In vitro anti-Helicobacter pylori activities of new rifamycin derivatives, KRM-1648 and KRM-1657

Antimicrobial combinations against Helicobacter pylori including benzoxadiazol-based flavodoxin inhibitors: in vitro characterization

IMPORTANCE

The antimicrobial resistance of Helicobacter pylori (Hp) currently poses a threat to available treatment regimens. Developing antimicrobial drugs targeting new bacterial targets is crucial, and one such class of drugs includes Hp-flavodoxin (Hp-fld) inhibitors that target an essential metabolic pathway in Hp. Our study demonstrated that combining these new drugs with conventional antibiotics used for Hp infection treatment prevented the regrowth observed with drugs used alone. Hp-fld inhibitors show promise as new drugs to be incorporated into the treatment of Hp infection, potentially reducing the development of resistance and shortening the treatment duration.

Exploring Alternative Treatment Choices for Multidrug-Resistant Clinical Strains of Helicobacter pylori in Mongolia

Helicobacter pylori is a pathogen related to severe diseases such as gastric cancer; because of rising antimicrobial-resistant strains, failure to eradicate H. pylori with antibiotics has increased worldwide. Multidrug-resistant H. pylori and gastric cancer is common in Mongolia; therefore, we aimed to explore alternative antimicrobial treatments and the genomes of resistant strains in this country. A total of 361 H. pylori strains isolated from patients in Mongolia were considered. Minimal inhibitory concentrations for two fluoroquinolones (ciprofloxacin and moxifloxacin), rifabutin, and furazolidone were determined via two-fold agar dilution. Genomic mutations in antibiotic-resistant strains were identified by next-generation sequencing using the Illumina Miseq platform and compared with genes from a reference H. pylori strain (26695). The resistance rate of H. pylori strains to quinolones was high (44% to ciprofloxacin and 42% to moxifloxacin), and resistance to rifabutin was low (0.5%); none were resistant to furazolidone. Most quinolone-resistant strains possessed gyrA gene mutations causing amino acid changes (e.g., N87K, A88P, and D91G/Y/N). While one rifabutin-resistant strain had amino acid-substituting mutations in rpoB (D530N and R701C), the other had three novel rpoB mutations; both rifabutin-resistant strains were sensitive to furazolidone. Overall, our findings suggest that rifabutin and/or furazolidone may be an alternative, effective H. pylori treatment in patients who have failed to respond to other treatment regimens.

The Inappropriateness of Using Rifampicin E-Test to Predict Rifabutin Resistance in Helicobacter pylori

BACKGROUND

The aim of this study was to evaluate the rifamycin cross-resistance in Helicobacter pylori, and whether the use of rifampicin E-test strips to screen H. pylori rifabutin resistance is appropriate.

METHODS

A total of 89 H. pylori isolates were included. Rifampicin minimum inhibitory concentrations (MICs) were obtained by E-test, while the MICs for rifapentine, rifaximin, and rifabutin were determined by agar dilution method. The rifamycin resistance rates based on different breakpoints were compared. Isolates with high-level rifampicin resistance were subjected to whole-genome sequencing.

RESULTS

A wide distribution of MICs (mostly in the range 0.125-8 mg/L) was observed for rifampicin, rifapentine, and rifaximin. Using MIC >1, ≥ 4, and > 4 mg/L as the breakpoints, resistance rates to rifampicin/rifapentine/rifaximin were 60.4%/48.3%/38.2%, 28.1%/25.8%/23.6%, and 15.7%/16.9%/7.9%, respectively. However, the rifabutin MICs of all the tested H. pylori isolates were extremely low (≤0.016 mg/L). Applying MIC ≥ 0.125 mg/L as the breakpoint, rifabutin resistance was nil. No mutation was found in the rpoB gene sequences of the 2 isolates with high-level rifampicin resistance.

CONCLUSIONS

There is a lack of cross-resistance between rifabutin and other rifamycins in H. pylori. The use of rifampicin E-test to predict H. pylori rifabutin resistance is inappropriate.

Therapeutic efficacy of rifalazil (KRM-1648) in a M. ulcerans-induced Buruli ulcer mouse model

Buruli ulcer (BU) is a skin disease caused by Mycobacterium ulcerans infection that requires long-term antibiotic treatment and/or surgical excision. In this study, we investigated the therapeutic efficacy of the rifamycin derivative, rifalazil (RLZ) (also known as KRM-1648), in an advanced M. ulcerans infection model. Six-week-old female BALB/c mice were infected with 3.25 x 10⁴ colony-forming units (CFU) of M. ulcerans subcutaneously into the bilateral hind footpads. At 33 days post-infection, when the footpads exhibited significant redness and swelling, mice were treated orally with 5 or 10 mg/kg of RLZ for up to 15 weeks. Mice were followed for an additional 15 weeks following treatment cessation. Untreated mice exhibited a progressive increase in footpad redness, swelling, and erosion over time, and all untreated mice reached to endpoint within 5–8 weeks post-bacterial injection. In the RLZ-treated mice, footpad redness and swelling and general condition improved or completely healed, and no recurrence occurred following treatment cessation. After 3 weeks of treatment, the CFU counts from the footpads of recovered RLZ-treated mice showed a 10⁴ decrease compared with those of untreated mice. We observed a further reduction in CFU counts to the detection limit following 6 to 15 weeks of treatment, which did not increase 15 weeks after discontinuing the treatment. Histopathologically, bacteria in the treated mice became fragmented one week after RLZ-treatment. At the final point of the experiment, all the treated mice (5mg/kg/day; n = 6, 10mg/kg/day; n = 7) survived and had no signs of M. ulcerans infection. These results indicate that the rifamycin analogue, RLZ, is efficacious in the treatment of an advanced M. ulcerans infection mouse model.

Rifabutin for the Treatment of Helicobacter Pylori Infection: A Review

Nowadays, apart from having to know first-line Helicobacter pylori eradication regimens well, we must also be prepared to face treatment failures. The aim of this review is to summarize the role of rifabutin in the management of H. pylori infection. Bibliographical searches were performed in PubMed. Data on resistance and efficacy of rifabutin-containing regimens on H. pylori eradication were meta-analyzed. Mean H. pylori rifabutin resistance rate (39 studies, including 9721 patients) was 0.13%; when studies only including patients naïve to H. pylori eradication treatment were considered, this figure was even lower (0.07%). Mean H. pylori eradication rate (by intention-to-treat) with rifabutin-containing regimens (3052 patients) was 73%. Respective cure rates for second-, third-, fourth- and fifth-line therapies, were 79%, 69%, 69% and 72%. Most studies administered rifabutin 300 mg/day, which seemed to be more effective than 150 mg/day. The ideal length of treatment remains unclear, but 10–12-day regimens are generally recommended. Adverse events to rifabutin treatment in H. pylori studies were relatively infrequent (15%), and severe adverse events were exceptional (myelotoxicity was the most significant, although always reversible). In summary, rifabutin-containing therapy represents an encouraging strategy generally restricted, at present, to patients where previous (usually multiple) eradication regimens have failed.

Best Helicobacter pylori Eradication Strategy in the Era of Antibiotic Resistance

Antibiotic resistance is the major reason for Helicobacter pylori treatment failure, and the increasing frequency of antibiotic resistance is a challenge for clinicians. Resistance to clarithromycin and metronidazole is a particular problem. The standard triple therapy (proton pump inhibitor, amoxicillin, and clarithromycin) is no longer appropriate as the first-line treatment in most areas. Recent guidelines for the treatment of H. pylori infection recommend a quadruple regimen (bismuth or non-bismuth) as the first-line therapy. This treatment strategy is effective for areas with high resistance to clarithromycin or metronidazole, but the resistance rate inevitably increases as a result of prolonged therapy with multiple antibiotics. Novel potassium-competitive acid blocker-based therapy may be effective, but the data are limited. Tailored therapy based on antimicrobial susceptibility test results is ideal. This review discussed the current important regimens for H. pylori treatment and the optimum H. pylori eradication strategy.

