Multi-drug Resistant M. Tuberculosis Research Articles

Discordance in Phenotypic and Genotypic Susceptibility Testing for Streptomycin Due to Nonsynonymous/Nonsense/Deletion Frame-Shift Mutations in gidB among Clinical Mycobacterium tuberculosis Isolates in Kuwait

Objective: Increasing reports of resistance to newer antituberculosis drugs have prompted the search for other alternative drugs. Streptomycin (STR) could be used for the treatment of drug-resistant tuberculosis if susceptibility of Mycobacterium tuberculosis isolate to STR could be accurately detected. We performed phenotypic and genotypic drug susceptibility testing (DST) of 118 M. tuberculosis isolates for STR. Materials and Methods: Fifty pansusceptible and 68 multidrug-resistant M. tuberculosis (MDR-TB) isolates were used. Phenotypic DST for STR, rifampicin, isoniazid, and ethambutol was performed by mycobacteria growth indicator tube 960 System. Genotypic DST was done by GenoTypeMTBDRplus assay for rifampicin and isoniazid and by PCR-sequencing of rpsL, rrs, and gidB genes for STR. MDR-TB isolates were genotyped by spoligotyping. Results: Phenotypic DST identified 50 isolates susceptible to all four drugs (pansusceptible). Sixty-one of 68 MDR-TB isolates were resistant to STR. Genotypic testing for rifampicin and isoniazid yielded expected results. Fifty pansusceptible and 7 STR-susceptible MDR-TB isolates contained no mutation in rpsL or rrs, while 47, 2, and 1 STR-resistant isolate contained rpsL, rrs, and rpsL + rrs mutations, respectively. Of the remaining 11 STR-resistant MDR-TB, 9 isolates contained deletion frame-shift/nonsynonymous mutations in gidB. Surprisingly, 13 pansusceptible isolates also contained deletion frame-shift/nonsense/nonsynonymous mutations in gidB. Also, 30 of 68 MDR-TB but only 2 of 50 pansusceptible isolates belonged to the Beijing genotype. Conclusions: Our data show that, like rifampicin, ethambutol, and pyrazinamide, STR also exhibits discordant phenotypic and genotypic DST results for some M. tuberculosis isolates. Hence, STR should be included in therapy regimens only if both phenotypic and genotypic resistance testing indicate susceptibility to avoid amplification of resistance and drug toxicity.

Hierarchical true prevalence, risk factors and clinical symptoms of tuberculosis among suspects in Bangladesh.

The study was aimed to estimate the true prevalence of human tuberculosis (TB); identify risk factors and clinical symptoms of TB; and detect rifampicin (RIF) sensitivity in three study areas of Bangladesh. The cross-sectional study was conducted in three Bangladesh districts during 2018. Potential risk factors, clinical symptoms, and comorbidities were collected from 684 TB suspects. Sputum specimens were examined by LED microscopy. TB hierarchical true prevalence, risk factors and clinical symptoms were estimated and identified using a Bayesian analysis framework. Rifampicin sensitivity of M. tuberculosis (MTB) was detected by GeneXpert MTB/RIF assay. The median TB true prevalence was 14.2% (3.8; 34.5). Although overall clustering of prevalence was not found, several DOTS centers were identified with high prevalence (22.3% to 43.7%). Risk factors for TB identified (odds ratio) were age (> 25 to 45 years 2.67 (1.09; 6.99), > 45 to 60 years 3.43 (1.38; 9.19) and individuals in families/neighborhoods where a TB patient(s) has (ve) already been present (12.31 (6.79; 22.60)). Fatigue, night sweat, fever and hemoptysis were identified as important clinical symptoms. Seven of the GeneXpert MTB/RIF positive sputum specimens (65) were resistant to rifampicin. About one in every seven TB suspects was affected with TB. A number of the TB patients carry multi drug resistant MTB. Hierarchical true prevalence estimation allowed identifying DOTS centers with high TB burden. Insights from this study will enable more efficient use of DOTScenters-based TB surveillance to end the TB epidemic in Bangladesh by 2035.

