Frequency of drug resistant tuberculosis in Poland in 2000 as compared to 1997

Prevalence of drug resistance to one drug and multidrug resistance--MDR in different categories of tuberculosis patients is an important information about the susceptibility pattern of Mycobacterium tuberculosis isolates against antimycobacterial drugs. Poland joined WHO/IUATLD global project on TB drug resistance surveillance, and carried out in 1996/1997 the first prospective survey, simultaneously on primary and acquired drug resistance. This study is repeated in 2000 according to the WHO/IUATLD protocol. The programme covered the whole country. A total of 16 regional centers participated in the co-operative study. 3705 questionnaires and cultures were obtained from patients who excreted TB bacilli during the 12-months from 1 st. January to 31st December 2000. Drug resistance tests to INH, RMP, SM, EMB were performed on Lowenstein-Jensen medium according to the proportion method or/and Bactec 460 TB system. 3705 TB patients (3037 new and 668 treated cases) bacteriologically confirmed by culture were included in one-year study. Primary resistance to any drug was found in 6.12% (CI 5.27-6.56) of new cases. 35 patients (1.15%, CI 0.77-1.35) were infected with MDR strains. Acquired resistance to any drug was found in 16.6% (CI 5.27-6.56), 8.53% (CL 6.41-9.6) of the patients who excreted MDR strains. We have found increased resistance from 3.6% in 1997 to 6.12% (p < 0.001) in 2000 and MDR from 0.6% in 1997 to 1.15% (p < 0.001) in 2000 in untreated tuberculosis patients in Poland. The rate of resistance in the group of treated TB patients was very similar in 1997 (17.0%) and in 2000 (16.6%); except 20% increase of MDR cases--(7.0% in 1997, and 8.53% in 2000). We observed an increase in drug resistant tuberculosis first time during 40 years long period of its monitoring. Regular monitoring of drug resistance in TB patients in Poland is recommended.     

Magnitude of Gene Mutations Conferring Drug Resistance in Mycobacterium Tuberculosis Isolates from Lymph Node Aspirates in Ethiopia

Objective: Resistance to drugs is due to particular genomic mutations in the specific genes of Mycobacterium tuberculosis. Timely genetic characterization will allow identification of resistance mutations that will optimize an effective antibiotic treatment regimen. We determine the magnitude of gene mutations conferring resistance to isoniazid (INH), rifampicin (RMP) and ethambutol (EMB) among tuberculosis (TB) lymphadenitis patients.Methods: A cross sectional prospective study was conducted among 226 M.tuberculosis isolates from culture positive lymph node aspirates collected from TB lymphadenitis patients between April 2012 and May 2012. Detection of mutations conferring resistance to drugs was carried out using GenoType^® MTBDRplus and GenoType® MTBDRsl assay.Results: Out of the 226 strains, mutations conferring resistance to INH, RMP, multidrug resistance tuberculosis (MDR-TB) and EMB were 8, 3, 2 and 2 isolates, respectively. There was no isolated strain that showed mutation in the inhA promoter region gene. All INH resistant strains had mutations in the katG gene at codon 315 with amino acid change of S315T1. Among rifampicin resistant strains, two isolates displayed mutations at codon 531 in the rpoB gene with amino acid change of S531L and one isolate was by omission of wild type probes at Q513L. According to mutations associated with ethambutol resistance, all of the isolates had mutations in the embB gene with aminoacid change of M306I. All isolates resistant to INH, RMP and MDR using BacT/AlerT 3D system were correctly identified by GenoType® MTBDRplus assay.Conclusion: We observed mutations conferring resistance to INH at S315T1 of the katG gene, RMP at S531L and Q513L in the rpoB genes and EMB at M306I of the embB gene. In the absence of conventional drug susceptibility testing, the effort to develop easy, rapid and cost effective molecular assays for drug resistance TB monitoring is definitely desirable and the GenoType® MTBDRplus assay was found to be a useful method for diagnosis of resistance to INH, RMP and MDR from lymph node aspirates. Further molecular cluster analysis to determine transmission dynamics of mutated strain is required.     