Rifabutin and Furazolidone Could Be the Candidates of the Rescue Regimen for Antibiotic-Resistant H. pylori in Korea

Background/Aim. In Korea, the rate of Helicobacter pylori (H. pylori) eradication has declined steadily as a result of increasing resistance to antibiotics, especially dual resistance to clarithromycin and metronidazole. However, microbiological culture data on drug-resistant H. pylori is lacking. This study evaluated the antimicrobial efficacy of candidate antibiotics against resistant H. pylori strains. Methods. After retrospectively reviewing the data from the Helicobacter Registry in Gil Medical Center (GMC) and Asan Medical Center (AMC), along with 4 reference strains, we selected the 31 single- or multidrug-resistant strains. The susceptibility of the H. pylori strains to seven antibiotics (clarithromycin, metronidazole, levofloxacin, amoxicillin, tetracycline, rifabutin, and furazolidone) and minimum inhibitory concentration were tested using the broth microdilution technique. Results. Among 31 antibiotic resistance strains for H. pylori, there were no strains resistant to rifabutin or furazolidone, which had MICs of <0.008 and 0.5 μg/mL, respectively. Only one tetracycline-resistant strain was found (MIC < 2 μg/mL). Amoxicillin and levofloxacin were relatively less effective against the H. pylori strains compared to rifabutin or furazolidone (resistance rates 22.6%, 1.9%, respectively). Tetracycline showed the relatively low resistance rates (3.2%) for H. pylori strains. Conclusions. Therefore, along with tetracycline which has already been used as a component for second-line eradication regimen for Helicobacter, rifabutin and furazolidone, alone or in combination, could be used to eradicate antibiotic-resistant H. pylori strains where drug-resistant Helicobacter spp. are increasing.

Effective therapeutic regimens in two South Asian countries with high resistance to major Helicobacter pylori antibiotics

Background

Nepal and Bangladesh have a high prevalence of Helicobacter pylori with high resistance rates to clarithromycin, metronidazole, and levofloxacin. Here, we evaluated the susceptibility and genetic mutations of 5 alternative antibiotics against isolates from both countries to obtain an effective treatment regimen for H. pylori eradication.

Methods

We used the agar dilution method to determine the minimal inhibitory concentration of 5 alternative antibiotics against 42 strains from Nepal and 56 from Bangladesh and performed whole genome mutation analysis.

Results

No resistance to furazolidone or rifabutin and a high susceptibility of sitafloxacin (95.2% in Nepal and 98.2% in Bangladesh) were observed. In contrast, resistance to rifaximin (52.4% in Nepal and 64.3% in Bangladesh) was high. Moreover, resistance to garenoxacin was higher in Bangladesh (51.6%) than in Nepal (28.6%, P = 0.041), most likely due to its correlation with levofloxacin resistance (P = 0.03). Garenoxacin and rifaximin were significantly correlated in Bangladesh (P = 0.014) and occurred together with all sitafloxacin-resistant strains. Mutations of gyrA could play a significant role in garenoxacin resistance, and double mutations of A87 and D91 were associated with sitafloxacin resistance. Analysis of the rpoB gene demonstrated well-known mutations, such as V657I, and several novel mutations, including I2619V, V2592 L, T2537A, and F2538 L.

Conclusions

Rifabutin can be cautiously implemented as therapy for H. pylori infection due to its interaction with the tuberculosis endemic in Bangladesh. The high susceptibility of furazolidone and sitafloxacin suggests their possible future application in Nepal and Bangladesh.

Alternative eradication regimens for Helicobacter pylori infection in Indonesian regions with high metronidazole and levofloxacin resistance

Background

The prevalence of Helicobacter pylori resistance to metronidazole and clarithromycin is high in Indonesia. Moreover, the increasing levofloxacin resistance rates in the absence of bismuth treatment in Indonesia has led to the use of other antibiotics as alternative regimens.

Methods

We determined the minimum inhibitory concentrations (MICs) of five alternative antibiotics for H. pylori (rifaximin, rifabutin, furazolidone, garenoxacin, and sitafloxacin) using the agar dilution method and assessed mutations associated with antibiotic resistance using next-generation sequencing.

Result

Analysis of 106 strains isolated from 1039 adult dyspeptic patients revealed that none of the strains were furazolidone-resistant. All strains were also sensitive to rifabutin and sitafloxacin. In contrast, the rates of resistance to rifaximin and garenoxacin were high (38.9% and 6.7%, respectively). The strains isolated from patients on Java Island had the highest resistance rates to garenoxacin and rifaximin. In addition, the resistance was distributed evenly among the ethnic groups, ranging between 25.0% and 69.2%. Except for rifaximin, for which the resistance rate was 38.9%, the other four antibiotics could be successfully employed to eradicate levofloxacin- and metronidazole-resistant H. pylori infections in vitro. Interestingly, garenoxacin-sensitive strains were found in regions with high clarithromycin resistance rates such as Bali and Papua Islands. In contrast, rifaximin might not be considered as an alternative antibiotic in regions with high clarithromycin resistance. There was an inconsistent association between gyrA and gyrB mutations and garenoxacin resistance. We confirmed that the I837V (replacement of isoleucine at position 837 with valine), A2414T/V, Q2079K and K2068R were the predominant rpoB point mutations. There was an association between vacA genotypes of H. pylori and rifaximin resistance (P = 0.048).

Conclusion

furazolidone-, rifabutin-, and sitafloxacin-based therapies might be considered as alternative regimens to eradicate H. pylori in Indonesia, including regions with high metronidazole and clarithromycin resistance rates. Moreover, sitafloxacin but not garenoxacin should be considered for eradication of levofloxacin-resistant strains.

Effective antimicrobial activity of rifabutin against multidrug-resistant Helicobacter pylori

BACKGROUND

Helicobacter pylori resistance to more than one antibiotic is the main reason for failure in bacterial eradication in a considerable number of patients. Rifabutin (RFB) with a broad-spectrum of antimicrobial therapy has been suggested for treatment of refractory multidrug-resistant infections.

METHODS

Helicobacter pylori isolates from 104 patients were examined for resistance to 5 currently used antibiotics and RFB, using agar dilution method. Twofold serial dilutions of antibiotics were used and MICs (μg/mL) determined as metronidazole (MTZ 8), clarithromycin (CLR 2), amoxicillin (AMX 1), tetracycline (TET 0.5), furazolidone (FRZ 0.5), and RFB (0.06).

RESULTS

Of 104 H. pylori isolates, only 7 (6.7%) were sensitive to all the 6 antibiotics. However, 30 (28.8%) were resistant to one antibiotic, 28 (26.9%) to two, 19 (18.2%) to three, 14 (13.4%) to four, and 6 (5.7%) to five currently used antibiotics. Overall, 67(64.4%) of isolates were resistant to 2-5 currently used antibiotics and considered as multidrug-resistant (MDR), with 59 (88.1%) showing sensitivity to RFB and 8 (11.9%) resistance (P < 0.05). Of 33 isolates resistant to both MTZ and CLR, 25 (75.7%) were sensitive to RFB and 8 (24.3%) resistant (P < 0.05).

DISCUSSION

In vitro antimicrobial effectiveness of RFB on MDR H. pylori including those with resistance to both MTZ and CLR was demonstrated. However, RFB efficacy decreased as the number of antibiotics responsible for MDR increased. Considering that RFB inhibits both extra- and intracellular H. pylori, it can be suggested as an effective antibiotic against of MDR H. pylori.