Mutations in rpoB and katG genes and the inhA operon in multidrug-resistant Mycobacterium tuberculosis isolates from Zambia

ObjectivesIt is established that resistance to rifampicin (RIF) in 90% of RIF-resistant Mycobacterium tuberculosis isolates is attributable to point mutations in the rpoB gene, whilst 50–95% of M. tuberculosis resistance to isoniazid (INH) is caused by mutations in the katG gene. However, the patterns and frequencies of mutations vary by geographical region. In Zambia, the genetic mechanisms of resistance of M. tuberculosis to RIF and INH were unreported before this study. MethodsUsing gene sequencing, the rpoB, katG and inhA genes of 99 multidrug-resistant M. tuberculosis (MDR-TB) and 49 pan-susceptible M. tuberculosis isolates stored at a tuberculosis reference laboratory from 2013 to 2016 were analysed and were compared with published profiles from other African countries. ResultsOf the 99 MDR-TB isolates, 95 (96.0%) carried mutations in both rpoB and katG. No mutations were detected among the pan-susceptible isolates. The most common mutations among RIF- and INH-resistant isolates were in codon 531 of the rpoB gene (55.6%; 55/99) and codon 315 of the katG gene (94.9%; 94/99), respectively. Distinctly, katG mutations were predominantly high among Zambian isolates (96.0%) compared with other countries in the region. ConclusionResistance-associated mutations to RIF and INH circulating in Zambia are similar to those reported globally, therefore these data validate the applicability of molecular diagnostic tools in Zambia. However, katG mutations were predominantly high among M. tuberculosis isolates in this study compared with other regional countries and might distinguish cross-boundary transmission of MDR-TB from other African nations.

English

In this study, the infection of young children with Mycobacterium tuberculosis and drug-resistant M. tuberculosis in a mass gathering area in Al-Madinah Al-Munawwarah, was investigated and discussed. All the children, 15 years old and younger, who were referred to the central tuberculosis laboratory in Al-Madinah between January 2012 and December 2014 were included in this study. Among a total of 622 registered new cases, 68 (10.9%) were children, males were 40 (58.8%) while 28 (41.2 %) were females. All the children were vaccinated with Bacillus Calmette-Guérin (BCG) within their first week of birth. Sixty (88.2%) children were infected with M. tuberculosis, whereas 8 (11.8%) had non tuberculous mycobacteria (NTM). Clinically, pulmonary tuberculosis was confirmed in 20 (29.4%) cases, whereas the remaining 48 (70.6%) had extra pulmonary tuberculosis. Multidrug-resistant M. tuberculosis (MDR) was isolated from 3 (4.4%) cases, all of whom were younger than five years; one with pulmonary and two with extrapulmonary tuberculosis. All the isolated MDR organisms belonged to the M. tuberculosis complex. The rates of mono-resistance to isoniazid (H), streptomycin (S), ethambutol (E) and pyrazinamide (Z) were 5.9, 1.5, 5.9 and 8.8%, respectively. No case was registered as mono-resistant to rifampin (R). The prevalence of childhood tuberculosis in the current study area is higher than the globally estimated rate. Since all the cases were new, MDR-TB was mostly due to infection with originally MDR strains.   Key words: Mycobacteria, polymerase chain reaction, resistance, antibiotics, antimicrobials.

Multicomponent reactions in the synthesis of dihydropyrimidine-containing podands having tuberculostatic activity

Dihydropyrimidinethione podands, as well as podands containing 2-thienyl substituents have been synthesized via the multicomponent Biginelli reaction. Tuberculostatic activity of the novel podands was shown to depend on the polyether unit length. In particular, activity of dihydropyrimidinethione podands against laboratory strains of Mycobacterium tuberculosis, H37Rv, M. avium, M. terrae, and the clinical strain of multi-drug resistant M. tuberculosis (MDR), increases with a shortening of the polyether unit length.

