Mutations In rpoB Gene Research Articles

Construction and characterization of different MutS fusion proteins as recognition elements of DNA chip for detection of DNA mutations

Three MutS fusion systems were designed as the mutation recognition and signal elements of DNA chips for detection of DNA mutations. The expression vectors containing the encoding sequences of three recombinant proteins, Trx-His6-GFP-(Ser-Gly)6-MutS (THGLM), Trx-His6-(Ser-Gly)6-Strep tagII-(Ser-Gly)6-MutS (THLSLM) and Trx-His6-(Ser-Gly)6-MutS (THLM), were constructed by gene slicing in vitro. THGLM, THLSLM and THLM were then expressed in Escherichia coli AD494(DE3), respectively. SDS-PAGE analysis revealed that each of the expected proteins was approximately 30% of the total bacterial proteins. The recombinant proteins were purified to the purity over 90% by immobilized metal (Co2+) chelation affinity chromatography. Bioactivity assay indicated that three fusion proteins retained the mismatch-binding activity and the functions of other fusion partners. DNA chips arrayed both mismatched and unpaired DNA oligonucleotides as well as rpoB gene from Mycobacterium tuberculosis were prepared. THGLM, THLSLM and THLM that was labeled with Fluorolinktrade mark Cy3 reactive dye, were then used as both mutation recognition and labeling elements of DNA chips. The resulting DNA chips were used to detect the mismatched and unpaired mutations in the synthesized oligonucleotides and single base mutation in rpoB gene of M. tuberculosis that is resistant to rifamycin.

RpoB Gene Mutations in Rifampin-Resistant Mycobacterium tuberculosis Strains Isolated in the Aegean Region of Turkey

Although DNA sequencing method has not been used routinely for detecting resistance of Mycobacterium tuberculosis to antituberculosis drugs, it is suggested for the investigation of gene mutations causing resistance. Using DNA sequencing (Automated Applied Biosystems), we attempted to determine mutations in the 81- bp cor region (rifampin resistance determining region) of the rpoB gene in 48 Mycobacterium tuberculosis strains found to be rifampin resistant by classical phenotypic methods. Of the 48 strains, 46 (95.8%) were found to have rpo gene mutations with 13 different types while in two (4.2%) of the 48 strains, no mutations were detected. None of the strains had mutations at more than one codon. Point mutations at the 531st (52.1 %) and 526th (18.9 %) codons were frequent. The most frequent point mutation was Ser531Leu, and it was found in 21 (43,8 %) of 48 strains. This is the first study from Turkey, reporting Ser522Leu point mutation in one isolate and deletion of 515th codon (ATG - Met) in two isolates.

Oligonucleotide ligation assay-based DNA chip for multiplex detection of single nucleotide polymorphism

An oligonucleotide ligation assay-based DNA chip has been developed to detect single nucleotide polymorphism. Synthesized nonamers, complementary to the flanking sequences of the mutation sites in target DNA, were immobilized onto glass slides through disulfide bonds on their 5′ terminus. Allele-specific pentamers annealed adjacent to the nonamers on the complementary target DNA, containing 5′-phosphate groups and biotin labeled 3′-ends, were mixed with the target DNA in tube. Ligation reactions between nonamers and pentamers were carried out on chips in the presence of T4 DNA ligase. Ligation products were directly visualized on chips through enzyme-linked assay. The effect of G:T mismatch at different positions of pentamers on the ligation were evaluated. The results showed that any mismatch between pentamer and the target DNA could lead to the decrease of ligation, which can be detected easily. The established approach was further used for multiplex detection of mutations in rpoB gene of rifampin-resistant Mycobacterium tuberculosis clinical isolates.

