Fluoroquinolone resistance and mutational profile of gyrA in pulmonary MDR tuberculosis patients

Genetic diversities and drug resistance in Mycobacterium bovis isolates from zoonotic tuberculosis using whole genome sequencing

BACKGROUND

Zoonotic human tuberculosis (TB) caused by Mycobacterium bovis (M. bovis) is as vital as Mycobacterium tuberculosis, however with scarce available information. We aimed to use whole-genome sequencing (WGS) technology to take a deep insight into the circulating genotypes of human M. bovis and the genomic characteristics underlying virulence and drug resistance.

METHODS

The study included smear positive Ziehl-Neelsen samples from patients with suspected tuberculosis. Samples were cultured on Lowenstein-Jensen media and suspected colonies of M. bovis were selected to undergo DNA extraction and WGS. Data was analysed using the Bacterial and Viral Bioinformatics Resource Center (BV-BRC), and online bioinformatics tools. A phylogenetic tree was constructed for our sequenced strains, in addition to a set of 59 previously sequenced M. bovis genomes from different hosts and countries.

RESULTS

Out of total 112 mycobacterial positive cultures, five M. bovis were isolated and underwent WGS. All sequenced strains belonged to Mycobacterium tuberculosis var bovis, spoligotype BOV_1; BOV_11. Resistance gene mutations were determined in 100% of strains to pyrazinamide (pncA and rpsA), isoniazid (KatG and ahpC), ethambutol (embB, embC, embR and ubiA), streptomycin (rpsl) and fluoroquinolones (gyrA and gyrB). Rifampin (rpoB and rpoC) and delamanid (fbiC) resistance genes were found in 80% of strains. The major represented virulence classes were the secretion system, cell surface components and regulation system. The phylogenetic analysis revealed close genetic relatedness of three sequenced M. bovis strains to previous reported cow strains from Egypt and human strains from France, as well as relatedness of one M. bovis strain to four human Algerian strains. One sequenced strain was related to one cow strain from Egypt and a human strain from South Africa.

CONCLUSIONS

All sequenced M. bovis isolates showed the same spoligotype, but diverse phylogeny. Resistance gene mutations were detected for anti-TB drugs including pyrazinamide, isoniazid, streptomycin, ethambutol, fluoroquinolones, cycloserine, rifampin and delamanid. The virulence profile comprised genes assigned mainly to secretion system, cell surface components and regulation system. Phylogenetic analysis revealed genetic relatedness between our isolates and previously sequenced bovine strains from Egypt as well as human strains from other nearby countries in the region.

Risk assessment and transmission of fluoroquinolone resistance in drug-resistant pulmonary tuberculosis: a retrospective genomic epidemiology study

Fluoroquinolone resistance is a major challenge in treating Multidrug-Resistant Tuberculosis globally. The GenoType MTBDRsl Ver 2.0, endorsed by the WHO, was used to characterize fluoroquinolone resistance. The fluoroquinolone resistance rates in the MDR-TB, Rifampicin-Resistant TB, and non-MDR-TB were 33%, 16.5%, and 5.4%, respectively. The most common mutation found in fluoroquinolone-resistant isolates was D94G (49.5%) in the gyrA gene. Of the 150 MDR-TB isolates, the prevalence of Extensively Drug-Resistant Tuberculosis and pre-XDR-TB was 1.33% and 30%, respectively. Among the 139 RR-TB isolates, pre-XDR-TB prevalence was 15.8%. The fluoroquinolone resistance rates were 5.12% among the 1230 isoniazid-monoresistant isolates. The study found that MDR-TB and RR-TB have higher risk of fluoroquinolone resistance than non-MDR tuberculosis. Rifampicin-resistant isolates with a mutation at codon S450L have a higher risk (RR = 12.96; 95%CI: 8.34-20.13) of developing fluoroquinolone resistance than isolates with mutations at other codons in the rpoB gene. Isoniazid-resistant isolates with a mutation at codon S315T have a higher risk (RR = 2.09; 95%CI: 1.25-3.50) of developing fluoroquinolone resistance. The study concludes that rapid diagnosis of fluoroquinolone resistance before starting treatment is urgently needed to prevent the spread and increase of resistance and to achieve better treatment outcomes in areas where it is higher.

Evaluation of genetic correlation with fluoroquinolones resistance in rifampicin-resistant Mycobacterium tuberculosis isolates

Objective

To detect levofloxacin (LFX) and moxifloxacin (MFX) resistance among rifampicin-resistant tuberculosis (RR-TB) isolates, and predict the resistance level based on specific mutations in gyrA and gyrB genes.

Methods

A total of 686 RR-TB isolates were collected from Chinese Drug Resistance Surveillance Program from 2013 to 2020. The minimum inhibitory concentrations (MICs) of 12 anti-TB drugs were acquired using the broth microdilution method, followed by whole genome sequencing (WGS) analysis.

Results

Among the 686 RR isolates, the most prevalent resistance was to isoniazid (80.5 %) and ethambutol (28.4 %), followed by LFX (26.1 %) and MFX (21.9 %). The resistance rate of LFX (26.1%-99.4 %) was higher than that of MFX (21.9%-83.3 %) across various drug resistance patterns. Of the 180 fluoroquinolones (FQs) resistant isolates, 168 (93.3 %) had mutations in quinolone-resistant determining regions (QRDRs) with 21 mutation types, and Asp94Gly (32.7 %, 55/168) was the predominant mutation. Isolates with mutations in Asp94Asn and Asp94Gly were associated with high levels of resistance to LFX and MFX. Using broth microdilution method as gold standard, the sensitivities of WGS for LFX and MFX were 93.3 % and 98.0 %, and the specificities were 98.6 % and 95.0 %, respectively.

