Gotowa bibliografia na temat „Refampicin”

his study was carried out in order to determine the toxic and mutagenic and antimutagenic effects for Mallow (Malva parviflora) against the mutagenic effect of Methotrexate (MTX).The effect was studied in a bacterial system (G-system). The used system consisted of three isolates G3 Bacillus spp, G12 Arthrobacter spp and G27 Brevibacterium spp. The study depended on recording survival fraction (Sx) as an indicator for the induction of Streptomycin and Refampicin resistance mutants as a genetic marker. Water Extract was prepared from fresh and dry mallow leaves, stems, flowers and roots Gradual concentrations of plant water extracts were use to choose the suitable concentration which is remembered the negative control. The interactions included three types of treatments (pre - MTX, with- MTX and post-MTX) as a chemical mutagen in order to determine the mechanisms of this plant extracts in preventing or reducing the genotoxic effect of MTX. The results showed that the interaction effect between the optimum concentration of water extract and the mutagen on survival fraction (Sx) increase the value of the survival fraction of G-system isolates to reach normal value compare with positive control (MTX ). The results of the interaction between optimum concentration for extracts and the treatment with mutagen to induce resistance mutant for streptomycin and refampicin found that the MTX had no effect to induce resistance mutant for these two antibiotics, for the three types of treatment (pre-MTX, with-MTX, and post- MTX) for all extracts, the water extract suppress or repair mutant and give protection 100% for bacterial cells.

This study was carried out in order to determine the toxic, mutagenic and antimutagenic effects for Mallow (Malva parviflora) in comparison to its mutagenic effect of Ultraviolet (UV) because it is consider physical mutagen by using parameters for the extract pri , with , post UV exposure by using bacterial system (G-system). The used system consisted of three isolates G3 Bacillus spp., G12 Arthrobacter spp. and G27 Brevibacterium spp.. The study depended on recording survival fraction (Sx) for studying the effects and induction of Streptomycin and Refampicin resistance mutants as a genetic markers.Water Extract was prepared from fresh and dry mallow leaves, stems, flowers and roots, in optimum concentration equal to (125µg/ml) which is considered a negative control.The interactions included three types of treatments (pre, with and post –UV exposure) as a physical mutagen in order to determine the activity of this plant extracts in preventing or reducing the toxicity of the mutagen. The results of interaction effect between the optimum concentration of water extract and the mutagen on survival fraction (Sx) showed increasing in the value of the survival fraction of G-system isolates to reach normal value in comparison with positive control (UV). The results of the interaction between optimum concentration of extracts and the treatment with mutagen to induce resistance mutant for streptomycin and refampicin showed that the UV had no effect to induce resistance mutant for these two antibiotics, for the two types of treatment (with, post- UV) for all extracts, the water extract suppress or repair mutant and give protection 100% for bacterial cells, while the percentage of pre-UV treatment was (92- 97.3%).

INTRODUCTION:- Methicillin-resistant Staphylococcus aureus (MRSA) is a well-recognized public health problem throughout the world and community MRSA strains are now epidemic in India and others countries. The resistance rates of S. aureus infection and multidrug resistant strains are increasing, making the clinical anti-infective treatment and diagnosis more difficult. AIM:- To evaluate several phenotypic methods of the antibiotic susceptibility pattern for the detection of MRSA with Molecular Profiling Rt-PCR with the detection of MecA gene. MATERIALS AND METHODS:- The present study was a prospective observational study carried out at the Department of Microbiology, Santosh Medical College, Ghaziabad in a tertiary care hospital over a 12-month period from August 1, 2020 to July 31, 2021. Both IPD and OPD clinical sample comprised 385 clinical isolates as Staphylococcus aureus from various clinical specimens were included. Antibiotic susceptibility by the Kirby-Baure disc diffusion methods was performed according to the Clinical and Laboratory Standard Institute (CLSI) guidelines. Detection of MRSA by various methods like, Cefoxitin Disk diffusion Method, Oxacillin Disk diffusion method, E-Test method and detection of MecA gene by RT-PCR was carried out. RESULT:- In the present study out of 384 clinical samples, the majority of isolates from MRSA were found to be resistant to (E-Test) strip Oxacillin 114 (29.7%), followed by cefoxitin 113 (29.4%) and disc diffusion oxacillin 99 (25.8%). However, we observed a high incidence of resistance to other antibiotics such as Erythromycin 265 (69.0%), followed by Clotrimozole 228 (59.4%), Tetracyclin 144 (37.5), Vancomycin 102 (26.6%) and Refampicin 102 (26.6%). We also observed that Linezolid 354 (92.2%) followed by Teicoplanin 325 (84.6%), Gentamycin 272 (70.8%), Clindamycin 249 (64.8%) and Amoxyclave 281 (73.2%). In this study molecular RT-PCR test for the detection of mecA gene observed more in pus with 36 samples out of 113 followed by blood 17, urine 33, Sputum 05, pleural fluid 04, wound swab 16, Vaginal swab 06, CSF 01, Throat swab 2. CONCLUSION:- The gold standard assay for determining methicillin resistance is the PCR technique for detecting the mecA gene. But Because PCR is still time intensive and expensive, and it is not yet available in the 95% of routine clinical laboratories the phenotypic methods is still the choice where E-test is more reliable method than the disc diffusion method in detecting the drug resistance and can be utilised on a regular basis for better results.