Clinical Meaning of INNO-LiPA Test in the Diagnosis of Rifampin Resistant Tuberculosis

Background : The prevalence of multidrug resistant tuberculosis (MDR-TB), resistant to isoniazid (INH) and rifampin (RFP), was 5.3% worldwide in 1995 and its increment has raised important public health problems. Resistance to RFP, one of the key drugs in the treatment of tuberculosis, results in grim clinical outcome. Recently rapid detection of RFP-resistant mutations in rpoB gene based on PCR method has become available. This study evaluated the prevalence of RFP resistance in first diagnosed, treatment failure, and recurred patients using INNO-LiPA test, and compared the results of INNO-LiPA with those of conventional mycobacterial drug susceptibility test. Methods : Forty-six patients, who were diagnosed of pulmonary tuberculosis and had revealed positive sputum AFB smear, were enrolled in this study from 1998 to 2002. The cases were classified as one three groups; first diagnosed, treatment failure, or recurred. RFP resistance was studied using an INNO-LiPA Rif. TB kit and compared with that obtained from drug susceptibility based on M. tuberculosis culture study. Results : Twenty-one out of 46 patients were enrolled under first diagnosis of pulmonary tuberculosis,

Mutations in the rpoB and katG genes leading to drug resistance in Mycobacterium tuberculosis in Latvia.

To characterize the genetic basis of drug resistance in Mycobacterium tuberculosis in Latvia, mutations involved in rifampin (rpoB gene) and isoniazid (katG gene) resistance in DNA from 19 drug-susceptible and 51 multidrug-resistant M. tuberculosis complex isolates were analyzed. The most frequent rpoB gene mutations found by the Line Probe assay were the S531L (14 of 34 isolates), D516V (7 of 34), H526D (4 of 34), and D516Y plus P535S (4 of 34) mutations. Direct sequencing of seven isolates with unclear results from Line Probe assay showed the presence of the L533P mutation and the Q510H plus H526Y (1 of 34) and D516V plus P535S (4 of 34) double mutations, neither of which has been described previously. Single-strand conformation polymorphism analysis showed strand mobility differences between the rifampin-susceptible and -resistant samples for the D516V, H526D, and D516Y plus P535S mutations but not for the S531L mutation. Nucleotide substitution at codon 315 (AGC-->ACC) of the katG gene was found in 48 of 51 multidrug-resistant samples by sequencing. Furthermore, katG gene restriction fragment length polymorphism analysis with endonuclease AciI confirmed the nucleotide change in codon 315.

Characterization of rpoB mutations in rifampicin-resistant Mycobacterium tuberculosis isolated in China

The objective of this study was for the elucidation of the characteristics of the rpoB gene mutation in rifampicin (RIF)-resistant Mycobacterium tuberculosis strains isolated in China. The rifampicin resistance determination regions (RRDR) of the rpoB genes of 242 M. tuberculosis strains were sequenced, including 193 RIF-resistant, 46 RIF-sensitive clinical isolates and three manually induced RIF-resistant tuberculosis strains. Mutations in the 81 bp RRDR of the rpoB gene were identified in 89.6% (173/193) of RIF-resistant clinical isolates. No mutation was observed in RIF-sensitive strains. Ser531Leu mutations accounted for 46.1% (89/193) of RIF-resistant strains; the mutation frequency of 526-His was 17.6% (34/193) in RIF-resistant strains. Furthermore, a combination of 2–3 single-point mutations was observed in 24 RIF-resistant strains (12.4%; 24/193). Mutations in three manually induced RIF-resistant tuberculosis strains were located at codons 531 and 526, respectively. The results indicate that about 90% of rifampicin-resistant M. tuberculosis strains isolated in China had rpoB mutations;531-Ser and 526-His were the most common positions substituted; high-level rifampicin-resistant strains had a higher frequency of 531-Ser mutations than low-level rifampicin-resistant strains. Sequencing analysis of the 81 bp fragment in the rpoB gene is useful in predicting the rifampicin-resistant phenotype.

RpoB Gene mutations in rifampin-resistant Mycobacterium tuberculosis identified by polymerase chain reaction single-stranded conformational polymorphism.