Conclusion

The resistance rate of LFX was higher than that of MFX among various drug resistance patterns in RR-TB isolates. The gyrA Asp94Gly was the predominant mutation type underlying FQs resistance. However, no significant difference was observed between mutation patterns in gyrA gene and resistance level of FQs.

Development and evaluation of a triplex droplet digital PCR method for differentiation of M. tuberculosis, M. bovis and BCG

Introduction

Tuberculosis, caused by Mycobacterium tuberculosis complex (MTBC), remains a global health concern in both human and animals. However, the absence of rapid, accurate, and highly sensitive detection methods to differentiate the major pathogens of MTBC, including M. tuberculosis, M. bovis, and BCG, poses a potential challenge.

Methods

In this study, we have established a triplex droplet digital polymerase chain reaction (ddPCR) method employing three types of probe fluorophores, with targets M. tuberculosis (targeting CFP-10-ESAT-6 gene of RD1 and Rv0222 genes of RD4), M. bovis (targeting CFP-10-ESATs-6 gene of RD1), and BCG (targeting Rv3871 and Rv3879c genes of ΔRD1), respectively.

Results

Based on optimization of annealing temperature, sensitivity and repeatability, this method demonstrates a lower limit of detection (LOD) as 3.08 copies/reaction for M. tuberculosis, 4.47 copies/reaction for M. bovis and 3.59 copies/reaction for BCG, without cross-reaction to Mannheimia haemolytica, Mycoplasma bovis, Haemophilus parasuis, Escherichia coli, Pasteurella multocida, Ochrobactrum anthropi, Salmonella choleraesuis, Brucella melitensis, and Staphylococcus aureus, and showed repeatability with coefficients of variation (CV) lower than 10%. The method exhibits strong milk sample tolerance, the LOD of detecting in spike milk was 5 × 103 CFU/mL, which sensitivity is ten times higher than the triplex qPCR. 60 clinical DNA samples, including 20 milk, 20 tissue and 20 swab samples, were kept in China Animal Health and Epidemiology Center were tested by the triplex ddPCR and triplex qPCR. The triplex ddPCR presented a higher sensitivity (11.67%, 7/60) than that of the triplex qPCR method (8.33%, 5/60). The positive rates of M. tuberculosis, M. bovis, and BCG were 1.67, 10, and 0% by triplex ddPCR, and 1.67, 6.67, and 0% by triplex qPCR, with coincidence rates of 100, 96.7, and 100%, respectively.

Discussion

Our data demonstrate that the established triplex ddPCR method is a sensitive, specific and rapid method for differentiation and identification of M. tuberculosis, M. bovis, and BCG.

Patterns and profiles of drug resistance-conferring mutations in Mycobacterium tuberculosis genotypes isolated from tuberculosis-suspected attendees of spiritual holy water sites in Northwest Ethiopia

Purpose

This study examined the patterns and frequency of genetic changes responsible for resistance to first-line (rifampicin and isoniazid), fluoroquinolones, and second-line injectable drugs in drug-resistant Mycobacterium tuberculosis (MTB) isolated from culture-positive pulmonary tuberculosis (PTB) symptomatic attendees of spiritual holy water sites (HWSs) in the Amhara region.

Patients and methods

From June 2019 to March 2020, a cross-sectional study was carried out. A total of 122 culture-positive MTB isolates from PTB-suspected attendees of HWSs in the Amhara region were evaluated for their drug resistance profiles, and characterized gene mutations conferring resistance to rifampicin (RIF), isoniazid (INH), fluoroquinolones (FLQs), and second-line injectable drugs (SLIDs) using GenoType®MTBDRplus VER2.0 and GenoType®MTBDRsl VER2.0. Drug-resistant MTB isolates were Spoligotyped following the manufacturer's protocol.

Results

Genetic changes (mutations) responsible for resistance to RIF, INH, and FLQs were identified in 15/122 (12.3%), 20/122 (16.4%), and 5/20 (25%) of MTB isolates, respectively. In RIF-resistant, rpoB/Ser531Lue (n = 12, 80%) was most frequent followed by His526Tyr (6.7%). Amongst INH-resistant isolates, katG/Ser315Thr1 (n = 19, 95%) was the most frequent. Of 15 MDR-TB, the majority (n = 12, 80%) isolates had mutations at both rpoB/Ser531Leu and katG/Ser315Thr1. All 20 INH and/or RIF-resistant isolates were tested with the MTBDRsl VER 2.0, yielding 5 FLQs-resistant isolates with gene mutations at rpoB/Ser531Lue, katG/Ser315Thr1, and gyrA/Asp94Ala genes. Of 20 Spoligotyped drug-resistant MTB isolates, the majority (n = 11, 55%) and 6 (30%) were SIT149/T3-ETH and SIT21/CAS1-Kili sublineages, respectively; and they were any INH-resistant (mono-hetero/multi-). Of 15 RIF-resistant (RR/MDR-TB) isolates, 7 were SIT149/T3-ETH, while 6 were SIT21/CAS1-Kili sublineages. FLQ resistance was detected in four SIT21/CAS1-Kili lineages.

Conclusion

In the current study, the most common gene mutations responsible for resistance to INH, RIF, and FLQs were identified. SIT149/T3-ETH and SIT21/CAS1-Kili constitute the majority of drug-resistant TB (DR-TB) isolates. To further understand the complete spectrum of genetic changes/mutations and related genotypes, a sequencing technology is warranted.

