Physiological damages of Listeria monocytogenes treated by high hydrostatic pressure.
High hydrostatic pressure is a new food preservation technology known for its capacity to inactivate spoilage and pathogenic microorganisms. This study investigated the damages inflicted on Listeria monocytogenes cells treated by high pressure for 10 min at 400 MPa in pH 5.6 citrate buffer. Under these conditions, no cell growth occurred after 48 h on plate count agar. Scanning electron microscopy (SEM) revealed that cellular morphology was not really affected. Measuring propidium iodide (PI) staining followed by flow cytometry demonstrated that membrane integrity was damaged in a small part of the population, although the membrane potential evaluated by oxonol fluorescence or measured by analytical methods was reduced from - 86 to - 5 mV. These results for the first time showed that such combined methods as fluorescent dyes monitored by flow cytometry and physiological activity measurements provide valuable indications on cellular viability.
Ritz
M
M
Unité Mixte de Recherche 1014 INRA/ENVN d'Hygiène des Aliments, Ecole Nationale Vétérinaire de Nantes, France.
Tholozan
J L
JL
Federighi
M
M
Pilet
M F
MF
D005434:Flow Cytometry; D005519:Food Preservation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D006874:Hydrostatic Pressure / Q000009:adverse effects; D008089:Listeria monocytogenes / Q000502:physiology* / Q000648:ultrastructure*; D008564:Membrane Potentials; D008855:Microscopy, Electron, Scanning; D013997:Time Factors