Monoresistant Strains Research Articles

Early detection of multi-drug resistance and common mutations in Mycobacterium tuberculosis isolates from Delhi using GenoType MTBDRplus assay

Purpose: There is scarcity of prevalence data of multi-drug–resistant tuberculosis (MDR-TB) data and common mutations responsible in North India. This study aimed to detect MDR-TB among MDR-TB suspects from Delhi and mutation patterns using GenoType MTBDRplus assay. Materials and Methods: All MDR suspects in five districts of New Delhi were referred to the laboratory from 1st October 2011 to 31st December 2012 as per criterion defined by Programmatic Management of Drug Resistant Tuberculosis (PMDT). GenoType MTBDRplus assay was performed on 2182 samples or cultures and mutations in the rpoB gene for rifampicin (RIF) and katG and inhA genes for isoniazid (INH) were analyzed. Results: A total of 366 (16.8%) MDR-TB cases were diagnosed. MDR rate was found to be 32%, 16.6% and 10.2% during criterion A, B and C respectively. The most common mutation detected for RIF was S531L (59.0%) and for INH was S315T1 (88.3%). Mutations S531L and S315T1 occurred significantly higher in MDR strains as compared to RIF mono-resistant and INH mono-resistant strains, respectively. Average laboratory turn-around time (TAT) for dispatch of result to districts for test conducted on samples was 4.4 days. Conclusion: GenoType MTBDRplus is a useful assay for rapid detection of MDR-TB. The common mutations for RIF and INH were similar to those seen in other regions. However, mutations determining MDR strains and mono-resistant strains differed significantly for both RIF and INH.

First-line anti-tubercular drug resistance of mycobacterial strains from re-treatment cases that were smear-positive at 4(th) month onwards under the Revised National Tuberculosis Control Program.

Background:Programmatic management of drug-resistant TB (PMDT) under the RNTCP is being implemented in West Bengal in a phased manner since 2011. During the initial years MDR-TB cases were identified based on criteria A. This study examines the first line anti-tubercular drug resistance pattern of mycobacteria cultured from sputum samples of MDR suspects who were retreatment cases smear positive from 4th month onwards.Materials and Methods:In the following retrospective record based study, data on Drug Sensitivity Testing (DST) of sputum samples of MDR suspects between September 2011 and August 2012 were collected from the IRL Kolkata and analysed. Sputum samples, collected in the districts maintaining adequate aseptic containment measures, were decontaminated and centrifuged and the sediment inoculated on LJ medium. Probable M. tuberculosis colonies were identified by typical colony characteristics and Ziehl-Neelsen (ZN) staining. Sensitivity of the four 1st line drugs (Streptomycin, Isoniazid, Ethambutol and Rifampicin) was deduced by the economic variant of the proportion method.Results:Of all the 917 MDR suspects whose sputum was examined, 64 mycobacteria culture positive strains (6.98%) were mono-resistant to any of the four first line anti-tubercular drugs. Among the mono-resistant strains 43 (4.69%) were resistant to Rifampicin while 12 (1.31%) were resistant to INH. There were a total 78 (8.51%) poly drug-resistant strains. MDR-TB strains were seen in 741 (80.81%) samples.Conclusion:The magnitude of drug resistance were very high among retreatment patients that were smear positive from 4th months onwards probably because of repeated courses of anti-tubercular drugs prior to drug sensitivity testing (DST). The decision of the PMDT to enlist all retreatment patients as MDR suspects at initiation will result in early identification and treatment of MDR-TB patients.

Fluoroquinolone resistance in Mycobacterium tuberculosis isolates from Pakistan 2010–2014: Implications for disease control

