Sensitivity of amoxicillin-resistant Helicobacter pylori to other penicillins

Levofloxacin-amoxicillin/clavulanate-rabeprazole versus a standard seven-day triple therapy for eradication of Helicobacter pylori infection

The resistance rates of Helicobacter pylori to amoxicillin and metronidazole therapy are higher in eastern Taiwan as compared to national and worldwide rates. The high resistance rate in this territory justified a search for a better eradication regimen. We conducted an open-labeled, prospective, randomized, and controlled study in a tertiary referral hospital in eastern Taiwan. Between December 2007 and December 2009, a total of 153 Helicobacter pylori-positive, therapy-naïve patients with a positive rapid urease test were recruited for random assignment to two seven-day treatment groups: levofloxacin (500 mg), amoxicillin/clavulanate (875 mg/125 mg), and rabeprazole (20 mg) twice per day (LAcR) or clarithyromicin (500 mg), amoxicillin (1000 mg), and rabeprazole (20 mg) twice per day (CAR). Helicobacter pylori eradication was assessed using the ¹³C-urea breath test or rapid urease test performed at least 4 weeks after the end of treatment. After exclusion, 146 patients were enrolled and allocated in the study. The Helicobacter pylori eradication rates analyzed by both intention to treat (78.1% versus 57.5%, P = 0.008) and perprotocol (80.9% versus 61.8%, P = 0.014) were significantly higher for the LAcR group. In conclusion, the seven-day LAcR regimen provided improved Helicobacter pylori eradication efficacy when compared with the standard CAR triple therapy in eastern Taiwan.

Amoxicillin resistance with beta-lactamase production in Helicobacter pylori

BACKGROUND

Amoxicillin-resistant Helicobacter pylori with minimal inhibitory concentration (MIC) >or= 256 mg L(-1) was isolated from a gastritis patient. The aims were to investigate the mechanism of high-level amoxicillin resistance in H. pylori.

MATERIALS AND METHODS

The beta-lactamase production was determined by means of nitrocefin sticks and the presence of gene encoding the beta-lactam antibiotic resistance enzyme TEM beta-lactamase was analysed by polymerase chain reaction (PCR), sequencing and dot-blot hybridization. Sequencing analysis of pbp1A gene was performed and amoxicillin-susceptible isolate was transformed with pbp1A PCR products from the resistant isolate. The expression of hefC efflux system was analysed using real-time quantitative PCR.

RESULTS

Activity of beta-lactamase was detected. Sequence analysis showed that the PCR product derived from H. pylori 3778 was identical to the bla(TEM-1) (GenBank accession EU726527). Dot-blot hybridization confirmed the presence of beta-lactamase gene bla(TEM-1.) By transformation of PCR product of mutated pbp1A gene from H. pylori 3778 into amoxicillin-susceptible strain showed that substitutions in Thr(556)-->Ser, Lys(648)-->Gln, Arg(649)-->Lys and Arg(656)-->Pro contribute to low-level amoxicillin resistance. The MIC of amoxicillin for the transformants was 0.75 mg L(-1). Over-expression of hefC was not found.

CONCLUSIONS

High-level amoxicillin resistance is associated with beta-lactamase production in H. pylori. Low-level amoxicillin resistance is linked to a point mutation on pbp1A. Because H. pylori can exchange DNA through natural transformation, spreading of bla(TEM-1) amoxicillin resistance gene among H. pylori is a potential threat when treating H. pylori infection.

Furazolidone, co-amoxiclav, colloidal bismuth subcitrate, and esomeprazole for patients who failed to eradicate Helicobacter pylori with triple therapy

There is increasing evidence of Helicobacter pylori (H. pylori) resistance to the classical triple therapy consisting of a proton-pump inhibitor and clarithromycin with either amoxicillin or metronidazole. This study is aimed at establishing the efficacy and safety of a 14-day regimen to eradicate H. pylori in patients who have failed with the classical triple therapy given for 14 days. One hundred seventy-six patients diagnosed to have H. pylori infection were given triple therapy for 14 days. Fifty-two patients who failed to respond as evident from positive 14C-urea breath test (UBT) done 4-6 weeks after the completion of triple therapy were offered a combination regimen comprised of furazolidone 200 mg b.i.d, co-amoxiclav 1 g b.i.d., colloidal bismuth subcitrate 240 mg b.i.d., and esomeprazole 40 mg b.i.d. for 14 days. The mean age of these patients was 41 +/- 13 years (range 20-67). Thirty-four were males. To document eradication of H. pylori, UBT was repeated 4 weeks after the completion of treatment. On an intention-to-treat analysis, the eradication rate was 81% (42 out of 52) whereas on per-protocol basis, the eradication rate was 82.4% (42 out of 51). In conclusion, this new regimen represents a suitable second-line therapy.

