Detection of rifampin resistance patterns in Mycobacterium tuberculosis strains isolated in Iran by polymerase chain reaction-single-strand conformation polymorphism and direct sequencing methods

Mutations in the rpoB locus confer conformational changes leading to defective binding of rifampin (RIF) to rpoB and consequently resistance in Mycobacterium tuberculosis. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) was established as a rapid screening test for the detection of mutations in the rpoB gene, and direct sequencing has been unambiguously applied to characterize mutations. A total of 37 of Iranian isolates of M. tuberculosis, 16 sensitive and 21 resistant to RIF, were used in this study. A 193-bp region of the rpoB gene was amplified and PCR-SSCP patterns were determined by electrophoresis in 10% acrylamide gel and silver staining. Also, 21 samples of 193-bp rpoB amplicons with different PCR-SSCP patterns from RIFr and 10 from RIFs were sequenced. Seven distinguishable PCR-SSCP patterns were recognized in the 21 Iranian RIFr strains, while 15 out of 16 RIFs isolates demonstrated PCR-SSCP banding patterns similar to that of sensitive standard strain H37Rv. However one of the sensitive isolates demonstrated a different pattern. There were seen six different mutations in the amplified region of rpoB gene: codon 516(GAC/GTC), 523(GGG/GGT), 526(CAC/TAC), 531(TCG/TTG), 511(CTG/TTG), and 512(AGC/TCG). This study demonstrated the high specificity (93.8%) and sensitivity (95.2%) of PCR-SSCP method for detection of mutation in rpoB gene; 85.7% of RIFr strains showed a single mutation and 14.3% had no mutations. Three strains showed mutations caused polymorphism. Our data support the common notion that rifampin resistance genotypes are generally present mutations in codons 531 and 526, most frequently found in M. tuberculosis populations regardless of geographic origin.     

Amino acid substitutions in the beta-subunit of RNA-polymerase from E. coli compensating for mutation-induced damage of the rho termination factors

Ts-phenotype of the E. coli rho-factor mutant rho 15 is suppressed by two rifampicin-resistance mutations, rhoB1019 resulting in a single amino acid substitution Val146----Phe and rhoB268 resulting in a single substitution Gln513----Leu in beta-subunit of the E. coli RNA polymerase. Rifampicin-resistance mutations rhoB255 (Asp516----Val), rhoB1016 (Asp516----Asn), rhoB1001 (His526----Tyr), rhoB1004 (Ser531----Phe), rhoB1005 (Pro564----Leu), and streptolydigin-resistance' mutation rhoB1018 (double substitution Gly544----Asp and Phe545----Ser) do not suppress the rho15 mutation.     

Characterization of rpoB mutations associated with rifampin resistance in Mycobacterium tuberculosis from eastern China

Aims:  The aim of this study was to investigate the features of rpoB gene mutations associated with Rifampin (RIF) resistance in Mycobacterium tuberculosis ( M. tuberculosis ) in eastern China.
Methods and Results:  The mutations of rpoB gene in 56 clinical isolates of M. tuberculosis resisted to one to four first-line drugs (rifampin, isonicotinyl hydrazide, ethambutol and streptomycin) were analysed by polymerase chain reaction single strand conformation polymorphism analysis (PCR-SSCP) and DNA sequencing. The results of PCR-SSCP showed 52 isolates were positive (existing rpoB mutation) including 47 isolates resisted to RIF. Subsequent results of DNA sequencing showed that 54 isolates had rpoB gene mutation including 49 isolates resisted to RIF. The most frequently mutated sites were at codons 526 (73·2%), 513 (10·7%) and 531 (3·5%).
Conclusions:  The rpoB codon 526 was the most frequently mutated site of RIF-resistant M. tuberculosis strains in eastern China and its frequency is significantly higher ( P  < 0·0001) compared with that in other areas of China and in other geographic regions worldwide.
Significance and Impact of the Study:  Our results reveal that geographic variation is responsible for rpoB mutations in M. tuberculosis and the resulting information will be helpful to improve a novel rapid molecular drug resistance screening approach for MDR TB.     

