Inactivation of Salmonella Typhimurium and Listeria monocytogenes using high-pressure treatments: destruction or sublethal stress?

Abstract

Aims: To investigate potential resuscitation of Listeria monocytogenes and Salmonella Typhimurium after high hydrostatic pressure treatments. Methods and Results: Pressure treatments were applied at room temperature for 10 min on bacterial suspensions in buffers at pH 7 and 5·6. Total bacterial inactivation (8 log10 CFU ml−1 of bacterial reduction) obtained by conventional plating was achieved regarding both micro‐organisms. Treatments at 400 MPa in pH 5·6 and 600 MPa in pH 7 for L. monocytogenes and at 350 MPa in pH 5·6 and 400 MPa in pH 7 for S. Typhimurium were required respectively. A ‘direct viable count’ method detected some viable cells in the apparently totally inactivated population. Resuscitation was observed for the two micro‐organisms during storage (at 4 and 20°C) after almost all treatments. In the S. Typhimurium population, 600 MPa, 10 min, was considered as the treatment achieving total destruction because no resuscitation was observed under these storage conditions. Conclusions: We suggest a delay before performing counts in treated samples in order to avoid the under‐evaluation of surviving cells. Significance and Impact of the Study: The resuscitation of pathogen bacteria after physical treatments like high hydrostatic pressure has to be considered from the food safety point of view. Further studies should be performed in food products to study this resuscitation phenomenon.

Differential gene expression of Listeria monocytogenes during high hydrostatic pressure processing

“…Data obtained using microscopy and flow cytometry (Ananta et al, 2004;Ritz et al, 2001Ritz et al, , 2006 …”

“…Data obtained using microscopy and flow cytometry (Ananta et al, 2004;Ritz et al, 2001Ritz et al, , 2006 suggests that at pressure levels of approximately 400 MPa cell integrity is maintained, that only very limited cell destruction occurs and metabolic activity is largely retained for various Grampositive bacteria, including L. monocytogenes. It was concluded that although cell viability was lost, HPP-treated cells were sublethally injured and were potentially capable of recovery back to culturability (Ritz et al, 2006). Physiological studies have also demonstrated that increasing HPP pressure levels results in metabolic indicators (for example the activity of the LmrP membrane transporter) exhibiting an accelerated decline (Kilimann et al, 2005).…”

“…Physiological studies have also demonstrated that increasing HPP pressure levels results in metabolic indicators (for example the activity of the LmrP membrane transporter) exhibiting an accelerated decline (Kilimann et al, 2005). Over the last several years a number of studies have shown L. monocytogenes and other bacteria such as E. coli seem to be capable of recovering culturability following HPP exposure Bull et al, 2005;Jantzen et al, 2006;Ritz et al, 2006). Though these findings have not been followed up by more mechanistic investigations, they do suggest that HPP exposures cause injuries in cells that may or may not lead to permanent inactivation (death) and subsequently cells may have the capacity to repair and recommence growth assuming the correct conditions are available.…”

Biocontrol of Shigella flexneri in Ground Beef and Vibrio cholerae in Seafood with Bacteriophage-Assisted High Hydrostatic Pressure (HHP) Treatment

“…HHP results in a decrease in biomembrane fluidity brought about by phase transition, which can result in membrane rupture and in denaturation of the membrane-bound proteins causing a loss of functionality of these proteins (San Martin et al 2002). Additionally, HHP acts instantaneously and uniformly in a food product and its efficacy is independent of food composition, shape, size, as well as exerting a minimal adverse effect on food quality (Ritz et al 2006). The use of HHP systems for processing raw meat, fish, and shellfish has expanded, making it often the first choice for the preservation of heat-sensitive products.…”

Disinfection of Human Tissues in Orthopedic Surgical Oncology by High Hydrostatic Pressure

“…Likewise, different procedures are available to inactivate bacteria and fungi, including their spores, in human bone transplants (48). The most efficient methods of inactivation are gamma irradiation and thermal inactivation as well as chemical sterilization methods such as the peracetic acid-ethanol treatment of bone (49).…”