Combinations containing amoxicillin-clavulanate and tetracycline are inappropriate for Helicobacter pylori eradication despite high in vitro susceptibility

BACKGROUND

The purpose of the present paper was to evaluate the efficacy and tolerability of amoxicillin-clavulanate and tetracycline-based quadruple therapy as an alternative second-line treatment for H. pylori infection.

METHODS

The study subjects consisted of 54 patients infected with H. pylori, in whom initial triple therapy had failed. Subjects were randomized to receive the following 7-day therapies: (i) pantoprazole 40 mg b.i.d., tripotassium dicitrate bismuthate 300 mg q.i.d., amoxicillin-clavulanate 1000 mg b.i.d., and tetracycline 500 mg q.i.d. (PBAT); or (ii) pantoprazole 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. (PBMT). Eradication rates based on antibiotic susceptibility, drug compliance and side-effect rates were evaluated and compared.

RESULTS

The H. pylori eradication rates were 16.0%/17.4% with PBAT and 65.5%/70.4% with PBMT by intention-to-treat (P<0.001) and per-protocol analyses (P<0.001), respectively. In patients who received PBAT, the eradication rates were only 16.7% (2/12) for both amoxicillin and tetracycline-susceptible H. pylori strains. Drug compliance and side-effect rates were similar in the two groups.

CONCLUSIONS

Despite high individual in vitro antimicrobial activity, amoxicillin-clavulanate and tetracycline-based quadruple therapy showed low eradication rates, which strongly suggests that it should not be considered as a therapeutic option for H. pylori eradication.

In vitro activity of a novel antimicrobial agent, TG44, for treatment of Helicobacter pylori infection

Due to concerns about the current therapeutic modalities for Helicobacter pylori infection, e.g., the increased emergence of drug-resistant strains and the adverse reactions of drugs currently administered, there is a need to develop an anti-H. pylori agent with higher efficacy and less toxicity. The antibacterial activity of TG44, an anti-H. pylori agent with a novel structural formula, against 54 clinical isolates of H. pylori was examined and compared with those of amoxicillin (AMX), clarithromycin (CLR), and metronidazole (MNZ). Consequently, TG44 inhibited the growth of H. pylori in an MIC range of 0.0625 to 1 microg/ml. The MIC ranges of AMX, CLR, and MNZ were 0.0078 to 8 microg/ml, 0.0156 to 64 microg/ml, and 2 to 128 microg/ml, respectively. The antibacterial activity of TG44 against AMX-, CLR-, and MNZ-resistant strains was nearly comparable to that against drug-susceptible ones. In a pH range of 3 to 7, TG44 at 3.13 to 12.5 microg/ml exhibited potent bactericidal activity against H. pylori in the stationary phase of growth as early as 1 h after treatment began, in contrast to AMX, which showed no bactericidal activity at concentrations of up to 50 microg/ml at the same time point of treatment. TG44 at 25 microg/ml exhibited no antibacterial activity against 13 strains of aerobic bacteria, suggesting that its antibacterial activity against H. pylori is potent and highly specific. The present study indicated that TG44 possesses antibacterial activity which manifests quickly and is potentially useful for eradicating not only the antibiotic-susceptible but also the antibiotic-resistant strains of H. pylori by monotherapy.

Triple, standard quadruple and ampicillin-sulbactam-based quadruple therapies for H pylori eradication: A comparative three-armed randomized clinical trial

AIM: To compare the effectiveness of triple, standard quadruple and ampicillin-sulbactam-based quadruple therapies for H pylori eradication in a comparative three-armed randomized clinical trial.

METHODS: A total of 360 H pylori-positive patients suffering from dyspepsia and aging 24-79 years with a median age of 42 years were enrolled in the study and randomly allocated into the following three groups: group A (n = 120) received a standard 1-wk triple therapy (20 mg omeprazole b.i.d., 1000 mg amoxicillin b.i.d., 500 mg clarithromycin b.i.d.); group B (n = 120) received a 10-d standard quadruple therapy (20 mg omeprazole b.i.d., 1000 mg amoxicillin b.i.d., 240 mg colloidal bismuth subcitrate b.i.d., and 500 mg metronidazole b.i.d.); group C (n = 120) received the new protocol, i.e. 375 mg sultamicillin (225 mg ampicillin plus 150 mg sulbactam) b.i.d. (before breakfast and dinner), instead of amoxicillin in the standard quadruple therapy for the same duration. Chi-square test with the consideration of P < 0.05 as significant was used to compare the eradication rates by intention-to-treat and per-protocol analyses in the three groups.

RESULTS: The per-protocol eradication rate was 91.81% (101 patients from a total of 110) in group A, 85.84% (97 patients from a total of 113) in group B, and 92.85% (104 patients from a total of 112) in group C. The intention-to-treat eradication rate was 84.17% in group A, 80.83% in group B, and 86.67% in group C. The new protocol yielded the highest eradication rates by both per-protocol and intention-to-treat analyses followed by the standard triple and quadruple regimens, respectively. However, the differences were not statistically significant between the three groups.

