted by the National TB Programme were failure, relapse, default, and contacts of multidrug-resistant TB (MDR-TB). Statistical analyses were performed with Stata software, version 14, using chi-square tests and odds ratios.

Results

Six hundred seventeen cases were registered; 63.7% were male, 36.3% were female, and the mean age was 35.5 years (range from 2 to 81). GeneXpert MTB/RIF tests were positive in 79.1% (488/617), and resistance to rifampicin was positive in 42.2% (206/488), with 49.1% (56/114) in 2015, 34.7% (57/164) in 2016, and 44.3% (93/210) in 2017. Failure cases had the highest rate of resistance (70.4%), with a significant difference (P < .0001; odds ratio, 9.5; 95% confidence interval, 4.4–20.5). Resistance was observed in 40% of contacts of MDR-TB, 28.2% of the relapses and 20% of the defaults without significant difference.

Conclusions

Resistance to rifampicin is still high in the CAR and is most strongly associated with treatment failure. The Ministry of Health must to deploy GeneXpert MTB/RIF tests in the provinces to evaluate resistance to TB drugs in the country.