Contribution of rural-to-urban migration in the prevalence of drug resistant tuberculosis in China

Increased drug resistance rates to the first-line anti-tuberculosis drugs and multidrug resistance (MDR) were observed in China. The objectives of this study were to determine the prevalence and risk factors for drug-resistant tuberculosis (TB) in urban China and, more specifically, to determine the contribution of migration to case burden and drug resistance rates of urban cities. A facility-based epidemiological study of all active TB patients reported in the four districts of Shanghai and Ningbo between April 1, 2008 and March 31, 2009 was conducted. Residents had significantly higher drug-resistance rates than migrants (any drug resistance: 29.8% vs. 23.5%, respectively, P = 0.038; MDR: 10.9% vs. 6.1%, P = 0.048). Previously treated migrant patients were more likely to harbor drug-resistant TB and MDR-TB than new migrant cases, with adjusted odds ratios of 3.85 and 6.52, respectively. In total, 46.2% of the previously treated cases were resistant to INH, 38.5% to SM, 33.3% to RMP and 30.8% to EMB, while 13.1%, 17.5%, 7.0% and 6.8% of new cases were resistant to the four agents, respectively. To prevent the transmission of drug-resistant TB among migrants and residents, improved case management and appropriate treatment regimens should be sustained to prevent acquired drug resistance.     

Evaluation of a novel kit for use with the BacT/ALERT 3D system for drug susceptibility testing of Mycobacterium tuberculosis

We evaluated a new protocol for the BacT/ALERT MB susceptibility test (bioMérieux Inc., Durham, NC) using 80 Mycobacterium tuberculosis WHO challenge panel strains. The drug susceptibility profiles of these strains are well characterized, and consensus drug resistance results have been established after tests were performed at around 20 international reference laboratories using recommended reference drug susceptibility techniques. Strains were tested according to the bioMérieux protocol using the following critical concentrations: rifampin (RIF), 0.9 mg/liter; isoniazid (INH), 0.4 and 0.09 mg/liter; and ethambutol (EMB), 1.8 mg/liter. The BacT/ALERT system detected 36/37 RIF-resistant strains. For INH (low concentration), 59/59 resistant strains were detected, and for EMB, 34/34 resistant strains were detected. Thus, the sensitivities were 97%, 100%, and 100% for RIF, INH, and EMB, respectively. The corresponding specificities were 100%, 95%, and 98%, respectively, for the same drugs. As soon as the BacT/ALERT MP seed bottle flagged positive, the median time to obtain a susceptibility results was 7.8 days. The results show good concordance with the consensus results of the international reference laboratories and demonstrate that BacT/ALERT 3D should be considered as an alternative method for rapid and automated drug susceptibility testing of M. tuberculosis.     

Susceptibility of M. tuberculosis to antituberculosis drugs as determined by two methods, in Sucre state, Venezuela

The objective of this study was to evaluate the resistance to isoniazid (INH), rifampicin (RIF), streptomycin (STR) and ethambutol (EMB), with the Canetti's proportions method (PM) and the nitrate reductase assay (NRA) of 59 clinical strains of Mycobacterium tuberculosis, isolated in the period of august 2005 to december 2006, in Sucre state, Venezuela. Primary and acquired drug resistance was 6.3% and 14.3%, respectively. Only one strain was found to be multidrug resistant (MDR). The overall agreement between the NRA and PM was 100% for INH, RIF and EMB, and 96% for STR. The time to obtain results was 10 to 14 days for the NRA, compared to 42 days for the PM. The NRA was easy to perform and therefore represents a useful tool for rapid and accurate determination of drug-resistant M. tuberculosis. The sequence of the rpoB gene of the RIF resistant strain demonstrated a never described mutation (change in the codon 456; TCG > CAG) in the hypervariable region of 81 base pairs where most of the mutations of the RIF resistant strains have been reported. Comparison of our results with those of the last resistance prevalence study carried out in the years 1998-1999, shows a decrease in the studied area.     

