h. pylori is more easily transmitted by gastric mucus than saliva. transmission occurs mainly within families in developed nations, yet can also be acquired from the community in developing countries. h. pylori may also be transmitted orally by means of fecal matter through the ingestion of waste-tainted water, so a hygienic environment could help decrease the risk of h. pylori infection. prevention due to h. pylori's role as a major cause of certain diseases (particularly cancers) and its consistently increasing antibiotic resistance, there is a clear need for new therapeutic strategies to prevent or remove the bacterium from colonizing humans. much work has been done on developing viable vaccines aimed at providing an alternative strategy to control h. pylori infection and related diseases. researchers are studying different adjuvants, antigens, and routes of immunization to ascertain the most appropriate system of immune protection; however, most of the research only recently moved from animal to human trials. an economic evaluation of the use of a potential h. pylori vaccine in babies found its introduction could, at least in the netherlands, prove cost-effective for the prevention of peptic ulcer and stomach adenocarcinoma. a similar approach has also been studied for the united states. notwithstanding this proof-of-concept (i.e. vaccination protects children from acquisition of infection with h. pylori), as of late 2019 there have been no advanced vaccine candidates and only one vaccine in a phase i clinical trial. furthermore, development of a vaccine against h. pylori has not been a current priority of major pharmaceutical companies. many investigations have attempted to prevent the development of helicobacter pylori-related diseases by eradicating the bacterium during the early stages of its infestation using antibiotic-based drug regimens. studies find that such treatments, when effectively eradicating h. pylori from the stomach, reduce the inflammation and some of the histopathological abnormalities associated with the infestation. however studies disagree on the ability of these treatments to alleviate the more serious histopathological abnormalities in h. pylori infections, e.g. gastric atrophy and metaplasia, both of which are precursors to gastric adenocarcinoma. there is similar disagreement on the ability of antibiotic-based regiments to prevent gastric adenocarcinoma. a meta-analysis (i.e. a statistical analysis that combines the results of multiple randomized controlled trials) published in 2014 found that these regimens did not appear to prevent development of this adenocarcinoma. however, two subsequent prospective cohort studies conducted on high-risk individuals in china and taiwan found that eradication of the bacterium produced a significant decrease in the number of individuals developing the disease. these results agreed with a retrospective cohort study done in japan and published in 2016 as well as a meta-analysis, also published in 2016, of 24 studies conducted on individuals with varying levels of risk for developing the disease. these more recent studies suggest that the eradication of h. pylori infection reduces the incidence of h. pylori-related gastric adenocarcinoma in individuals at all levels of baseline risk. further studies will be required to clarify this issue. in all events, studies agree that antibiotic-based regimens effectively reduce the occurrence of metachronous h. pylori-associated gastric adenocarcinoma. (metachronous cancers are cancers that reoccur 6 months or later after resection of the original cancer.) it is suggested that antibiotic-based drug regimens be used after resecting h. pylori-associated gastric adenocarcinoma in order to reduce its metachronus reoccurrence. treatment further information: helicobacter pylori eradication protocols gastritis superficial gastritis, either acute or chronic, is the most common manifestation of h. pylori infection. the signs and symptoms of this gastritis have been found to remit spontaneously in many individuals without resorting to helicobacter pylori eradication protocols. the h. pylori bacterial infection persists after remission in these cases. various antibiotic plus proton pump inhibitor drug regimens are used to eradicate the bacterium and thereby successfully treat the disorder with triple-drug therapy consisting of clarithromycin, amoxicillin, and a proton-pump inhibitor given for 14–21 days often being considered first line treatment. peptic ulcers once h. pylori is detected in a person with a peptic ulcer, the normal procedure is to eradicate it and allow the ulcer to heal. the standard first-line therapy is a one-week "triple therapy" consisting of