BACKGROUND: Despite the emerging danger of MDR-TB to human beings, there have only been a limited number of drugs developed to treat MDR-TB since 1970. This study investigated the cross-resistance rate between rifampicin (RFP) and rifabutin (RBU) in order to determine the efficacy of rifabutin in treating MDR-TB. In addition, the results of rifabutin were correlated with the rpoB mutations, which are believed to be markers for MDR-TB and RFP resistance. METHODS: The MICs of RBU were tested against 126 clinical isolates of MDR-TB submitted to the clinical laboratory of National Masan TB Hospital in 2004. Five different concentrations (10-160 microgram/ml) were used for the MICs. The detection of the rpoB mutations was performed using a RFP resistance detection kit with a line probe assay(LiPA), which contains the oligonucleotide probes for 5 wide type and 3 specific mutations (513CCA, 516GTC, and 531TTG). The rpoB mutation was determined by direct sequencing. RESULTS: The rate of cross-resistance between RFP and RBU was 70.5%(74/105) at 20 microgram/ml RBU(ed note: How much RFP?) Most mutations (86.3%) occurred in the 524~534 codons. The His526Gln, His526Leu, Leu533Pro, Gln513Glu, and Leu511Pro mutations(Ed note: Is this correct?) were associated with the susceptibilty to RBU. CONCLUSION: Based on the cross-resistance rate between RFP and RBU, RBU may be used effectively in some MDR-TB patients. Therefore, a conventional drug susceptibility test for RBU and a determination of the critical concentration are needed. However, rpoB gene mutation test may be have limited clinical applications in detecting RBU resistance.
Codon ; Humans ; Oligonucleotide Probes ; Rifabutin* ; Rifampin*

BACKGROUND: Rifabutin (ansamycin) is a spiro-piperidyl rifamycin, which is highly active against Mycobacterium tuberculosis. It has been found that some clinical isolates of tubercle bacilli that are resistant to rifampicin are susceptible to rifabutin, with some patients with multi-drug resistant pulmonary tuberculosis having shown favorable clinical and bacteriological responses to the rifabutin. This study was conducted to find the proportion of rifabutin- susceptible strains among rifampicin-resistant isolates from Korean MDR-TB patients, and investigate the presence of specific rpoB mutations, which may confer resistance to rifampicin, but not to rifabutin. METHODS: 201 rifampicin-resistant and 50 pan-susceptible M. tuberculosis isolates were randomly selected for this study. The isolates were retested at rifampicin and rifabutin concentrations of 0, 20, 40 and 80 microgram/ml, respectively. The isolates that grew at and/or over a rifabutin concentration of 20 microgram/ml were judged rifabutin-resistant. The rpoB gene was extracted from the isolates, and then amplified for direct sequencing to investigate specific rpoB mutations that conferred rifabutin- susceptibility but rifampicin-resistance. RESULTS: Out of the 201 rifampicin-resistant M. tuberculosis, 41 strains (20.4%) were susceptible to rifabutin using the absolute concentration method on Lowenstein-Jensen media. The rpoB mutation types that showed susceptibility to rifabutin were Leu511Pro, Ser512Arg, Gln513Glu, Asp516Ala, Asp516Gly, Asp516Val, Asp516Tyr, Ser522Leu, His526Asn, His526Leu, His526Cys, Arg529Pro and Leu533Pro. A reverse hybridization technique was able to detect 92.5% of the rifabutin-susceptible isolates, with a specificity of 96.1% among 195 M. tuberculosis isolates with the rpoB mutation. CONCLUSIONS: Around 20% of the rifampicin-resistant isolates in Korea showed susceptibility to rifabutin, which was associated with some specific mutations of rpoB. Rifabutin could be used for the treatment of MDR-TB patients, especially when drug susceptibility testing reveals susceptibility to rifabutin.
Humans ; Korea ; Mycobacterium tuberculosis ; Rifabutin ; Rifampin ; Tuberculosis ; Tuberculosis, Pulmonary

Over-expression of the pathway specific positive regulator gene is an effective way to activate silent gene cluster. In the curret study, the SARP family regulatory gene, vasR2, was over-expressed in strain Verrucosispora sp. NS0172 and the cryptic gene cluster responsible for the biosynthesis of pentaketide ansamycin was partially activated. Two tetraketides (1 and 2) and a triketide (3) ansamycins, together with five known compounds (4-8), were isolated and elucidated from strain NS0172OEvasR2. Their NMR data were completely assigned by analysis of their HR-ESI-MS and
Micromonosporaceae/metabolism* ; Multigene Family ; Polyketides/metabolism* ; Rifabutin/metabolism*