Molecular Evolution of Multisubunit RNA Polymerases: Structural Analysis

Comprehensive multiple sequence alignments of the multisubunit DNA-dependent RNA polymerase (RNAP) large subunits, including the bacterial β and β′ subunits and their homologs from archaebacterial RNAPs, eukaryotic RNAPs I-III, nuclear-cytoplasmic large double-stranded DNA virus RNAPs, and plant plastid RNAPs, were created [Lane, W. J. and Darst, S. A. (2009). Molecular evolution of multisubunit RNA polymerases: sequence analysis. In press]. The alignments were used to delineate sequence regions shared among all classes of multisubunit RNAPs, defining common, fundamental RNAP features as well as identifying highly conserved positions. Here, we present a systematic, detailed structural analysis of these shared regions and highly conserved positions in terms of the RNAP structure, as well as the RNAP structure/function relationship, when known.     

Molecular profiling of drug resistant isolates of Mycobacterium tuberculosis in the state of Santa Catarina,southern Brazil

Drug resistance is a global threat and one of the main contributing factors to tuberculosis (TB) outbreaks. The goal of this study was to analyse the molecular profile of multidrug-resistant TB (MDR-TB) in the state of Santa Catarina in southern Brazil. Fifty-three MDR Mycobacterium tuberculosisclinical isolates were analysed by spoligotyping and a partial region of therpoB gene, which is associated with rifampicin resistance (RMP-R), was sequenced. Some isolates were also distinguished by their mycobacterial interspersed repetitive units (MIRU). S531L was the most prevalent mutation found within rpoB in RMP-R isolates (58.5%), followed by S531W (20.8%). Only two MDR isolates showed no mutations withinrpoB. Isolates of the Latin American Mediterranean (LAM) family were the most prevalent (45.3%) found by spoligotyping, followed by Haarlem (9.4%) and T (7.5%) families. SIT106 was found in 26.4% of isolates and all SIT106 isolates typed by MIRU-12 (5 out of 14) belong to MIT251. There was a high correlation between the S531W mutation and the LAM family mainly because all SIT2263 (LAM9) isolates carry this mutation. Among isolates with the S531W mutation in rpoB MIRU demonstrates a cluster formed by four isolates (SIT2263 and MIT163) and very similar profiles were observed between eight of the nine isolates. Better characterisation of TB isolates may lead to new ways in which to control and treat TB in this region of Brazil.     

Structural and functional characterization of a triple mutant form of S100A7 defective for Jab1 binding

S100A7 (psoriasin) is a calcium‐ and zinc‐binding protein implicated in breast cancer. We have shown previously that S100A7 enhances survival mechanisms in breast cells through an interaction with c‐jun activation domain binding protein 1 (Jab1), and an engineered S100A7 triple mutant (Asp⁵⁶Gly, Leu⁷⁸Met, and Gln⁸⁸Lys—S100A7₃) ablates Jab1 binding. We extend these results to include defined breast cancer cell lines and demonstrate a disrupted S100A7₃/Jab1 phenotype is maintained. To establish the basis for the abrogated Jab1 binding, we have recombinantly produced S100A7₃, demonstrated that it retains the ability to form an exceptionally thermostable dimer, and solved the three dimensional crystal structure to 1.6 Å. Despite being positioned at the dimer interface, the Leu⁷⁸Met mutation is easily accommodated and contributes to a methionine‐rich pocket formed by Met¹², Met¹⁵, and Met³⁴. In addition to altering the surface charge, the Gln⁸⁸Lys mutation results in a nearby rotameric shift in Tyr⁸⁵, leading to a substantially reorganized surface cavity and may influence zinc binding. The final mutation of Asp⁵⁶ to Gly results in the largest structural perturbation shortening helix IV by one full turn. It is noteworthy that position 56 lies in one of two divergent clusters between S100A7 and the functionally distinct yet highly homologous S100A15. The structure of S100A7₃ provides a unique perspective from which to characterize the S100A7‐Jab1 interaction and better understand the distinct functions between S100A7, and it is closely related paralog S100A15.     

Mutations in the rpoB gene of rifampicin-resistant Mycobacterium tuberculosis strains isolated in Brazil and France

We evaluated the mutations in a 193bp of the rpoB gene by automated sequencing of rifampicin (RMP)-resistant and susceptible Mycobacterium tuberculosis strains isolated from Brazil (25 strains) and France (37 strains). In RMP-resistant strains, mutations were identified in 100% (16/16) from France and 89% (16/18) from Brazil. No mutation was detected in the 28 RMP-susceptible strains. Among RMP-resistant or RMP-susceptible strains deletion was observed. A double point mutation which had not been reported before was detected in one strain from France. Among French resistant strains mutations were found in codons 531 (31.2%), 526, 513 and 533 (18.7% each). In Brazilian strains the most common mutations were in codons 531 (72.2%), 526 (11.1%) and 513 (5.5%). The heterogeneity found in French strains may be related to the fact that most of those strains were from African or Asian patients.     