IntroductionFluoroquinolones (FQ) are an essential component of current and new regimens for the treatment of tuberculosis (TB). The 2014 Global TB report indicates a FQ resistance rate of 17% amongst multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (MTB) tested in 2013. There is, however, a paucity of FQ-resistance data from high burden countries. In this study the trend of FQ-resistance amongst MDR–MTB and non-MDR–MTB is analyzed over a four-and-a-half-year period (January 2010–July 2014). MethodsThis study was conducted at the Aga Khan University laboratory, a technical partner of the Pakistan National TB Program and part of the World Health Organization (WHO) Supra-national Laboratory Network for TB. The laboratory receives specimens from across the country through its peripheral collection units. MTB was isolated using standard methods. Susceptibility testing was performed using the agar proportion method with drug concentrations as recommended by Clinical Laboratory Institute Standards (CLSI). FQ susceptibilities were determined using ofloxacin (2μg/ml). MTB H37Rv was used as a control with each batch of susceptibility testing. MDR was defined as resistance to both isoniazid (0.2μg/ml) and rifampicin (1.0μg/ml). ResultsDuring the study period 14,711 MTB strains were isolated. Of these, 6403 (43.5%) were MDR and 8308 were non-MDR. FQ resistance in MDR strains ranged between 54% and 58%.Amongst non-MDR MTB strains, FQ resistance increased from 214/2059 (10.3%) in 2010 to 180/1049 (17.1%) in 2014. The proportion of FQ mono-resistant TB strains averaged at 10.5% of the non-MDR isolates during this period. ConclusionsFQ resistance in non-MDR–MTB strains with a considerable proportion of FQ mono-resistant strains in Pakistan is alarming. These data highlight the limited potential of empirical FQ usage for TB treatment in both MDR and non-MDR cases and the need to implement regular surveillance for FQ-resistance in MTB in the country. High FQ resistance amongst MTB isolates further emphasizes the importance of stewardship and the responsible use of FQs in particular, and antimicrobials in general in the country.

A proportion of mutations fixed in the genomes of in vitro selected isogenic drug-resistant Mycobacterium tuberculosis mutants can be detected as minority variants in the parent culture.

We studied genomic variation in a previously selected collection of isogenic Mycobacterium tuberculosis laboratory strains subjected to one or two rounds of antibiotic selection. Whole genome sequencing analysis identified eleven single, unique mutations (four synonymous, six non-synonymous, one intergenic), in addition to drug resistance-conferring mutations, that were fixed in the genomes of six monoresistant strains. Eight loci, present as minority variants (five non-synonymous, three synonymous) in the genome of the susceptible parent strain, became fixed in the genomes of multiple daughter strains. None of these mutations are known to be involved with drug resistance. Our results confirm previously observed genomic stability for M. tuberculosis, although the parent strain had accumulated allelic variants at multiple locations in an antibiotic-free in vitro environment. It is therefore likely to assume that these so-called hitchhiking mutations were co-selected and fixed in multiple daughter strains during antibiotic selection. The presence of multiple allelic variations, accumulated under non-selective conditions, which become fixed during subsequent selective steps, deserves attention. The wider availability of 'deep' sequencing methods could help to detect multiple bacterial (sub)populations within patients with high resolution and would therefore be useful in assisting in the detailed investigation of transmission chains.

Determination of in vitro synergy for dual antimicrobial therapy against resistant Neisseria gonorrhoeae using Etest and agar dilution

In response to antimicrobial resistance of Neisseria gonorrhoeae to last-resort extended-spectrum cephalosporins, combination therapy of azithromycin+ceftriaxone is now recommended. Dual therapy can be effective to treat monoresistant strains as well as multidrug-resistant strains, preferably employing the effect of in vitro synergy. As reports on in vitro synergy of azithromycin+ceftriaxone in N. gonorrhoeae are conflicting, in this study an evaluation of this combination was performed using a cross-wise Etest method and agar dilution. Synergy was defined as a fractional inhibitory concentration index (FICI) of ≤0.5. To identify other dual treatment options for gonorrhoea, in vitro synergy was evaluated for 65 dual antimicrobial combinations using Etest. Azithromycin, cefixime, ceftriaxone, colistin, ertapenem, fosfomycin, gentamicin, minocycline, moxifloxacin, rifampicin, spectinomycin and tigecycline were screened for synergy in all possible combinations. No synergy or antagonism was found for any of the 65 combinations. The geometric mean FICI ranged from 0.82 to 2.00. The mean FICI of azithromycin+ceftriaxone was 1.18 (Etest) and 0.55 (agar dilution). The difference between both methods did not result in a difference in interpretation of synergy. Ceftriaxone-resistant strain F89 was tested in all combinations and no synergy was found for any of them. Most importantly, the ceftriaxone minimum inhibitory concentration of F89 was not decreased below the breakpoint with any concentration of azithromycin.

In vitro and in vivo activities of the nitroimidazole TBA-354 against Mycobacterium tuberculosis.