分析5种结核杆菌耐药基因突变与耐药水平的关系

目的：分析5种结核杆菌（M.tb)耐药基因突变的情况，了解基因突变和耐药水平的关系。方法：134例临床分离株均做传统梯度药敏试验和聚合酶链反应－单链构象多态性I（PCR－SSCP）试验。结果：耐PZA(pncA),SM(rpsL),REP(rpoB),INH(katG),EMB(embB)基因突变率分别为42．7％、72％、78％、69％和43．9％，其中，上述高耐株基因突变率分别为70％、87．2％、93．4％、80％、43．9％。低耐株分别为12．5％、28．5％、45．4％、18．7％，EMB在低耐区无基因突变，结论：M.tb耐药基因变与耐药水平联系密切，多数M.tb耐药基因突变易发生在高耐药区，也有少数菌基因突变易发生在低耐药区。     

Early detection of Pre-XDR TB with line probe assay in a high TB burden country

BackgroundWorldwide, tuberculosis (TB) is one of the top 10 causes of death. Drug resistant tuberculosis has lately become a major public health problem that threatens progress made in Tuberculosis (TB) care and control worldwide. The aim of this study was to determine the prevalence of Pre-extensive drug resistant TB among MDR TB in North Central of Nigeria.MethodsThis study was conducted from October, 2018 to August, 2019 with 150 samples. In Nigeria, guidelines for DR-TB as recommended by WHO is followed. All the samples from the patients who gave their consent were transported to a zonal reference TB laboratory (ZRL).ResultsMean age was 38.6 ± 13.4 years with peak age at 35–44. Out of these 103 samples processed with LPA, 101(98%) were rifampicin resistant and 2 were rifampicin sensitive, 99(96%) were INH resistant and 4 (4%) were INH sensitive, 5(5%) were fluoroquinolone resistant, 98(95%) were fluoroquinolone sensitive, 12 (12%) were Aminoglycoside + Capreomycin resistant, 91(83%) were Aminoglycoside + Capreomycin sensitive.ConclusionMultidrug resistant TB and its severe forms (Pre-extensive & extensively drug resistant TB) can be detected early with rapid tool- Line Probe Assay rapid and prevented timely by early initiation on treatment.     

Characterisation of rpsL, rrs and embB mutations associated with streptomycin and ethambutol resistance in Mycobacterium tuberculosis

In order to characterise molecular mechanisms of first-line drug resistance in Mycobacterium tuberculosis and to evaluate the use of molecular markers of resistance (gene point mutations), we analysed 66 multi-drug-resistant (MDR) isolates from Latvian tuberculosis patients. They were all resistant to rifampin (RIF), isoniazid (INH) and streptomycin (SM), and 33 were resistant to ethambutol (EMB). Enzymatic digestion by MboII and nucleotide sequencing of the rpsL gene fragment detected a single nucleotide substitution K43R in 40 (61%) of the 66 SM-resistant M. tuberculosis isolates. Of the other 26 SM-resistant isolates, 16 (24%) had mutations at positions 513A-->C and 516C-->T of the rrs gene and 10 (15%) had the wild-type sequence. The single-stranded DNA conformation polymorphism (SSCP) method was used to detect mutations in the embB gene associated with EMB resistance. Substitutions in the embB gene were found by SSCP analysis in 15 (45%) and by sequencing in 17 (52%) of the 33 EMB-resistant isolates. Surprisingly, SSCP revealed a nucleotide mutation at codon M306 in five (15%) of 33 in vitro EMB-susceptible MDR isolates.     

Concordance between Molecular and Phenotypic Testing of Mycobacterium tuberculosis Complex Isolates for Resistance to Rifampin and Isoniazid in the United States

Multidrug-resistant (MDR) isolates of Mycobacterium tuberculosis complex (MTBC) are defined by resistance to at least rifampin (RMP) and isoniazid (INH). Rapid and accurate detection of multidrug resistance is essential for effective treatment and interruption of disease transmission of tuberculosis (TB). Overdiagnosis of MDR TB may result in treatment with second-line drugs that are more costly, less effective, and more poorly tolerated than first-line drugs. CDC offers rapid confirmation of MDR TB by the molecular detection of drug resistance (MDDR) for mutations associated with resistance to RMP and INH along with analysis for resistance to other first-line and second-line drugs. Simultaneously, CDC does growth-based phenotypic drug susceptibility testing (DST) by the indirect agar proportion method for a panel of first-line and second-line antituberculosis drugs. We reviewed discordance between molecular and phenotypic DST for INH and RMP for 285 isolates submitted as MTBC to CDC from September 2009 to February 2011. We compared CDC''s results with those from the submitting public health laboratories (PHL). Concordances between molecular and phenotypic testing at CDC were 97.4% for RMP and 92.5% for INH resistance. Concordances between CDC''s molecular testing and PHL DST results were 93.9% for RMP and 90.0% for INH. Overall concordance between CDC molecular and PHL DST results was 91.7% for RMP and INH collectively. Discordance was primarily attributable to the absence of known INH resistance mutations in isolates found to be INH resistant by DST and detection of mutations associated with low-level RMP resistance in isolates that were RMP susceptible by phenotypic DST. Both molecular and phenotypic test results should be considered for the diagnosis of MDR TB.     