The use of polymerase chain reaction-single-stranded conformational polymorphism (PCR-SSCP) to study rpoB gene mutations in rifampin-resistant (RIFr) Mycobacterium tuberculosis has yielded contradictory results. To determine the sensitivity of this method, we analyzed 35 RIFr strains and 11 rifampin-susceptible (RIFs) strains, using the DNA sequencing of the core region of rpoB for comparison. Of the RIFr, 24 had a PCR-SSCP pattern identical to that of H37Rv; the other 11 had four different patterns. The 11 RIFs had PCR-SSCP patterns identical to that of H37Rv. The sensitivity of the assay was 31.4%; its specificity was 100%. We observed a strong correlation between the degree of resistance and the type of mutation.

Clinical Usefulness of the Line Probe Assay for Rapid Detection of Rifampicin-resistant Tuberculosis

Background : RpoB gene mutations have been found in about 96-98% of rifampicin (RMP)-resistant Mycobacterium tuberculosis. Recent reports confirm that the in laboratory settings a rpoB gene mutation can be used as a surrogate marker for multi-drug resistant tuberculosis. However, its usefulness in clinical applications has not been evaluated. This study was performed to confirm whether mutation analysis of the rpoB gene of M. tuberculosis is useful in clinical settings. Methods : The medical records of 33 patients in whom rpoB gene analysis was conducted using an INNOLiPA Rif. TB assay (LiPA) from June, 1998, to July, 2000, at the Asan Medical Center were retrospectively reviewed in 33 patients. The clinical characteristics in addition to the drug susceptibility and LiPA results were analyzed. The drug susceptibility test was considered as a gold standard method for M. tuberculosis susceptibility and these results were compared with those of the rpoB gene study and sequencing analysis. Sequencing analysis of the rpoB gene was done in cases where there was a discrepancy between the results of the drug susceptibility an d rpoB gene study. Results : The mean age and sex ratio was $42{\pm}18$, and 24:9 (M:F), respectively. There were 19 RMP susceptible (58%) and 14 RMP-resistant cases (42%) according to the rpoB gene study. The mean time from the request to reporting the results of the rpoB gene study was $5.2{\pm}2.6$ days. The mean gap from reporting the rpoB gene study to reporting the susceptibility was $56{\pm}35$ days. Twenty-eight cases (85%) showed identical results compared with the drug susceptibility results, whereas five cases (15%) showed contradictory results. When compared with the sequencing analysis, of the five cases that showed contradictory results, two had LiP A analysis errors and the remaining three were identical to the sequencing results. The rpoB gene study was of assistance in choosing the appropriate drugs in 28 cases (85%). Conclusions : An rpoB gene study using an LiP A assay was useful in rapidly diagnosing RMP-resistant tuberculosis, which enabled a proper choice of the appropriate drugs in clinical practices. However, an LiPA assay always should be performed in conjunction with microscopy, culture, and susceptibility tests.

RNA polymerase inhibitors with activity against rifampin-resistant mutants of Staphylococcus aureus.

A collection of rifampin-resistant mutants of Staphylococcus aureus with characterized RNA polymerase beta-subunit (rpoB) gene mutations was cross-screened against a number of other RNA polymerase inhibitors to correlate susceptibility with specific rpoB genotypes. The rpoB mutants were cross-resistant to streptolydigin and sorangicin A. In contrast, thiolutin, holomycin, corallopyronin A, and ripostatin A retained activity against the rpoB mutants. The second group of inhibitors may be of interest as drug development candidates.