Commensal antimicrobial resistance mediates microbiome resilience to antibiotic disruption

Despite their therapeutic benefits, antibiotics exert collateral damage on the microbiome and promote antimicrobial resistance. However, the mechanisms governing microbiome recovery from antibiotics are poorly understood. Treatment of Mycobacterium tuberculosis, the world's most common infection, represents the longest antimicrobial exposure in humans. Here, we investigate gut microbiome dynamics over 20 months of multidrug-resistant tuberculosis (TB) and 6 months of drug-sensitive TB treatment in humans. We find that gut microbiome dynamics and TB clearance are shared predictive cofactors of the resolution of TB-driven inflammation. The initial severe taxonomic and functional microbiome disruption, pathobiont domination, and enhancement of antibiotic resistance that initially accompanied long-term antibiotics were countered by later recovery of commensals. This resilience was driven by the competing evolution of antimicrobial resistance mutations in pathobionts and commensals, with commensal strains with resistance mutations reestablishing dominance. Fecal-microbiota transplantation of the antibiotic-resistant commensal microbiome in mice recapitulated resistance to further antibiotic disruption. These findings demonstrate that antimicrobial resistance mutations in commensals can have paradoxically beneficial effects by promoting microbiome resilience to antimicrobials and identify microbiome dynamics as a predictor of disease resolution in antibiotic therapy of a chronic infection.

Impact of Whole-Genome Sequencing of Mycobacterium tuberculosis on Treatment Outcomes for MDR-TB/XDR-TB: A Systematic Review

The emergence and persistence of drug-resistant tuberculosis is a major threat to global public health. Our objective was to assess the applicability of whole-genome sequencing (WGS) to detect genomic markers of drug resistance and explore their association with treatment outcomes for multidrug-resistant/extensively drug-resistant tuberculosis (MDR/XDR-TB).

METHODS

Five electronic databases were searched for studies published in English from the year 2000 onward. Two reviewers independently conducted the article screening, relevant data extraction, and quality assessment. The data of the included studies were synthesized with a narrative method and are presented in a tabular format.

RESULTS

The database search identified 949 published articles and 8 studies were included. An unfavorable treatment outcome was reported for 26.6% (488/1834) of TB cases, which ranged from 9.7 to 51.3%. Death was reported in 10.5% (194/1834) of total cases. High-level fluoroquinolone resistance (due to gyrA 94AAC and 94GGC mutations) was correlated as the cause of unfavorable treatment outcomes and reported in three studies. Other drug resistance mutations, like kanamycin high-level resistance mutations (rrs 1401G), rpoB Ile491Phe, and ethA mutations, conferring prothionamide resistance were also reported. The secondary findings from this systematic review involved laboratory aspects of WGS, including correlations with phenotypic DST, cost, and turnaround time, or the impact of WGS results on public health actions, such as determining transmission events within outbreaks.

CONCLUSIONS

WGS has a significant capacity to provide accurate and comprehensive drug resistance data for MDR/XDR-TB, which can inform personalized drug therapy to optimize treatment outcomes.

A precision overview of genomic resistance screening in Ecuadorian isolates of Mycobacterium tuberculosis using web-based bioinformatics tools

INTRODUCTION

Tuberculosis (TB) is among the deadliest diseases worldwide, and its impact is mainly due to the continuous emergence of resistant isolates during treatment due to the laborious process of resistance diagnosis, nonadherence to treatment and circulation of previously resistant isolates of Mycobacterium tuberculosis. In this study, we evaluated the performance and functionalities of web-based tools, including Mykrobe, TB-profiler, PhyResSE, KvarQ, and SAM-TB, for detecting resistance in 88 Ecuadorian isolates of Mycobacterium tuberculosis drug susceptibility tested previously. Statistical analysis was used to determine the correlation between genomic and phenotypic analysis. Our results showed that with the exception of KvarQ, all tools had the highest correlation with the conventional drug susceptibility test (DST) for global resistance detection (98% agreement and 0.941 Cohen's kappa), while SAM-TB, PhyResSE, TB-profiler and Mykrobe had better correlations with DST for first-line drug analysis individually. We also identified that in our study, only 50% of mutations characterized by the web-based tools in the rpoB, katG, embB, pncA, gyrA and rrs regions were canonical and included in the World Health Organization (WHO) catalogue. Our findings suggest that SAM-TB, PhyResSE, TB-profiler and Mykrobe were efficient in determining canonical resistance-related mutations, but more analysis is needed to improve second-line detection. Improving surveillance programs using whole-genome sequencing tools for first-line drugs, MDR-TB and XDR-TB is essential to understand the molecular epidemiology of TB in Ecuador.

IMPORTANCE

Tuberculosis, an infectious disease caused by Mycobacterium tuberculosis, most commonly affects the lungs and is often spread through the air when infected people cough, sneeze, or spit. However, despite the existence of effective drug treatment, patient adherence, long duration of treatment, and late diagnosis have reduced the effectiveness of therapy and increased drug resistance. The increase in resistant cases, added to the impact of the COVID-19 pandemic, has highlighted the importance of implementing efficient and timely diagnostic methodologies worldwide. The significance of our research is in evaluating and identifying a more efficient and user-friendly web-based tool to characterize resistance in Mycobacterium tuberculosis by whole-genome sequencing, which will allow more routine application to improve TB strain surveillance programs locally.

