AIM： To investigate overlapping regions of the rpoB gene previously involved with rifamycin resistance in M. tuberculosis and seek correlation between rpoB mutations in dinical MAP strains with susceptibility to RIF ...AIM： To investigate overlapping regions of the rpoB gene previously involved with rifamycin resistance in M. tuberculosis and seek correlation between rpoB mutations in dinical MAP strains with susceptibility to RIF and RFB. METHODS： We designed a molecular-based PCR method for the evaluation of rifabutin （RFB） and rifampicin （RIF） resistance based on probable determinant regions within the rpoB gene of MAP, including the 81 bp variable site located between nucleotides 1363 and 1443. The minimum inhibitory concentration （MIC） for RIF was also determined against 11 MAP isolates in attempt to seek correlation with rpoB sequences. RESULTS： We determined that MAP strain 18 had an MIC of 〉 30 mg/L and ≤ 5 mg/L for RIF and RFB respectively, and a significant and novel rpoB mutation C1367T, compared to an MIC of ≤ 1.0 mg/L for both drugs in the wild type MAP. The 30-fold increase in the MIC was a direct result of the rpoB mutation C1367T, which caused an amino acid change Thr456 to Ile456 in the drug＇s binding site. In addition, MAP strain 185 contained five silent rpoB mutations and exhibited an MIC comparable to the wild-type. Moreover, our in vitro selected mutation in MAP strain UCF5 resulted in the generation of a new resistant strain （UCF5-RIF16r） that possessed T1442C rpoB mutation and an MIC 〉 30 mg/L and 〉 10 mg/L for RIF and RFB respectively. Sequencing of the entire rpoB gene in MAP strains UCF4, 18, and UCF5-RIF16r revealed an rpoB mutation A2284C further downstream of the 81 bp variable region in UCF4, accounting for observed slight increase in MIC. In addition, no other significant mutations were found in strains 18 and UCF-RIF16r. CONCLUSION： The data clearly illustrates that clinical and in vitro-selected MAP mutants with rpoB mutations result in resistance to RIF and RFB, and that a single amino acid change in the beta subunit may have a significant impact on RIF resistance. Unconventional drug susceptibility testing such as our molecular approach will be beneficial for evaluation of antibiotic effectiveness. This molecular approach may also serve as a model for other drugs used for treatment of MAP infections.展开更多
When several Helicobacter pylori eradication treatments fail,guidelines recommend a cultured guided approach;however,culture is not widely available.Therefore,a rifabutin based regimen could be the best solution.Rifab...When several Helicobacter pylori eradication treatments fail,guidelines recommend a cultured guided approach;however,culture is not widely available.Therefore,a rifabutin based regimen could be the best solution.Rifabutin indeed shows a low rate of antibiotic resistance.Rifabutin is generally used in combination with amoxicillin in a triple therapy,with eradication rates about 80%in third-line regimens.The ideal duration of this therapy should range between 10 and 12 d.Combinations with antibiotics other than amoxicillin have demonstrated even better results,such as vonoprazan,which is a type of novel acid suppressor drug.Finally,a new formulation of triple therapy in a single capsule is under investigation,which is a field that deserves further investigation.Some notes of caution about rifabutin should be mentioned.This drug is used to treat tuberculosis or atypical mycobacteria;therefore,before starting a rifabutin-based eradication regimen,Mycobacterium tuberculosis infection should be thoroughly tested,since its use could promote the development of antibiotic resistance,thus affecting its effectiveness against Koch’s bacillus.Additionally,some serious side effects must be evaluated before starting any rifabutin-based therapy.Adverse effects include fever,nausea,vomiting and bone marrow suppression.For this reason,full blood count surveillance is required.展开更多
H pylori gastric infection is one of the most prevalent infectious diseases worldwide. The discovery that most upper gastrointestinal diseases are related to Hpylori infection and therefore can be treated with antibio...H pylori gastric infection is one of the most prevalent infectious diseases worldwide. The discovery that most upper gastrointestinal diseases are related to Hpylori infection and therefore can be treated with antibiotics is an important medical advance. Currently, a first-line triple therapy based on proton pump inhibitor （PPI） or ranitidine bismuth citrate （RBC） plus two antibiotics （darithromycin and amoxicillin or nitroimidazole） is recommended by all consensus conferences and guidelines. Even with the correct use of this drug combination, infection can not be eradicated in up to 23% of patients. Therefore, several second line therapies have been recommended. A 7 d quadruple therapy based on PPI, bismuth, tetracycline and metronidazole is the more frequently accepted. However, with second-line therapy, bacterial eradication may fail in up to 40% of cases. When Hpylori eradication is striclly indicated the choice of further treatment is controversial. Currently, a standard third-line therapy is lacking and various protocols have been proposed. Even after two consecutive failures, the most recent literature data have demonsbated that Hpylori eradication can be achieved in almost all patients, even when antibiotic susceptibility is not tested. Different possibilities of empirical treatment exist and the available third-line strategies are herein reviewed.展开更多