Туберкулостатическая активность производных 2-амино-6-хлорпурина

В результате изучения антимикобактериальной активности 2-амино-6-хлорпурина и его N-ацилпроизводных в отношении лабораторных (Mycobacterium tuberculosis H37Rv, M. avium, M. terrae) и клинических штаммов микобактерий туберкулеза (МЛУ-ТБ) выявлены соединения, проявляющие высокую туберкулостатическую активность (МИК от 0,35 до 1,5 мкг/мл). Изучена цитотоксическая активность соединений, проявивших антимикобактериальную активность, в отношении фибробластов эмбриона человека в МТТ-тесте и установлено, что изученные соединения являются практически нетоксичными (IC50 > 50 мкМ). Их дальнейшая химическая модификация может привести к получению соединений, перспективных для создания лекарственных средств лечения туберкулеза. С целью выяснения возможного механизма туберкулостатической активности проверена способность тестируемых соединений ингибировать микобактериальные серин-треониновые протеинкиназы (СТПК). Установлено, что туберкулостатическая активность производных 2-амино-6-хлорпурина не связана с ингибированием ими СТПК.

Diagnosis of tuberculous meningitis: Current scenario from a Tertiary Neurocare Centre in India

BackgroundTuberculous meningitis (TBM) is a condition that is caused by Mycobacterium tuberculosis complex and is difficult to diagnose due to the nonspecificity of the presentations. The study analyzed the different modes of diagnosis available in a developing country set up over a period of five years to understand the diagnostic values of the current conventional and automated methods of diagnosis of TBM among the patients suspected with chronic meningitis. MethodsA total of 10,281 cerebrospinal fluid samples (CSF) were collected from suspected chronic meningitis patients, of which 790 samples were from individuals who had clinically suspected TBM. The samples were subjected to CSF cytology and staining, culturing, immunological tests, molecular techniques, and methods for detection of drug resistance. ResultsThe TBM patients were predominantly male, with a mean age of 21–40 years. CSF pleocytosis and lymphocytic predominance were noted. Culture had 40.13% positivity among clinically suspected TBM patients. The multidrug-resistant M. tuberculosis (MDR-TB) constituted 3.14% of the total clinical isolates. With IS6110 PCR, a specificity of 92.86% and sensitivity of 100% are seen with an assay threshold of 30pg/ml. Line probe assay (LPA) using culture isolates had a sensitivity of 97.67% and a specificity of 100%. Direct CSF LPA showed a sensitivity of 96.15% and a specificity of 100%. ConclusionsA combination of techniques that involved culture, cytology, and DNA amplification methods was found to be promising in specific, accurate, and rapid detection of M. tuberculosis in the CSF samples from patients.

Evaluation of Sensitivity of Molecular Methods for Detection of Rifampin-Resistant Strains Amongst Drug-resistant Mycobacterium tuberculosis Isolates

Background: Resistance to rifampin in multidrug-resistant M. tuberculosis (MDR-TB) is one of the major threats to the global public health system. Objectives: The aim of the present study was to explore the molecular characterization of resistance against rifampin amongst multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates obtained from patients. Methods: In this study, we used XDR (n = 6), MDR (n = 9) and rifampin sensitive (n = 39) isolates whose drug susceptibility patterns were identified by proportion method. A simple single-step multiplex-allele specific-polymerase chain reaction (MAS-PCR) assay was optimized to detect the three most frequent mutations in rifampin resistance-determining region (RRDR) fragment of rpoB gene. Additionally, single-strand conformational polymorphism (SSCP)-PCR and Sequencing were utilized. Results: Out of nine MDR isolates, five were detected by MAS-PCR as rifampin resistant (sensitivity; 55.5). In comparison with the proportion method, the sensitivity of SSCP for XDR, MDR and rifampin sensitive isolates were 83.3, 77.7 and 97.4, respectively. The DNA sequencing revealed that three of the 6 XDR isolates had several silent mutations, one isolate had one silent mutation, one strain had no mutations and only one isolate had mutations at codon 531. Conclusions: In sum, although the molecular methods are rapid, they are not able to identify resistance against rifampin efficiently. © 2016, Pediartric Infections Research Center.