Rifampicin resistance in Mycobacterium kansasii is associated with RPOB gene mutations

Rifampicin resistance in Mycobacterium kansasii is associated with RPOB gene mutations

Rifabutin susceptibility and rpoB gene mutations in multi-drug resistant mycobacterium tuberculosis

연구배경 : 최근 세계적으로 결핵의 증가와 함께 다제내성 결핵의 조절이 문제가 되고 있으며, 결핵 및 약제갑수성의 신속한 진단과 새로운 약제의 개발이 시급하다. Rifabutin (RBU)은 rifampicin (RFP)과 같은 rifamycin계통의 약제로, 일부 다제내성 결핵에서 효과가 있음이 보고되어 있다. 소수의 국외 연구에서 RFP내성과 관련된 rpoB 유전자의 돌연변이 양상에 따라 rifamycin계통 약제의 감수성여부가 결정된다고 보고 되었다. 아직도 내성율이 높은 국내 현실에서 다제내성 결핵균의 rpoB 유전자 돌연변이 양상을 파악하고, RBU감수성을 나타내는 돌연변이 양상을 확인하여 RBU감수성 다제내성 결핵을 신속하게 확인할 수 있는 진단법의 기초자료를 구하고자 하였다. 방법 : 1997년 7월에서 1999년 6월 사이에 서울중앙병원을 방문한 65명의 다제내성결핵환자에서 얻은 균주를 대상으로 RBU감수성검사와 rpoB 유전자 염기서열결정법을 시행하여 그 결과를 비교하였다. 결과 : 다제내성 결핵균 65균주중 52균주에서 RBU약제감수성검사를 시행하였고, 56균주에서 rpoB 유전자 염기서열이 확인되었다. 44균주에서 rpoB 유전자 염기서열분석과 RBU약제감수성검사가 동시에 시행되었다. 염기서열이 확인된 56균주중 53균주(95%)에서 rpoB 유전자 돌연변이가 발견되었다. 발견된 60개 돌연변이중 531 코돈 돌연변이가 26개(43%)로 가장 많았으며, 7예에서는 돌연변이가 2가지씩 존재하였다. RBU감수성 균주는 10% (5/53) 이었다. RBU감수성 균주가 채취된 5명중 1명에서 RBU를 복용하였으나 균음전에는 실패하였다. RBU감수성 다제내성 결핵균과 관련된 rpoB 유전자 돌연변이는 526 코돈의 CAC - > AAC, GCC, TGC, 516 코돈의 GAC - > TAC 또는 GAG, 그리고 509 코돈의 AGC - > AGA 점돌연변이 이었다. 결론 : 국내 다제내성 결핵균에서 rpoB 유전자 돌연변이의 빈도 및 양상은 결핵의 유병율이 낮은 국외의 보고와 비슷하였으며, 일부는 RBU에 감수성을 나타내었다. RBU감수성올 나타내는 rpoB 유전자 돌연변이 양상을 이용하여 다제내성 결핵균에서 RBU감수성인 균주를 신속히 진단할 수 있을 것으로 사료되었다. 【Background : Following several decades of decline, the incidence of tuberculosis has recent1y begun to increase in many countries of this the control of this disease has been impeded by the emergence of multi-drug resistant tuberculosis (MDR-TB). The development of rapid diagnostic methods and effective new drugs are needed to control MDR-TB. One of the new drugs for MDR-TB is rifabutin (RBU) which has been known to be effective in some patients with MDR-TB. A few reports showed that some types of mutations of the rpoB gene, which were known to be present in 96-98% of rifampicin-resistant M. tuberculosis, were associated with the rifampicin-resistant but RBU-susceptible phenotype. This study was performed to investigate the correlation between RBU susceptibility and the patterns of rpoB gene mutations in Korean MDR-TB. Methods : Sixty-five clinical isolates of multi-drug resistant Mycobacterium tuberculosis, gathered from patients who visited the Asan Medical Center from July 1997 to June 1999, were investigated. Clinical responses to rifabutin-containing regimen were evaluated. An RBU susceptibility test and sequencing analysis of rpoB gene were performed, and the results were analyzed to confirm which mutations correlated with RBU-susceptible MDR-TB. Results : Fifty-three of 56 (95%) clinical isolates of MDR-TB had 60 mutations of the rpoB gene. The most frequent mutations were found at codon 531 (43%), and two mutations were combined in seven clinical isolates. Five of 53 (10%) clinical isolates showed the RBU-susceptible phenotype, and in them the characteristic patterns of point mutations were found at codon 509, 516, and 526. Conclusion : The frequency and pattern of mutations of the rpoB gene of Korean MDR-TB isolates were similar to those in western countries, where the prevalence of tuberculosis is low, but some show RBU-susceptible phenotypes. RBU-susceptible MDR-TB isolates showed the characteristic pattern of mutations of the rpoB gene which could be used to rapidly diagnose RBU susceptibility.】

