Use of growth curves to measure the adherence of Campylobacter sp. on HeLa cells

Campylobacter sp. is a clinically significant food and water-borne bacterial pathogen, often causing gastroenteritis and, in some cases, paralysis in humans.  The molecular basis of its pathogenicity and virulence remains elusive due in part to difficulties in culturing and measuring the organism's interaction with intestinal epithelial cells.  To overcome this limitation we developed a way to assess virulence in a novel microtiter plate based assay system using growth curve analysis.  Strains of Campylobacter were grown under a variety of conditions, including the presence of human cervical cancer cells (HeLa cells).  After an initial incubation and extensive washing, the adherence and/or the invasion of the organism onto or into the HeLa cells was assessed by performing growth curves in an automated, incubating plate reader measuring optical density (OD) at multiple intervals over a 48 hour period.  By measuring and comparing the time intervals needed to reach log phase we could determine whether or not significant numbers of bacteria were either adhering to or entering the cells they were grown with.  We could also correlate adherence/invasion with HeLa cell density as well as bacterial cell density and we also could measure differences between the bacterial strains in their abiltiy to interact with the HeLa cells.  This high-throughput protocol will allow us to investigate various questions posed by our initial experiments and challenge previous research done with less sensitive techniques.