Antimycobacterial, docking and molecular dynamic studies of pentacyclic triterpenes from Buddleja saligna leaves

Buddleja saligna (family Buddlejaceae) is a medicinal plant endemic to South Africa. Two isomeric pentacyclic triterpenes, oleanolic acid and ursolic acid, were isolated from the leaves of B. saligna using silica gel column chromatography. Compounds oleanolic acid and ursolic acid were subjected to derivatization with acetic anhydride in the presence of pyridine to obtain oleanolic acid-3-acetate and ursolic acid-3-acetate, respectively. The structures of these compounds were fully characterized by detailed nuclear magnetic resonance (NMR) investigations, which included 1H and 13C NMR. Molecular docking studies predicted the free binding energy of the four triterpenes inside the steroid binding pocket of Mycobacterium tuberculosis fadA5 thiolase compared to a reported inhibitor. Thus, their ability to inhibit the growth of M. tuberculosis was predicted and was confirmed to possess significant antimycobacterial activity when tested against Mycobacterium smegmatis, M. tuberculosis H37Rv (ATCC 25177), clinical isolates of multi-drug-resistant M. tuberculosis (MDR-TB) and extensively drug-resistant M. tuberculosis (XDR-TB) using the Micro Alamar Blue Assay. Ursolic acid was isolated from this plant for the first time.

Molecular analysis of rpoB gene mutations in rifampicin resistant Mycobacterium tuberculosis isolates by multiple allele specific polymerase chain reaction in Puducherry, South India.

rpoB gene mutations in Mycobacterium tuberculosis (MTB) make the bacteria resistant to rifampicin. Thus, these mutations are surrogate markers for multi-drug resistance (MDR). The objective of this study was to evaluate an allele-specific multiplex-polymerase chain reaction (MAS-PCR) assay to detect mutations at codons 516, 526 and 531 of the rpoB gene. In total, 127 M. tuberculosis clinical isolates were subjected to standard drug susceptibility tests. A MAS-PCR assay was then performed to detect mutations in the rpoB gene. Three different allele-specific PCR assays were performed (single-step MAS-PCR) and the amplified products were sequenced. Of the 127 isolates, 69 (54.3%) were multidrug resistant M. tuberculosis (MDR-TB), 21 (16.5%) were rifampicin mono-resistant and 37 (29.1%) were drug susceptible. The frequency of mutations at codons 531, 526 and 516 was 54.4%, 18.9% and 5.6%, respectively. A triple mutation was found in 4 (4.4%) isolates. Mutations in regions other than the 81-bp region were observed at codons 413 (11.1%), 511 (12.2%) and 521 (15.6%) of the rpoB gene. The simplicity and specificity of the MAS-PCR assay allows for easy implementation in clinical laboratories to detect rifampicin drug resistance in MDR-TB strains.

A solvent free, four-component synthesis and 1,3-dipolar cycloaddition of 4(H)-pyrans with nitrile oxides: Synthesis and discovery of antimycobacterial activity of enantiomerically pure 1,2,4-oxadiazoles

Four-component reactions of (R)-1-(1-phenylethyl)tetrahydro-4(1H)-pyridinone, aromatic aldehydes and malononitrile in a 1:2:1 molar ratio in the presence of solid sodium ethoxide under solvent free conditions afforded an inseparable mixture of two diastereomeric 4(H)-pyrans in near quantitative yields. These compounds upon 1,3-dipolar cycloaddition with nitrile oxides furnished two enantiomerically pure 1,2,4-oxadiazoles in moderate yields, which were screened for in vitro activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among the compounds screened, compound 10h was found to be the most active in vitro with a MIC value of 0.07 and 0.14μM against MTB and MDR-TB respectively.

ChemInform Abstract: Synthesis and Antimycobacterial Evaluation of 3a,4‐Dihydro‐3H‐indeno[1,2‐c]pyrazole‐2‐carboxamide Analogues.

AbstractAll new pyrazole‐2‐carboxamide analogues (III) show low to good antimycobacterial effects.

