Abstract

The infectivity rates of Qβ phage is used as a bio-indicator of the physiological state of host cells and for the detection of active Escherichia coli irradiated by an increasing number of pulsed ultra-violet (UV) light. Indeed, the combination of a conventional method used to measure colony-forming ability of tested bacteria after exposure to an increase number of pulsed UV light, and the simulation of phage adsorption kinetic, can reveal the existence of active bacteria which lose the cultivability in usual culture media, but keep viability and phage susceptibility.

Keys words: Ultra-violet inactivation, viable but non-culturable bacteria, Qβ phage, active bacteria.