Rapid detection of resistance against rifampicin in isolates of Mycobacterium tuberculosis from Brazilian patients using a reverse-phase hybridization assay

The main objective of this study was to evaluate INNO-LiPA Rif.TB and to determine the frequency of mutations in rpoB in rifampicin-resistant Mycobacterium tuberculosis isolates of Brazilian tuberculosis patients. We used the reverse hybridization assay on 113 resistant and 15 sensitive clinical isolates of M. tuberculosis and on reference strains belonging to 37 different species. All MTB complex strains and none of the other strains reacted with the MTB complex-specific probe, meaning that the assay is 100% specific and 100% sensitive for detection of strains of the MTB complex. In 80 resistant strains, mutations causing S531L (n=55), H526Y (n=9), H526D (n=12) or D516V (n=9) were detected while in 30 strains, mutations were present but their exact nature was not determined by the assay (DeltaS patterns). All sensitive strains had the sensitive genotype while among resistant isolates, a sensitive genotype was obtained in three due to the absence of mutations in the hot spot region, demonstrating an assay accuracy of 97.6% for detection of drug susceptibility. In 10 resistant cultures, two or more mutations were detected and in five, mixed sensitive and resistant genotypes were observed. The sensitivity of the assay for detection of resistant organisms in a mixture with sensitive ones were 2% and 70%, respectively, considering the appearance and disappearance of the R2 and S2 bands. The sensitivity to detect heteroresistance is similar to that of the proportion method when a specific probe for the mutation is present but the performance of the assay in the patient population will depend on the frequency of mutation distribution.     

Application of Genotype MTBDRplus in rapid detection of the Mycobacterium tuberculosis complex as well as its resistance to isoniazid and rifampin in a high volum laboratory in Southern China

The alarmingly worsening epidemics of drug-resistant tuberculosis (TB) call urgent need for a simple method for the rapid detection of drug-resistant TB in clinical settings. In an attempt to establish a rapid procedure for laboratory diagnosis of TB and investigate the local TB epidemiology, molecular line probe assay of the Genotype MTBDRplus was used to identify Mycobacterium tuberculosis complex (MTBC) and detect mutations conferring resistance to two most active first-line drugs against TB: Rifampin and Isoniazid. 96 acid-fast bacillus (AFB) smear- positive sputums and 18 PCR-positive non-sputum specimens have been determined for the MTBC and resistance to Rifampin and Isoniazid. The MTBC detection rates in two sources of specimens were 93.8% (90/96) and 77.8% (14/18) respectively. The overall drug resistance (Rifampin or Isoniazid) occurred in 34.6% (36/104). Resistance to rifampin (RMP) was 28.8% (30/104) and 25% (26/104) was to Isoniazid (INH), in which high level drug resistance accounted for 88.5% (23/26) and low level drug resistance accounted for 7.7% (2/26). Multidrug resistance (MDR), defined as resistant to both RMP and INH, was found in 19.2% (20/104) of clinical samples, which was double that of official statistics. In addition, 63.3% (19/30) RMP-resistant mutations were identified in the region of RopB 530–533 and 57.9% (11/19) were the S531L mutation. 84.6% (22/26) of resistance to INH was mediated by Kat S315T1 mutations which conferred the high-level resistance to INH. The Genotype MTBDRplus line probe assay is a suitable and applicable method for establishing the rapidness in detection of drug-resistant TB in clinical laboratory. It will be a valuable addition to the conventional TB diagnostic approaches.     

Homology Modeling of Wild-type,D516V,and H526L Mycobacterium Tuberculosis RNA Polymerase and Their Molecular Docking Study with Inhibitors

Abstract

Rifamicyns (Rifs) are antibiotic widely used for the treatment of tuberculosis (TB); nevertheless, their efficacy has been limited by a high percentage of mutations, principally in the rpoB gene. In this work, the first three-dimensional molecular model of the hypothetical structures for the wild-type and D516V and H526L mutants of Mycobacterium tuberculosis (mtRNAP) were elucidated by a homology modeling method. In addition, the orientations and binding affinities of some Rifs with those new structures were investigated. Our findings could be helpful for the design of new more potent rifamycin analogs.