EFFECT OF AN OXYGEN‐REDUCING MEMBRANE FRACTION ON HELICOBACTER PYLORI

Abstract

The emerging gastric pathogen Helicobacter pylori is an oxygen‐sensitive fastidious microaerophile. Culturability of this organism is rapidly lost in oxygen levels present in the atmosphere due to its morphological transformation into a viable but not culturable state. The effect of the OxyraseTM system of oxygen‐reducing membrane fragments on H. pylori was evaluated at levels ranging from 0.1 to 0.6 Units/mL in Brucella broth supplemented with 5% horse serum. Duplicate sets of OxyraseTM dilutions inoculated with H. pylori were incubated at 35C aerobically and microaerobically. At these OxyraseTM levels, a logarithmic loss of H. pylori viability was evident in the aerobic cultures. The inoculum remained recoverable for 24 h in the presence of OxyraseTM, whereas recovery of inoculum in untreated broth was greatly reduced after 8 h of aerobic incubation, and the organism was unrecoverable after 24 h. OxyraseTM‐containing broth cultures of H. pylori incubated microaerobically showed a similar drop in viable counts for the first 48 h of incubation; however, at the lower levels of OxyraseTM, some cells survived, and resumed logarithmic growth at 96 h. To explore the effects of short term aerobic incubation in the presence of 0, 0.005, 0.05, and 0.5 Units OxyraseTM, cultures were examined microscopically after 4, 8, and 24 h. In the OxyraseTM‐containing broths, <90% of the cells exhibited rod shape morphology after 8 h, whereas in the untreated broth, most cells appeared coccoid. After 24 h, all cells exhibited coccoid morphology.