Macromolecular crowding potently stimulates DNA supercoiling activity of Mycobacterium tuberculosis DNA gyrase

Macromolecular crowding, manifested by high concentrations of proteins and nucleic acids in living cells, significantly influences biological processes such as enzymatic reactions. Studying these reactions in vitro, using agents such as polyetthylene glycols (PEGs) and polyvinyl alcohols (PVAs) to mimic intracellular crowding conditions, is essential due to the notable differences from enzyme behaviors observed in diluted aqueous solutions. In this article, we studied Mycobacterium tuberculosis (Mtb) DNA gyrase under macromolecular crowding conditions by incorporating PEGs and PVAs into the DNA supercoiling reactions. We discovered that high concentrations of potassium glutamate, glycine betaine, PEGs, and PVA substantially stimulated the DNA supercoiling activity of Mtb DNA gyrase. Steady-state kinetic studies showed that glycine betaine and PEG400 significantly reduced the KM of Mtb DNA gyrase and simultaneously increased the Vmax or kcat of Mtb DNA gyrase for ATP and the plasmid DNA molecule. Molecular dynamics simulation studies demonstrated that PEG molecules kept the ATP lid of DNA gyrase subunit B in a closed or semiclosed conformation, which prevented ATP molecules from leaving the ATP-binding pocket of DNA gyrase subunit B. The stimulation of the DNA supercoiling activity of Mtb DNA gyrase by these molecular crowding agents likely results from a decrease in water activity and an increase in excluded volume.

A Fluorescence-Based, T5 Exonuclease-Amplified DNA Cleavage Assay for Discovering Bacterial DNA Gyrase Poisons

Fluoroquinolones (FQs) are potent antibiotics of clinical significance, known for their unique mechanism of action as gyrase poisons, which stabilize gyrase-DNA cleavage complexes and convert gyrase into a DNA-damaging machinery. Unfortunately, FQ resistance has emerged, and these antibiotics can cause severe side effects. Therefore, discovering novel gyrase poisons with different chemical scaffolds is essential. The challenge lies in efficiently identifying them from compound libraries containing thousands or millions of drug-like compounds, as high-throughput screening (HTS) assays are currently unavailable. Here we report a novel fluorescence-based, T5 exonuclease-amplified DNA cleavage assay for gyrase poison discovery. This assay capitalizes on recent findings showing that multiple gyrase molecules can simultaneously bind to a plasmid DNA molecule, forming multiple gyrase-DNA cleavage complexes on the same plasmid. These gyrase-DNA cleavage complexes, stabilized by a gyrase poison, can be captured using sarkosyl. Proteinase K digestion results in producing small DNA fragments. T5 exonuclease, selectively digesting linear and nicked DNA, can fully digest the fragmented linear DNA molecules and, thus, "amplify" the decrease in fluorescence signal of the DNA cleavage products after SYBR Green staining. This fluorescence-based, T5 exonuclease-amplified DNA cleavage HTS assay is validated using a 50-compound library, making it suitable for screening large compound libraries.

Deciphering the emerging role of phytocompounds: Implications in the management of drug-resistant tuberculosis and ATDs-induced hepatic damage

Tuberculosis is a disease of poverty, discrimination, and socioeconomic burden. Epidemiological studies suggest that the mortality and incidence of tuberculosis are unacceptably higher worldwide. Genomic mutations in embCAB, embR, katG, inhA, ahpC, rpoB, pncA, rrs, rpsL, gyrA, gyrB, and ethR contribute to drug resistance reducing the susceptibility of Mycobacterium tuberculosis to many antibiotics. Additionally, treating tuberculosis with antibiotics also poses a serious risk of hepatotoxicity in the patient's body. Emerging data on drug-induced liver injury showed that anti-tuberculosis drugs remarkably altered levels of hepatotoxicity biomarkers. The review is an attempt to explore the anti-mycobacterial potential of selected, commonly available, and well-known phytocompounds and extracts of medicinal plants against strains of Mycobacterium tuberculosis. Many studies have demonstrated that phytocompounds such as flavonoids, alkaloids, terpenoids, and phenolic compounds have antibacterial action against Mycobacterium species, inhibiting the bacteria's growth and replication, and sometimes, causing cell death. Phytocompounds act by disrupting bacterial cell walls and membranes, reducing enzyme activity, and interfering with essential metabolic processes. The combination of these processes reduces the overall survivability of the bacteria. Moreover, several phytochemicals have synergistic effects with antibiotics routinely used to treat TB, improving their efficacy and decreasing the risk of resistance development. Interestingly, phytocompounds have been presented to reduce isoniazid- and ethambutol-induced hepatotoxicity by reversing serum levels of AST, ALP, ALT, bilirubin, MDA, urea, creatinine, and albumin to their normal range, leading to attenuation of inflammation and hepatic necrosis. As a result, phytochemicals represent a promising field of research for the development of new TB medicines.

Pattern and characteristics of mutations conferring resistance to second line drugs in Mycobacterium tuberculosis isolates of pulmonary and extrapulmonary TB samples

BACKGROUND & OBJECTIVES

The purpose of present study is to analyse the distribution and pattern of genetic mutations in PRE-XDR-TB and extensive drug resistant Mycobacterium tuberculosis (XDR-TB) using second-line line probe assay and to compare them with different parameters.

METHOD

Sputum, Lymph node aspirate and cold accesses from patients with rifampicin resistant Tuberculosis were subjected to first line and second line Probe Assay (Genotype MTBDRsl by Hain Life Science, Germany) to assess additional drug resistance to fluroquinolones (Levofloxacin & Moxifloxacin) and Aminoglycosides (Amikacin, Ofloxacin and Kanamycin). The genetic mutation pattern was analysed and compared with demographic, clinical and other parameters.