acid-suppressive therapy, most commonly proton-pump inhibitors, such as omeprazole, or potassium-competitive acid blockers, such as vonoprazan, combined with the antibiotics clarithromycin and amoxicillin. (the actions of proton pump inhibitors against h. pylori may reflect their direct bacteriostatic effect due to inhibition of the bacterium's p-type atpase and/or urease.) variations of the triple therapy have been developed over the years, such as using a different proton pump inhibitor, as with pantoprazole or rabeprazole, or replacing amoxicillin with metronidazole for people who are allergic to penicillin. in areas with higher rates of clarithromycin resistance, other options are recommended. such a therapy has revolutionized the treatment of peptic ulcers and has made a cure to the disease possible. previously, the only option was symptom control using antacids, h2-antagonists or proton pump inhibitors alone. antibiotic-resistant disease an increasing number of infected individuals are found to harbor antibiotic-resistant bacteria. this results in initial treatment failure and requires additional rounds of antibiotic therapy or alternative strategies, such as a quadruple therapy, which adds a bismuth colloid, such as bismuth subsalicylate. in patients with any previous macrolide exposure or who are allergic to penicillin, a quadruple therapy that consisting of a proton pump inhibitor, bismuth, tetracycline, and a nitroimidazole for 10–14 days is a recommended first-line treatment option. for the treatment of clarithromycin-resistant strains of h. pylori, the use of levofloxacin as part of the therapy has been suggested. ingesting lactic acid bacteria exerts a suppressive effect on h. pylori infection in both animals and humans, and supplementing with lactobacillus- and bifidobacterium-containing yogurt improved the rates of eradication of h. pylori in humans. symbiotic butyrate-producing bacteria which are normally present in the intestine are sometimes used as probiotics to help suppress h. pylori infections as an adjunct to antibiotic therapy. butyrate itself is an antimicrobial which destroys the cell envelope of h. pylori by inducing regulatory t cell expression (specifically, foxp3) and synthesis of an antimicrobial peptide called ll-37, which arises through its action as a histone deacetylase inhibitor. the substance sulforaphane, which occurs in broccoli and cauliflower, has been proposed as a treatment. periodontal therapy or scaling and root planing has also been suggested as an additional treatment. extranodal marginal zone b-cell lymphomas main article: malt lymphoma extranodal marginal zone b-cell lymphomas (also termed malt lymphomas) are generally indolent malignancies. recommended treatment of h. pylori-positive extranodal marginal zone b-cell lymphoma of the stomach, when localized (i.e. ann arbor stage i and ii), employs one of the antibiotic-proton pump inhibitor regiments listed in the h. pylori eradication protocols. if the initial regimen fails to eradicate the pathogen, patients are treated with an alternate protocol. eradication of the pathogen is successful in 70–95% of cases. some 50-80% of patients who experience eradication of the pathogen develop within 3–28 months a remission and long-term clinical control of their lymphoma. radiation therapy to the stomach and surrounding (i.e. peri-gastric) lymph nodes has also been used to successfully treat these localized cases. patients with non-localized (i.e. systemic ann arbor stage iii and iv) disease who are free of symptoms have been treated with watchful waiting or, if symptomatic, with the immunotherapy drug, rituximab, (given for 4 weeks) combined with the chemotherapy drug, chlorambucil, for 6–12 months; 58% of these patients attain a 58% progression-free survival rate at 5 years. frail stage iii/iv patients have been successfully treated with rituximab or the chemotherapy drug, cyclophosphamide, alone. only rare cases of h. pylori-positive extranodal marginal zone b-cell lymphoma of the colon have been successfully treated with an antibiotic-proton pump inhibitor regimen; the currently recommended treatments for this disease are surgical resection, endoscopic resection, radiation, chemotherapy, or, more recently, rituximab. in the few reported cases of h. pylori-positive extranodal marginal zone b-cell lymphoma of the esophagus, localized disease has been successfully treated with antibiotic-proton pump inhibitor regimens; however, advanced disease appears less responsive or unresponsive to these regimens but partially responsive to rituximab. antibiotic-proton pump inhibitor eradication therapy and localized radiation therapy have been used successfully to treat h. pylori-positive