Nitroimidazoles are a promising new class of antitubercular agents. The nitroimidazo-oxazole delamanid (OPC-67683, Deltyba) is in phase III trials for the treatment of multidrug-resistant tuberculosis, while the nitroimidazo-oxazine PA-824 is entering phase III for drug-sensitive and drug-resistant tuberculosis. TBA-354 (SN31354[(S)-2-nitro-6-((6-(4-trifluoromethoxy)phenyl)pyridine-3-yl)methoxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine]) is a pyridine-containing biaryl compound with exceptional efficacy against chronic murine tuberculosis and favorable bioavailability in preliminary rodent studies. It was selected as a potential next-generation antituberculosis nitroimidazole following an extensive medicinal chemistry effort. Here, we further evaluate the pharmacokinetic properties and activity of TBA-354 against Mycobacterium tuberculosis. TBA-354 is narrow spectrum and bactericidal in vitro against replicating and nonreplicating Mycobacterium tuberculosis, with potency similar to that of delamanid and greater than that of PA-824. The addition of serum protein or albumin does not significantly alter this activity. TBA-354 maintains activity against Mycobacterium tuberculosis H37Rv isogenic monoresistant strains and clinical drug-sensitive and drug-resistant isolates. Spontaneous resistant mutants appear at a frequency of 3 × 10(-7). In vitro studies and in vivo studies in mice confirm that TBA-354 has high bioavailability and a long elimination half-life. In vitro studies suggest a low risk of drug-drug interactions. Low-dose aerosol infection models of acute and chronic murine tuberculosis reveal time- and dose-dependent in vivo bactericidal activity that is at least as potent as that of delamanid and more potent than that of PA-824. Its superior potency and pharmacokinetic profile that predicts suitability for once-daily oral dosing suggest that TBA-354 be studied further for its potential as a next-generation nitroimidazole.

Mechanisms of fluoroquinolone monoresistance in Mycobacterium tuberculosis.

The gyrase mutations and efflux pumps confer fluoroquinolones (FQ) resistance in Mycobacterium tuberculosis. However, the contribution of two mechanisms in FQ mono-resistant M. tuberculosis is still unclear. Here, we investigated the contribution of gyrase mutations and efflux pumps to FQ resistance among 17 clinical FQ mono-resistant strains. Our data showed that gyrase mutations in gyrA QRDR were only responsible for four FQ mono-resistant strains. Mutations located in Ala90 and Asp94 of GyrA confer high-level LFX resistance, which can be explained by 3D modeling affinity change between GyrA and LFX. In addition, we found that a high level of efflux pump pstB transcripts may confer FQ resistance in two high-level FQ-resistant isolates (MIC ≥ 4 μg mL−1). The recombinant Escherichia coli with pstB revealed greatly increased MIC level from < 0.125 μg mL−1 to 2 μg mL−1. For the two isolates harboring high-level pstB transcripts, the presence of CCCP reduced LFX resistance to 1.0 μg mL−1. The transcriptional levels of pstB showed no significant difference among 10 clinical M. tuberculosis isolates with different drug susceptibility profiles. In conclusion, our findings demonstrate that both QRDR mutation and efflux pump mechanisms are responsible for monoresistance to FQ. PstB may serve as FQ-related efflux pumps in M. tuberculosis.

Ursolic and oleanolic acids as antimicrobial and immunomodulatory compounds for tuberculosis treatment

BackgroundNew alternatives for the treatment of Tuberculosis (TB) are urgently needed and medicinal plants represent a potential option. Chamaedora tepejilote and Lantana hispida are medicinal plants from Mexico and their hexanic extracts have shown antimycobacterial activity. Bioguided investigation of these extracts showed that the active compounds were ursolic acid (UA) and oleanolic acid (OA).MethodsThe activity of UA and OA against Mycobacterium tuberculosis H37Rv, four monoresistant strains, and two drug-resistant clinical isolates were determined by MABA test. The intracellular activity of UA and OA against M. tuberculosis H37Rv and a MDR clinical isolate were evaluated in a macrophage cell line. Finally, the antitubercular activity of UA and OA was tested in BALB/c mice infected with M. tuberculosis H37Rv or a MDR strain, by determining pulmonary bacilli loads, tissue damage by automated histomorphometry, and expression of IFN-γ, TNF-α, and iNOS by quantitative RT-PCR.ResultsThe in vitro assay showed that the UA/OA mixture has synergistic activity. The intracellular activity of these compounds against M. tuberculosis H37Rv and a MDR clinical isolate in a macrophage cell line showed that both compounds, alone and in combination, were active against intracellular mycobacteria even at low doses. Moreover, when both compounds were used to treat BALB/c mice with TB induced by H37Rv or MDR bacilli, a significant reduction of bacterial loads and pneumonia were observed compared to the control. Interestingly, animals treated with UA and OA showed a higher expression of IFN-γ and TNF-α in their lungs, than control animals.ConclusionUA and OA showed antimicrobial activity plus an immune-stimulatory effect that permitted the control of experimental pulmonary TB.