Rifabutin Containing Triple Therapy and Rifabutin with Bismuth Containing Quadruple Therapy for Third-Line Treatment of Helicobacter pylori Infection: Two Pilot Studies

AIM

To evaluate the therapeutic gain of the addition of bismuth to a rifabutin containing triple therapy with amoxicillin and pantoprazole at standard dosages for the treatment of third-line Helicobacter pylori infection after a preliminary susceptibility test.

METHODS

Two separate groups of patients in two pilot studies which were carried out simultaneously. One group was treated with rifabutin 150 mg b.i.d., pantoprazole 20 mg b.i.d., and amoxicillin 1 g b.i.d. for 10 days and the other group with rifabutin 150 mg b.i.d., pantoprazole 20 mg b.i.d., amoxicillin 1 g b.i.d., and bismuth subcitrate 240 mg b.i.d. for 10 days. All patients underwent to culture and susceptibility testing prior to their inclusion in the study. A successful outcome was confirmed with an Urea Breath test performed 8 weeks after the end of treatment. A blood cell count was performed for all patients at the start and after 5 days of treatment since rifabutin has been shown to inhibit the growth of leucocytes.

RESULTS

Twenty-nine patients were recruited in the pantoprazole, amoxicillin, rifabutin group and 30 in the pantoprazole, amoxicillin, rifabutin, and bismuth subcitrate group. All patients had a positive H. pylori culture and the susceptibility test used showed H. pylori sensitivity to rifabutin and amoxicillin. H. pylori eradication during follow-up was 18/27 (66.7%, 95% CI: 47.7-85.7%) in the pantoprazole, amoxicillin, rifabutin group and 28/29 (96.6%, 95% CI: 89.5-100.0%) in the pantoprazole, amoxicillin, rifabutin, and bismuth subcitrate group. Both treatments were well-tolerated with no reported side effects. Blood cell count remained normal in all patients.

CONCLUSION

The addition of bismuth subcitrate to a triple therapy that includes proton pump inhibitors, amoxicillin, and rifabutin in patients who are treated for the third time for H. pylori infection resulted in a 30% therapeutic gain.

Rescue Therapy with a Proton Pump Inhibitor Plus Amoxicillin and Rifabutin for Helicobacter pylori Infection: A Systematic Review and Meta-Analysis

Background. To conduct a systematic review and meta-analysis of clinical trials for eradication of Helicobacter pylori (H. pylori) that included a treatment arm with a proton pump inhibitor, rifabutin, and amoxicillin. Materials and Methods. We selected clinical trials that examined the efficacy of H. pylori eradication therapies and included a study arm using the test regimen from major medical literature databases and abstracts from major gastroenterology meetings. We also did subgroup and sensitivity analyses. Results. Twenty-one studies were included in systematic review. The total eradication rates of the test regimen were 70.4% by intent-to-treat (ITT) and 72.0% by per-protocol (PP) analyses. The pooled odds ratio (OR) was 0.55 using fixed effects model (P = 0.283) for the test regimen versus other triple regimens. The total eradication rates were 68.4% for the test regimen and 81.9% in the control group by ITT, while the OR was 1.08 using random effects model (P = 0.019). The pooled eradication rate was 66.4% for the test regimen and 67.4% for the control group by ITT. The total adverse effects incidence were 25.1% for the test regimen. Conclusions. The test regimen for H. pylori rescue therapy may be not superior to control regimens in efficacy.

Recent Insights into Antibiotic Resistance in Helicobacter pylori Eradication

Antibiotics have been useful in the treatment of H. pylori-related benign and malignant gastroduodenal diseases. However, emergence of antibiotic resistance often decreases the eradication rates of H. pylori infections. Many factors have been implicated as causes of treatment failure, but the main antibiotic resistance mechanisms described to date are due to point mutations on the bacterial chromosome, a consequence of a significantly phenotypic variation in H. pylori. The prevalence of antibiotic (e.g., clarithromycin, metronidazole, tetracycline, amoxicillin, and furazolidone) resistance varies among different countries; it appears to be partly determined by geographical factors. Since the worldwide increase in the rate of antibiotic resistance represents a problem of relevance, some studies have been performed in order to identify highly active and well-tolerated anti-H. pylori therapies including sequential, concomitant quadruple, hybrid, and quadruple therapy. These represent a promising alternatives in the effort to overcome the problem of resistance. The aim of this paper is to review the current status of antibiotic resistance in H. pylori eradication, highlighting the evolutionary processes in detail at alternative approaches to treatment in the past decade. The underlying resistance mechanisms will be also followed.

Fourth-line rescue therapy with rifabutin in patients with three Helicobacter pylori eradication failures

BACKGROUND

In some cases, Helicobacter pylori infection persists even after three eradication treatments.

AIM

To evaluate the efficacy of an empirical fourth-line rescue regimen with rifabutin in patients with three eradication failures.

DESIGN

Multicentre, prospective study.

PATIENTS

In whom the following three treatments had consecutively failed: first (PPI + clarithromycin + amoxicillin); second (PPI + bismuth + tetracycline + metronidazole); third (PPI + amoxicillin + levofloxacin).

INTERVENTION

A fourth regimen with rifabutin (150 mg b.d.), amoxicillin (1 g b.d.) and a PPI (standard dose b.d.) was prescribed for 10 days.

OUTCOME

Eradication was confirmed by (13) C-urea breath test 4-8 weeks after therapy. Compliance and tolerance: Compliance was determined through questioning and recovery of empty medication envelopes. Adverse effects were evaluated using a questionnaire.

RESULTS

One-hundred patients (mean age 50 years, 39% men, 31% peptic ulcer/69% functional dyspepsia) were included. Eight patients did not take the medication correctly (in six cases due to adverse effects). Per-protocol and intention-to-treat eradication rates were 52% (95% CI = 41-63%) and 50% (40-60%). Adverse effects were reported in 30 (30%) patients: nausea/vomiting (13 patients), asthenia/anorexia (8), abdominal pain (7), diarrhoea (5), fever (4), metallic taste (4), myalgia (4), hypertransaminasemia (2), leucopenia (<1,500 neutrophils) (2), thrombopenia (<150,000 platelets) (2), headache (1) and aphthous stomatitis (1). Myelotoxicity resolved spontaneously in all cases.

CONCLUSIONS

Even after three previous H. pylori eradication failures, an empirical fourth-line rescue treatment with rifabutin may be effective in approximately 50% of the cases. Therefore, rifabutin-based rescue therapy constitutes a valid strategy after multiple previous eradication failures with key antibiotics, such as clarithromycin, metronidazole, tetracycline and levofloxacin.

Review article: rifabutin in the treatment of refractory Helicobacter pylori infection

BACKGROUND

Even with the current most effective treatment regimens, a relevant proportion of patients will fail to eradicate Helicobacter pylori infection.

AIM

To evaluate the role of rifabutin in the treatment of H. pylori infection.

METHODS

Bibliographical searches were performed in MEDLINE. Data on the efficacy of rifabutin-containing regimens on H. pylori eradication were combined and meta-analysed using the generic inverse variance method.

