Variation in Resistance to Hydrostatic Pressure among Strains of Food-Borne Pathogens

Abstract

Among food-borne pathogens, some strains could be resistant to hydrostatic pressure treatment. This information is necessary to establish processing parameters to ensure safety of pressure-pasteurized foods (N. Kalchayanand, A. Sikes, C. P. Dunne, and B. Ray, J. Food Prot. 61:425–431, 1998). We studied variation in pressure resistance among strains of Listeria monocytogenes, Staphylococcus aureus,Escherichia coli O157:H7, and Salmonellaspecies at two temperatures of pressurization. Early-stationary-phase cells in 1% peptone solution were pressurized at 345 MPa either for 5 min at 25°C or for 5, 10, or 15 min at 50°C. The viability loss (in log cycles) following pressurization at 25°C ranged from 0.9 to 3.5 among nine L. monocytogenes strains, 0.7 to 7.8 among sevenS. aureus strains, 2.8 to 5.6 among six E. coliO157:H7 strains, and 5.5 to 8.3 among six Salmonellastrains. The results show that at 25°C some strains of each species are more resistant to pressure than the others. However, when one resistant and one sensitive strain from each species were pressurized at 345 MPa and 50°C, the population of all except the resistantS. aureus strain was reduced by more than 8 log cycles within 5 min. Viability loss of the resistant S. aureusstrain was 6.3 log cycles even after 15 min of pressurization. This shows that strains of food-borne pathogens differ in resistance to hydrostatic pressure (345 MPa) at 25°C, but this difference is greatly reduced at 50°C. Pressurization at 50°C, in place of 25°C, will ensure greater safety of foods.

High-pressure processing – effects on microbial food safety and food quality

“…Recent years have seen significant research on the inactivation of microorganisms in foods by HP (Dogan & Erkmen, 2004;Smiddy et al, 2004Smiddy et al, , 2005Donaghy et al, 2007). Different microorganisms react with different degrees of resistance to HPP treatment, and indeed there can be vast HPP sensitivity among bacterial species and even strains (Alpas et al, 1999;Benito et al, 1999;Pagán & Mackey, 2000). Alpas et al (1999) reported viability losses of between 0.5 and 8.5 logs among pathogenic bacterial strains.…”

“…Different microorganisms react with different degrees of resistance to HPP treatment, and indeed there can be vast HPP sensitivity among bacterial species and even strains (Alpas et al, 1999;Benito et al, 1999;Pagán & Mackey, 2000). Alpas et al (1999) reported viability losses of between 0.5 and 8.5 logs among pathogenic bacterial strains. Prokaryotic cells tend to be more pressure resistant than eukaryotes (Patterson, 1999).…”

Variation in resistance of natural isolates of Staphylococcus aureus to heat, pulsed electric field and ultrasound under pressure

“…A number of studies have reported that the resistance of a given species to a preservation technology may greatly vary amongst strains. Intraspecies resistance variation has been reported for several food preservation technologies (Patterson et al 1995;Alpas et al 1999;Benito et al 1999;Mañas et al 2000;Lado and Yousef 2003;Á lvarez et al 2003;Sherry et al 2004). Results published by Alpas et al (1999) showed that intraspecies variation in resistance to high hydrostatic pressure was remarkably wider for Staphylococcus aureus than for other micro-organisms.…”

Effects of ultra high hydrostatic pressure on Listeria monocytogenes and natural flora in broth, milk and fruit juices

“…The sensitivity of microbial cells to UHHP depends on factors such as magnitude of pressure, pressurization time, temperature, initial number of cells, types of microbial cells, suspending media, and presence of antimicrobial substances (Mackey et al, 1995;Patterson et al, 1995;Benito et al, 1999;Alpas et al, 2000;Ritz et al, 2000;Furukawa et al, 2002). In view of the limited available information on the pressure resistance of foodborne pathogens (Metrick et al, 1989;Isaacs & Chilton, 1995;Patterson et al, 1995;Alpas et al, 1999Alpas et al, , 2000Benito et al, 1999), the current study was undertaken to determine the interactions between hydrostatic pressure, pressurization time, composition of media and cell age during pressurization on Listeria monocytogenes.…”