The effects of high pressure, temperature, and antimicrobial compounds on endospores of Clostridium
spp. were examined. Minimal inhibitory concentrations (MIC) of nisin and reutericyclin were determined
for vegetative cells and endospores of Clostridium sporogenes ATCC 7955, Clostridium beijerinckii ATCC
8260, and Clostridium difficile 3195. Endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260
were exposed to 90
C and 90
C/600 MPa in the presence of 16 mg L1
nisin or 6.4 mg L1
reutericyclin
for 0e60 min in a 0.9% saline solution. Dipicolinic acid (DPA) release was measured using a terbium-DPA
fluorescence assay, and endospore permeability was assessed using 40
,6-diamidino-2-phenylindole
(DAPI) fluorescence. Vegetative cells of C. sporogenes ATCC 7955 exhibited higher sensitivity to nisin
relative to endospores, with MIC values 0.23 0.084 mg L1
and 1.11 0.48 mg L1
, respectively. Nisin
increased DPA release when endospores were treated at 90
C; however, only C. sporogenes ATCC 7955
exhibited higher inactivation, suggesting strain or species specific effects. Reutericyclin did not enhance
spore inactivation or DPA release. Use of nisin in combination with high pressure, thermal treatments
enhanced inactivation of endospores of Clostridium spp. and may have application in foods.