BACKGROUND: The appearance of multiple-drug-resistant Mycobacterium tuberculosis strains has been seriously compromising successful control of tuberculosis. Rifampin-resistance, caused by mutations in the rpoB gene, can be indicative of multiple-drug-resistance, and its detection is of great importance. The present study aimed to develop an oligonucleotide chip for accurate and convenient screening of drug-resistance. METHODS: In order to detect point mutations in the rpoB gene, an oligonucleotide chip was prepared by immobilizing specific probe DNA to a microscopic slide glass by a chemical reaction. The probe DNA that was selected from the 81 bp core region of the rpoB gene was designed to have mutation sites at the center. A total of 17 mutant probes related to rifampin-resistance including 8 rifabutin-sensitive mutant probes were used in this study. For accurate determination, wild type probes were prepared for each mutation position with an equal length, which enabled a direct comparison of the hybridization intensities between the mutant and wild type. RESULTS: Mycobacterial genomic DNA from clinical samples was tested with the oligonucleotide chip and the results were compared with those of the drug-susceptibility test in addition to sequencing and INNO-LiPA Rif. TB kit test in some cases. Out of 15 samples, the oligonucleotide chip results of 13 samples showed good agreement with the rifabutin-sensitivity results. The two samples with conflicting result also showed a discrepancy between the other tests, suggesting such possibilities as existence of mixed strains and difference in drug-sensitivity. Further verification of these samples in addition to more case studies are required before the final evaluation of the oligonucleotide chip can be made. CONCLUSION: An oligonucleotide chip was developed for the detection of rpoB gene mutations related to drug-susceptibility. The results to date show the potential for using the oligonucleotide chip for accurate and convenient screening of drug-resistance to provide useful information in antituberculosis drug therapy.
DNA ; Drug Therapy ; Glass ; Mass Screening ; Mycobacterium tuberculosis* ; Mycobacterium* ; Point Mutation* ; Rifabutin ; Rifampin ; Tuberculosis

Standard short-course chemotherapy (SSC) is recommended for new patients with pulmonary tuberculosis (TB). This approach has been regarded as among the most effective tools for preventing the development of resistance to anti-TB drugs. We report on the development of multidrug-resistance during SSC in a patient with drug-susceptible TB. Isoniazid, rifampin, pyrazinamide, and ethambutol were started, and negative culture conversion was obtained. Ethambutol was discontinued after 5 weeks of treatment due to visual dysfunction, and pyrazinamide was discontinued after a 2-month phase of intensive treatment. However, M. tuberculosis was cultivated from sputum collected after 9 weeks of treatment. Drug-susceptibility testing revealed resistance to isoniazid, rifampin, ethambutol, and rifabutin. Given that the patient took medication regularly, this observation suggests the possibility that some patients acquire drug resistance during SCC.
Antitubercular Agents ; Drug Resistance ; Drug Resistance, Multiple ; Ethambutol ; Humans ; Isoniazid ; Pyrazinamide ; Rifabutin ; Rifampin ; Sputum ; Tuberculosis ; Tuberculosis, Pulmonary

BACKGROUND: Following several decades of decline, the incidence of tuberculosis has recently begun to increase in many countries and 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 mutaitions 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 two 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 result 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.
Chungcheongnam-do ; Codon ; Humans ; Incidence ; Mycobacterium tuberculosis* ; Mycobacterium* ; Phenotype ; Point Mutation ; Prevalence ; Rifabutin* ; Tuberculosis ; Tuberculosis, Multidrug-Resistant

The eradication rate of Helicobacter pylori has been decreasing progressively, primarily due to increased resistance to antibiotics. The widely used standard clarithromycin-based triple therapy regimen is no longer achieving eradication rate of 80% in intent-to-treat analysis in many countries. Due to the primary and secondary resistance to metronidazole, the key antibiotic for second line regimen, eradication rate of standard metronidazole based quadruple therapy is also decreasing. It is rational to check antibiotic resistance for selecting regimens in third-line rescue eradication therapy, but it requires time and resource. Limited studies regarding the efficacy of a dual regimen consisting of high dose proton pump inhibitor and amoxicillin showed controversial results. Efficacy of rescue regimens containing fluoroquinolones, such as levofloxacin and moxifloxacin, were reported to be insufficient due to increasing incidence of primary and secondary resistance. Eradication result of third-line rescue regimens with sitafloxacin, a novel quinolone of which the antibacterial activity towards H. pylori is more than 100-fold that of ciprofloxacin in vitro, is promising. Although prevalence of serious side effect such as myelotoxicity with rifabutin-based rescue regimen is reported to be lower than expected, wider use of rifabutin is still concerned regarding the emergence of resistant mycobacterial species. Rifaximin based rescue regimen is safer and cheaper than rifabuitin based regimen. However, further investigation for better eradication rates by enhancing higher drug concentration in the gastric mucus layer needs to be evaluated.
Amoxicillin ; Anti-Bacterial Agents ; Ciprofloxacin ; Drug Resistance, Microbial ; Fluoroquinolones ; Helicobacter pylori* ; Incidence ; Levofloxacin ; Metronidazole ; Mucus ; Prevalence ; Proton Pumps ; Rifabutin

