Helicobacter pylori is a Gram-negative bacterium living in the stomach of its
human host. The infection causes chronic gastric mucosal inflammation and is
etiologically related to gastritis-associated diseases, gastric cancer and peptic ulcer
disease. As with other chronic infectious diseases associated with a long latent period
(e.g., syphilis and tuberculosis), clinical manifestations develop in only a minority of
infected individuals. The outcome for any of these diseases is dependent on the
interplay between host, environmental, and bacterial factors. The variable virulence of
H. pylori in relation to the presence or absence of a specific virulence factor reflects the
differences in risk of a clinical outcome. The best-studied virulence factors are the
vacuolating cytotoxin A (VacA) and cytotoxin-associated gene A product (CagA). This
chapter will discuss the clinical relevance of typing H. pylori virulence factors CagA
and VacA. Approximately 1,600 genes make up the H. pylori genome suggesting that
there may be other unidentified virulence factors, many likely to be discovered using
whole-genome sequencing.
Keywords: Helicobacter pylori, gastric cancer, peptic ulcer, virulence factors,
vacuolating cytotoxin (VacA), cytotoxin-associated gene A product (CagA), nextgeneration
sequencers.