Antiprotozoal and antimycobacterial activities of Persea americana seeds

BackgroundPersea americana seeds are widely used in traditional Mexican medicine to treat rheumatism, asthma, infectious processes as well as diarrhea and dysentery caused by intestinal parasites.MethodsThe chloroformic and ethanolic extracts of P. americana seeds were prepared by maceration and their amoebicidal, giardicidal and trichomonicidal activity was evaluated. These extracts were also tested against Mycobacterium tuberculosis H37Rv, four mono-resistant and two multidrug resistant strains of M. tuberculosis as well as five non tuberculosis mycobacterium strains by MABA assay.ResultsThe chloroformic and ethanolic extracts of P. americana seeds showed significant activity against E. histolytica, G. lamblia and T. vaginalis (IC50 <0.634 μg/ml). The chloroformic extract inhibited the growth of M. tuberculosis H37Rv, M. tuberculosis MDR SIN 4 isolate, three M. tuberculosis H37Rv mono-resistant reference strains and four non tuberculosis mycobacteria (M. fortuitum, M. avium, M. smegmatis and M. absessus) showing MIC values ≤50 μg/ml. Contrariwise, the ethanolic extract affected only the growth of two mono-resistant strains of M. tuberculosis H37Rv and M. smegmatis (MIC ≤50 μg/ml).ConclusionsThe CHCl3 and EtOH seed extracts from P. americana showed amoebicidal and giardicidal activity. Importantly, the CHCl3 extract inhibited the growth of a MDR M. tuberculosis isolate and three out of four mono-resistant reference strains of M. tuberculosis H37Rv, showing a MIC = 50 μg/ml. This extract was also active against the NTM strains, M. fortuitum, M. avium, M. smegmatis and M. abscessus, with MIC values <50 μg/ml.

Chemical composition of hexane extract of Citrus aurantifolia and anti-Mycobacterium tuberculosis activity of some of its constituents.

The main aim of this study was to isolate and characterize the active compounds from the hexane extract of the fruit peels of Citrus aurantiifolia, which showed activity against one sensitive and three monoresistant (isoniazid, streptomycin or ethambutol) strains of Mycobacterium tuberculosis H37Rv. The active extract was fractionated by column chromatography, yielding the following major compounds: 5-geranyloxypsoralen (1); 5-geranyloxy-7-methoxycoumarin (2); 5,7-dimethoxycoumarin (3); 5-methoxypsoralen (4); and 5,8-dimethoxypsoralen (5). The structures of these compounds were elucidated by 1D and 2D NMR spectroscopy. In addition, GC-MS analysis of the hexane extract allowed the identification of 44 volatile compounds, being 5,7-dimethoxycoumarin (15.79%), 3-methyl-1,2-cyclopentanedione (8.27%), 1-methoxy-ciclohexene (8.0%), corylone (6.93%), palmitic acid (6.89%), 5,8-dimethoxypsoralen (6.08%), α-terpineol (5.97%), and umbelliferone (4.36%), the major constituents. Four isolated coumarins and 16 commercial compounds identified by GC-MS were tested against M. tuberculosis H37Rv and three multidrug-resistant M. tuberculosis strains using the Microplate Alamar Blue Assay. The constituents that showed activity against all strains were 5 (MICs = 25–50 μg/mL), 1 (MICs = 50–100 μg/mL), palmitic acid (MICs = 25–50 μg/mL), linoleic acid (MICs = 50–100 μg/mL), oleic acid (MICs = 100 μg/mL), 4-hexen-3-one (MICs = 50–100 μg/mL), and citral (MICs = 50–100 μg/mL). Compound 5 and palmitic acid were the most active ones. The antimycobacterial activity of the hexane extract of C. aurantifolia could be attributed to these compounds.

Complete atrioventricular block due to overdose of pregabalin

Pregabalin, a synthetic derivate of the inhibitory neurotransmitter γ-aminobutyric acid, shows antiepileptic, analgesic, anticonvulsant, anxiolytic, and sleep-modulating activities. The major advantage of pregabalin is its relative reliability, easy use, high tolerance, and lack of negative interaction with other drugs. A 65-year-old woman with medical histories of diabetes mellitus, lumbar spondylosis, diabetic nephropathy, chronic renal failure, and anemia of chronic disease was admitted with the complaint of dizziness and syncope. She had been taking pregabalin 300 mg daily for 8 months. Electrocardiogram revealed complete atrioventricular (AV) block and right bundle-brunch block with a heart rate of 39 per minute. Her creatinine was 1.8 mg/dL, and creatinine clearance was 50 mL/min. Pregabalin treatment was discontinued. Four days later, the complete AV block resolved spontaneously to Mobitz type II block and to sinus rhythm with right bundle-brunch block on the seventh day. To our knowledge, this is the first case of complete AV block associated with pregabalin. We believe that AV block occurred as a result of pregabalin's effect on L-type Ca++ channels in the heart. Pregabalin's different effects on electrocardiogram and on the heart in different individuals may have an association with the patterns of distribution of the L-type calcium channels in myocardium.

