Influence of oropharyngeal flora and specimen pretreatment on the recovery of Helicobacter pylori.

The recovery of Helicobacter pylori was studied in vitro in the presence of different concentrations of oropharyngeal flora. The effect on the bacterial yield of Helicobacter pylori and oropharyngeal flora of washing biopsies once, twice or thrice before culture was then studied in biopsies taken from 35 patients. A low rate of recovery of low Helicobacter pylori concentrations (< or = 10(3) cfu/ml) was related to the presence of relatively high oropharyngeal flora concentrations (> or = 10(4) cfu/ml). After three washings a decrease in oropharyngeal flora between 10-fold and 100-fold cfu/biopsy was observed in seven patient samples. In another three specimens a more than 100-fold reduction in cfu/biopsy was observed. In the case of Helicobacter pylori, a 60-fold decrease in log cfu/biopsy was observed in only one patient. Pretreatment of the specimens by washing of the biopsies improved the recovery of small amounts of Helicobacter pylori in 10 of 28 patients. For optimal detection of Helicobacter pylori in gastric mucosal biopsies, washing of the specimens in addition to the use of selective media is recommended.