RESULTS

The final study population included 123 fluoroquinolone resistant isolates including 14 isolates with additional second line aminoglycosides drug resistance. The most frequent mutation observed among Gyr A drug resistance mutation was D94G (Gyr A MUT3C, 50/123,40%) corresponding to high level resistance to levofloxacin and moxifloxacin. The most frequent wild type mutant among Gyr A gene locus was WT 3 (85/123,69%). The most common mutation among second line aminoglycoside resistant isolates was at eis WT2 (7/14,50%) followed by rrs MUT 2 (4/14,29%).

CONCLUSIONS

GyrA MUT3C (Asp94Gly) was the most common mutation in Gyr A gene locus in M. tuberculosis causing high level levofloxacin and moxifloxacin resistance. Patients with Asp94Gly mutation was significantly associated with underweight body mass index (p = 0.026). This study also observed that history of anti-tuberculosis therapy is a risk factor for FQ drug resistance mutations (p < 0.001).

Analysis of drug resistance among difficult-to-treat tuberculosis patients in Ghana identifies several pre-XDR TB cases

Background

Resistance to tuberculosis (TB) drugs has become a major threat to global control efforts. Early case detection and drug susceptibility profiling of the infecting bacteria are essential for appropriate case management. The objective of this study was to determine the drug susceptibility profiles of difficult-to-treat (DTT) TB patients in Ghana.

Methods

Sputum samples obtained from DTT-TB cases from health facilities across Ghana were processed for rapid diagnosis and detection of drug resistance using the Genotype MTBDRplus and Genotype MTBDRsl.v2 from Hain Life science.

Results

A total of 298 (90%) out of 331 sputum samples processed gave interpretable bands out of which 175 (58.7%) were resistant to at least one drug (ANYr); 16.8% (50/298) were isoniazid-mono-resistant (INHr), 16.8% (50/298) were rifampicin-mono-resistant (RIFr), and 25.2% (75/298) were MDR. 24 (13.7%) of the ANYr were additionally resistant to at least one second line drug: 7.4% (2 RIFr, 1 INHr, and 10 MDR samples) resistant to only FQs and 2.3% (2 RIFr, 1 INHr, and 1 MDR samples) resistant to AMG drugs kanamycin (KAN), amikacin (AMK), capreomycin (CAP), and viomycin (VIO). Additionally, there were 4.0% (5 RIFr and 2 MDR samples) resistant to both FQs and AMGs. 81 (65.6%) out of 125 INH-resistant samples including INHr and MDR had katG-mutations (MT) whereas 15 (12%) had inhApro-MT. The remaining 28 (22.4%) had both katG and inhA MT. All the 19 FQ-resistant samples were gyrA mutants whereas the 10 AMGs were rrs (3), eis (3) as well as rrs, and eis co-mutants (4). Except for the seven pre-XDR samples, no sample had eis MT.

Conclusion

The detection of several pre-XDR TB cases in Ghana calls for intensified drug resistance surveillance and monitoring of TB patients to, respectively, ensure early diagnosis and treatment compliance.

Profile and Frequency of Mutations Conferring Drug-Resistant Tuberculosis in the Central, Southeastern and Eastern Ethiopia

Purpose

Advances in molecular tools that assess genes harboring drug resistance mutations have greatly improved the detection and treatment of drug-resistant tuberculosis (DR-TB). This study was conducted to determine the frequency and type of mutations that are responsible for resistance to rifampicin (RIF), isoniazid (INH), fluoroquinolones (FLQs) and second-line injectable drugs (SLIDs) in Mycobacterium tuberculosis (MTB) isolates obtained from culture-positive pulmonary tuberculosis (TB) patients in the central, southeastern and eastern Ethiopia.

Patients and Methods

In total, 224 stored culture-positive MTB isolates from pulmonary TB patients referred to Adama and Harar regional TB laboratories between August 2018 and January 2019 were assessed for mutations conferring RIF, INH, FLQs and SLIDs resistance using GenoType^®MTBDRplus (MTBDRplus) and GenoType^®MTBDRsl (MTBDRsl).

Results

RIF, INH, FLQs and SLIDs resistance-conferring mutations were identified in 88/224 (39.3%), 85/224 (38.0%), 7/77 (9.1%), and 3/77% (3.9%) of MTB isolates, respectively. Mutation codons rpoB S531L (59.1%) for RIF, katG S315T (96.5%) for INH, gyrA A90V (42.1%) for FLQs and WT1 rrs (100%) for SLIDs were observed in the majority of the isolates tested. Over a 10th of rpoB mutations detected in the current study were unknown.

Conclusion

In this study, the most common mutations conferring drug resistance to RIF, INH, FLQs were identified. However, a significant proportion of RIF-resistant isolates manifested unknown rpoB mutations. Similarly, although few in number, all SLID-resistant isolates had unknown rrs mutations. To further elucidate the entire spectrum of mutations, tool such as whole-genome sequencing is imperative. Furthermore, the expansion of molecular drug susceptibility testing services is critical for tailoring patient treatment and preventing disease transmission.

