Novel C-3-(N-alkyl-aryl)-aminomethyl rifamycin SV derivatives exhibit activity against rifampicin-resistant Mycobacterium tuberculosis RpoBS522L strain and display a different binding mode at the RNAP β-subunit site compared to rifampicin
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Rifamycin
Rifabutin is a spiro-piperidyl-rifamycin derived from rifamycin-S. This study was planned to determine the minimal inhibitory concentrations (MICs) of rifabutin and rifampicin against Mycobacterium tuberculosis strains and to investigate cross resistance between two drugs. The agar dilution method was performed for detection of MICs of rifabutin and rifampicin for 112 M. tuberculosis strains obtained from patients with active pulmonary tuberculosis. Cross resistance between rifampicin and rifabutin was detected in 73.1%. Rifabutin MICs for rifampicin resistant strains were three- to four-fold higher than rifabutin-susceptible and/or -resistant strains' MIC values for rifampicin. Despite having 73% cross-resistance with rifampicin in M. tuberculosis isolates, it was concluded that rifabutin might be a valid component of combination therapy in rifampicin resistant tuberculosis cases when the isolate is tested and detected susceptible to rifabutin.
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Rifamycin
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Rifamycin B biosynthesis in Amycolatopsis mediterranei N/813 was inactivated by introducing a small deletion in the rifF gene situated directly downstream of the rifamycin polyketide synthase (PKS) gene cluster. The corresponding mutant strain produced a series of linear intermediates of rifamycin B biosynthesis that are most probably generated by obstruction of the normal release of the end product of the rifamycin PKS. This result provides evidence that the rifF gene product catalyses the release of the completed linear polyketide from module 10 of the PKS and the intramolecular macrocyclic ring closure by formation of an amide bond, as indicated by sequence similarity of this protein to amide synthases. The chemical structures of the new rifamycin polyketide synthase intermediates released from modules 4 to 10 were determined by spectroscopic methods (UV, IR, NMR and MS) and gave insight into the reaction steps of rifamycin ansa chain biosynthesis and the timing of the formation of the naphthoquinone ring. The intermediates released from modules 6 and 8 were isolated as lactones formed by the terminal carboxyl group; proton NMR double resonance and ROESY(rotated frame nuclear Overhauser enhancement spectroscopy) experiments enabled the deduction of the relative configurations in the linear chain which correspond to the known absolute stereochemistry of rifamycin B.
Polyketide synthase
Rifamycin
Gene cluster
Thioester
Amide
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Objective
To study the antibacterial activity of anti-tuberculosis decoction against clinical isolated rifampicin drug-resistant mycobacterium tuberculosis (number: A) and rifampicin sensitive mycobacterium tuberculosis (number: B) in vitro.
Methods
Rifampicin was selected as a positive control medicine.Anti-tuberculosis decoction and rifampicin were respectively used to test the bacteria through absolute concentration method and the direct effect method, then recorded and analyzed the observation phenomenon.
Results
The MIC of anti-tuberculosis decoction for A, B was 64.00mg/mL by using the absolute concentration method, and the MIC of anti-tuberculosis decoction for A, B was 8.00mg/mL by using direct effect method.
Conclusion
Anti-tuberculosis decoction had a good antibacterial activity for rifampicin resistant mycobacterium tuberculosis and rifampicin sensitive mycobacterium tuberculosis in vitro.
Key words:
Anti-Tuberculosis decoction; Rifampicin; Mycobacterium tuberculosis; Antibacterial
Decoction
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Rifabutin
Rifapentine
Rifamycin
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Comparative activities of various rifamycin analogues against leprosy were studied by evaluating their effects on in vitro growth of Mycobacterium leprae in DH medium as described earlier. Among the seven analogues studied, KRM-1648 was found to be the most potent in inhibiting the growth of rifampicin-sensitive strains of M. leprae, MIC being 0.05 microgram/ml. This was followed by KRM-2312 and T9 (MIC of each being 0.1 microgram/ml) and rifabutin (MIC, 0.2 microgram/ml). Rifampicin, along with KRM-1657 and KRM-1668, were least effective, with MIC for each being 0.4 microgram/ml. The effects of each at their respective MICs were bactericidal. The results were similar for rifampicin-resistant strains of M. leprae, but the MICs were higher than those obtained with rifampicin-sensitive strains of M. leprae. Thus, even though rifampicin has been the first-line drug in the treatment of leprosy, the results in present studies suggest that other rifamycin analogues are available that are more potent than rifampicin against both rifampicin-sensitive as well as rifampicin-restraint strains of M. leprae.
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Mycobacterium leprae
Rifabutin
Microgram
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Rifamycin W, the most predominant intermediate in the biosynthesis of rifamycin, needs to undergo polyketide backbone rearrangement to produce rifamycin B via an oxidative cleavage of the C-12/C-29 double bond. However, the mechanism of this putative oxidative cleavage has not been characterized yet. Rif-Orf5 (a putative cytochrome P450 monooxygenase) was proposed to be involved in the cleavage of this olefinic moiety of rifamycin W. In this study, the mutant strain
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The new 3-azinomethyl-rifamycin, SPA-S-565, was shown to exert an effective antibacterial activity in vitro comparable to that of rifampicin. In fact, the antibacterial activity of SPA-S-565 against numerous Gram-positive cocci belonging to Staphylococcus and Streptococcus species as well as against 20 strains of Mycobacterium tuberculosis, was similar to that of rifampicin. In Swiss albino mice intraperitoneally infected with Staphylococcus aureus Oxford strain or Streptococcus pyogenes, the protective activity of SPA-S-565 and rifampicin was quite remarkable, and no significant difference was noted between the two antibiotics. In M. tuberculosis-infected mice treated with the antibacterial agents every seven days, the protection exerted by SPA-S-565 was significantly greater than that exerted by rifampicin.
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Streptococcus Pyogenes
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Rifamycin
Spectinomycin
Neisseria gonorrhoeae
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Quinolone
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