Detection of rpoB Gene Mutation in Rifampin-Resistant M. Tuberculosis by Oligonucleotide Chip

Background Oligonucleotide chip technology has proven to be a very useful tool in the rapid diagnosis of infectious disease. Rifampin resistance is considered as a useful marker of multidrug-resistance in tuberculosis. Mutations in the rpoB gene coding β subunit of RNA polymerase represent the main mechanism of rifampin resistance. The purpose of this study was to develop a diagnosis kit using oligonucleotide chip for the rapid and accurate detection of rifampin-resistance in Mycobacterium tuberculosis. Method Tle sequence specific probes for mutations in the rpoB gene were designed and spotted onto the glass slide, oligonucleotide chip. 38 clinical isolates of Mycobacterium were tested. A part of rpoB was amplified, labelled, and hybridized on the oligonucleotide chip with probes. Results were analyzed with a laser scanner. Direct sequencing was done to verify the results. Result The low-density oligonucleotide chip designed to determine the specific mutations in the rpoB gene of M. tuberculosis accurately detected rifampin resistance associated with mutations in 28 clinical isolates. Mutations at codons 531, 526, and 513 were confirmed by direct sequencing analysis. Conclusion Mutant detection using oligonucleotide chip technology is a reliable and useful diagnostic tool for the detection of multidrug-resistance in M. tuberculosis.

Mutations in rpoB gene and rifabutin susceptibility of multidrug-resistant mycobacterium tuberculosis strains isolated in australia

Control of tuberculosis, the single largest killer among the infectious diseases, has been threatened by the emergence of multidrug-resistant Mycobacterium tuberculosis (MDRTB) infection due to the limited treatment options. Rifampicin (RIF) resistance is considered as a marker for MDRTB. The aim of this study was the detection of rpoB gene mutations and rifabutin resistance in MDRTB strains recently isolated in Australia by a line probe assay (INNO-LiPA Rif. TB, Innogenetics). Rifabutin and RIF susceptibility of 20 MDRTB and 16 RIF-sensitive M. tuberculosis complex clinical isolates were studied. The overall concordance of the line probe assay (LiPA) with phenotypic RIF susceptibility test was 96%. Seven distinct nucleotide substitutions were identified in 21 of 22 RIF-resistant isolates of diverse geographical origins, but in none of the RIF-sensitive strains. The majority (71%) of mutations occurred in the 526-533 codons and were associated with resistance to rifabutin and RIF. Of the RIF-resistant MDRTB strains, 18% appeared to be rifabutin-sensitive and produced delta S2 and delta S3 INNO-LiPA patterns. We conclude that amino acid substitutions at Asp516 and Ser522 in the rpoB gene in RIF-resistant M. tuberculosis predict rifabutin susceptibility for MDRTB. Use of the LiPA for RIF and rifabutin resistance may facilitate the rapid response required to limit the extent and severity of MDRTB transmission and infection.

Comparison of PCR-Line Probe and PCR-SSCP Methods for the Detection of Rifampicin Resistant Mycobacterium Tuberculosis.