Comparative genomics of drug-resistant strains of Mycobacterium tuberculosis in Ecuador

BACKGROUND

Tuberculosis is a serious infectious disease affecting millions of people. In spite of efforts to reduce the disease, increasing antibiotic resistance has contributed to persist in the top 10 causes of death worldwide. In fact, the increased cases of multi (MDR) and extreme drug resistance (XDR) worldwide remains the main challenge for tuberculosis control. Whole genome sequencing is a powerful tool for predicting drug resistance-related variants, studying lineages, tracking transmission, and defining outbreaks. This study presents the identification and characterization of resistant clinical isolates of Mycobacterium tuberculosis including a phylogenetic and molecular resistance profile study by sequencing the complete genome of 24 strains from different provinces of Ecuador.

RESULTS

Genomic sequencing was used to identify the variants causing resistance. A total of 15/21 isolates were identified as MDR, 4/21 as pre-XDR and 2/21 as XDR, with three isolates discarded due to low quality; the main sub-lineage was LAM (61.9%) and Haarlem (19%) but clades X, T and S were identified. Of the six pre-XDR and XDR strains, it is noteworthy that five come from females; four come from the LAM sub-lineage and two correspond to the X-class sub-lineage. A core genome of 3,750 genes, distributed in 295 subsystems, was determined. Among these, 64 proteins related to virulence and implicated in the pathogenicity of M. tuberculosis and 66 possible pharmacological targets stand out. Most variants result in nonsynonymous amino acid changes and the most frequent genotypes were identified as conferring resistance to rifampicin, isoniazid, ethambutol, para-aminosalicylic acid and streptomycin. However, an increase in the resistance to fluoroquinolones was detected.

CONCLUSION

This work shows for the first time the variability of circulating resistant strains between men and women in Ecuador, highlighting the usefulness of genomic sequencing for the identification of emerging resistance. In this regard, we found an increase in fluoroquinolone resistance. Further sampling effort is needed to determine the total variability and associations with the metadata obtained to generate better health policies.

The resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing the efficacy of this antibiotic

For around three decades, the fluoroquinolone (FQ) antibiotic ciprofloxacin has been used to treat a range of diseases, including chronic otorrhea, endocarditis, lower respiratory tract, gastrointestinal, skin and soft tissue, and urinary tract infections. Ciprofloxacin's main mode of action is to stop DNA replication by blocking the A subunit of DNA gyrase and having an extra impact on the substances in cell walls. Available in intravenous and oral formulations, ciprofloxacin reaches therapeutic concentrations in the majority of tissues and bodily fluids with a low possibility for side effects. Despite the outstanding qualities of this antibiotic, Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa have all shown an increase in ciprofloxacin resistance over time. The rise of infections that are resistant to ciprofloxacin shows that new pharmacological synergisms and derivatives are required. To this end, ciprofloxacin may be more effective against the biofilm community of microorganisms and multi-drug resistant isolates when combined with a variety of antibacterial agents, such as antibiotics from various classes, nanoparticles, natural products, bacteriophages, and photodynamic therapy. This review focuses on the resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing its efficacy.

Genomic analysis of Mycobacterium tuberculosis variant bovis strains isolated from bovine in the state of Mato Grosso, Brazil

The species Mycobacterium tuberculosis variant bovis (M. tuberculosis var. bovis) is associated with tuberculosis, mainly in cattle and buffaloes. This pathogen has the potential to infect other mammals, including humans. Tuberculosis caused by M. tuberculosis var. bovis is a zoonosis clinically identical to tuberculosis caused by Mycobacterium tuberculosis, and the recommended treatment in humans results in the use of antibiotics. In this study, we used the whole genome sequencing (WGS) methodology Illumina NovaSeq 6000 System platform to characterize the genome of M. tuberculosis var. bovis in cattle circulating in Mato Grosso, identify mutations related to drug resistance genes, compare with other strains of M. tuberculosis var. bovis brazilian and assess potential drug resistance. Four isolates of M. tuberculosis var. bovis of cattle origin representing the main livestock circuits, which had been more prevalent in previous studies in the state of Mato Grosso, were selected for the genomic study. The genome sizes of the sequenced strains ranged from 4,306,423 to 4,332,964 bp, and the GC content was 65.6%. The four strains from Mato Grosso presented resistance genes to pncA (pyrazinamide), characterized as drug-resistant strains. In addition to verifying several point mutations in the pncA, rpsA, rpsL, gid, rpoB, katG, gyrB, gyrA, tlyA, embA, embB, embC, fgd, fbiB, and fbiC genes, these genes were similar to antibiotic resistance in more than 92% of the Brazilian strains. Therefore, our results indicated a high genetic diversity between our isolates and other M. tuberculosis var. bovis isolated in Brazil. Thus, multiple transmission routes of this pathogen may be present in the production chain. So, to achieve a bovine tuberculosis-free health status, the use of the WGS as a control and monitoring tool will be crucial to determine these transmission routes.

Resistance patterns among drug-resistant tuberculosis patients and trends-over-time analysis of national surveillance data in Gabon, Central Africa

Objective

Routinely generated surveillance data are important for monitoring the effectiveness of MDR-TB control strategies. Incidence of rifampicin-resistant tuberculosis (RR-TB) is a key indicator for monitoring MDR-TB.

Methods

In a longitudinal nationwide retrospective study, 8 years (2014–2021) of sputum samples from presumptively drug-resistant tuberculosis patients from all regions of Gabon were referred to the national tuberculosis reference laboratory. Samples were analysed using GeneXpert MTB/RIF and Genotype MTBDRsl version 2/Line Probe Assay.

