Helicobactor pylori: H. pylori

One of the most common bacterial infections in humans, affecting ~4.4billion individuals worldwide. 1/2 of adults in industrialized countries are infected, and up to 90% in the developing world. These infections persist for life unless treated with antibiotics.

The Pathogen

H. pylori is a gram-negative, helical shaped bacteria which infects the stomach. After entering the host stomach, H. pylori produces a large amount of an enzyme Urease. Urease locally raises the pH from ~2 to ~6-7, making the stomach hospitable to the bacteria. The bacteria then uses its flagella to move to the stomach epithelial cells, where it can then use it's adhesin proteins to interact with host cell receptors. Once successfully colonized, the infection can persist. H. pylori then releases several toxins, including cytotoxin-associated gene A (CagA), and vacuolating cytotoxin A (VacA), which cause host tissue damage.

H. pylori infections


While more than half of the world's population is infected with H. pylori, most don't know it because they don't get sick. Those with symptoms can have an aching/burning pain in their abdomen, nausea, loss of appetite, frequent burping, bloating, and unintentional weight loss. Potential complications of infections are ulcers, where the bacteria damages the lining of the stomach and intestine allowing stomach acid to create an open sore, inflammation of the stomach lining, or stomach cancer. In fact, since 1994 H. pylori has been classified as a carcinogen.

H. pylori antibiotic resistance

Resistance of H. pylori to antibiotics has reached alarming levels worldwide, although there are regional differences to resistance rates. In the 1990's, the standard treatment of a triple therapy regimen of 7-10 days of twice-daily clarithromycin, metronidazole/amoxicillin, and a proton pump inhibitor eradicated the infection 90% of the time. Success with this has rapidly declined due to increasing resistance to clarithromycin and it's alternative levofloxacin.