基金Supported by Grant RO1-AI51251-01 from NIH-NIAID
文摘AIM： To investigate overlapping regions of the rpoB gene previously involved with rifamycin resistance in M. tuberculosis and seek correlation between rpoB mutations in dinical MAP strains with susceptibility to RIF and RFB. METHODS： We designed a molecular-based PCR method for the evaluation of rifabutin （RFB） and rifampicin （RIF） resistance based on probable determinant regions within the rpoB gene of MAP, including the 81 bp variable site located between nucleotides 1363 and 1443. The minimum inhibitory concentration （MIC） for RIF was also determined against 11 MAP isolates in attempt to seek correlation with rpoB sequences. RESULTS： We determined that MAP strain 18 had an MIC of 〉 30 mg/L and ≤ 5 mg/L for RIF and RFB respectively, and a significant and novel rpoB mutation C1367T, compared to an MIC of ≤ 1.0 mg/L for both drugs in the wild type MAP. The 30-fold increase in the MIC was a direct result of the rpoB mutation C1367T, which caused an amino acid change Thr456 to Ile456 in the drug＇s binding site. In addition, MAP strain 185 contained five silent rpoB mutations and exhibited an MIC comparable to the wild-type. Moreover, our in vitro selected mutation in MAP strain UCF5 resulted in the generation of a new resistant strain （UCF5-RIF16r） that possessed T1442C rpoB mutation and an MIC 〉 30 mg/L and 〉 10 mg/L for RIF and RFB respectively. Sequencing of the entire rpoB gene in MAP strains UCF4, 18, and UCF5-RIF16r revealed an rpoB mutation A2284C further downstream of the 81 bp variable region in UCF4, accounting for observed slight increase in MIC. In addition, no other significant mutations were found in strains 18 and UCF-RIF16r. CONCLUSION： The data clearly illustrates that clinical and in vitro-selected MAP mutants with rpoB mutations result in resistance to RIF and RFB, and that a single amino acid change in the beta subunit may have a significant impact on RIF resistance. Unconventional drug susceptibility testing such as our molecular approach will be beneficial for evaluation of antibiotic effectiveness. This molecular approach may also serve as a model for other drugs used for treatment of MAP infections.
文摘When several Helicobacter pylori eradication treatments fail,guidelines recommend a cultured guided approach;however,culture is not widely available.Therefore,a rifabutin based regimen could be the best solution.Rifabutin indeed shows a low rate of antibiotic resistance.Rifabutin is generally used in combination with amoxicillin in a triple therapy,with eradication rates about 80%in third-line regimens.The ideal duration of this therapy should range between 10 and 12 d.Combinations with antibiotics other than amoxicillin have demonstrated even better results,such as vonoprazan,which is a type of novel acid suppressor drug.Finally,a new formulation of triple therapy in a single capsule is under investigation,which is a field that deserves further investigation.Some notes of caution about rifabutin should be mentioned.This drug is used to treat tuberculosis or atypical mycobacteria;therefore,before starting a rifabutin-based eradication regimen,Mycobacterium tuberculosis infection should be thoroughly tested,since its use could promote the development of antibiotic resistance,thus affecting its effectiveness against Koch’s bacillus.Additionally,some serious side effects must be evaluated before starting any rifabutin-based therapy.Adverse effects include fever,nausea,vomiting and bone marrow suppression.For this reason,full blood count surveillance is required.
文摘H pylori gastric infection is one of the most prevalent infectious diseases worldwide. The discovery that most upper gastrointestinal diseases are related to Hpylori infection and therefore can be treated with antibiotics is an important medical advance. Currently, a first-line triple therapy based on proton pump inhibitor （PPI） or ranitidine bismuth citrate （RBC） plus two antibiotics （darithromycin and amoxicillin or nitroimidazole） is recommended by all consensus conferences and guidelines. Even with the correct use of this drug combination, infection can not be eradicated in up to 23% of patients. Therefore, several second line therapies have been recommended. A 7 d quadruple therapy based on PPI, bismuth, tetracycline and metronidazole is the more frequently accepted. However, with second-line therapy, bacterial eradication may fail in up to 40% of cases. When Hpylori eradication is striclly indicated the choice of further treatment is controversial. Currently, a standard third-line therapy is lacking and various protocols have been proposed. Even after two consecutive failures, the most recent literature data have demonsbated that Hpylori eradication can be achieved in almost all patients, even when antibiotic susceptibility is not tested. Different possibilities of empirical treatment exist and the available third-line strategies are herein reviewed.