RESULTS

Rifabutin shows good in vitro activity against H. pylori. Mean H. pylori rifabutin resistance rate (calculated from 11 studies including 2982 patients) was 1.3% (95% confidence interval = 0.9-1.7%). When only studies including patients naïve to H. pylori eradication treatment were considered, this figure was even lower (0.6%). On the other hand, higher values of rifabutin resistance were calculated (1.59%) when only post-treatment patients were considered. Overall, mean H. pylori eradication rate (intention-to-treat analysis) with rifabutin-containing regimens (1008 patients) was 73% (67-79%). Respective cure rates for second-line (223 patients), third-line (342 patients) and fourth/fifth-line (95 patients) rifabutin therapies were 79% (67-92%), 66% (55-77%) and 70% (60-79%) respectively. For treating H. pylori infection, almost all studies have administered rifabutin 300 mg/day; this dose seems to be more effective than 150 mg/day. The ideal length of treatment remains unclear, but 10- to 12-day regimens are generally recommended. The mean rate of adverse effects was 22% (19-25%). Myelotoxicity is the most significant, although this complication was rare. Until now, all patients have recovered of leucopenia uneventfully in a few days, and there have been no reports of infection or other adverse outcomes related to it.

CONCLUSION

Rifabutin-containing rescue therapy constitutes an encouraging strategy after multiple (usually three) previous eradication failures with key antibiotics such as amoxicillin, clarithromycin, metronidazole, tetracycline and levofloxacin.

In vitro antibacterial activity of Phx-3 against Helicobacter pylori

Phx-3, one of the phenoxazine derivatives, is reported to have inhibitory effect on Mycobacterium species and Chlamydia pneumoniae but not Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus, Listeria monocytogenes. The bactericidal activities of Phx-3 against Helicobacter pylori strains have not been assessed. Then, we measured minimum inhibitory concentration of Phx-3 for Helicobacter strains and assessed the morphological and biochemical effects of Phx-3 on H. pylori. In present study, it has shown that H. pylori strains including clarithromycin resistant strain and Helicobacter musterae were killed effectively by the treatment with Phx-3. Furthermore, severe morphological changes such as membrane blebbing and formation of hollows in H. pylori were detected. In addition, induction of heat shock protein 60 was observed. Taken together, Phx-3 has antibacterial activity against Helicobacter pylori.

Rescue therapy using a rifabutin-based regimen is effective for cure of Helicobacter pylori infection

OBJECTIVE

To evaluate the efficacy of rescue therapy using rifabutin, amoxicillin and a proton pump inhibitor (PPI) in the eradication of Helicobacter pylori in patients who have failed at least one course of PPI-based triple therapy.

METHODS

The present study was a single-centre case series of 16 consecutive patients who had received at least one course of standard eradication therapy. Pretreatment evaluation included endoscopy with biopsies for histology and culture for H pylori infection. Treatment consisted of a one-week regimen containing a PPI twice daily, amoxicillin (A) 1 g twice daily and rifabutin (R) 300 mg once daily (PPI-AR). Post-treatment evaluation consisted of a repeat endoscopy with biopsy for histology and culture, or a validated urea breath test at least four weeks after treatment was completed. Pretreatment antibiotic susceptibility to metronidazole, clarithromycin and A was evaluated using a validated epsilometer test.

RESULTS

Of the 16 patients, four had previously received one course of triple therapy, 10 had received two courses and two had received more than two courses. The overall success rate of PPI-AR was 63% (10 of 16). Resistance to A was 0% (0 of 13), metronidazole 77% (10 of 13), clarithromycin 70% (seven of 10), and both metronidazole and clarithromycin 60% (six of 10). There was no correlation between resistance patterns and cure rate.

CONCLUSIONS

An R-containing regimen such as PPI-AR is a viable option as rescue therapy for H pylori infection.

Second-line rescue therapy of helicobacter pylori infection

Helicobacter pylori infection is the main known cause of gastritis, gastroduodenal ulcer disease and gastric cancer. After more than 20 years of experience in H. pylori treatment, however, the ideal regimen to treat this infection has still to be found. Nowadays, apart from having to know well first-line eradication regimens, we must also be prepared to face treatment failures. Therefore, in designing a treatment strategy we should not focus on the results of primary therapy alone, but also on the final (overall) eradication rate. The choice of a 'rescue' treatment depends on which treatment is used initially. If a first-line clarithromycin-based regimen was used, a second-line metronidazole-based treatment (quadruple therapy) may be used afterwards, and then a levofloxacin-based combination would be a third-line 'rescue' option. Alternatively, it has recently been suggested that levofloxacin-based 'rescue' therapy constitutes an encouraging second-line strategy, representing an alternative to quadruple therapy in patients with previous PPI-clarithromycin-amoxicillin failure, with the advantage of efficacy, simplicity and safety. In this case, quadruple regimen may be reserved as a third-line 'rescue' option. Finally, rifabutin-based 'rescue' therapy constitutes an encouraging empirical fourth-line strategy after multiple previous eradication failures with key antibiotics such as amoxicillin, clarithromycin, metronidazole, tetracycline, and levofloxacin. Even after two consecutive failures, several studies have demonstrated that H. pylori eradication can finally be achieved in almost all patients if several 'rescue' therapies are consecutively given. Therefore, the attitude in H. pylori eradication therapy failure, even after two or more unsuccessful attempts, should be to fight and not to surrender.

New agents for Clostridium difficile-associated disease

BACKGROUND

Clostridia-derived diseases, in particular C. difficile-associated disease (CDAD), have been increasing in incidence, severity, and morbidity. The mainstay of treatment options has relied upon metronidazole and vancomycin, but these treatments routinely result in high relapse rates (20%) and, in the case of metronidazole, decreasing efficacy.

OBJECTIVE

Evaluate and compare the current clinical and preclinical therapies of CDAD.

METHODS

RESULTS/CONCLUSION

The new antibiotics in development and preclinical development reflect next-generation versions of older drugs or two new mechanism-of-action class drugs (OPT-80, REP3123). Based on the current preclinical and clinical data, the next-generation drugs impart only a subtle difference from the intrinsic weaknesses of their genre. In contrast, OPT-80 and REP3123 seem to be differentiated.

“Rescue” regimens after Helicobacter pylori treatment failure

Helicobacter pylori (H pylori) infection is the main cause of gastritis, gastroduodenal ulcer disease, and gastric cancer. After more than 20 years of experience in H pylori treatment, in my opinion, the ideal regimen to treat this infection is still to be found. Currently, apart from having to know first-line eradication regimens well, we must also be prepared to face treatment failures. Therefore, in designing a treatment strategy we should not focus on the results of primary therapy alone, but also on the final (overall) eradication rate. The choice of a “rescue” treatment depends on which treatment is used initially. If a clarithromycin-based regimen was used initially, a subsequent metronidazole-based treatment (quadruple therapy) may be used afterwards, and then a levofloxacin-based combination would be a third “rescue” option. Alternatively, it has recently been suggested that levofloxacin-based rescue therapy constitutes an encouraging second-line strategy, representing an alternative to quadruple therapy in patients with previous PPI-clarithromycin-amoxicillin failure, with the advantage of efficacy, simplicity and safety. In this case, a quadruple regimen may be reserved as a third-line rescue option. Finally, rifabutin-based rescue therapy constitutes an encouraging empirical fourth-line strategy after multiple previous eradication failures with key antibiotics such as amoxicillin, clarithromycin, metronidazole, tetracycline, and levofloxacin. Even after two consecutive failures, several studies have demonstrated that H pylori eradication can finally be achieved in almost all patients if several rescue therapies are consecutively given. Therefore, the attitude in H pylori eradication therapy failure, even after two or more unsuccessful attempts, should be to fight and not to surrender.

Who's Winning the War? Molecular Mechanisms of Antibiotic Resistance in Helicobacter pylori

The ability of clinicians to wage an effective war against many bacterial infections is increasingly being hampered by skyrocketing rates of antibiotic resistance. Indeed, antibiotic resistance is a significant problem for treatment of diseases caused by virtually all known infectious bacteria. The gastric pathogen Helicobacter pylori is no exception to this rule. With more than 50% of the world's population infected, H. pylori exacts a tremendous medical burden and represents an interesting paradigm for cancer development; it is the only bacterium that is currently recognized as a carcinogen. It is now firmly established that H. pylori infection is associated with diseases such as gastritis, peptic and duodenal ulceration and two forms of gastric cancer, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. With such a large percentage of the population infected, increasing rates of antibiotic resistance are particularly vexing for a treatment regime that is already fairly complicated; treatment consists of two antibiotics and a proton pump inhibitor. To date, resistance has been found to all primary and secondary lines of antibiotic treatment as well as to drugs used for rescue therapy.