Multicenter Evaluation of Fully Automated BACTEC Mycobacteria Growth Indicator Tube 960 System for Susceptibility Testing of Mycobacterium tuberculosis

The reliability of the BACTEC Mycobacteria Growth Indicator Tube (MGIT) 960 system for testing of Mycobacterium tuberculosis susceptibility to the three front-line drugs (isoniazid [INH], rifampin [RIF], and ethambutol [EMB]) plus streptomycin (STR) was compared to that of the BACTEC 460 TB system. The proportion method was used to resolve discrepant results by an independent arbiter. One hundred and ten strains were tested with an overall agreement of 93.5%. Discrepant results were obtained for seven strains (6.4%) with INH (resistant by BACTEC MGIT 960; susceptible by BACTEC 460 TB), for one strain (0.9%) with RIF (resistant by BACTEC MGIT 960; susceptible by BACTEC 460 TB), for seven strains (6.4%) with EMB (six resistant by BACTEC MGIT 960 and susceptible by BACTEC 460 TB; one susceptible by BACTEC MGIT 960 and resistant by BACTEC 460 TB), and for 19 strains (17.3%) with STR (resistant by BACTEC MGIT 960 and susceptible by BACTEC 460 TB). After resolution of discrepant results, the sensitivity of the BACTEC MGIT 960 system was 100% for all four drugs and specificity ranged from 89.8% for STR to 100% for RIF. Turnaround times were 4.6 to 11.7 days (median, 6.5 days) for BACTEC MGIT 960 and 4.0 to 10.0 days (median, 7.0 days) for BACTEC 460 TB. These data demonstrate that the fully automated and nonradiometric BACTEC MGIT 960 system is an accurate method for rapid susceptibility testing of M. tuberculosis.     

Current interest of isoniazid in the chemotherapy of tuberculosis in the light of its in vitro activity

Isoniazid is one of the most useful drugs for the treatment of tuberculosis. However, in the last few years treatment with this drug has become long, complicated, and occasionally inefficient because of the increasing number of cases with resistance. The aim of our work was to know the isoniazid resistance level of 1,496 Mycobacterium tuberculosis strains that were submitted to the Mycobacteria Reference Center, Córdoba, during the years 1993-2000. A total of 1,186 strains were from pulmonary sources and 196 from extrapulmonary sources; no source was provided for 114 strains. All M. tuberculosis strains were previously identified by different methods. For sensitivity testing, the BACTEC 460 TB system was used initially and then the ESP II system was also used. The control strains used in this study were ATCC27294 (sensitive to SM, RP, EB, and INH) and ATCC35822, resistant to INH. The overall resistance rate obtained was 14.8%, of which 2.3% and 1.4% accounted for primary and secondary resistance types, respectively. Ninety-six out of the 221 resistant strains were resistant to INH only, and 8 strains were resistant to INH plus SM. A total of 117 multiresistant strains were found. An apparent increase in the resistance rate to INH in the last few years was observed. Secondary resistance has decreased, whereas primary resistance has increased. A continuous surveillance of resistance is required and, therefore, any patient with tuberculosis should undergo sensitivity testing to confirm therapy to be used.     

The use of E-test for the drug susceptibility testing of Mycobacterium tuberculosis – A solution or an illusion?

