Research in the Laboratory of Medical Microbiology is centered on mechanisms by which human pathogens manifest their virulence. Our model organism is Helicobacter pylori, a Gram-negative, microaerophilic, mobile, spiral bacterium which is an etiologic factor for the development of chronic gastritis and gastric or duodenal ulcer and a major risk factor for the development of gastric adenocarcinoma (class 1 carcinogen, WHO). In the past years work focused on the study of:

• Epidemiology of H. pylori infection by studying prevalence and transmission within the Greek adult and children population, as well as H. pylori antibiotic resistance. We are recognized by the European Helicobacter pylori study Group as the reference laboratory in Greece, involved in the monitoring of H. pylori antibiotic resistance. For the successful implementation of the above tasks, we have established a network of collaborating Gastroenterology clinics in 4 major hospitals in Athens and hold a good library of more than 300 clinical isolates of H. pylori isolated from healthy volunteers or patients with gastroduodenal ulcer, gastritis and gastric cancer. (Panayotopoulou et al. 2007).
  
  
• Anti-H. pylori activity of new antimicrobial agents of synthetic or natural origin (Paraschos et al 2007).
  
  
• Virulence factors:
1. Characterization of H. pylori clinical strains with reference to presence and functional expression of virulence factors (cagA, vacA) and correlation to the clinical outcome of the disease.
2. Involvement of H. pylori virulence factor CagA in the HGF/cMet signaling pathway in gastric epithelial cells and its potential link to cellular deregulation and cancer.
3. Induction of pro-inflammatory chemokines in the early stages of H. pylori infection focusing on the interaction and potentially beneficial effects of lactic acid producing bacteria in the H. pylori infection during the early stages of infection (Sgouras et al. 2004, Sgouras et al. 2005).

Studies are mainly performed with the use of H. pylori-infected gastric epithelial cell lines in vitro or in vivo models of infection in mice. Currently, we house two animal models, the H. pylori Sydney Strain 1 infecting C57BL6 mice and the B127 strain infecting Mongolian Gerbils, which are currently utilized for (a) the study of H. pylori virulence mechanisms and (b) the assessment of anti-H. pylori activity of new drugs and natural products.

Andreas Mentis is a founding member and past-President (2002) of the Hellenic Helicobacter pylori Study Group (HHPSG)-a member of the European Helicobacter pylori Study Group. Dionyssios Sgouras is currently in the Board of Governors of HHPSG.

In addition to H. pylori-related work we have collaborated in various research projects covering areas of: