A patient with a burning epigastric pain is admitted to the hospital, and a gastric biopsy is performed. The tissue is cultured on chocolate agar incubated in a microaerophilic environment at 98.6degF (37degC) for 5 to 7 days. On fifth day of incubation, colonies appear on the plate and curved, gram-negative, oxidase-positive rods are observed. Which of the following is the most likely identity of this organism?

Helicobacter pylori was first recognized as a possible cause of gastritis and peptic ulcer by Marshall and Warren in 1984. This organism is readily isolated from gastric biopsies but not from stomach contents. It is similar to Campylobacter species and grows on chocolate agar at 98.6degF (37degC) in the same microaerophilic environment suitable for C. jejuni (Campy-Pak or anaerobic jar without the catalyst). Helicobacter pylori, however, grows more slowly than C. jejuni, requiring 5 to 7 days incubation. C. jejuni grows optimally at 107.6degF (42degC), not 98.6degF (37degC), as does H. pylori.DIAGNOSTIC TESTS FOR HELICOBACTER PYLORINon-invasive Advantages Disadvantages Serum ELISAInexpensiveNot useful for follow-upUrea breath testUseful for follow-upExpensive; may be falsely negative in patients on acid suppression therapyStool antigen testInexpensive; useful for follow-upInconvenientWhole blood assayInexpensive; rapidLess accurate than serum ELISAInvasive (endoscopic)HistologyVisualization of pathologyMay miss low-grade infectionRapid ureaseRapidMay be falsely positive in bacterial overgrowthCultureAntibiotic susceptibilityNot maximally sensitive; not available routinely; requires 4-7 daysELISA, enzyme-linked immunosorbent assay.