CONCLUSION: The results of this study provide further support for the equivalence of triple and quadruple therapies in terms of effectiveness, compliance and side-effect profile when administered as first-line treatment for H pylori infection. Moreover, the new protocol using ampicillin-sulbactam instead of amoxicillin in the quadruple regimen is a suitable first-line alternative to be used in regions with amoxicillin-resistant H pylori strains.

The status of antimicrobial resistance of Helicobacter pylori in eastern Europe

OBJECTIVE

To evaluate the primary, secondary and combined resistance to five antimicrobial agents of 2340 Helicobacter pylori isolates from 19 centers in 10 countries in eastern Europe.

METHODS

Data were available for centers in Bulgaria, Croatia, the Czech Republic, Estonia, Greece, Lithuania, Poland, Russia, Slovenia and Turkey. Susceptibility was tested by agar dilution (seven countries), E test (five countries) and disk diffusion (three countries) methods. Resistance breakpoints (mg/L) were: metronidazole 8, clarithromycin 1, amoxicillin 0.5, tetracycline 4, and ciprofloxacin 1 or 4 in most centers. Primary and post-treatment resistance was assessed in 2003 and 337 isolates respectively. Results for 282 children and 201 adults were compared.

RESULTS

Primary resistance rates since 1998 were: metronidazole 37.9%, clarithromycin 9.5%, amoxicillin 0.9%, tetracycline 1.9%, ciprofloxacin 3.9%, and both metronidazole and clarithromycin 6.1%. Isolates from centers in Slovenia and Lithuania exhibited low resistance rates. Since 1998, amoxicillin resistance has been detected in the southeastern region. From 1996, metronidazole resistance increased significantly from 30.5% to 36.4%, while clarithromycin resistance increased slightly from 8.9% to 10.6%. In centers in Greece, Poland, and Bulgaria, the mean metronidazole resistance was slightly higher in adults than in children (39% versus 31.2%, P > 0.05); this trend was not found for clarithromycin or amoxicillin (P > 0.20). Post-treatment resistance rates exhibited wide variations.

CONCLUSIONS

In eastern Europe, primary H. pylori resistance to metronidazole is considerable, and that to clarithromycin is similar to or slightly higher than that in western Europe. Resistance to amoxicillin, ciprofloxacin and tetracycline was detected in several centers. Primary and post-treatment resistance rates vary greatly between centers.

Resistance of Helicobacter pylori to antibiotics and its impact on treatment options

The treatment of Helicobacter pylori infection is jeopardized by resistance to the antibiotics used, which turns out to be the main risk factor for failure. Resistance is due to point mutations. For clarithromycin only two sites in the 23S rRNA sequence are concerned and can be easily detected by molecular methods, while for metronidazole several mutations on rdxA and other genes can be responsible and so do not allow such detection. The situation for the rare cases of amoxicillin resistance is not fully determined. The impact of resistance on the clinical outcome is dramatic for clarithromycin while it only decreases the success by 20% for metronidazole.

Characterization of an In vitro-selected amoxicillin-resistant strain of Helicobacter pylori

An amoxicillin-resistant (Amox(r)) strain of Helicobacter pylori was selected for by culturing an amoxicillin-sensitive (Amox(s)) strain in increasingly higher concentrations of amoxicillin, resulting in a 133-fold increase in MIC, from 0.03 to 0.06 microg/ml to 4 to 8 microg/ml. This resistance was stable upon freezing for at least 6 months and conferred cross-resistance to seven other beta-lactam antibiotics. beta-Lactamase activity was not detected in this Amox(r) strain; however, analysis of the penicillin-binding protein (PBP) profiles generated from isolated bacterial membranes of the Amox(s) parental strain and the Amox(r) strain revealed a significant decrease in labeling of PBP 1 by biotinylated amoxicillin (bio-Amox) in the Amox(r) strain. Comparative binding studies of PBP 1 for several beta-lactams demonstrated that PBP 1 in the Amox(r) strain had decreased affinity for mezlocillin but not significantly decreased affinity for penicillin G. In addition, PBP profiles prepared from whole bacterial cells showed decreased labeling of PBP 1 and PBP 2 in the Amox(r) strain at all bio-Amox concentrations tested, suggesting a diffusional barrier to bio-Amox or a possible antibiotic efflux mechanism. Uptake analysis of (14)C-labeled penicillin G showed a significant decrease in uptake of the labeled antibiotic by the Amox(r) strain compared to the Amox(s) strain, which was not affected by pretreatment with carbonyl cyanide m-chlorophenylhydrazone, eliminating the possibility of an efflux mechanism in the resistant strain. These results demonstrate that alterations in PBP 1 and in the uptake of beta-lactam antibiotics in H. pylori can be selected for by prolonged exposure to amoxicillin, resulting in increased resistance to this antibiotic.