Effects of nisin and reutericyclin on resistance of endospores of Clostridium spp. to heat and high pressure

In Situ Determination of Clostridium Endospore Membrane Fluidity during Pressure-Assisted Thermal Processing in Combination with Nisin or Reutericyclin

“…Conversely, 90°C and 600 MPa treatments released DPA from clostridial endospores and inactivated a majority of the spore population (11) but did not severely alter membrane rigidity (this study). The presence of nisin during treatment at 90°C and 600 MPa did not affect spore membranes (this study) but accelerated endospore inactivation (11). Addition of reutericyclin resulted in more-fluid membranes during and after high-pressure thermal processing (this study) but did not consistently enhance spore inactivation (11).…”

“…Nisin is a pore-forming lantibiotic (6), reutericyclin is a proton ionophore (8). Remarkably, nisin enhances pressure-induced spore inactivation (9, 10), whereas reutericyclin had no effect or even attenuated pressure-induced inactivation of bacterial endospores (11).…”

“…Nisin and reutericyclin were selected because they are both membrane active but differ in their modes of action and their effects on spore survival after heat or pressure treatment (7,8,11). Nisin and reutericyclin were applied at 16 and 6.4 mg liter Ϫ1 , respectively, concentrations that exceed their MICs 16-fold.…”

“…Nisin and reutericyclin were applied at 16 and 6.4 mg liter Ϫ1 , respectively, concentrations that exceed their MICs 16-fold. Experiments employed Clostridium sporogenes ATCC 7955 and Clostridium beijerinckii ATCC 8260, which were previously characterized with respect to spore inactivation and DPA release by heat and pressure (11). Membrane fluidity changes and phase transitions were assessed with the fluorescent dye laurdan (6-dodecanoyl-2-dimethylaminonaphthalene).…”

“…GP values of laurdan-labeled endospores exposed to nisin or reutericyclin at 90°C or 90°C and 600 MPa were measured ex situ to relate membrane properties to spore inactivation. Spore preparation, treatments, and GP measurements were performed as described previously (11,20). Treatment of spores at 90°C for 8 min reduced viable spore counts by less than 1 log CFU ml Ϫ1 , and the spores released less than 5% DPA (11) but GP values of clostridial endospores were lowered (Fig.…”