Helicobacter pylori eradication therapy: indications, efficacy and safety

BACKGROUND

Helicobacter pylori infects up to half of the world's population. It remains the major cause of peptic ulcer disease and is recognised as a carcinogen for its role in gastric carcinogenesis. Successful eradication of the bacteria is associated with improved health outcomes including fewer dyspeptic symptoms, reduced peptic ulcer recurrence and rebleeding, reduced peptic ulcer risk with NSAIDs and as a cure for low-grade gastric MALT lymphoma. The risk of gastric cancer is reduced in those without premalignant mucosal abnormalities at the time of eradication.

OBJECTIVE

This review outlines the current indications and options for therapy of H. pylori with particular reference to drug-induced adverse events associated with treatment.

METHODS

The indications for H. pylori eradication are evidence-based and in accordance with recent consensus statements and recommendations. The eradication treatment is based on numerous clinical trials and meta-analyses.

RESULTS/CONCLUSION

Eradication therapy, in general, is safe and well tolerated. Antibiotic therapy may be associated with significant drug adverse reactions, especially gastrointestinal symptoms.

Empirical rescue therapy after Helicobacter pylori treatment failure: a 10-year single-centre study of 500 patients

BACKGROUND

Several 'rescue' therapies have been recommended to eradicate Helicobacter pylori, but they still fail in >20% of the cases, and these patients constitute a therapeutic dilemma.

AIM

To evaluate the efficacy of different 'rescue' therapies empirically prescribed during 10 years to 500 patients in whom at least one eradication regimen had failed to cure H. pylori infection.

DESIGN

Prospective single-centre study.

PATIENTS

Consecutive patients in whom at least one eradication regimen had failed.

INTERVENTION

Rescue regimens included: (i) quadruple therapy with omeprazole-bismuth-tetracycline-metronidazole; (ii) ranitidine bismuth citrate-tetracycline-metronidazole; (iii) omeprazole-amoxicillin-levofloxacin; and (iv) omeprazole-amoxicillin-rifabutin. Antibiotic susceptibility was unknown (rescue regimens were chosen empirically).

OUTCOME

Eradication was defined as a negative (13)C-urea breath test 4-8 weeks after completing therapy.

RESULTS

Five hundred patients were included (76% functional dyspepsia, 24% peptic ulcer). Compliance rates with first-, second- and third-line regimens were 92%, 92%, and 95%, respectively. Adverse effects were reported by 30%, 37%, and 55% of the patients receiving second-, third-, and fourth-line regimens. Overall, H. pylori cure rates with the second-, third-, and fourth-line rescue regimens were 70%, 74%, and 76%, respectively. Cumulative H. pylori eradication rate with four successive treatments was 99.5%.

CONCLUSION

It is possible to construct an overall treatment strategy to maximize H. pylori eradication, on the basis of administration of four consecutive empirical regimens; thus, performing bacterial culture even after a second or third eradication failure may not be necessary.

Efficacy of rifabutin-based triple therapy as second-line treatment to eradicate helicobacter pylori infection

Background

Rifabutin has been found to be effective in multi-resistant patients after various treatment cycles for Helicobacter pylori (HP) infection, but it has not been analysed as a second-line treatment. Therefore, we seek to compare the effectiveness of a treatment regimen including rifabutin versus conventional quadruple therapy (QT).

Methods

Open clinical trial, randomised and multi-centre, of two treatment protocols: A) Conventional regime -QT- (omeprazole 20 mg bid, bismuth citrate 120 mg qid, tetracycline 500 mg qid and metronidazole 500 mg tid); B) Experimental one -OAR- (omeprazole 20 mg bid, amoxicillin 1 gr bid, and rifabutin 150 mg bid), both taken orally for 7 days, in patients with HP infection for whom first-line treatment had failed. Eradication was determined by Urea Breath Test (UBT). Safety was determined by the adverse events.

Results

99 patients were randomised, QT, n = 54; OAR, n = 45. The two groups were homogeneous. In 8 cases, treatment was suspended (6 in QT and 2 in OAR). The eradication achieved, analysed by ITT, was for QT, 38 cases (70.4%), and for OAR, 20 cases (44.4%); p = 0.009, OR = 1.58. Of the cases analysed PP, QT were 77.1%; OAR, 46.5%; p = 0.002. Adverse effects were described in 64% of the QT patients and in 44% of the OAR patients (p = 0.04).

Conclusion

A 7-day rifabutin-based triple therapy associated to amoxicillin and omeprazole at standard dose was not found to be effective as a second-line rescue therapy. The problem with quadruple therapy lies in the adverse side effects it provokes. We believe the search should continue for alternatives that are more comfortably administered and that are at least as effective, but with fewer adverse side effects.

Trial Registration

Current Controlled Trials ISRCTN81058036

Quantifying gastric Helicobacter pylori infection: a comparison of quantitative culture, urease breath testing, and histology

Although there are several methods to detect Helicobacter pylori infection, there is no simple validated test to quantify the density of infection, which is believed to play a major role in the pathogenesis of H. pylori-associated gastritis and peptic ulceration. The aim of this study was to evaluate and compare noninvasive and invasive tests for assessing the level of H. pylori infection so as to facilitate the development and clinical testing of new antibiotic treatments. Healthy volunteers (n=323) were screened for H. pylori infection by serology and, if positive (n=86), invited to undergo (13)C urea breath testing (UBT) (n=55). An increase of >2.4 parts per thousand (13)CO(2) at 15 min compared to baseline was considered a positive test. Total cumulative urease activity (mumol) at 60 min was also calculated. UBT-positive subjects underwent endoscopy and nine biopsies were obtained from defined sites for quantitative culture and histological grading using the modified Sydney System. A total of 19 subjects were studied, 4 of whom underwent repeat testing. All subjects were positive for H. pylori by serology, UBT, culture, and histology. The increase in (13)CO(2) at 30 min correlated with the total cumulative urease activity at 60 min (r (2)=0.92, P< 0.0001). Bacterial counts (log cfu/biopsy; mean+/-SD) were 3.9+/-0.5, 3.9+/-0.4, and 3.9+/-0.6 at the lesser curve antrum, greater curve antrum, and corpus, respectively. There was no significant correlation between UBT results and bacterial counts at any biopsy site. Nor was there any significant correlation between the histology grading and either the UBT or the bacterial counts at any site. This study indicates that there is little correlation among the three methods used to measure bacterial burden in H. pylori infection. Thus, decrements in bacterial numbers during single-agent therapy cannot be measured reliably by UBT and therefore cannot be used to evaluate the potential efficacy of novel agents to treat gastric H. pylori infection.

Effective regimens for the treatment of Helicobacter pylori infection

Successful Helicobacter pylori eradication therapy remains a challenge in medical practice. Currently, a proton pump inhibitor-based triple therapy containing clarithromycin, amoxicillin or nitroimidazole for 7 days is the recommended first-line treatment approach with an expected eradication success rate of approximately 80%. As a second-line treatment option in the case of failure, a ranitidine bismuth citrate-based quadruple therapy is currently recommended curing another 80% of patients, leaving a subset of patients with persistent H. pylori infection. For these patients, promising rescue options have been evaluated including regimens that contain rifabutin, quinolones, furazolidone or high-dose amoxicillin. The role of susceptibility testing is still under discussion. It is not generally recommended prior to first-line treatment but guidelines propose a role for culture and antibiotic sensitivity testing after failure of the second attempt. Meanwhile, data on the geographic distribution of resistance pattern are available and may guide therapeutic decisions with regard to the combination of antibiotics chosen for the individual patients aiming at 100% cure rate in each individual patient.

