SUSCEPTIBILITY OF SUSPENDED AND SURFACE-ATTACHED SALMONELLA-ENTERITIDIS TO BIOCIDES AND ELEVATED-TEMPERATURES

The differential resistance of substratum-attached, detached, and plan ktonic cells of Salmonella enteritidis phage type 4 was studied by usi ng several inimical processes and in vivo bioluminescence as a nondest ructive, real-time reporter of metabolic activity. Bioluminescence in this strain was mediated by a construction containing the entire lux o peron from Photorhabdus luminescens. An excellent correlation between bioluminescence and classical plate count data was obtained when we co mpared attachment profiles, biocide concentration exponents, and therm al inactivation D values (D value was the time required for a 10-fold reduction in the number of survivors). Biocide challenge of surface-ad herent S. enteritidis resulted in concentration exponents that were ex perimentally indistinguishable from those obtained with Luria-Bertani broth-grown planktonic cells. It appears that cleansing regimes develo ped by using planktonic cell data are effective against surface-attach ed cells of this bacterium, Both attached and detached cells exhibited an approximately twofold increase in D values at 52 degrees C compare d with values calculated for planktonic cells, strongly indicating tha t the detached cells exhibited an attached phenotype during the heatin g process. A model of a physiological adaptive response induced in att ached cells and also reflected in detached cells is presented.