BACKGROUND/AIMS: Proton pump inhibitor (PPI)-based standard triple therapy for Helicobacter pylori infection is widely used, but it has a considerable failure rate. The aim of this study was to evaluate the efficacy and tolerability of rescue therapies with a quadruple regimen and a rifabutin-based regimen for patients who experienced failure with PPI-based standard triple therapy. METHODS: From July 2004 through October 2006, 52 patients for whom first line triple therapy (PPI, amoxicillin and clarithromycin) had failed were included in this study. They were treated with a quadruple regimen for 7 days (PPI, bismuth, tetracycline and metronidazole) as a second line therapy. For third line therapy, a rifabutin-based regimen (PPI, rifabutin and amoxicillin) was prescribed for 14 days. The H. pylori status was determined before and at least 4 weeks after therapy by the 13C urea breath test or by endoscopy with antral and corpus biopsies for a rapid urease test, histological examination and culture. RESULTS: The mean age was 52.6 years. Thirteen patients (25%) of the 52 patients were dropped. The eradication rate of the quadruple therapy was 84.6% (33/39). Three patients of the 6 failures with quadruple therapy were then treated with the rifabutin-based regimen. The eradication rate of the rifabutin-based therapy was 100% (3/3). Adverse effects (10.2%) were reported in 4 patients who were treated with quadruple regimen. CONCLUSIONS: The quadruple regimen is still an effective second-line therapy for Korean patients who experience failure with PPI-based standard triple therapy. The rifabutin-based regimen could be used as a third-line rescue therapy in Korea.
Amoxicillin ; Biopsy ; Bismuth ; Breath Tests ; Carbamates ; Endoscopy ; Helicobacter ; Helicobacter pylori ; Humans ; Organometallic Compounds ; Proton Pumps ; Protons ; Rifabutin ; Tetracycline ; Urea ; Urease

The seroprevalence of Helicobacter pylori (H. pylori) in Korea was found to be decreased. However eradication rate of 1st line therapy has become lower and antimicrobial resistance has increased, recently. Therefore we must also be prepared to face treatment failure and in designing a treatment strategy we should not focus on the results of 1st line therapy alone, but also on the rescue therapy. Some studies have demonstrated that levofloxacine-based triple regimen shows favourable results in 2nd or 3rd line therapy. However, it has shown that resistance to quinolones is easily acquired, and in Korea with a high consumption of these drugs, the resistance rate is increasing and is already relatively high. Therefore it should be reserved for final rescue treatment. Another potential regimen for final rescue therapy is rifabutin-based regimen which is known to be effective for H. pylori strains resistant to clarithromycin or metronidazole. Several concerns still remain, however, regarding rifabutin treatment. Firstly it is very expensive. Secondly myelotoxicity such as leukopenia and thrombocytopenia have been reported in some patients treated with rifabutin. Finally because of multiresistant strains of Mycobacterium tuberculosis increasing in numbers, indications for these drugs should be chosen very carefully to avoid further acceleration of development of resistance. Therefore refabutin should be considered only as the last option. It is difficult to choose proper treatment in Korea after failure of 2nd line treatment, because only a few study about 3rd line rescue therapy have been reported. Therefore we need more well designed randomized controlled studies.
Acceleration ; Clarithromycin ; Helicobacter ; Helicobacter pylori ; Humans ; Korea ; Leukopenia ; Metronidazole ; Mycobacterium tuberculosis ; Quinolones ; Rifabutin ; Seroepidemiologic Studies ; Thrombocytopenia ; Treatment Failure

Seven day regimen of proton pump inhibitor (PPI)-clarithromycin-amoxicillin triple therapy has been the main first line therapy for H. pylori infection. However, recently, the efficacy of this triple therapy becomes lower and the main cause of treatment failure is antibiotic resistance. As a first line treatment option, extended treatment duration and new treatment regimen, such as quadruple therapy, need to be considered. In the case of first line treatment failure, quadruple therapy consisting of PPI-bismuth-tetracycline-metronidazole is an effective second line regimen. After the failure of a second line treatment, rescue treatment should be based on antimicrobial susceptibility testing. Triple therapies based on levofloxacin, moxifloxacin, or rifabutin are options if multiple eradication failure occurs. Several problems of drug treatment for H. pylori infection, such as antibiotics resistance and high re-infection rates, would be overcome by the use of an efficacious vaccine. Although extensive studies in the mouse model have demonstrated the feasibility of both therapeutic and prophylactic vaccine, few clinical trials with various formulations have provided satisfactory results. To develop a successful vaccine, better understanding of the mechanism of the immune response to H. pylori infection as well as more information on suitable antigens, route of immunization, and adjuvants will be required.
Animals ; Anti-Bacterial Agents ; Drug Resistance, Microbial ; Helicobacter pylori ; Immunization ; Levofloxacin ; Mice ; Proton Pumps ; Rifabutin ; Treatment Failure ; Vaccines*