Aim: To evaluate E-test as a tool for rapid determination of drug susceptibility against the conventional LJ method focusing on reliability, expense, ease of standardization and performance of the technique in low resource settings. Materials and Methods: A total of 74 clinical isolates (2004-2005) of Mycobacterium tuberculosis were tested using E-test for susceptibility to streptomycin (STM), isoniazid (INH), rifampicin (RIF) and ethambutol (EMB) by E-strip and LJ (LJPM) proportion methods. Results: The LJPM method, the gold standard, detected resistance against STM in 16.2%, INH in 40.5%, RIF in 18.9% and EMB in 27% cases. In comparison, the resistance values showed by E-test was 66.67% for STM, 57.14% for INH 71.43% for RIF and 80% for EMB. The susceptible correlation was 90.32% for STM, 73.91% for INH, 93.33% for RIF and 59.26% for EMB. E-test correctly identified only eight of the 12 (66.6%) MDR isolates and wrongly identified four isolates which were not MDR. The overall agreement between the two methods was only 48.6%. Resistant isolates showed false positive resistance observed while using E-strip towards all the drugs. Conclusion: E-strips are not quite feasible as a replacement for LJ-proportion method on a large scale due to high risk of cross contamination, laboratory infection, expense associated with it and high false positive resistance observed to all first line drugs. However, the good correlation observed for RIF between the two methods indicates that E-test could contribute to the role in rapid screening of MDR TB isolates as rifampicin mutations are invariably observed in MDR TB isolates.     

Rapid, standardized method for determination of Mycobacterium tuberculosis drug susceptibility by use of mycolic acid analysis

Multidrug-resistant (MDR) Mycobacterium tuberculosis and extrensively drug-resistant (XDR) M. tuberculosis are emerging public health threats whose threats are compounded by the fact that current techniques for testing the susceptibility of M. tuberculosis require several days to weeks to complete. We investigated the use of high-performance liquid chromatography (HPLC)-based quantitation of mycolic acids as a means of rapidly determining drug resistance and susceptibility in M. tuberculosis. Standard susceptibility testing and determination of the MICs of drug-susceptible (n = 26) and drug-resistant M. tuberculosis strains, including MDR M. tuberculosis strains (n = 34), were performed by using the Bactec radiometric growth system as the reference method. The HPLC-based susceptibilities of the current first-line drugs, isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA), were determined. The vials were incubated for 72 h, and aliquots were removed for HPLC analysis by using the Sherlock mycobacterial identification system. HPLC quantitation of total mycolic acid peaks (TMAPs) was performed with treated and untreated cultures. At 72 h, the levels of agreement of the HPLC method with the reference method were 99.5% for INH, EMB, and PZA and 98.7% for RIF. The inter- and intra-assay reproducibilities varied by drug, with an average precision of 13.4%. In summary, quantitation of TMAPs is a rapid, sensitive, and accurate method for antibiotic susceptibility testing of all first-line drugs currently used against M. tuberculosis and offers the potential of providing susceptibility testing results within hours, rather than days or weeks, for clinical M. tuberculosis isolates.     

Use of the genotype MTBDR assay for rapid detection of rifampin and isoniazid resistance in Mycobacterium tuberculosis complex isolates

A commercially available DNA strip assay (Genotype MTBDR; Hain Lifescience, Nehren, Germany) was evaluated for its ability to detect mutations conferring resistance to rifampin (RMP) and isoniazid (INH) in clinical Mycobacterium tuberculosis complex isolates. A total of 103 multidrug-resistant (MDR; i.e., at least resistant to RMP and INH) and 40 fully susceptible strains isolated in Germany in 2001 in which resistance mutations have been previously defined by DNA sequencing and real-time PCR analysis were investigated. The Genotype MTBDR assay identified 102 of the 103 MDR strains with mutations in the rpoB gene (99%) and 91 strains (88.4%) with mutations in codon 315 of katG. All 40 susceptible strains showed a wild-type MTBDR hybridization pattern. The concordance between the MTBDR assay and the DNA sequencing results was 100%. Compared to conventional drug susceptibility testing, the sensitivity and specificity were 99 and 100% for RMP resistance and 88.4 and 100% for INH resistance, respectively. In conclusion, the MTBDR assay is a rapid and easy-to-perform test for the detection of the most common mutations found in MDR M. tuberculosis strains that can readily be included in a routine laboratory work flow.     

