ObjectiveThe pathogenesis of acute gastric stress ulceration in the seriously ill is uncertain, and any role of Helicobacter pylori infection is unknown. We aimed to assess the relationship between H. pylori serological status and stress ulceration in seriously ill patients, as well as H. pylori serological status in intensive care nurses as a marker for nosocomial infection.DesignProspective epidemiologic survey.SettingAdult intensive care unit in a university teaching hospital.PatientsOne hundred patients, 100 nurses, and 500 blood donors as community controls.InterventionsH. pylori serological status was measured in patients, staff, and controls using a rapid whole blood test. Upper gastrointestinal bleeding and risk factors for acute stress ulceration were recorded.Measurements and Main ResultsIn seriously ill patients, H. pylori seropositivity (67%) was significantly higher than in the control group (39%) (p < .001). In patients, seropositivity was not related to age, country of birth, diagnostic category, severity of illness, or risk score for stress ulceration. There was a trend toward increased macroscopic gastric bleeding in seropositive patients. In intensive care nurses, H. pylori seropositivity (40%) was significantly higher than in age-matched controls (19%) (p < .001). Only duration of intensive care nursing was significantly associated with seropositivity (p = .02).ConclusionsThe unexpectedly high H. pylori seropositivity rate in this seriously ill cohort raises the possibility that under intensive care conditions, H. pylori infection may modulate responses to illness and injury, with consequent clinical implications. Furthermore, the elevated seropositivity rate in intensive care nurses suggests that H. pylori can be nosocomially transmitted. (Crit Care Med 1999; 27:1276-1280)