Helicobacter pylori and antimicrobial resistance: molecular mechanisms and clinical implications

Antimicrobial activity of commercial Olea europaea (olive) leaf extract

The aim of this research was to investigate the activity of a commercial extract derived from the leaves of Olea europaea (olive) against a wide range of microorganisms (n=122). Using agar dilution and broth microdilution techniques, olive leaf extract was found to be most active against Campylobacter jejuni, Helicobacter pylori and Staphylococcus aureus [including meticillin-resistant S. aureus (MRSA)], with minimum inhibitory concentrations (MICs) as low as 0.31-0.78% (v/v). In contrast, the extract showed little activity against all other test organisms (n=79), with MICs for most ranging from 6.25% to 50% (v/v). In conclusion, olive leaf extract was not broad-spectrum in action, showing appreciable activity only against H. pylori, C. jejuni, S. aureus and MRSA. Given this specific activity, olive leaf extract may have a role in regulating the composition of the gastric flora by selectively reducing levels of H. pylori and C. jejuni.

Failure of first-line eradication treatment significantly increases prevalence of antimicrobial-resistant Helicobacter pylori clinical isolates

OBJECTIVES

Helicobacter pylori infection is a major health problem worldwide, and effective eradication of the infection is mandatory. The efficacy of recommended eradication regimens is approximately 70%. To avoid treatment failure and the consequent development of secondary resistance(s), it is important to choose the most appropriate first-line treatment regimen. This choice should also be made based on the knowledge of the antimicrobial resistance peculiar to a given geographical area. We evaluated the prevalence of antimicrobial-resistant H pylori strains isolated from naive patients and from patients with previous unsuccessful treatments.

METHODS

This study examined 109 H pylori-infected subjects (Group 1) who had never received an eradication treatment and 104 H pylori-infected subjects (Group 2) who had failed one or more eradication treatments. Resistance to amoxicillin (AMO), tetracycline (TET), clarithromycin (CLA), metronidazole (MET) and levofloxacin (LEV) was determined using the epsilometer test. The significance of differences was evaluated by the chi2 test.

RESULTS

The prevalence of antimicrobial resistance was 0% versus 3.1% to AMO, 0% versus 2% to TET, 27% versus 41.3% to MET (p<0.05), 18% versus 45.8% to CLA (p<0.05) and 3% versus 14.6% to LEV (p<0.05) in Group 1 vs Group 2, respectively. In Group 2, there was an increased prevalence of H pylori strains resistant to multiple antimicrobials.

CONCLUSIONS

This study confirms the high prevalence of H pylori strains resistant to CLA and MET, and indicates that unsuccessful treatments significantly increase resistance. Choosing eradication regimens other than standard triple therapy as a first-line therapy should be advisable in areas with high primary antimicrobial resistance prevalence.

Prevalence of A2143G mutation of H. pylori-23S rRNA in Chinese subjects with and without clarithromycin use history

BACKGROUND

A2143G mutation of 23S rRNA gene of H. pylori results in clarithromycin (CLR) resistance. To investigate the prevalence of the CLR resistance-related A2143G mutation of the H. pylori-specific 23S rRNA gene in Chinese subjects with and without CLR use history, 307 subjects received the treatment with amoxicillin and omeprazole (OA) and 310 subjects received a placebo in 1995, and 153 subjects received a triple therapy with OA and CLR (OAC) in 2000. DNA was extracted from fasting gastric juice at the end of the intervention trial in 2003. H. pylori infection was determined by H. pylori-specific 23S rRNA PCR, ELISA, and13C-urea breath test assays. Mutations of the 23S rRNA gene were detected by RFLP assays.

RESULTS

The presence of 23S rRNA due to H. pylori infection in the OA group remained lower than that in the placebo group 7.3 yrs after OA-therapy [51.1% (157/307) vs. 83.9% (260/310), p = 0.0000]. In the OAC group, the 23S rRNA detection rate was 26.8% (41/153) three yrs after OAC-treatment. The A2143G mutation rate among the 23S rRNA-positive subjects in the OAC group [31.7% (13/41)] was significantly higher than that in the OA group [10.2% (16/157)] and the placebo group [13.8% (36/260)]. The frequency of the AAGGG --> CTTCA (2222-2226) and AACC --> GAAG (2081-2084) sequence alterations in the OAC group was also significantly higher than those in the OA group and the placebo group.

CONCLUSION

Primary prevalence of the A2143G mutation was 10~14% among Chinese population without history of CLR therapy. Administration of CLR to eliminate H. pylori infection increased the prevalence of the A2143G mutation in Chinese subjects (32%) significantly.

Helicobacter pylori as a class I carcinogen: physiopathology and management strategies

The gram-negative bacterium Helicobacter pylori is known as a persistent colonizer of the human stomach, and probably less known is that it is also involved in extraintestinal diseases. Public awareness of its contribution in the development of gastric cancer is less than 15 years old. The efficacy of the current therapies based on antibiotics against H. pylori has been limited by difficulties such as antibiotic resistance and recurrence. As a consequence, the development of promising vaccines was prompted as the best preventive measure. Unfortunately, so far vaccines failed the transition from animal models to human trials. This keynote presentation is to provide a bird's eye view of H. pylori-related gastric diseases, including gastric cancer, with a synthesis of the molecular mechanisms involved, and an exhaustive presentation and discussion of the current therapeutic guidelines and future strategies for prevention or therapy.

