Degrees of Microbial Injury and Survival
Degrees of Microbial Injury and Survival
A microbial survival curve is a plot of the number or fraction of the survivors as a function of their exposure time to a hostile environment or lethal agent. It is traditionally determined by counting the survivors' colonies after incubation under optimal conditions to maximize recovery. Simultaneous incubation under stressful conditions only allows intact microbes to grow, and the difference is used to calculate the number of injured cells or spores. However, one can also incubate the survivors under several intermediate stress levels in order to assess different degrees of injury. The principle is demonstrated with simulated original survival curves following the Weibullian model, supplemented by three curves representing the fractions of intact, slightly injured, and gravely injured survivors.