Multidrug-resistant Pulmonary Tuberculosis Among Young Korean Soldiers in a Communal Setting

The goal of this study was to evaluate the prevalence of first-line anti-tuberculosis drug resistance and risk factors associated with multidrug-resistant tuberculosis (MDR TB) among young soldiers in the Korean military, which has a strict tuberculosis control program. All patients with culture-confirmed pulmonary tuberculosis during their service at the Armed Forces Capital Hospital from January 2001 to December 2006 were enrolled in the study. Drug resistant Mycobacterium tuberculosis was isolated from 18 patients (12.2%) and multidrug-resistant M. tuberculosis was isolated from 12 patients (8.1%). Previous treatment of tuberculosis and the presence of a cavity on the patient''s chest computed tomography scan were associated with MDR TB; military rank, smoking habits, and positive acid-fast bacilli smears were not associated with MDR TB. In a multiple logistic regression analysis, previous treatment of tuberculosis was a significant independent risk factor for MDR TB (odds ratio 6.12, 95% confidence interval 1.53-24.46). The prevalence of drug resistant tuberculosis among young soldiers in the Korean military was moderately high and the majority of resistant cases were found in patients who had undergone previous treatment of tuberculosis. Based on our results, we suggest that relapsed tuberculosis cases within communal settings should be cautiously managed until the drug susceptibility tests report is completed, even if previous treatment results were satisfactory.     

Performance of the GenoType? MTBDRPlus assay in routine settings: a multicenter study

Former Soviet Union countries including the Baltic States (Latvia, Lithuania, and Estonia) are hot spots for an emerging epidemic of drug resistant tuberculosis (TB). As a part of the development of a co-ordinated network of centers for diagnostic trials across Eastern Europe we conducted a retrospective multicenter analysis of the performance of the GenoType? MTBDRPlus assay for TB identification and susceptibility to isoniazid (INH) and rifampicin (RIF) in routine settings. A total of 1,045 primary samples, 1045?TB cultures derived from these specimens and 306 separate M. tuberculosis isolates tested in 2007-2010 at four participating sites (Tartu, Estonia; Riga, Latvia; Vilnius, Lithuania; and Samara, Russian Federation) were included in the analysis. The pooled sensitivity and specificity values for RIF and INH were 95.3% and 95.5%, 89.9 and 87.1%, respectively; there were no statistically significant variations in performance across sites. The proportion of multidrug resistant (MDR) strains in the collections ranged from 21.8% (in Estonia) to 55.9% (in Russia). In a routine non-trial context, the assay reliably detected both rifampicin and isoniazid resistance. The absence of statistically significant differences between sites suggested that the comparable performance obtained using these assays has helped demonstrate the formation of a successful diagnostic trial network.     

Extremely high prevalence of multidrug resistant tuberculosis in Murmansk, Russia: a population-based study

Drug resistance and molecular epidemiology of tuberculosis (TB) in the Murmansk region was investigated in a 2-year, population-based surveillance of the civilian population. During 2003 and 2004, isolates from all culture-positive cases were collected (n?=?1,226). Prevalence of multi-drug resistance (MDR) was extremely high, as 114 out of 439 new cases (26.0%), and 574 out of 787 previously treated cases (72.9%) were resistant to at least isoniazid (INH) and rifampin (RIF). Spoligotyping of the primary MDR-TB isolates revealed that most isolates grouped to the Beijing SIT1 genotype (n?=?91, 79.8%). Isolates of this genotype were further analyzed by IS6110 RFLP. Sequencing of gene targets associated with INH and RIF resistance further showed that the MDR-TB strains are highly homogeneous as 78% of the MDR, SIT1 strains had the same resistance-conferring mutations. The genetic homogeneity of the MDR-TB strains indicates that they are actively transmitted in Murmansk.     

Molecular characterization and drug resistance patterns of strains of Mycobacterium tuberculosis isolated from patients in an AIDS counseling center in Port-au-Prince,Haiti: a 1-year study