Asia-Pacific consensus guidelines on gastric cancer prevention

BACKGROUND AND AIM

Gastric cancer is a major health burden in the Asia-Pacific region but consensus on prevention strategies has been lacking. We aimed to critically evaluate strategies for preventing gastric cancer.

METHODS

A multidisciplinary group developed consensus statements using a Delphi approach. Relevant data were presented, and the quality of evidence, strength of recommendation, and level of consensus were graded.

RESULTS

Helicobacter pylori infection is a necessary but not sufficient causal factor for non-cardia gastric adenocarcinoma. A high intake of salt is strongly associated with gastric cancer. Fresh fruits and vegetables are protective but the use of vitamins and other dietary supplements does not prevent gastric cancer. Host-bacterial interaction in H. pylori infection results in different patterns of gastritis and differences in gastric acid secretion which determine disease outcome. A positive family history of gastric cancer is an important risk factor. Low serum pepsinogens reflect gastric atrophy and may be useful as a marker to identify populations at high risk for gastric cancer. H. pylori screening and treatment is a recommended gastric cancer risk reduction strategy in high-risk populations. H. pylori screening and treatment is most effective before atrophic gastritis has developed. It does not exclude the existing practice of gastric cancer surveillance in high-risk populations. In populations at low risk for gastric cancer, H. pylori screening is not recommended. First-line treatment of H. pylori infection should be in accordance with national treatment guidelines.

CONCLUSION

A strategy of H. pylori screening and eradication in high-risk populations will probably reduce gastric cancer incidence, and based on current evidence is recommended by consensus.

Inhibitory effect of nordihydroguaiaretic acid, a plant lignan, on Helicobacter pylori-associated gastric carcinogenesis in Mongolian gerbils

Recent epidemiological studies have demonstrated that consumption of certain natural products can lower cancer risk in humans. For example, plant-derived lignans have been shown to exert chemopreventive effects against cancer in vitro and in vivo. In the present study, the effects of three such lignans, termed arctiin, arctigenin, and nordihydroguaiaretic acid (NDGA), on the proliferation of Helicobacter pylori and the prevention of H. pylori-associated gastric cancer were investigated in Mongolian gerbils. To examine the effects of arctigenin and NDGA on stomach carcinogenesis, specific pathogen-free male, 5-week-old gerbils were infected with H. pylori, administered 10 p.p.m. N-methyl-N-nitrosourea in their drinking water and fed diets containing various concentrations of lignans until they were killed after 52 weeks. At a dietary level of 0.25%, NDGA significantly decreased the incidence of gastric adenocarcinomas. Arctigenin, in contrast, failed to attenuate neoplasia at a level of 0.1%. Both NDGA and arctigenin significantly reduced serum 8-hydroxy-2'-deoxyguanosine levels at doses of 0.25 and 0.05% (NDGA), and 0.1% (arctigenin). Administration of 0.25% NDGA significantly suppressed the formation of intestinal metaplasia both in the antrum and the corpus. Although all three lignans dose-dependently inhibited the in vitro proliferation of H. pylori, there were no differences in the titers of anti-H. pylori antibodies or the amount of the H. pylori-specific urease A gene among all H. pylori-infected groups. These results suggest that NDGA might be effective for prevention of gastric carcinogenesis. The possible mechanisms appear to be related to inhibitory effects on progression of gastritis and antioxidative activity rather than direct antimicrobial influence.

An alternative salvage regimen for Helicobacter pylori-resistant patients with heart failure

Helicobacter pylori infects over 50% of the worldwide population. For eradication, European, Canadian, and American guidelines recommend a regimen consisting of a proton pump inhibitor, clarithromycin, and metronidazole or amoxicillin dosed twice daily for at least 7 days. When this treatment strategy fails, a complex, multidosed bismuth-based quadruple regimen is recommended. Unfortunately, for patients with heart failure, this salvage regimen can be potentially hazardous due to the drug-drug interaction with tetracycline and digoxin, as well as the large salicylate content with bismuth subsalicylate. As H. pylori infection is so prevalent, providers will most likely encounter such a therapeutic dilemma. A safe, effective, and simplistic alternative is a 10-day fluoroquinolone-based regimen consisting of a proton pump inhibitor, levofloxacin and either clarithromycin or amoxicillin. Levofloxacin demonstrates excellent bioavailability, widespread tissue and fluid distribution, extended half-life, limited drug interaction profile, low incidence of side effects, and remarkable activity against H. pylori with minimal primary resistance. Compared to the 7-day quadruple regimen, a 10-day levofloxacin-based regimen demonstrated a greater eradication rate, better tolerability, and a lower rate of therapy discontinuation. We briefly provide a summary of the data regarding this levofloxacin-based regimen and two successful cases from our heart failure clinic.

