Mycoplasma contamination of canine gastric biopsy samples and cultures of gastric Helicobacter spp.

Helicobacter felis and H. bizzozeronii are canine gastric helicobacters related to H. pylori. The growth of gastric helicobacters requires a complex medium including blood and serum. We found that some of our blood agar cultures were contaminated with mycoplasmas, which were isolated from one biopsy sample and several blood agar cultures of canine gastric helicobacters by PCR or culture method. However, none of our other 18 Helicobacter strains, subcultured 10-15 times since 1990, were found to be contaminated when studied in spring 1996. Nor was horse serum used as a growth supporter found to be contaminated with mycoplasmas. All our mycoplasma isolates grew as pure cultures and as cocultures with H. bizzozeronii on a selective medium containing vancomycin, polymyxin B and trimethoprim used in cultivation of helicobacters. Our data suggest that mycoplasmas occurring on biopsy samples can grow as contaminants on Helicobacter cultures.