Comparison of the Efficacy of Triple Therapy With or Without Acetylcysteine in the First Line of Helicobacter Pylori Infection- A Multicenter Randomized Comparative Trial

Helicobacter pylori infection has been shown to be associated with the development of gastric cancer and peptic ulcer diseases. Eradication of H. pylori infection could reduce the occurrence or recurrence of these diseases. The triple treatment including a proton pump inhibitor, clarithromycin, and amoxicillin or metronidazole to treat H pylori infection, proposed at the first Maastricht conference has become universal since all the consensus conferences and guidelines around the world recommended it. However, the eradication rate of clarithromycin-based triple therapy has been declining in recent years, probably related to the increasing resistant rate to clarithromycin. It was estimated that 15-20% of patients would fail from first line standard eradication therapy and need second line rescue therapy. Measures to improved H. pylori eradication rate include (1) increase treatment duration, (2) add other antibiotics or use antibiotics not previously used, (3) introducing new therapeutic agents, and (4) potent acid inhibition. Our group has shown the 10- or 14-day sequential therapy, which consists of a proton-pump inhibitor and amoxicillin for the first 5 or 7 days, followed by a proton-pump inhibitor plus clarithromycin and metronidazole (or tinidazole) for another 5 or 7days, provides good eradication in first line H. pylori eradication. However, complexity of sequential therapy is complex and adverse effect resulted from adding one more antibiotic may have poor effect on compliance and leads to treatment failure. A simplified regimen for H. pylori infection is worthy of investigation.

Introducing new therapeutic agents The H. pylori persistence in human infections and its resistance to the drugs commonly used in antimicrobial therapy have been attributed not only to genetic variability, but also to ability of H. pylori to form biofilm as a strategy to overcome environmental stress and to protect itself. A biofilm is a dense aggregation of microbial cells bound together by a slimy extracellular matrix of polysaccharide and protein. When bacteria group together in these multicellular communities, they are able to tolerate antimicrobial challenges that normally eradicate free-floating individual cells. It is currently accepted that biofilms are implicated in over 80% of the chronic infections caused by bacteria, including middle ear otitis, endocarditis, urinary tract infections and lung infections of patients with cystic fibrosis. The importance of biofilm in medicine is due to its role in persistence of the infection because biofilm is not removed and bacteria in biofilms are 1000 more resistant to antibiotics and host defenses as compared to those free living bacteria.

Several recent reports indicate that H. pylori forms biofilm either in vitro or in vivo, Cole et al studied the ability of 19 H. pylori clinical isolates and reference strains in Brain Heart Infusion broth supplemented with 0.1% β-cyclodextrin. Both strains were able to form biofilm and the biofilm produced had a similar progression when compared to biofilm formed by other bacterial species. The first evidence of in vivo biofilm formation arose in 2006. The authors compared, by scanning electron microscopy, gastric biopsies from urease positive and negative patients, detecting the presence of dense mature biofilm in the pathogen positive biopsies while biofilm was absent in the urease negative biopsies, which is indicative that H. pylori is able to form biofilm in the human gastric mucosa. To this context, it is notable that stress conditions stimulate H. pylori to enter coccoid forms that when the antibiotic concentration reduces, can resuscitate and repopulate the biofilm and the infection relapses. In vitro study, H. pylori biofilm formation decreases the susceptibility to clarithromycin and that H. pylori clarithromycin resistance mutations are more frequently generated in biofilms than in planktonic cells.

Because antibacterial susceptibility of a particular strain is favored when the biofilm is destabilized, it is believed that a combination of antimicrobial agents and anti-biofilm molecules should be synergistic. N-acetylcysteine (NAC) being both a mucolytic agent and a thiol-containing antioxidant agent was successfully used in medical practice for the treatment of patients with chronic respiratory tract infections. The NAC positive effects were thought to be due not only to mucus-dissolving properties, but also, interestingly, to the capability to reduce and prevent biofilm formation. NAC was able to avoid biofilm formation and to destabilize the already formed biofilm at concentrations over 10 mg/mL, similar to results observed with other pathogens. On the other hand, in vivo studies with two groups of 20 individuals each, one group (treated) received N-acetyl-cysteine for one week before the anti-H. pylori treatment for refractory H. pylori infection while the other group (untreated controls) did not received the destabilizing agent, showed eradication of the infection in 65% of the cases for the N-acetyl-cysteine treated group as detected by the urea breath test. The control group showed only 20% of successful eradication, suggesting that N-acetyl-cysteine act as a biofilm destabilizing agent that favor in vivo the activity of antibiotic substances.

Potent acid inhibition Acid inhibition has also proven an important component of eradication therapy. The antibiotics, particularly clarithromycin, which is used against H. pylori, are subject to pH-dependent degradation. This degradation is reduced by increasing gastric pH. Achieving a pH above 4 maximizes the efficacy of the antibiotic. Second, proton pump inhibitors (PPIs) may alter the transport of antibiotics from the plasma to the gastric juice and mucosa by altering the pH or by affecting active transport processes. The minimum inhibitory concentration (MIC) of the antibiotics against H. pylori is often lower at higher pHs. Finally, because H. pylori is sensitive to changes in gastric pH, PPI-induced elevations of pH, the gastric contents may become less hospitable to H. pylori. The importance of achieving adequate acid inhibition has been highlighted by recent studies. First, increasing the PPI dose was found to raise cure rates when used in dual anti-Helicobacter pylori therapies. Second, a previous meta-analysis by our group showed that triple therapy using a standard dose of PPI twice a day achieves higher cure rates than the same antibiotics plus the PPI once daily. Previous meta-analyses show that H. pylori treatment achieves lower cure rates in extensive metabolizers than in poor PPI metabolizers. All this evidence supports the hypothesis that achieving a potent acid inhibition can improve cure rates of H. pylori treatment.