Efficacy of novel rifamycin derivatives against rifamycin-sensitive and -resistant Staphylococcus aureus isolates in murine models of infection

Novel rifamycins (new chemical entities [NCEs]) having MICs of 0.002 to 0.03 microg/ml against Staphylococcus aureus and retaining some activity against rifampin-resistant mutants were tested for in vivo efficacy against susceptible and rifampin-resistant strains of S. aureus. Rifalazil and rifampin had a 50% effective dose (ED50) of 0.06 mg/kg of body weight when administered as a single intravenous (i.v.) dose in a murine septicemia model against a susceptible strain of S. aureus. The majority of NCEs showed efficacy at a lower i.v. dose (0.003 to 0.06 mg/kg). In addition, half of the NCEs tested for oral efficacy had ED50s in the range of 0.015 to 0.13 mg/kg, i.e., lower or equivalent to the oral ED50s of rifampin and rifalazil. NCEs were also tested in the septicemia model against a rifampin-resistant strain of S. aureus. Twenty-four of 169 NCEs were efficacious when administered as a single oral dose of 80 mg/kg. These NCEs were examined in the murine thigh infection model against a susceptible strain of S. aureus. Several NCEs dosed by intraperitoneal injection at 0.06 mg/kg caused a significant difference in bacterial titer compared with placebo-treated animals. No NCEs showed efficacy in the thigh model against a highly rifampin-resistant strain. However, several NCEs showed an effect when tested against a partially rifampin-resistant strain. The NCEs having a 25-hydroxyl moiety were more effective as a group than their 25-O-acetyl counterparts. These model systems defined candidate NCEs as components of potential combination therapies to treat systemic infections or as monotherapeutic agents for topical applications.

Development potential of rifalazil and other benzoxazinorifamycins

Rifalazil and other benzoxazinorifamycins (new chemical entities [NCEs]) are rifamycins that contain a distinct planar benzoxazine ring. Rifalazil has excellent antibacterial activity, high intracellular levels and high tissue penetration, which are attributes that favour its use in treating diseases caused by the obligate intracellular pathogens of the genus Chlamydia. Recent studies have shown that rifalazil has efficacy in the treatment of human sexually transmitted disease caused by Chlamydia trachomatis. The extraordinary potency of rifalazil and other NCEs, such as ABI-0043, extends to the related microorganism, C. pneumoniae, a respiratory pathogen that can disseminate and persist chronically in the vasculature, resulting in increased plaque formation in animal studies. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. Other opportunities include gastric ulcer disease caused by Helicobacter pylori and antibiotic-associated colitis caused by infection with Clostridium difficile in the colon. The NCEs could prove to be valuable as follow-on compounds in these indications, as rifampin replacements in antibacterial combination therapy or as stand-alone topical antibacterials (e.g., to treat acne). Neither rifalazil nor NCEs appear to induce the cytochrome P450 3A4, an attribute of rifampin that can result in adverse events due to drug-drug interactions.

Efficacy of moxifloxacin-based triple therapy as second-line treatment for Helicobacter pylori infection

BACKGROUND AND AIM

Metronidazole and tetracycline-based second-line quadruple therapy, widely used for Helicobacter pylori infection, often ends up in failure due to antibiotic resistance and poor compliance in Korea. Our aim is to evaluate the efficacy and tolerability of moxifloxacin-based triple therapy as an alternative second-line treatment for H. pylori infection.

METHODS

The subjects consisted of 85 patients infected with H. pylori, in whom initial proton pump inhibitor triple therapy had failed. They were randomized to receive the following 7-day therapy: 1, moxifloxacin 400 mg q.d., esomeprazole 20 mg b.i.d., and amoxicillin 1 g b.i.d.; and 2, esomeprazole 40 mg b.i.d., tripotassium dicitrate bismuthate 300 mg q.i.d., metronidazole 500 mg t.i.d., and tetracycline 500 mg q.i.d. Eradication rates, drug compliance, and side-effect rates of each group were evaluated.

RESULTS

The eradication rates were 75.6 and 83.8% with moxifloxacin triple therapy, and 54.5 and 72.7% with quadruple therapy by intention-to-treat (p = .042) and per-protocol analyses (p = .260), respectively. Moxifloxacin triple therapy was significantly superior to quadruple therapy in terms of side-effect rates (p = .039). Compliance for therapy, i.e., the percentage of tablets taken (> 85%), was 90.2 and 75.0%, numerically higher in moxifloxacin triple therapy group than in quadruple therapy group, but without statistical difference (p = .065).

CONCLUSIONS

Moxifloxacin-based triple therapy showed high eradication rates with few side effects and good drug compliance, suggesting this regimen could be a safe and effective option as second-line therapy for H. pylori infection in Korea.

Helicobacter pylori "rescue" therapy after failure of two eradication treatments

Nowadays, apart from having to know well first-line eradication regimens, we must also be prepared to face Helicobacter pylori treatment failures. Therefore, in designing a treatment strategy we should not focus on the results of primary therapy alone, but also on the final--overall--eradication rate. After failure of a combination of proton pump inhibitor (PPI), amoxicillin, and clarithromycin, the use of empirical quadruple therapy (PPI-bismuth-tetracycline-metronidazole), has been generally used as the optimal second-line therapy. Even after two consecutive failures, several studies have demonstrated that H. pylori eradication can finally be achieved in almost all patients if several "rescue" therapies are consecutively given. It seems that performing culture even after a second eradication failure may not be necessary, as it is possible to construct an overall strategy to maximize H. pylori eradication, based on the different possibilities of empirical treatment (when antibiotic susceptibilities are unknown). Thus, if one does not want to perform culture before the administration of the third treatment after failure of the first two, different empirical treatments exist, including regimens based on: 1, amoxicillin (amoxicillin-PPI at high doses); 2, amoxicillin plus tetracycline (PPI-bismuth-tetracycline-amoxicillin, or ranitidine-bismuth-citrate-tetracyline-amoxicillin); 3, rifabutin (rifabutin-amoxicillin-PPI); 4, levofloxacin (levofloxacin-amoxicillin-PPI); and 5, furazolidone (furazolidone-bismuth-tetracycline-PPI).

Rifalazil treats and prevents relapse of clostridium difficile-associated diarrhea in hamsters

Although vancomycin and metronidazole effectively treat Clostridium difficile-associated diarrhea and colitis (CDAD), their use is associated with a high incidence of relapsing C. difficile infection. Rifalazil is a new benzoxazinorifamycin that possesses activity against Mycobacterium tuberculosis and gram-positive bacteria. Here we compared rifalazil and vancomycin for effectiveness in preventing or treating clindamycin-induced cecitis in a hamster model of CDAD. Golden Syrian hamsters were injected subcutaneously with clindamycin phosphate (10 mg/kg), followed 24 h later by C. difficile gavage. Hamsters received by gavage for 5 days vehicle, vancomycin (50 mg/kg), or rifalazil (20 mg/kg) either simultaneously with (prophylactic protocol) or 24 h after C. difficile administration (treatment protocol). While all vehicle-administered animals became moribund within 48 h of C. difficile administration, no rifalazil- or vancomycin-treated animals in either protocol showed signs of morbidity after 7 days. Ceca of rifalazil-treated animals showed absence of epithelial cell damage, significantly reduced congestion and edema, and less, but not statistically significantly less, neutrophil infiltration compared to those of vehicle-treated animals. In contrast, vancomycin-treated animals demonstrated severe epithelial cell damage and mildly reduced congestion and edema. Moreover, hamsters relapsed and tested C. difficile toxin positive (by enzyme-linked immunosorbent assay) 10 to 15 days after discontinuation of vancomycin treatment. None of the rifalazil-treated hamsters showed signs of disease or presence of toxins in their feces 30 days after discontinuation of treatment. Our results indicate that once daily rifalazil may be superior to vancomycin for curative treatment of CDAD.

