Development of media for the isolation and selection of Helicobacter pylori

Abstract

Media formulations for the selection and isolation of Helicobacter pylon were examined. Skirrow's medium, a selective medium, was developed to isolate Campylobacter, and has occasionally been used for selection of H. pylon (Skirrow, 1977). One drawback commonly associated with Skirrow's medium is fecal flora overgrowth. Initial experiments conducted used Skirrow's medium formulations and additional modified versions. Experimentation with Skirrow's medium led to further investigations of a selective media for H. pylori. Several aspects of the media and their effects on growth of H. pylori were considered: presence of sulfites and sulfates, presence and absence of urea, effect of volatile fatty acids, antibiotic combinations, and effect of pH. Several media supplements and antibiotics were found to actually inhibit growth of H. pylori, such as ferrous sulfate, sodium metabisulfite, cephalothin, vancomycin, and novobiocin. Although H. pylori typically colonizes a site of low pH, the organism was sensitive to low pH in laboratory experiments. This is exemplified by the fact that growth of H. pylori was inhibited at pH 4.0, but was supported at pH 6.8. However, at pH 6.8, ground beef flora also flourished. After H. pylori was exposed to volatile fatty acid concentrations similar to that found in the gastrointestinal tract, it was determined that H. pylori will grow in the presence of volatile fatty acids, but varying the concentrations of them does not significantly effect growth rates of H. pylori. Although H. pylori requires urea for survival in the gastric epithelium, results of experiments indicate urea is not necessary for growth under the conditions of the study.