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Stomach ulcer and cancer due to Helicobacter pylori

By Tayo Fasuan (Microbiologist)

800px-Gastric_Ulcer

There are many causes of ulcer. But the most identified cause is known to be as a result of stomach acidity. Only few knows about microorganism-induced chronic ulcer that may eventually lead to stomach cancer if not treated early enough.

Helicobacter pylori is a microaerophilic microorganism, a bacterium, that has an unusual multiple flagella that look like sheaths. It is a prominent causative agent of gastritis or commonly known as gastric ulcer. For years, it is one of the scariest microbes around because most times, its infection is lifelong, and prolonged infection can lead to cancer.

Let’s briefly look at the summarised version of its transmission, pathogenesis and treatment.

Transmission: It is usually transmitted through the feacal-oral route, that is, through eating and drinking feacal-contaminated foods and drinks. It has been found in well water, and could as well be transmitted by flies. As usual, infections is higher in low socioeconomic areas and unhygienic environments. Susceptibility to the infection also increases with age.

Pathogenesis: Once the organism get inside the stomach, it ought to be ideally killed by the stomach acidity as in the case of Salmonella typhi. However, it survives the acidity of the stomach by producing an enzyme called urease which neutralizes the acidity. Using its sheath-like flagella, it screws and penetrates the mucus layer and breach the surface of the stomach wall, producing inflamatory products which cause the stomach walls to be attacked by the immune system of the body.

Complications: Infection may sometimes persist for years, and often for life. 10-20% of infected individuals develop ulcer, and a smaller percentage may graduate to stomach/gastric cancer if untreated. 60-80% of those with gastric ulcer are infected by H. pylori, and 95% of this population may progress to gastroduodenal ulcer and gastric peptic ulcer.

Symptoms: At the initial stages of infection, symptoms include belching and vomiting. However when complicated by ulcer or cancer, symptoms will include localised abdominal pain, bloody vomit, loss of appetite, weight loss, nausea, foul-smelling stool, and bleeding, usually along defecation. Though rare, it can lead to a gastric or duodenal perforation, causing acute peritonitis, extreme and stabbing pain, which requires immediate surgery.

Treatment/Prevention: Helicobacter pylori’s infection can be treated with any two antibiotics among amoxicillin, clarithromycin and metronidazole, given for 7-14 days. However, the bacterium has developed resistance to some of these drugs due to abuse and misuse of the drugs. According to a publication in 2010, H. pylori eradication failure using this first-line therapy is still seen in more than 20% of patients, usually owing to the indiscriminate use of the antibiotics.

The recommended second-line therapy is a quadruple regimen composed of tetracycline, metronidazole, a bismuth salt and a PPI. Proton-pump inhibitors (PPIs) are a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production. The combination of PPI-amoxicillin-levofloxacin is a good option as second-line therapy. In the case of failure of second-line therapy, the patients should be evaluated using a case-by-case approach.

Most clinical guidelines recommend microbial culture before the selection of a third-line treatment based on the microbial antibiotic sensitivity. H. pylori isolates after two eradication failures are often resistant to both metronidazole and clarithromycin. The alternative candidates for third-line therapy are quinolones, tetracycline, rifabutin and furazolidone; high-dose PPI/amoxicillin therapy might also be promising. It is instructive to know that PPIs however have adverse effects, hence care should be taken when administered and taken.

Stay safe.

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