Conversion of Campylobacter upsaliensis to the coccoid form during aerobic incubation at 37oC was not prevented by treatment with chloramphenicol and was accompanied by severe decreases in isocitrate dehydrogenase activity and oxygen uptake. Although the coccoid forms fluoresced orange red by acridine orange staining, agarose gel electrophoresis indicated an extensive degradation of the ribosomal RNA. This suggests that acridine orange staining may not be a good indicator of viability and that the coccoid form of C. upsaliensis at 37oC is degenerative rather than part of the life cycle.

Keywords: Acridine orange, Viable but nonculturable, Nonculturable form, VBNC, Campylobacter upsaliensis