COMPARISON OF THE NUCLEIC-ACIDS OF HELICAL AND COCCOID FORMS OF HELICOBACTER-PYLORI

The nucleic acids of the helical and coccoid forms of Helicobacter pyl ori were studied to determine if the coccoid forms are ''viable (capab le of growing) but nonculturable.'' Using a reference strain (NCTC 116 38) and five clinical strains, the nucleic acid contents, DNA integrit y, and results of PCR and reverse transcription-PCR (RT-PCR) were comp ared for helical H. pylori and coccoid forms induced using glycochenod eoxycholic acid or bismuth citrate. The DNA and RNA contents of the co ccoid forms were respectively 6.8- and 8.1-fold lower than those of he lical H. pylori after 3 days of induction and 11.5- and 14.7-fold lowe r after 7 days. Agarose gel electrophoresis of DNA extracted from the coccoid forms after 3 days of induction showed a smear pattern indicat ing DNA cleavage, whereas DNA from helical H. pylori showed a single b and with a high molecular mass. After 12 days of induction, all RNA sa mples from 100% coccoid cultures were negative for the mRNA of urease A or the 26-kDa species-specific protein by RT-PCR. However, most RNA samples obtained after 3 or 7 days of induction were positive at low l evels despite the lack of recovery from these cultures. These results suggest that the coccoid form of H. pylori has impaired genomic DNA an d is in the process of cellular degeneration, thus being still alive b ut nonincreasable.