Contribution of efflux to the emergence of isoniazid and multidrug resistance in Mycobacterium tuberculosis.

Multidrug resistant (MDR) tuberculosis is caused by Mycobacterium tuberculosis resistant to isoniazid and rifampicin, the two most effective drugs used in tuberculosis therapy. Here, we investigated the mechanism by which resistance towards isoniazid develops and how overexpression of efflux pumps favors accumulation of mutations in isoniazid targets, thus establishing a MDR phenotype. The study was based on the in vitro induction of an isoniazid resistant phenotype by prolonged serial exposure of M. tuberculosis strains to the critical concentration of isoniazid employed for determination of drug susceptibility testing in clinical isolates. Results show that susceptible and rifampicin monoresistant strains exposed to this concentration become resistant to isoniazid after three weeks; and that resistance observed for the majority of these strains could be reduced by means of efflux pumps inhibitors. RT-qPCR assessment of efflux pump genes expression showed overexpression of all tested genes. Enhanced real-time efflux of ethidium bromide, a common efflux pump substrate, was also observed, showing a clear relation between overexpression of the genes and increased efflux pump function. Further exposure to isoniazid resulted in the selection and stabilization of spontaneous mutations and deletions in the katG gene along with sustained increased efflux activity. Together, results demonstrate the relevance of efflux pumps as one of the factors of isoniazid resistance in M. tuberculosis. These results support the hypothesis that activity of efflux pumps allows the maintenance of an isoniazid resistant population in a sub-optimally treated patient from which isoniazid genetically resistant mutants emerge. Therefore, the use of inhibitors of efflux should be considered in the development of new therapeutic strategies for preventing the emergence of MDR-TB during treatment.

Antibiotic resistance andcagAgene correlation: A looming crisis ofHelicobacter pylori

To determine antibiotic resistance of Helicobacter pylori (H. pylori) in Pakistan and its correlation with host and pathogen associated factors. A total of 178 strains of H. pylori were isolated from gastric biopsies of dyspeptic patients. Susceptibility patterns against first and second-line antibiotics were determined and trends of resistance were analyzed in relation to the sampling period, gastric conditions and cagA gene carriage. The effect of cagA gene on the acquisition of resistance was investigated by mutant selection assay. The observations showed that monoresistant strains were prevalent with rates of 89% for metronidazole, 36% for clarithromycin, 37% for amoxicillin, 18.5% for ofloxacin and 12% for tetracycline. Furthermore, clarithromycin resistance was on the rise from 2005 to 2008 (32% vs 38%, P = 0.004) and it is significantly observed in non ulcerative dyspeptic patients compared to gastritis, gastric ulcer and duodenal ulcer cases (53% vs 20%, 18% and 19%, P = 0.000). On the contrary, metronidazole and ofloxacin resistance were more common in gastritis and gastric ulcer cases. Distribution analysis and frequencies of resistant mutants in vitro correlated with the absence of cagA gene with metronidazole and ofloxacin resistance. The study confirms the alarming levels of antibiotic resistance associated with the degree of gastric inflammation and cagA gene carriage in H. pylori strains.

Antiprotozoal and Antimycobacterial Activities of Pure Compounds fromAristolochia elegansRhizomes

We analyzed the antimycobacterial activity of the hexane extract of rhizomes from Aristolochia elegans. Some compounds of this extract were purified and tested against a group of drug-resistant Mycobacterium tuberculosis strains. We also evaluated their antiprotozoal activities. The hexane extract was active against M. tuberculosis H37Rv at a MIC = 100 μg mL−1; the pure compounds eupomatenoid-1, fargesin, and (8R,8′R,9R)-cubebin were active against M. tuberculosis H37Rv (MIC = 50 μg mL−1), while fargesin presented activity against three monoresistant strains of M. tuberculosis H37Rv and a MDR clinical isolate of M. tuberculosis (MIC < 50 μg mL−1). Both the extract and eupomatenoid-1 were very active against E. histolytica and G. lamblia (IC50 < 0.624 μg mL−1); in contrast, fargesin and (8R,8′R,9R)-cubebin were moderately active (IC50 < 275 μg mL−1). In this context, two compounds responsible for the antimycobacterial presented by A. elegans are fargesin and cubebin, although others may exert this activity also. In addition to the antimycobacterial activity, the hexane extract has important activity against E. histolytica and G. lamblia, and eupomatenoid-1 is one of the compounds responsible for the antiparasite activity.