extranodal marginal zone b-cell lymphomas of the rectum; however radiation therapy has given slightly better results and therefore been suggested to be the disease' preferred treatment. the treatment of localized h. pylori-positive extranodal marginal zone b-cell lymphoma of the ocular adenexa with antibiotic/proton pump inhibitor regimens has achieved 2 year and 5 year failure-free survival rates of 67% and 55%, respectively, and a 5-year progression-free rate of 61%. however, the generally recognized treatment of choice for patients with systemic involvement uses various chemotherapy drugs often combined with rituximab. diffuse large b-cell lymphoma main article: diffuse large b-cell lymphoma diffuse large b-cell lymphoma is a far more aggressive cancer than extranodal marginal zone b-cell lymphoma. cases of this malignancy that are h. pylori-positive may be derived from the latter lymphoma and are less aggressive as well as more susceptible to treatment than h. pylori negative cases. several recent studies strongly suggest that localized, early-stage diffuse helicobacter pylori positive diffuse large b-cell lymphoma, when limited to the stomach, can be successfully treated with antibiotic-proton pump inhibitor regimens. however, these studies also agree that, given the aggressiveness of diffuse large b-cell lymphoma, patients treated with one of these h. pylori eradication regimes need to be carefully followed. if found unresponsive to or clinically worsening on these regimens, these patients should be switched to more conventional therapy such as chemotherapy (e.g. chop or a chop-like regimen), immunotherapy (e.g. rituximab), surgery, and/or local radiotherapy. h. pylori positive diffuse large b-cell lymphoma has been successfully treated with one or a combination of these methods. stomach adenocarcinoma helicobacter pylori is linked to the majority of gastric adenocarcinoma cases, particularly those that are located outside of the stomach's cardia (i.e. esophagus-stomach junction). the treatment for this cancer is highly aggressive with even localized disease being treated sequentially with chemotherapy and radiotherapy before surgical resection. since this cancer, once developed, is independent of h. pylori infection, antibiotic-proton pump inhibitor regimens are not used in its treatment. prognosis helicobacter pylori colonizes the stomach and induces chronic gastritis, a long-lasting inflammation of the stomach. the bacterium persists in the stomach for decades in most people. most individuals infected by h. pylori never experience clinical symptoms, despite having chronic gastritis. about 10–20% of those colonized by h. pylori ultimately develop gastric and duodenal ulcers. h. pylori infection is also associated with a 1–2% lifetime risk of stomach cancer and a less than 1% risk of gastric malt lymphoma. in the absence of treatment, h. pylori infection – once established in its gastric niche – is widely believed to persist for life. in the elderly, however, infection likely can disappear as the stomach's mucosa becomes increasingly atrophic and inhospitable to colonization. the proportion of acute infections that persist is not known, but several studies that followed the natural history in populations have reported apparent spontaneous elimination. it is possible for h. pylori to re-establish in a person after eradication. this recurrence can be caused by the original strain (recrudescence), or be caused by a different strain (reinfection). according to a 2017 meta-analysis by hu et al., the global per-person annual rates of recurrence, reinfection, and recrudescence is 4.3%, 3.1%, and 2.2% respectively. it is unclear what the main risk factors are. mounting evidence suggests h. pylori has an important role in protection from some diseases. the incidence of acid reflux disease, barrett's esophagus, and esophageal cancer have been rising dramatically at the same time as h. pylori's presence decreases. in 1996, martin j. blaser advanced the hypothesis that h. pylori has a beneficial effect by regulating the acidity of the stomach contents. the hypothesis is not universally accepted as several randomized controlled trials failed to demonstrate worsening of acid reflux disease symptoms following eradication of h. pylori. nevertheless, blaser has reasserted his view that h. pylori is a member of the normal flora of the stomach. he postulates that the changes in gastric physiology caused by the loss of h. pylori account for the recent increase in incidence of several diseases, including type 2 diabetes, obesity, and asthma. his group has recently shown that h. pylori colonization is associated with a lower incidence of childhood asthma. epidemiology as of 1995 at