Diagnosis of Helicobacter pylori

Although there are attempts to perform Helicobacter pylori diagnosis directly in vivo using magnification endoscopy, most articles on diagnosis this year concerned non-invasive tests and molecular methods. For urea breath tests, there are attempts to have a quicker and cheaper test and to evaluate its role in cases of premalignant lesions. For stool antigens tests, evaluation of kits using monoclonal antibodies was carried out. Molecular tests have been applied for typing and detection of resistant mutants.

Treatment of Helicobacter pylori

Since the discovery of Helicobacter pylori in the early 1980s many treatment regimes have been developed to effectively treat this infection. International guidelines have allowed consensus on the best management and improved eradication rates. In recent years, increasing antimicrobial resistance has resulted in falling eradication rates with standard therapies. In this article, we review the most recent studies and guidelines in the treatment of H. pylori. Currently, the first-line treatment remains clarithromycin, amoxicillin or metronidazole and proton pump inhibitor twice daily, but a number of recent studies have shown low eradication rates with this treatment. Increased duration of therapy has been recommended to overcome the falling eradication rates. However, conflicting findings have been reported on the benefits of extending the length of traditional therapy. Sequential therapy may be an effective alternative to standard triple therapy in regions of increased antimicrobial resistance. Probiotics reduce side-effects from traditional regimens and may improve eradication rates. A quinolone-based second-line triple therapy appears to be effective and well tolerated. Bismuth-based quadruple therapy is also an effective alternative if available. In the future, regional antimicrobial resistance and eradication rates will determine the best treatment for H. pylori.

Reversal of migraine symptoms by Helicobacter pylori eradication therapy in patients with hepatitis-B-related liver cirrhosis

Helicobacter pylori infection might be associated with vascular diseases, such as primary Raynaud phenomenon and coronary heart diseases. The possible mechanism might be due to H. pylori antigens causing intermittent vasospasm of arterioles, which also played roles in the development of liver cirrhosis. Migraine, a functional vascular disease, was observed in many patients with cirrhosis in the clinic. This study aimed to assess the effects of H. pylori eradication on migraine symptoms in patients with hepatitis-B-virus-related cirrhosis. The results clearly showed that the intensity, duration, and frequency of attacks of migraine were significantly reduced in all the patients in whom H. pylori has been eradicated. Thus, the study pushed further insight into the mechanisms of migraine pathogenesis.

Levofloxacin-containing triple therapy to eradicate the persistent H. pylori after a failed conventional triple therapy

OBJECTIVE

To identify the optimal dosage of levofloxacin to eradicate persistent Helicobacter pylori when triple therapy with amoxicillin, clarithromycin, and omeprazole fails.

METHODS

We investigated 124 patients whose triple therapy including clarithromycin had failed. Clarithromycin resistance was indirectly assessed by the (13)C-urea breath test, with a post-treatment value cut-off point at 15. All patients were randomly divided into two groups, to receive 1-week amoxicillin 1 g and lansoprazole 30 mg twice daily, plus either levofloxacin 500 mg once (ALL-500 group) or twice daily (ALL-1000 group). Six weeks later, the (13)C-urea breath test was repeated to assess whether H. pylori was eradicated.

RESULTS

Intention-to-treat (ITT) and per-protocol (PP) analysis showed no difference in H. pylori eradication rates in both the ALL-500 and ALL-1000 groups (ITT: 79% vs. 80.6%, p > .05; PP: 86% vs. 87.5%, p > .05). For both groups, the per-protocol H. pylori eradication rates were also similarly high between patients with a post-treatment value of (13)C-urea breath test < or = 15 and those with a value > 15 (ALL-500: 85% vs. 86.5%, p > .05; ALL-1000: 88.9% vs. 86.8%, p > .05).

CONCLUSION

One-week levofloxacin 500 mg daily-based triple therapy is effective for eradicating the persistent H. pylori after a failed triple therapy with amoxicillin, clarithromycin, and omeprazole.

Serum- and animal tissue-free medium for transport and growth of Helicobacter pylori

The important human gastric pathogen Helicobacter pylori is the subject of many studies, and as a consequence it is frequently being transported between national and international laboratories. Unfortunately, common bacterial growth and transport media contain serum- and animal tissue-derived materials, which carry the risk of spreading infectious diseases. We have therefore developed a growth and transport medium for H. pylori, designated 'Serum- and Animal Tissue-Free Medium' (SATFM), which does not contain serum- or animal tissue-derived components. SATFM supported growth of H. pylori isolates to similar levels as obtained with serum-supplemented Brucella medium, and SATFM with 0.5% agar supported transport and storage of H. pylori strains, as 4/4 reference strains and 11/11 clinical isolates survived for at least 3 days at room temperature in SATFM, with some strains (2/15) even surviving for up to 7 days. In conclusion, SATFM can be used both as transport and growth medium for H. pylori. The formulation of SATFM may allow its use in international transport of H. pylori, and may also allow certified use in immunization studies requiring growth of H. pylori and other bacterial pathogens.