Genitourinary and Pulmonary Multidrug ResistantMycobacterium tuberculosisInfection in an Asian Elephant (Elephas maximus)

A female Asian elephant (Elephas maximus) developed vaginal and trunk discharge. Cultures were positive for pan-susceptible Mycobacterium tuberculosis. Isoniazid and pyrazinamide were given rectally and monitored by serum levels. After being trained at 10 mo to accept oral dosing, treatment was changed and rifampin was added. Oral medications were administered for another 10 mo. A year after completion of therapy, the vaginal discharge increased and cultures yielded M. tuberculosis, resistant to isoniazid and rifampin. Treatment with oral ethambutol, pyrazinamide, and enrofloxacin and intramuscular amikacin was initiated. Although followup cultures became negative, adverse reactions to medications precluded treatment completion. Due to public health concerns related to multidrug resistant M. tuberculosis (MDR-TB), the elephant was euthanized. Postmortem smears from the lung, peribronchial, and abdominal lymph nodes yielded acid-fast bacteria, although cultures were negative. This case highlights important considerations in the treatment of M. tuberculosis in animals and the need for a consistent approach to diagnosis, treatment, and follow-up.

Synthesis and antimycobacterial evaluation of 3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide analogues

In the present investigation, a series of 3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide analogues were synthesized and were evaluated for antitubercular activity by two fold serial dilution technique. All the newly synthesized compounds showed low to good inhibitory activities against Mycobacterium tuberculosis H37Rv and multi-drug resistant M. tuberculosis (MDR-TB). 3-(4-fluorophenyl)-N-(4-chlorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide (4c) was found to be the most promising compound active against M. tuberculosis, H37Rv and MDR-TB with minimum inhibitory concentrations 0.83 μM and 3.32 μM respectively.

Synthesis and anti-mycobacterial activities of triazoloquinolones

A number of quinolone derivatives have been reported to possess anti-mycobacterial activity. Generally. Mycobacterium tuberculosis isolates expressing resistance to both isoniazid and rifampin are susceptible to fluoroquinolones. Benzotriazole is a hetero-bicyclic aromatic ring endowed with interesting chemical and biological properties and pharmacological activities. In a preliminary study we have recently reported the activity of triazolo[4,5-h]quinolone-carboxylic acids, a new class of benzotriazole derivatives active against multi-drug resistant M. tuberculosis (MDR-Mtb). In this study we confirm that this novel class of quinolones is endowed with a selective anti-mycobacterial activity, coupled with absence of cytotoxicity.The SAR analysis of the new derivatives in comparison with the previous series shows that the methyl group is the most effective substituent in both N-3 and N-9 positions of the ring system.

1,3-Dipolar cycloaddition of nitrile oxides to ( R)-1-(1-phenylethyl)-3,5-bis[( E)-arylmethylidene]tetrahydro-4(1 H)-pyridinones: synthesis and antimycobacterial evaluation of novel enantiomerically pure di- and trispiroheterocycles

Enantiomerically pure ( R)-(1-phenylethyl)-3,5-bis[( E)-arylmethylidene]tetrahydro-4(1 H)-pyridinones were synthesized for the first time, and their 1,3-dipolar cycloaddition with nitrile oxides affording di- and trispiroheterocycles regio- and stereoselectively in moderate yields was investigated. These compounds were evaluated against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug-resistant M. tuberculosis (MDR-TB). Among the compounds screened, the dispiroheterocycle, namely, (5 R,6 R,10 S)-3,9-bis(4-chlorophenyl)-10-(2,4-dichlorophenyl)-14-[( E)-(2,4-dichlorophenyl)methylidene]-12-[( R)-1-phenylethyl]-1,4,7-trioxa-2,8,12-tri-azadispiro[4.0.4.4]tetradeca-2,8-diene 5m was found to possess the maximum activity with MIC of 0.49 μM against MTB, being 9.6 and 15.6 times more potent than ciprofloxacin and ethambutol, respectively. Against MDR-TB, 5m displayed maximum activity with an MIC of 0.49 μM, with it thus being more active than rifampicin, isoniazid, ciprofloxacin and ethambutol by 7.8, 23, 77 and 124 times, respectively.