[Evaluation of Helicobacter pylori susceptibility to rifaximin]

INTRODUCTION

Helicobacter pylori infection affects more than half the world's population. It is a major cause of chronic gastritis and there is a strong association with peptic ulceration and gastric adenocarcinoma. Rifaximin is a new nonabsorbable broad-spectrum antimicrobial agent that reaches high concentrations in the gastrointestinal tract.

AIM

To evaluate the in vitro activity of rifaximin against H. pylori isolates.

METHODS

Thirty-one H. pylori strains were analyzed by the agar dilution method. Clarithromycin was used as the control antibiotic. Staphylococcus aureus and Streptococcus pneumoniae were used as quality control strains. Plates were read at days 4 and 7 of incubation. The MIC50 and MIC90 of each antibiotic were calculated. Strains with a clarithromycin MIC of > 1 microg/ml were considered resistant.

RESULTS

The MIC50 of clarithromycin at days 4 and 7 was 0.125 microg/ml and the MIC90 at days 4 and 7 ranged from 8 to 16 microg/ml, respectively. The MIC50 of rifaximin at days 4 and 7 ranged from 1 to 2 microg/ml, respectively, and the MIC90 was 4 microg/ml at both days 4 and 7. Twenty percent of H. pylori strains were resistant to clarithromycin. All clarithromycin-resistant strains were inhibited at a maximal rifaximin concentration of 4 microg/ml.

CONCLUSION

These results indicate that this new antibiotic may be useful for eradication of H. pylori infection. Because rifaximin is active against H. pylori strains resistant to clarithromycin, it could be useful in combination with this drug or in the treatment of therapeutic failure.

Empirical Helicobacter pylori "rescue" therapy after failure of two eradication treatments

AIM

Even with the current most effective Helicobacter pylori treatment regimens, approximately 20% of patients do not eradicate the infection. Several "rescue" therapies have been recommended, but they still fail to eradicate H. pylori in approximately 20-30% of the cases. Our aim was to evaluate the efficacy of different rescue therapies prescribed to patients in whom two consecutive H. pylori eradication regimens had failed.

METHODS

Design. Prospective single-centre study. Patients. Consecutive patients in whom two eradication regimens had failed to eradicate H. pylori. Intervention. Third eradication regimens included: (1) omeprazole-amoxicillin-clarithromycin for 7 days; (2) quadruple therapy with omeprazole-bismuth-tetracycline-metronidazole for 7 days; (3) omeprazole-amoxicillin-clarithromycin-bismuth for 14 days; and (4) omeprazole-amoxicillin-rifabutin for 14 days. H. pylori antibiotic susceptibility was unknown and, therefore, rescue regimens were chosen empirically. In no case, was the same regimen repeated. Outcome. H. pylori eradication was defined as a negative in 13C-urea breath test 8 weeks after completing the therapy.

RESULTS

Forty-eight patients were included (mean age 45 years, 44% males, 82% with peptic ulcer and 18% with functional dyspepsia). No patient was lost from follow-up. Adverse effects were described in 21% of the patients. One patient receiving omeprazole, amoxicillin and rifabutin was removed from medication due to adverse effects (vomiting). Overall, mean H. pylori eradication with third therapy after failure of two eradication treatments was 34/48 (71%; 95% confidence interval 57-82%) by intention-to-treat and 34/47 (72%; 95% confidence interval 58-83%) by per-protocol.

CONCLUSION

It seems that performing culture even after a second eradication failure may not be necessary, as it is possible to construct an overall strategy to maximise H. pylori eradication, based on the different possibilities of empirical treatment.

'Rescue' therapy with rifabutin after multiple Helicobacter pylori treatment failures

AIM

Eradication therapy with proton pump inhibitor, clarithromycin and amoxicillin is extensively used, although it fails in a considerable number of cases. A 'rescue' therapy with a quadruple combination of omeprazole, bismuth, tetracycline and metronidazole (or ranitidine bismuth citrate with these same antibiotics) has been recommended, but it still fails in approximately 20% of cases. Our aim was to evaluate the efficacy and tolerability of a rifabutin-based regimen in patients with two consecutive H. pylori eradication failures.

PATIENTS AND METHODS

DESIGN

Prospective multicenter study.

PATIENTS

Consecutive patients in whom a first eradication trial with omeprazole, clarithromycin and amoxicillin and a second trial with omeprazole, bismuth, tetracycline and metronidazole (three patients) or ranitidine bismuth citrate with these same antibiotics (11 patients) had failed were included.

INTERVENTION

A third eradication regimen with rifabutin (150 mg bid), amoxicillin (1 g bid) and omeprazole (20 mg bid) was prescribed for 14 days. All drugs were administered together after breakfast and dinner. Compliance with therapy was determined from the interrogatory and the recovery of empty envelopes of medications.

OUTCOME

H. pylori eradication was defined as a negative 13C-urea breath test 8 weeks after completing therapy.

RESULTS

Fourteen patients have been included. Mean age +/- SD was 42 +/- 11 years, 41% males, peptic ulcer (57%), functional dyspepsia (43%). All patients took all the medications and completed the study protocol. Per-protocol and intention-to-treat eradication was achieved in 11/14 patients (79%; 95% confidence interval = 49-95%). Adverse effects were reported in five patients (36%), and included: abdominal pain (three patients), nausea and vomiting (one patient), and oral candidiasis (one patient); no patient abandoned the treatment due to adverse effects.

CONCLUSION

Rifabutin-based rescue therapy constitutes an encouraging strategy after multiple previous eradication failures with key antibiotics such as amoxicillin, clarithromycin, metronidazole and tetracycline.

Treatment of Helicobacter pylori Eradication Failures

Even with the current most effective treatment regimens, about 10% to 20% of patients will fail to eradicate Helicobacter pylori infection. Therefore, in designing a treatment strategy, we should not focus on the results of primary therapy alone but also on the final (overall) eradication rate. The choice of a second-line treatment depends on which treatment was used initially, because retreatment with the same regimen is not recommended. Therefore, it seems that performing culture after a first eradication failure is not necessary and assessing H. pylori sensitivity to antibiotics only after failure of the second treatment is suggested in clinical practice. Different possibilities of empirical treatment are suggested. After failure of proton pump inhibitor (PPI)-amoxicillin-clarithromycin, quadruple therapy has been generally used. More recently, replacing the PPI and the bismuth compound by ranitidine bismuth citrate has also achieved good results. After PPI-amoxicillin-nitroimidazole failure, retreatment with PPI-amoxicillin-clarithromycin has proved to be effective. Finally, the first therapy should not combine clarithromycin and metronidazole in the same regimen because of the problem of resistance against both antibiotics. Recently, rifabutin-based rescue therapies have been shown to constitute an encouraging strategy for eradication failures because they are effective for H. pylori strains resistant to antibiotics.

