Coccoid forms of Helicobacter pylori can be viable.

Controversy exists as to whether the coccoid form of Helicobacter pylori can exist in a viable form. Conversion of helical to coccoid morphology occurs in culture over several days. In this study, the morphology was correlated with parameters of genetic integrity in the reference NCTC 11637 strain over 21 days of culture. The capacity to regrow colonies of helical form was demonstrated from a culture where the coccoid form constituted up to 95% and negligible urease activity could be detected. Urease enzyme activity and its mRNA decreased between day 0 and 10 while 26 kD mRNA and 16S rRNA were expressed unchanged for up to 14 and 21 days of culture, respectively. Expression of mRNA for the Cag A gene behaved in a similar fashion to that of urease. No evidence of DNA fragmentation was detected. These data suggest that a viable form of non-urease producing H. pylori exists after short to intermediate culture and that some if not all of these viable bacteria have coccoid morphology.