Rifampicin reduces susceptibility to ofloxacin in rifampicin-resistant Mycobacterium tuberculosis through efflux.

Central dogma suggests that rifampicin resistance in Mycobacterium tuberculosis develops solely through rpoB gene mutations. To determine whether rifampicin induces efflux pumps activation in rifampicin resistant M. tuberculosis strains thereby defining rifampicin resistance levels and reducing ofloxacin susceptibility. Rifampicin and/or ofloxacin minimum inhibitory concentrations (MICs) were determined in rifampicin resistant strains by culture in BACTEC 12B medium. Verapamil and reserpine were included to determine their effect on rifampicin and ofloxacin susceptibility. RT-qPCR was applied to assess expression of efflux pump/transporter genes after rifampicin exposure. To determine whether verapamil could restore susceptibility to first-line drugs, BALB/c mice were infected with a MDR-TB strain and treated with first-line drugs with/without verapamil. Rifampicin MICs varied independently of rpoB mutation and genetic background. Addition reserpine and verapamil significantly restored rifampicin susceptibility (p = 0.0000). RT-qPCR demonstrated that rifampicin induced differential expression of efflux/transporter genes in MDR-TB isolates. Incubation of rifampicin mono-resistant strains in rifampicin (2 μg/ml) for 7 days induced ofloxacin resistance (MIC > 2 μg/ml) in strains with an rpoB531 mutation. Ofloxacin susceptibility was restored by exposure to efflux pump inhibitors. Studies in BALB/c mice showed that verapamil in combination with first-line drugs significantly reduced pulmonary CFUs after 1 and 2 months treatment (p < 0.05). Exposure of rifampicin resistant M. tuberculosis strains to rifampicin can potentially compromise the efficacy of the second-line treatment regimens containing ofloxacin, thereby emphasising the need for rapid diagnostics to guide treatment. Efflux pump inhibitors have the potential to improve the efficacy of anti-tuberculosis drug treatment.

Spoligotype-Based Comparative Population Structure Analysis of Multidrug-Resistant and Isoniazid-Monoresistant Mycobacterium tuberculosis Complex Clinical Isolates in Poland

The spoligotyping-based population structure of multidrug-resistant (MDR) Mycobacterium tuberculosis strains isolated in Poland (n = 46), representing all culture-positive MDR tuberculosis (MDR-TB) cases, was compared to that of isoniazid (INH)-monoresistant strains (n = 71) isolated in 2004. The latter data set from a previous study (E. Augustynowicz-Kopeć, T. Jagielski, and Z. Zwolska, J. Clin. Microbiol. 2008, 46:4041-4044) represented 87% of all INH-monoresistant strains. The clustering rates and genotypic-diversity indexes for the 2 subpopulations were not significantly different (P = 0.05). The results were entered in the SITVIT2 database to assign specific shared type designations, corresponding genotypic lineages, and geographical distributions and compared to available data from neighboring countries (Germany, n = 704; Czech Republic, n = 530; Sweden, n = 379; Kaliningrad, Russia, n = 90) and strains from previous studies in Poland (n = 317). MDR strains resulted in 27 patterns (20 unique strains within the study and 7 clusters containing 2 to 6 isolates per cluster with a clustering rate of 56.5%) and belonged to the following genotypic lineages: ill-defined T family (28.3%), Haarlem (17.4%), Latin American and Mediterranean (LAM) (13%), Beijing (8.7%), S family (4.35%), and the X clade (2.17%). Comparison of the genetic structure of the MDR strains with that of INH-monoresistant strains showed that a total of 9 patterns were shared by both groups; these represented 1/3 of the MDR strains and 2/3 of the INH-monoresistant strains. Interestingly, 76.1% of the MDR isolates and 71.8% of the INH-resistant isolates yielded spoligotypes that were previously reported from Poland. The observation that nearly half of the spoligotypes identified among both MDR (48.1%) and INH-monoresistant (43.3%) M. tuberculosis isolates were present in Poland's neighboring countries suggested that a significant proportion of MDR and INH-resistant TB cases in Poland were caused by strains actively circulating in Poland or its neighbors. Our results corroborate the leading role of the T and Haarlem genotypes in the epidemiology of drug-resistant TB in Poland. Nevertheless, the LAM and Beijing family strains that infected, correspondingly, 13% and 9% of patients with MDR-TB were absent among the strains from patients with INH-monoresistant TB, suggesting that a proportion of MDR-TB cases in Poland are due to ongoing transmission of MDR clones exhibiting specific genotypes. Study of the population genetic relationships between MDR and INH-monoresistant strains by drawing minimum spanning trees showed that ill-defined T1 sublineage strains (1/3 of all INH-monoresistant strains), represented by its prototype, SIT53, constituted the central node of the tree, followed by strains belonging to the well-defined H3, H1, and S subgroups. However, the MDR group, in addition, contained LAM (n = 6) and Beijing (n = 4) lineage isolates. With the exception of the 4 Beijing lineage strains in the latter group and a single orphan isolate in the INH-monoresistant group, none of the remaining 112/117 isolates belonged to principal genetic group 1 (PGG1) in our study. Given the high rate of clustering and the near absence of immigrants in the study, the persistence of MDR-TB in Poland seems to result from active transmission of MDR strains within the autochthonous population, the bulk of it caused by evolutionarily recent tubercle bacilli.