A microwave-assisted, facile, regioselective Friedländer synthesis and antitubercular evaluation of 2,9-diaryl-2,3-dihydrothieno-[3,2-b]quinolines

A series of 2,9-diaryl-2,3-dihydrothieno[3,2-b]quinolines have been synthesized regioselectively by Friedländer annulation of 5-aryldihydro-3(2H)-thiophenones and 2-aminobenzophenones in the presence of trifluoroacetic acid in good yields under microwave irradiation at 100 °C. The 2,9-diaryl-2,3-dihydrothieno[3,2-b]quinolines were screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among the 17 compounds screened, 7-chloro-2-(2,4-dichlorophenyl)-9-phenyl-2,3-dihydrothieno-[3,2-b]quinoline and 7-chloro-2-(3-nitrophenyl)-9-phenyl-2,3-dihydrothieno[3,2-b]quinoline display maximum activity with MIC of 0.90 and 0.95 μM against MTB and MDR-TB respectively.

A highly atom economic, chemo-, regio- and stereoselective synthesis and evaluation of spiro-pyrrolothiazoles as antitubercular agents

The 1,3-dipolar cycloaddition of azomethine ylides derived from substituted isatins and 1,3-thiazolane-4-carboxylic acid to a series of 1-methyl-3,5-bis[( E)-arylmethylidene]-tetrahydro-4(1 H)-pyridinones afforded novel spiro-pyrrolothiazoles chemo-, regio- and stereoselectively in quantitative yields. These compounds were screened for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB) using agar dilution method. Among the synthesized compounds, spiro[5.3′′]-5′′-nitrooxindole-spiro-[6.3′]-1′-methyl-5′-(2,4-di-chlorophenylmethylidene)tetrahydro-4′(1 H)-pyridinone-7-(2,4-dichlorophenyl)tetra-hydro-1 H-pyrrolo[1,2- c][1,3]thiazole ( 9k) was found to be the most active with a minimum inhibitory concentration (MIC) of 0.6 μM against MTB and MDR-TB.

Discovery of novel antitubercular 2,10-dihydro-4a H-chromeno[3,2- c]pyridin-3-yl derivatives

Twenty two novel 2,10-dihydro-4a H-chromeno[3,2- c]pyridin-3-yl derivatives were synthesized by reacting 3-formyl chromone, (sub)-2-amino pyridines, N1-(prop-2-ynyl)arylamides in the presence of indium triflate. The compounds were evaluated their preliminary in-vitro and in-vivo activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among them N-[(4a S)-2-(3-methyl-2-pyridinyl)-10-oxo-2,10-dihydro-4a H-chromeno[3,2- c]pyridin-3-yl]methyl-4-ethylbenzenecarboxamide 4d was found to be the most active compound in-vitro with MIC's of 0.22 and 0.07 μg/mL against MTB and MDR-TB respectively. In the in-vivo animal model 4d decreased the bacterial load in lung and spleen tissues with 1.11 and 2.94-log10 protections respectively at 25 mg/kg body weight dose.

L-Proline-catalysed facile green protocol for the synthesis and antimycobacterial evaluation of [1,4]-thiazines

A series of ethyl 6-(4-chlorobenzoyl)-1,1-dioxo-3,5-diaryl-1,4-thiazinane-2-carboxylates was prepared in good yields (72–90%) from the reaction of ethyl 2-[(2-oxo-2-arylethyl)sulfonyl]acetate, substituted aromatic aldehydes and amines in presence of green catalyst, l-proline. These compounds were evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant M. tuberculosis (MDR-TB) and Mycobacterium smegmatis (MC 2) using agar dilution method. Ethyl 6-(4-chlorobenzoyl)-3,5-di(4-nitrophenyl)-1,1-dioxo-1,4-thiazinane-2-carboxylate was found to be the most promising compound (MIC: 0.68 μM) active against MTB and MDR-TB.