Results

Of 3057 sputum samples from presumptive tuberculosis patients, both from local hospital and from referral patients, 334 were RR-TB. The median patient age was 33 years (interquartile range 26–43); one third was newly diagnosed drug-resistant tuberculosis patients; one-third was HIV-positive. The proportion of men with RR-TB was significantly higher than that of women (55% vs 45%; p < 0.0001). Patients aged 25–35 years were most affected (32%; 108/334). The cumulative incidence of RR-TB was 17 (95% CI 15–19)/100,000 population over 8 years. The highest incidences were observed in 2020 and 2021. A total of 281 samples were analysed for second-line drug resistance. The proportions of study participants with MDR-TB, pre-XDR-TB and XDR-TB were 90.7% (255/281), 9% (25/281) and 0.3% (1/281), respectively. The most-common mutations in fluoroquinolones resistance isolates was gyrA double mutation gyrA MUT3B and MUT3C (23%; 4/17). Most (64%; 6/8) second-line injectable drugs resistance isolates were characterised by missing both rrs WT2 and MUT2 banding.

Conclusion

The increasing incidence of MDR-TB infection in Gabon is alarming. It is highest in the 25–35 years age category. The incidence of MDR-TB infection in treatment-naïve patients calls for case finding and contact tracing strategy improvement.

Diagnostic utility of GenoType MTBDRsl assay for the detection of moxifloxacin-resistant mycobacterium tuberculosis, as compared to phenotypic method and whole-genome sequencing

Background

Recently, moxifloxacin (MFX)-resistant results of Mycobacterium tuberculosis (Mtb) obtained by GenoType MTBDRsl (second-line line probe assay [SL-LPA]) have been stratified to determine their resistance level; however, its accuracy has not been well studied. Therefore, the study aimed to evaluate the diagnostic accuracy of SL-LPA, with phenotypic drug susceptibility testing (pDST) and whole-genome sequencing (WGS) for the detection of MFX-resistant Mtb and their resistance level.

Methods

A total of 111 sputum samples were subjected to SL-LPA according to the diagnostic algorithm of the National Tuberculosis Elimination Program. Results were compared with pDST of MFX (at critical concentration [CC, 0.25 μg/ml] and clinical breakpoint [CB, 1.0 μg/ml] using BACTEC mycobacterial growth indicator tube-960), and WGS.

Results

At CC, SL-LPA and pDST yielded concordant results of MFX for 104 of 111 (94%). However, at CB, 23 of 30 (77%) isolates carrying gyrA mutation known to confer low-level resistance to MFX were scored as susceptible by pDST. Among 46 Mtb isolates carrying gyrA mutations known to confer high-level resistance to MFX, 36 (78%) isolates yielded concordant results, while 10 (22%) isolates were scored as susceptible at CB by pDST. WGS identified gyrA mutations in all isolates suggested by SL-LPA.

Conclusion

It is concluded that the stratification of MFX-resistant results by SL-LPA/genotypic method is not very well correlated with pDST (at CB), and hence, pDST may not be completely replaced by SL-LPA. gyrA D94G and gyrAA90V are the most prevalent mutations in MFX-resistant Mtb.

MDR Tuberculosis Treatment

Multidrug-resistant (MDR) tuberculosis (TB), resistant to isoniazid and rifampicin, continues to be one of the most important threats to controlling the TB epidemic. Over the last few years, there have been promising pharmacological advances in the paradigm of MDR TB treatment: new and repurposed drugs have shown excellent bactericidal and sterilizing activity against Mycobacterium tuberculosis and several all-oral short regimens to treat MDR TB have shown promising results. The purpose of this comprehensive review is to summarize the most important drugs currently used to treat MDR TB, the recommended regimens to treat MDR TB, and we also summarize new insights into the treatment of patients with MDR TB.

Correlation of gyr Mutations with the Minimum Inhibitory Concentrations of Fluoroquinolones among Multidrug-Resistant Mycobacterium tuberculosis Isolates in Bangladesh

Fluoroquinolone (FQ) compounds-moxifloxacin (MOX), levofloxacin (LEV), and ofloxacin (OFL)-are used to treat multidrug-resistant tuberculosis (MDR-TB) globally. In this study, we investigated the correlation of gyr mutations among Mtb isolates with the MICs of MOX, LEV, and OFL in Bangladesh. A total of 50 MDR-TB isolates with gyr mutations, detected by the GenoType MTBDRsl assay, were subjected to drug susceptibility testing to determine the MICs of the FQs. Spoligotyping was performed to correlate the genetic diversity of the gyr mutant isolates with different MIC distributions. Among the 50 isolates, 44 (88%) had mutations in the gyrA gene, one (2%) had a mutation in the gyrB gene, and five (10%) isolates had unidentified mutations. The substitutions in the gyrA region were at A90V (n = 19, 38%), D94G (n = 16, 32%), D94A (n = 4, 8%), D94N/D94Y (n = 4, 8%), and S91P (n = 1, 2%), compared to the gyrB gene at N538D (n = 1.2%). D94G mutations showed the highest MICs for MOX, LEV, and OFL, ranging between 4.0 and 8.0 μg/mL, 4.0 and 16.0 μg/mL, and 16.0 and 32.0 μg/mL, respectively; while the most common substitution of A90V showed the lowest ranges of MICs (1.0-4.0 μg/mL, 2.0-8.0 μg/mL, and 4.0-32.0 μg/mL, respectively). Spoligotyping lineages demonstrated no significant differences regarding the prevalence of different gyr mutations. In conclusion, the substitutions of codon A90V and D94G in the gyr genes were mostly responsible for the FQs' resistance among Mtb isolates in Bangladesh. Low levels of resistance were associated with the substitutions of A90V, while the D94G substitutions were associated with a high level of resistance to all FQs.