BACKGROUND: Rifampicin (RFP) is a key component of the antituberculous short-course chemotherapy and the RFP resistance is a marker of multi-drug resistant (MDR) tuberculosis. RpoB gene encodes the beta-subunit of RNA polymerase of M. tuberculosis which is the target of RFP. And the mutations of rpoB gene have been found in about 96% of rifampicin resistant clinical isolates of M. tuberculosis. So in order to find a rapid and clinically useful diagnostic method in identifying the REP resistance, we compared the PCR-line probe method with PCR-SSCP for the detection of the rpoB gene mutation in cultured M. tuberculosis. METHODS: 45 clinical isoLates were collected from patients who visited Sung Kyun Kwan University Hospital. The REP susceptibility test was referred to the referral laboratory of the Korean Tuberculosis Institute. 33 were rifampicin resistant and 12 were rifampicin susceptible. The susceptibility results were compared with the results of the PCR-SSCF and PCR-line probe method. RESULTS: We could find rpoB mutations in 27/33(81.8%) RFP-resistant strains by PCR-line probe method, and in 23/33(69.7%) by PCR-SSCP and there was no significant difference between two methods. There was no mutation in rifampicinn susceptible strains by both methods.: Comparison of PCR-line probe and PCR-SSCP methods for detection rifampicin resistance CONCLUSION: PCR-Iine probe method would be a rapid, sensitive and specific method for the detection of rifampicin resistant Mycobacterium tuberculosis.

Analysis of rpoB Gene in Rifampin-Resistant M. Tuberculosis by Direct Sequencing and Line Probe Assay

BACKGROUND: The emergence of multidrug-resistant strains of Mycobacterium tuberculosis presents a significant challange to the treatment and control of tuberculosis, and there is an urgent need to understand the mechanisms by which strains acquire multidrug resistance. Recent advances in molecular methods for the detection of M. tuberculosis genetic targets have approached the sensitivity of culture Furthermore the prospect of determining resistance in mycobacteria at the nucleic acid level particulary to first-line drugs like rifampin, isoniazid has provided a glimps of the next generation of sensitivity test for M. tuberculosis. Previous studies in RMP resistant M. tuberculosis have shown that mutation in beta subunit of RNA polymerase is main mechanism of resistance. METHOD: In this study, rpoB gene for the ~3 subunit of RNA polymerase from M. tuberculosis of 42 cultured samples (32 were RMP resistant and 10 were sensitive cases) were isolated and characterised the mutations. Direct sequencing data were compared with the results of INNO-LiPA Line Probe Assay (LiPA, Innogenetics, Belgium), commercial RMP resistance detecting kit using reverse hybridization method. RESULTS: All of the RMP resistant samples were revealed the presence of mutation by LiPA. In 22 samples (68.8%) out of 32 RMP resistant cases, the mutation types were confirmed by the positive signal at one of 4 mutation bands in the strip. The most frequent type was R5 (S53 IL) which were 17 cases (77.3%). Results of direct sequencing were identified the exact characteristics of 8 mutations which were not comfirmed by LiPA. S522W type point mutation and 9 base pair deletion at codon 513-515 were new identified mutations for the first time. CONCLUSION: Mutations in rpoB gene is the main mechanism of RMP resistance in M. tuberculosis and LiPA is a very useful diagnostic tool for the early diagnosis of RMP resistance in M. tuberculosis.

Rapid Detection of Rifampicin Resistant M. tuberculosis by PCR-SSCP of rpoB Gene in Clinical Specimens

Background : Rifampicin(RFP) is a key component of the antituberculous short-course chemotherapy and the RFP resistance is a marker of multi-drug resistant(MDR) tuberculosis. RPoB gene encodes the -subunit of RNA polymerase of M. tuberculosis which is the target of RFP. And rpoB gene mutations are the cause of RFP resistance of M. tuberculosis. Although several reports showed that PCR-SSCP would be a rapid diagnostic method for identifying the RFP resistance, there were few reports Performed using direct, clinical specimens. So we Performed PCR-SSCP analysis of rpoB gene of M. tuberculosis in direct, clinical specimens. Methods : 75 clinical specimens were collected from patients at Asan Medical Center from June to August 1996. After PCR of IS 6110 fragments, 43 both AFB smear-positive and IS6110 fragment PCR-positive specimens were evaluated. The RFP susceptibility test was referred to the referral laboratory of the Korean Tuberculosis Institute. DNA was extracted by bead beater method. And heminested PCR was done using 0.1ul(1uCi) []-dCTP. SSCP analysis was done using non-denaturating MDE gel electrophoresis. Results : The results of PCR of IS6110 fragments of M. tuberculosis were positive in 55(73%) cases of 75 AFB smear-positive clinical specimens. Of the 55 specimens, RFP susceptibility was confirmed in only 43 specimens. Of the 43 AFB smear-positive and IS6110 fragment-positive specimens, 29 were RFP susceptible and 14 were RFP resistant. All the RFP susceptible 29 strains showed the same mobility compared with that of RFP sensitive H37Rv in SSCP analysis of ropB gene. And all the other RFP resistant 13 strains showed the different mobility. In other words they showed 100% identical results between PCR-SSCP analysis and traditional susceptibility test. Conclusion : The PCR-sseP analysis of rpoB gene in direct clinical specimens could be used as a rapid diagnostic method for detecting RFP resistant M. tuberculosis.

