Description
Helicobacter is a gram negative, spirally shaped, flagellated bacterium. Microbiological identification of H. pylori is made by positive urease, catalase and oxidase tests as well as missing hippurate hydrolysis and nitrate reductase support.
Helicobacter pylori is specific for humans. Other helicobacter species are found in mammals such as cats, dogs, pigs, and mice.
H. pylori isolates may differ phenotypically in expression/non-expression of vacuolating cytotoxin (VacA) and a second toxin which is encoded by cytotoxin-associated gene (CagA). Virulent (Type I) and non-virulent (Type II) helicobacter strains can be distinguished by these phenotypical differences. VacA and CagA expressing Type I H. pylori strains have been associated with duodenal ulcers.
Transmission of Helicobacter pylori to humans is still not well understood. Oral-oral and oral-fecal transmission have been suggested