Computational modeling and bioinformatic analyses of functional mutations in drug target genes in Mycobacterium tuberculosis

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MycoTRAP-DB, a database of mutations and their impact on normal functionality of protein in M.tb genes.

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Several secondary mutations were identified with significant impact on protein structure and function.

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Comprehensive information gives insight for screening of suspected hotspots in advance to combat drug resistant TB.

Tuberculosis (TB) continues to be the leading cause of deaths due to its persistent drug resistance and the consequent ineffectiveness of anti-TB treatment. Recent years witnessed huge amount of sequencing data, revealing mutations responsible for drug resistance. However, the lack of an up-to-date repository remains a barrier towards utilization of these data and identifying major mutations-associated with resistance. Amongst all mutations, non-synonymous mutations alter the amino acid sequence of a protein and have a much greater effect on pathogenicity. Hence, this type of gene mutation is of prime interest of the present study. The purpose of this study is to develop an updated database comprising almost all reported substitutions within the Mycobacterium tuberculosis (M.tb) drug target genes rpoB, inhA, katG, pncA, gyrA and gyrB. Various bioinformatics prediction tools were used to assess the structural and biophysical impacts of the resistance causing non-synonymous single nucleotide polymorphisms (nsSNPs) at the molecular level. This was followed by evaluating the impact of these mutations on binding affinity of the drugs to target proteins. We have developed a comprehensive online resource named MycoTRAP-DB (Mycobacterium tuberculosis Resistance Associated Polymorphisms Database) that connects mutations in genes with their structural, functional and pathogenic implications on protein. This database is accessible at http://139.59.12.92. This integrated platform would enable comprehensive analysis and prioritization of SNPs for the development of improved diagnostics and antimycobacterial medications. Moreover, our study puts forward secondary mutations that can be important for prognostic assessments of drug-resistance mechanism and actionable anti-TB drugs.

Identification of drug resistance mutations among Mycobacterium bovis lineages in the Americas

Identifying the Mycobacterium tuberculosis resistance mutation patterns is of the utmost importance to assure proper patient's management and devising of control programs aimed to limit spread of disease. Zoonotic Mycobacterium bovis infection still represents a threat to human health, particularly in dairy production regions. Routinary, molecular characterization of M. bovis is performed primarily by spoligotyping and mycobacterial interspersed repetitive units (MIRU) while next generation sequencing (NGS) approaches are often performed by reference laboratories. However, spoligotyping and MIRU methodologies lack the resolution required for the fine characterization of tuberculosis isolates, particularly in outbreak settings. In conjunction with sophisticated bioinformatic algorithms, whole genome sequencing (WGS) analysis is becoming the method of choice for advanced genetic characterization of tuberculosis isolates. WGS provides valuable information on drug resistance and compensatory mutations that other technologies cannot assess. Here, we performed an analysis of the most frequently identified mutations associated with tuberculosis drug resistance and their genetic relationship among 2,074 Mycobacterium bovis WGS recovered primarily from non-human hosts. Full-length gene sequences harboring drug resistant associated mutations and their phylogenetic relationships were analyzed. The results showed that M. bovis isolates harbor mutations conferring resistance to both first- and second-line antibiotics. Mutations conferring resistance for isoniazid, fluoroquinolones, streptomycin, and aminoglycosides were identified among animal strains. Our findings highlight the importance of molecular surveillance to monitor the emergence of mutations associated with multi and extensive drug resistance in livestock and other non-human mammals.

Variations in rifampicin and isoniazid resistance associated genetic mutations among drug naïve and recurrence cases of pulmonary tuberculosis

BACKGROUND

The resistance to first-line drugs can increase the risk of treatment failure and development of resistance to other anti-TB drugs. In TB endemic settings, a considerable rate of recurrence cases exhibited each, year which adds significant burden to the prevalence of disease worldwide.

METHODS

A total of 562 sputum samples were collected from presumptive positive clinical cases of MDR tuberculosis. Treatment history and demographic data of the patients were obtained after informed consent. Xpert MTB/RIF assay was performed for simultaneous detection of MTB and rifampicin resistance. The mutation patterns of isoniazid and rifampicin were observed after multiplex PCR and reverse hybridization by Genotype® MTBDRplus version 2.0 assay.

RESULTS

A total of 73 of 97 cases (75.2%) of treatment failure were found positive for MDR-TB, whereas 79.6% newly diagnosed and 72.9% default cases were MDR in our isolates. The mutation of rpoB S531L was slightly higher in new treatment cases (89.3%) as compared to the default (80.4%) and failure cases (84.8%), whereas rpoB D516V mutation was more prevalent in default cases (19.6%) with complete absence of rpoB 526 mutation, which was observed in the other two types of cases. The mutation pattern of katG resistance differed among drug naïve and recurrence cases. The resistance in newly diagnosed cases was mostly conferred by katG 315 (49.1%) whereas in default (70.8%) and failure cases (63.3%) isoniazid resistance was commonly associated with katG S315T1 mutation. Mutations in inhA promoter region occurred at nucleotide position -8 and -15. In new cases the rate of mutation of C-15T was 3.7% and T-8A was 1.5% while in treatment failure cases the frequency for C-15T and T-8C was 2.5 and 3.8% respectively. However, no inhA promoter region mediated mutations were detected in default treatment cases.

CONCLUSION

Retreated cases are at more risk of developing hot spot mutations. An unusual difference in mutation pattern was determined in naïve and recurrence cases. Some mutations were exclusively associated with the retreatment of 35anti-TB drugs which suggest the increased risk of resistance with poor treatment outcome.