Rifampicin is a non-competitive inhibitor of bacterial RNA polymerase (RNAP). The knowledge about the mechanism of action of this drug has emanated from the genetic and the biochemical studies carried out on Escherichia coli RNAP. The complete picture about the steric mechanism was obtained from structural studies on Thermus aquaticus core RNAP in complex with rifampicin. Resistance to rifampicin has been attributed to mutations in its binding pocket lying within the β-subunit of RNAP. The phenomenon of molecular tolerance to this drug came to light with the discovery of differential inhibition of transcription from σ70- and σ32- dependent promoters by rifampicin. After the discovery of the differential inhibition of transcription from σ70- and σ32- dependent promoters by rifampicin, similar instances of proteins were reported. In all such cases, their association with RNAP reduced its susceptibility to rifampicin. In an independent line of study, a new protein, RbpA, was discovered in Streptomyces coelicolor. This protein has the capability of interacting with RNAP, causes rifampicin tolerance to RNAP activity in vitro and leads to basal levels of rifampicin resistance in vivo. Moreover, this protein has sequence homologs exclusively in the actinomycete family, with nearest neighbors in mycobacteria. Interestingly, when rbpA null mutants in S. coelicolor were transformed with M. tuberculosis rbpA gene, the resistance to rifampicin grew from 0.75μg/ml to 2μg/ml in vivo, which pointed towards an analogous role of rbpAMTB. Saturation mutagenesis studies carried out on M. tuberculosis have placed rbpAMTB (Rv2050) on the list of genes imperative for optimal growth. The similarities and the speculations over mycobacterial RbpA made a compelling case in its favour for deciphering the role it played in the mycobacterial paradigm especially in the backdrop of rifampicin tolerance. This work focuses on the discovery of MsRbpA in M. smegmatis as an RNAP-interacting protein, characterization of MsRbpA with respect to its role in conferring phenotypic tolerance to rifampicin, molecular mechanism of the release of rifampicin from RNAP-rifampicin complex, location of MsRbpA on RNAP and studies on the probable role of MsRbpA in a rifampicin-resistant strain. The thesis is organized as follows: Chapter 1 deals with the literature survey on rifampicin with an all-inclusive perspective. It provides a brief history on the evolution of antibiotics as principal inhibitors against essential macromolecular assemblies, like RNAP and ribosomes, which control major cellular processes. Subsequently, we discuss the inhibitors of the transcription process, with a major emphasis on the mechanisms of inhibition of transcription activity by rifampicin. We also present an in-depth bibliomic analysis of the response to rifampicin across the microbial spectrum, which scratches the physiological and molecular landscape in a comprehensive manner. Finally, we present the justification for undertaking this work, and the proximate aims of this study. Chapter 2 informs about the identification of MSMEG_3858 as an RNAP-interacting protein. It details the cloning, expression and purification of MsRbpA. The focus then shifts towards the interact omics of MsRbpA and RNAP. Studies on the in vivo expression of MsRbpA form the concluding part of this chapter. Investigation into the outcome of interaction between MsRbpA and RNAP forms the central theme of Chapter 3. In this regard, first of all, we report the in vitro reconstitution of a heterologous mycobacterial core RNAP and its competence in carrying out gel-based in vitro promoter-specific transcription assays. Consequently, we apply this transcription apparatus in judging the role of MsRbpA in preventing the rifampicin-mediated inhibition of transcription activity, both in single- and multiple-round gel-based transcription assays. As a corroboration of this work, it is shown as to how the induction of MsRbpA in vivo causes an increase in the rifampicin-tolerance levels of M. smegmatis. Finally, we probe the existence of any possible interaction between MsRbpA and rifampicin as a prelude to ensuing investigations into the mechanism of phenotypic tolerance to rifampicin. In Chapter 4 we decipher the molecular mechanism of MsRbpA-mediated release of rifampicin from RNAP-rifampicin complex. A two-pronged strategy comprising of fluorescence-based and mass spectrometry-based approaches helps us to elucidate the aforesaid mechanism in greater detail. As a result, the location of interaction of MsRbpA on M. smegmatis RNAP is found to be at the junction of β and β' subunit. Chapter 5 attempts to explain the existence of RbpA homologs in microorganisms with two copies of β-subunit, one of which is Rifampicin susceptible (RifS) and the other being Rifampicin resistant (RifR). Using M. smegmatis as a model organism, we induce rifampicin resistance in M. smegmatis and create 3 variants with graded rifampicin resistance. After confirming the non-revertant nature of these strains, we assay the role of MsRbpA in rescuing the activity of RifR RNAPs at their respective IC50 values. The results show a redundancy of MsRbpA in rescuing RifR RNAPs. Alongside, we compare the colony morphology of MsRbpA overexpressing strain and the RifR strains at subinhibitory concentrations of rifampicin. The comparison shows a similarity in colony morphology typical to stress-induced conditions. Combining these results, we attempt to visualize the role of MsRbpA in species carrying two copies of the β-subunit. Chapter 6 studies the coevolution of RbpA and RNAP in the actinomycete phylum. The studies presented involve bioinformatics and statistics to decipher the cause of the exclusive existence of this protein in actinobacteria. The results show that RbpA appears to have co-evolved with actinobacterial RNAP as a defense system. This could be one of the ways of survival in the soil environment where metabolites like rifampicin are secreted by the producing organisms during struggle for existence. Chapter 7 summarizes the work presented in this thesis.