Detection of rifampicin-resistant strains of Mycobacterium tuberculosis by a non-radioactive PCR-SSCP method

PCR-SSCP method to detect genetic mutations in rpoB gene as a marker of rifampicin-resistance was developed by Telenti et al., and we have modified it applying non-radioactive PhastSystem for more practical use in the detection of rifampicin-resistance of Mycobacterium tuberculosis. PCR products amplified with the primers specific to rpoB gene using extracted DNA from 89 strains of M. tuberculosis were sequenced and the amino acid sequences were morphism was determined by the PhastSystem. The bands were stained by silver staining. Among 89 strains of M. tuberculosis, 43 were confirmed as rifampicin-resistant (RFPr) and 46 were rifampicin-sensitive (RFPs) by the culture on the drug-containing media. All of the 43 RFPr strains had one or more mutations in the DNA sequence of rpoB gene, while none of the RFPs strains had such mutations. However, by PCR-SSCP, only 20 out of 43 RFPr strains showed clear differences in the band pattern of electrophoresis from that of RFPs strains. Other 23 RFPr strains had only slight differences in the band pattern of the PCR-SSCP from that of RFPs strains. But it was noticed that the main bands of RFPr strains were distinguishable from the main bands of RFPs strains even their patterns were similar. Thus, it is possible to apply a non-radioactive PCR-SSCP for the detection of rifampicin resistance of M. tuberculosis with further improvement of the condition of gel electrophoresis or staining techniques.

Molecular Characterization And Comparison Of Multi Drug Resistant Strains Of Mycobacterium Tuberculosis By Phenotypic And Genotypic Method

Introduction: Drug resistant tuberculosis is a signifi cant threat to tuberculosis control because only a few effective drugs are available against M. tuberculosis. The aims of this study were to compare multi drug resistant (MDR) strains of tuberculosis by phenotypic and genotypic method and determine type, location and frequency of rpoB and KatG gene mutations. Methodology: Anti-tuberculosis drugs susceptibility test of M. tuberculosis grown on Lowenstein Jensen medium was performed by proportion method. MDR cases were analyzed for mutation of rpoB and KatG genes. The regions of these genes were amplifi ed by polymerase chain reaction (PCR) and sequenced. Results: Two different mutations were identifi ed in rifampicin resistant strains. The most common point mutations were in codons TCG 531→TTG (85%) and GAC 516→TTC (15%) of the rpoB gene. Two different mutations in KatG gene were detected. The most common KatG point mutations were AGC 315 ACC (Ser→Thr) (85%) and CGG 463 CTG (Arg→Leu) (10%). In this study DNA sequencing analysis did not fi nd mutation on KatG gene of one of the strain tested. Male and female were equally affected by MDR tuberculosis and majorities (35%) of them were found in 21-30 years age group. Conclusion: The present investigation agrees that genetic mutation is responsible for change in phenotypic characteristics of M. Tuberculosis. DOI: http://dx.doi.org/10.3126/saarctb.v8i2.5896 SAARCTB 2011; 8(2): 17-22