High hydrostatic pressure treatment is regarded as a possible alternative p
rocess for food preservation. One of the primary considerations for industr
ial applications is the ability of this technique to destroy pathogenic mic
roorganisms. The inactivation of microorganism populations after high press
ure treatment is well described, but their residual pathogenicity is less d
ocumented. This study compared the virulence of Listeria monocytogenes scot
t A before and after high pressure treatments. The pressurized samples were
composed of 1 ml of Listeria monocytogenes culture diluted into 9 ml of bu
ffer. Two buffers are used: phosphate buffer (pH 7) and citrate buffer (pH
5.6).
The virulence of cells is estimated by their association and invasion capac
ities to Hela cells. These characteristics of pathogenity were compared bet
ween untreated and pressurized cells (400 MPa, 10 min, in citrate buffer) o
r (600 MPa, 10 min, in phosphate buffer). These results showed that, after
treatment in citrate buffer, the treated cells lost their association and i
nvasion capacities. However, in a phosphate buffer, treated cells have lose
their invasion properties, but retain their association capacities to Hela
cells. These results showed that the inactivation of Listeria monocytogene
s population involve a loss of their pathogenic properties. However, the co
nservation of association capacities of some inactivated cells show that th
ese cells seem to continue to express adhesion molecules and, in certain co
nditions, can re-establish their multiplication properties.