Tuberculosis (TB) is one of the most common opportunistic diseases that appear among human immunodeficiency virus (HIV)-positive patients in Haiti. In this context the probable emergence of multidrug-resistant (MDR) strains of Mycobacterium tuberculosis is of great epidemiological concern. However, as routine culture of M. tuberculosis and drug susceptibility testing are not performed in Haiti, it has not been possible so far to evaluate the rate of drug resistance among M. tuberculosis isolates from circulating TB cases. This report describes the first study on the molecular typing and drug resistance of M. tuberculosis isolates from patients with culture-positive pulmonary tuberculosis monitored at the GHESKIO Centers in Haiti during the year 2000. Clinical, epidemiological, and drug susceptibility testing results were available for 157 patients with confirmed cases of TB, with a total of 8.9% of patients harboring MDR M. tuberculosis. A significant association between the occurrence of resistance and previous TB treatment was observed (P < 0.001), suggesting that a previous history of TB treatment was a risk factor associated with MDR TB in Haiti. The DNAs of individual isolates from 106 samples were available and were typed by spoligotyping and determination of the variable number of tandem DNA repeats. Both typing methods provided interpretable results for 96 isolates, and the clusters observed were further confirmed by ligation-mediated PCR to define potential cases of active transmission. Thirty-three (34%) of the isolates were found to be grouped into 11 clusters with two or more identical patterns. However, an assessment of risk factors (sex, HIV positivity, previous treatment, drug resistance) showed that none was significantly associated with the active transmission of TB. These observations suggest that acquired MDR TB is prevalent in Haiti and may be associated with compliance issues during TB treatment since prior TB therapy is the strongest risk factor associated with MDR TB. Prevention of TB transmission in Haiti should target active case investigation, routine detection of drug resistance, and adequate treatment of patients. The use of directly observed short-course therapy should be enforced throughout the country; and relapses, reactivations, or newly acquired infections should be discriminated by genotyping methods.     

Declining drug resistance of Mycobacterium tuberculosis isolates from elderly patients in Taiwan, 2000–2008

We retrospectively investigated the prevalence of drug resistance in Mycobacterium tuberculosis (MTB) isolates recovered from elderly patients and compared the drug resistance patterns between the elderly (≥65 years old) and adult (15–64 years old) patients. Data on the prevalence of drug resistance in clinical and non-duplicate isolates of MTB recovered from 2000 to 2008 were evaluated. Among the 3,186 non-duplicate MTB isolates found during the study period, 1,497 isolates were recovered from elderly patients. Thirty-eight (2.54%) isolates were multidrug-resistant tuberculosis (MDRTB). The rates of resistance to isoniazid (INH), rifampicin (RIF), ethambutol (EMB), streptomycin (SM), ofloxacin, rifabutin, any one drug-resistant (ADR), and multidrug-resistant (MDR) were significantly lower in isolates from the elderly than from adults (p < 0.05). Significant decreasing trends in resistance rates to EMB, SM, at least any one of the four first-line agents (ADR), and MDRTB were observed (p < 0.05) . In conclusion, elderly patients had a lower rate of anti-TB drug resistance than adults and a decreasing overall trend of anti-TB drug resistance was found in the elderly in recent years, but the higher rate of MDRTB in Taiwan continues to present a challenge for the control of TB in the elderly.     

Performance of the Genotype® MTBDRPlus assay in the diagnosis of tuberculosis and drug resistance in Samara, Russian Federation

Background

Russia is a high tuberculosis (TB) burden country with a high prevalence of multidrug resistant tuberculosis (MDRTB). Molecular assays for detection of MDRTB on clinical specimens are not widely available in Russia.

Results

We performed an evaluation of the GenoType^® MTBDRplus assay (HAIN Lifescience GmbH, Germany) on a total of 168 sputum specimens from individual patients at a public health laboratory in Central Russia, as a model of a middle income site in a region with high levels of drug resistance. Phenotypic drug resistance tests (DST) were performed on cultures derived from the same sputum specimens using the BACTEC 960 liquid media system. Interpretable GenoType^® MTBDRplus results were obtained for 154(91.7%) specimens with readability rates significantly higher in sputum specimens graded 2+ and 3+ compared to 1+ (RR = 1.17 95%CI 1.04–1.32). The sensitivity and specificity of the assay for the detection of rifampicin (RIF) and isoniazid (INH) resistance and MDR was 96.2%, 97.4%, 97.1% and 90.7%, 83.3%, 88.9% respectively. Mutations in codon 531 of the rpoB gene and codon 315 of the katG gene dominated in RIF and INH resistant strains respectively. Disagreements between phenotypical and molecular tests results (12 samples) could be explained by the presence of rare mutations in strains circulating in Russia and simultaneous presence of resistant and sensitive bacilli in sputum specimens (heteroresistance).

Conclusion

High sensitivity, short turnaround times and the potential for screening large numbers of specimens rapidly, make the GenoType^® MTBDRplus assay suitable as a first-line screening assay for drug resistant TB.