Coexistence of Helicobacter pylori spiral and coccoid forms in experimental mice

mouse AIM To infect mice with Helicobacter pylori and detect immune response against two form of H. pylori. METHODS An isolate of H. pylori obtained from a patient with gastric cancer was used to infect mice. Fifty mice were divided into eight groups. Two groups served as negative control without any inoculation and internal negative control with 0.5M NaHCO3 and brain heart infusion ( HBI), respectively. Mice in each experimental group were first inoculated with 0.5M NaHCO3 and then H. pylori suspension for 3 times at a 2-day interval. Mice from controls and infectious groups were sacrificed at a weekly interval postinfection. Gastric samples were trimmed, inoculated onto chocolate blood agar and then incujbated in microaerophilic atmosphere at 37¡æ for 14 days. Sera were examined for immunoglobulins against H. pylori spiral and coccoid antigens by ELISA. RESULTS After inoculation H. pylori was isolated in one mouse from one week postinfection. No H. pylori was detected in control mice. However, urease test was positive in 50 % (5/10) control mice, 70 % (7/10) mice inoculated with NaHCO3 and BHI and 77 % (23/30) mice infected with H. pylori. The systemic immune responses of the mice to H. pylori strain were determined by ELISA. The mice showed immune responses to both H. pylori spiral and coccoid antigens one week after infection with H. pylori. The peak mean absorbances of antibodies against spiral and coccoid forms were four weeks postinfection which showed 6 and 18 times higher than that of negative control group respectively (P<0.01). CONCLUSION Spiral and coccoid forms of H. pylori coexist in experimental mice studied