Molecular characterization of Isoniazid and Rifampicin resistance strains of Mycobacterium tuberculosis isolated from new tuberculosis cases in Lagunes Region (Cote DIvoire)

Tuberculosis remains in the world an important problem of public health. This study objective was to investigate the genetic basis of resistance to Isoniazid and Rifampicin of Mycobacterium tuberculosis complex strains collected in Lagunes region, an area of high burden of tuberculosis. During primary resistance study, 196 smears positive new cases of tuberculosis were recruited in Lagunes region. Out of a sample of 31 strains, 17 were Isoniazid mono-resistant strains, 7 were multi-drug resistant (MDR) strains and 7 were susceptible to both Isoniazid and Rifampicin. Genotype MTBC assays and sequencing of mabA-inhA regulatory region, katG, inhA and rpoB genes were performed on all the strains. At least one mutation in the genes studied was found in 20 (83%) of the 24 resistant strains. Ser315Thr mutation was prominent in Isoniazid mono-resistant strains (9/13) and in MDR strains (7/8). Three of 16 Isoniazid resistant strains with Ser315Thr mutation had an additional mutation in the regulatory region. No mutation were found in 6 of the 7 susceptible strains. Molecular methods in tuberculosis laboratory may improve detection of tuberculosis case with drug resistance case. Key words: Mycobacterium tuberculosis complex, susceptibility testing, resistant genes.

M. tuberculosis genotypic diversity and drug susceptibility pattern in HIV- infected and non-HIV-infected patients in northern Tanzania

BackgroundTuberculosis (TB) is a major health problem and HIV is the major cause of the increase in TB. Sub-Saharan Africa is endemic for both TB and HIV infection. Determination of the prevalence of M. tuberculosis strains and their drug susceptibility is important for TB control.TB positive culture, BAL fluid or sputum samples from 130 patients were collected and genotyped. The spoligotypes were correlated with anti-tuberculous drug susceptibility in HIV-infected and non-HIV patients from Tanzania.ResultsOne-third of patients were TB/HIV co-infected. Forty-seven spoligotypes were identified.Fourteen isolates (10.8%) had new and unique spoligotypes while 116 isolates (89.2%) belonged to 33 known spoligotypes. The major spoligotypes contained nine clusters: CAS1-Kili 30.0%, LAM11- ZWE 14.6%, ND 9.2%, EAI 6.2%, Beijing 5.4%, T-undefined 4.6%, CAS1-Delhi 3.8%, T1 3.8% and LAM9 3.8%. Twelve (10.8%) of the 111 phenotypically tested strains were resistant to anti-TB drugs. Eight (7.2%) were monoresistant strains: 7 to isoniazid (INH) and one to streptomycin. Four strains (3.5%) were resistant to multiple drugs: one (0.9%) was resistant to INH and streptomycin and the other three (2.7%) were MDR strains: one was resistant to INH, rifampicin and ethambutol and two were resistant to all four anti-TB drugs. Mutation in the katG gene codon 315 and the rpoB hotspot region showed a low and high sensitivity, respectively, as predictor of phenotypic drug resistance.ConclusionCAS1-Kili and LAM11-ZWE were the most common families. Strains of the Beijing family and CAS1-Kili were not or least often associated with resistance, respectively. HIV status was not associated with spoligotypes, resistance or previous TB treatment.

Risk of Acquired Drug Resistance during Short-Course Directly Observed Treatment of Tuberculosis in an Area with High Levels of Drug Resistance

Data on the performance of standardized short-course directly observed treatment (DOTS) of tuberculosis (TB) in areas with high levels of drug resistance and on the potential impact of DOTS on amplification of resistance are limited. Therefore, we analyzed treatment results from a cross-sectional sample of patients with TB enrolled in a DOTS program in an area with high levels of drug resistance in Uzbekistan and Turkmenistan in Central Asia. Sputum samples for testing for susceptibility to 5 first-line drugs and for molecular typing were obtained from patients starting treatment in 8 districts. Patients with sputum smear results positive for TB at the end of the intensive phase of treatment and/or at 2 months into the continuation phase were tested again. RESULTS. Among 382 patients with diagnoses of TB, 62 did not respond well to treatment and were found to be infected with an identical Mycobacterium tuberculosis strain when tested again; 19 of these patients had strains that developed new or additional drug resistance. Amplification occurred in only 1.2% of patients with initially susceptible or monoresistant TB strains, but it occurred in 17% of those with polyresistant strains (but not multidrug-resistant strains, defined as strains with resistance to at least isoniazid and rifampicin) and in 7% of those with multidrug-resistant strains at diagnosis. Overall, 3.5% of the patients not initially infected with multidrug-resistant TB strains developed such strains during treatment. Amplification of resistance, however, was found only in polyresistant Beijing genotype strains. High levels of amplification of drug resistance demonstrated under well-established DOTS program conditions reinforce the need for implementation of DOTS-Plus for multidrug-resistant TB in areas with high levels of drug resistance. The strong association of Beijing genotype and amplification in situations of preexisting resistance is striking and may underlie the strong association between this genotype and drug resistance.

Tuberculosis in prisons

Sir—In their report on tuberculosis treatment in prisons, Rudi Coninx and colleagues (March 20, p 969) highlight the low rates of treatment success (54%) obtained in a situation where resistance to antituberculosis drugs is high, despite use of the directly observed (short-course) treatment strategy (DOTS). This finding leads the researchers to question the strategy, particularly the first-line regimens. What is surprising in their results is the low efficacy of treatment in individuals with susceptible bacilli. Results of drug susceptibility testing before treatment are available for only 101 (28%) of the 357 participants who completed treatment in prison. Of the 101 patients, 37 were failures (sputumpositive at the end of treatment), of whom three were not resistant and seven were resistant to a single drug before treatment. The treatment failure rate in Coninx’s study is 12% in susceptible patients and 28% in monoresistant patients (table). These results conflict with those reported by Mitchison and Nunn in a review of clinical trials that aimed to analyse the effect of primary resistance on treatment results. They showed that if the strain was susceptible to all antituberculosis drugs or monoresistant to isoniazid or streptomycin, the failure rate of treatment regimens that contain rifampicin for 6 months was less than 1% (table). Coninx and colleagues argue that the three failures with strains initially sensitive to all drugs may have been reinfected during treatment by a multiresistant strain. The same would need to be true for the seven monoresistant individuals. Even in a situation where the prevalence of HIV-1 is high, which does not appear to be the case here, this hypothesis does not seem reasonable. If the first-line regimens were truly so ineffective with susceptible or monoresistant strains, any antituberculosis treatment strategy would be vain. The third-line regimens, which are much less effective and more toxic, can in no way represent an alternative. These results question the data presented by Coninx and colleagues. Their report is more an analysis of routine data within a programme than a prospective study; there may have been bias in the recruitment of patients or errors in recording results. Furthermore, the prison context creates behaviour patterns that are unusual. As indicated by the researchers, patients with tuberculosis are better off than the other prisoners, if only from the point of view of diet. As a result, it is not in their interests to be cured. Although they are theoretically under DOTS, do prisoners really swallow the drugs? Do the sputum samples at the end of treatment belong to the right patients? Whatever the reasons for these failures, changing the first-line regimen itself will not provide better results. If the results for susceptible and monoresistant strains are doubtful, what could one say of the others? The difficulty posed by cases of multidrug-resistant tuberculosis in exUSSR prisons is serious. This issue requires particular attention, starting with a better understanding of what causes these multiresistant cases. The question is an important one, and it is not groundless criticism of DOTS, which has proved successful e l s e w h e r e , , 5 that will help find a solution to the problem.