In vitro activities of rifamycin derivatives ABI-1648 (Rifalazil, KRM-1648), ABI-1657, and ABI-1131 against Chlamydia trachomatis and recent clinical isolates of Chlamydia pneumoniae

ABI-1648 (rifalazil) is a semisynthetic rifamycin with potent bactericidal activity against intracellular respiratory bacteria, including Mycobacterium tuberculosis, and a long half-life (approximately 60 h) and thus can be administered once weekly. We therefore tested the in vitro activities of ABI-1648, its derivatives ABI-1657 and ABI-1131, azithromycin, and levofloxacin against 10 strains of Chlamydia trachomatis and 10 recent clinical isolates of Chlamydia pneumoniae. The MICs at which 90% of the isolates were inhibited and the minimal bactericidal concentration at which 90% of the isolates were killed for ABI-1648, ABI-1657, and ABI-1131 were 0.0025 micro g/ml for C. trachomatis and 0.00125 to 0.0025 micro g/ml for C. pneumoniae. ABI-1648, ABI-1657, and ABI-1131 were 10- to 1,000-fold more active than azithromycin and levofloxacin.

Randomized controlled study of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy as second-line treatment for Helicobacter pylori infection

AIM

To test the efficacy of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy for the second-line treatment of Helicobacter pylori infection.

METHODS

One hundred and nine patients who had failed previous H. pylori eradication were randomized to receive: (i) rabeprazole, 20 mg b.d., rifabutin, 300 mg once daily, and levofloxacin, 500 mg once daily, for 7 days (triple therapy); or (ii) rabeprazole, 20 mg b.d., metronidazole, 400 mg t.d.s., bismuth subcitrate, 120 mg q.d.s., and tetracycline, 500 mg q.d.s., for 7 days (quadruple therapy). Endoscopy and culture were performed before treatment.

RESULTS

The clarithromycin (79% vs. 21%, P < 0.001) and metronidazole (89% vs. 40%, P < 0.001) resistance rates were significantly higher in patients with previous exposure than in those with no previous exposure. The intention-to-treat and per protocol eradication rates were 91%/91% for the triple therapy group and 91%/92% for the quadruple therapy group. For patients with double resistance to metronidazole and clarithromycin, the eradication rates were 85% (17/20) in the triple therapy group and 87% (13/15) in the quadruple therapy group. Compliance was greater than 95% for both regimens.

CONCLUSION

Rabeprazole, levofloxacin and rifabutin-based triple therapy and quadruple therapy were equally effective as second-line treatments for H. pylori infection.

Development potential of rifalazil

Rifalazil represents a new generation of ansamycins that contain a unique four-ring structure. Originally rifalazil was developed as a therapeutic agent to replace rifampin as part of a multiple drug regimen in the treatment of tuberculosis. As a result of its superior antimicrobial activity and high intracellular levels, rifalazil has potential to treat indications caused by the intracellular pathogen, Chlamydia trachomatis, which causes non-gonococcal urethritis and cervicitis, often leading to pelvic inflammatory disease. Rifalazil also has potential to treat the related microorganism, Chlamydia pneumoniae, which may be involved in chronic inflammatory processes thought to be partly responsible for atherosclerosis. Due to its favourable antimicrobial spectrum and other positive attributes, rifalazil may also prove valuable in the treatment of gastric ulcer disease, caused by Helicobacter pylori, and antibiotic-associated colitis, the result of toxin production following the growth of Clostridium difficile in the colon. The potential value of rifalazil in the treatment of these indications will be assessed in human clinical trials.

Review article: Helicobacter pylori "rescue" regimen when proton pump inhibitor-based triple therapies fail

Even with the currently most effective treatment regimens, about 10-20% of patients will fail to obtain eradication of Helicobacter pylori infection. Therefore, in designing a treatment strategy, we should not focus on the results of primary therapy alone, but also on the final (overall) eradication rate. The choice of second-line treatment depends on which treatment was used initially, as re-treatment with the same regimen is not recommended. Therefore, it is not necessary to perform culture after the first eradication failure. Assessment of the sensitivity of H. pylori to antibiotics only after failure of the second treatment is suggested in clinical practice. Different possibilities of empirical treatment have been suggested. After failure of proton pump inhibitor-amoxicillin-clarithromycin, quadruple therapy has generally been used. More recently, replacement of the proton pump inhibitor and the bismuth compound by ranitidine bismuth citrate has also achieved good results. After proton pump inhibitor-amoxicillin-nitroimidazole failure, re-treatment with proton pump inhibitor-amoxicillin-clarithromycin has been proven to be effective. Finally, first-line treatment should not combine clarithromycin and metronidazole in the same regimen, because of the problem of resistance to both antibiotics. Recently, rifabutin-based rescue therapies have been shown to constitute an encouraging strategy for eradication failures, as they are effective against H. pylori strains resistant to antibiotics.

Allelic exchange mutagenesis of rpoN encoding RNA-polymerase sigma54 subunit in Helicobacter pylori

The rpoN gene, encoding the alternative sigma factor (sigma54) of Helicobacter pylori, was amplified from genomic DNA. H. pylori rpoN has an overall similarity to the rpoN of other bacteria, but lacks a glutamine (Q)-rich region in region I and an acidic region in region II. When the rpoN gene was disrupted, the mutant was found to be completely nonmotile. Because the flaB gene has an rpoN consensus sequence in its promoter region, we assessed the transcriptional activity of the flaB gene, using xylE transcriptional fusion. In the isogenic mutant of rpoN, transcription of the flaB gene was severely affected, but transcription of the ureA gene (control) was intact. In late stationary phase, the rpoN mutant showed marked decreases in viability: i.e., the number of colony-forming units (CFU) at 100 h was 4 log lower in the rpoN mutant than in the wild-type strain. By morphological examination with acridine orange staining, the rpoN mutant showed green and faintly orange-stained irregularly shaped cells with a few orange-stained rod/spiral cells. In contrast, the wild-type strain and the non-flagella flgE mutant (control) contained many orange-stained rod/spiral and coccoid cells. These results indicated that in H. pylori, RpoN is involved not only in motility but also in viability, through the morphological changes in the stationary phase.

Rifabutin-based triple therapy after failure of Helicobacter pylori eradication treatment: preliminary experience

Despite continuous improvement of Helicobacter pylori (Hp) eradication therapy, new treatment regimens are necessary if established first-line treatments fail. In the present pilot study, a recently described rifabutin-based triple therapy was evaluated after preceding failure of triple therapy. Rifabutin (150 mg), amoxicillin (1 g), and lansoprazole (30 mg) were administered twice daily for 1 week to 25 patients infected with Hp who had previously failed to respond to eradication treatment and/or who had developed resistance to macrolides and nitroimidazoles. Four patients were lost to follow-up. Eradication rate of rifabutin-based triple therapy was 86% (18/21; per protocol) and 72% (18/25; intention-to-treat). Side effects were minimal. It is concluded that this new drug combination is an effective therapy for Hp strains resistant to clarithromycin or metronidazole; however, rifabutin-based treatment regimens for Hp eradication should be restricted to patients infected with resistant strains.

Mutations at four distinct regions of the rpoB gene can reduce the susceptibility of Helicobacter pylori to rifamycins

The transformation of a panel of rpoB mutations (codons 525 to 586) from rifampin-resistant donor strains into Helicobacter pylori 2802A confirmed the MICs associated with the respective mutations. RpoB V149X random mutations were generated and induced different levels of resistance, depending on the replacement amino acid. Mutagenesis of the rpoB gene at codon position 701 (R701H) induced low-level resistance.

Mutations in the beginning of the rpoB gene can induce resistance to rifamycins in both Helicobacter pylori and Mycobacterium tuberculosis

A clinical isolate of Helicobacter pylori that developed resistance to rifabutin during therapy carried an rpoB gene that retained a wild-type cluster region sequence but had acquired a novel codon 149 (V149F) mutation. In transformation experiments, the mutation was shown to confer high-level rifabutin resistance. The equivalent mutation (V176F) was present in several resistant isolates of Mycobacterium tuberculosis.