Thermal Inactivation of Sodium-Habituated Staphylococcus aureus in Ready-to-Heat Sauces

Abstract

The objective of this study was to evaluate the effect of sodium habituation on thermal resistance of Staphylococcus aureus in various ready-to-heat (RTH) sauces. The strain mixture of S. aureus strains KACC10768, KACC10778, KACC11596, KACC13236 and NCCP10862 was habituated up to 9% of NaCl. The inocula of NaCl-habituated and nonhabituated S. aureus were inoculated in 5 g portions of pork cutlet, meat and Carbonara sauces at 7 Log CFU/g, and the samples were vortexed vigorously. The inoculated samples were then exposed to 60 and 70 o C in a water-bath, and survivals of total bacteria and S. aureus were enumerated on tryptic soy agar and mannitol salt agar, respectively, every 30 min for 120 min. At 60 o C, the cell counts of total bacteria and the significant difference in survivals between sodium-habituated and non-habituated S. aureus were observed only in the Carbonara sauce; the tailing effect, which is the period of no reduction of bacterial cell counts, was observed in pork cutlet, meat and Carbonara sauces subjected to 60 o C. At 70 o C, total bacterial populations and sodium-habituated and non-habituated S. aureus cell counts in meat and Carbonara sauce also significantly decreased (p<0.05) after 30 min of heat treatment, followed by the obvious tailing effect. Sodium-habituated S. aureus cell counts in meat and Carbonara sauces were higher (p<0.05) than those of non-habituated S. aureus at 70 o C. The results indicate that sodium habituation of S. aureus cells may increase the thermal resistance of the pathogen in RTH sauces; moreover, heating RTH sauces for a short time before serving may not sufficiently decrease the cell counts of S. aureus, particularly for sodium-habituated strain.

Effect of NaCl on Heat Resistance, Antibiotic Susceptibility, and Caco-2 Cell Invasion ofSalmonella

“…A study by Oscar [7] showed that previous exposure of Salmonella to NaCl affected the kinetic parameters of the bacteria, such as lag phase duration and maximum specific growth rate. For Staphylococcus aureus , exposure to NaCl increased its thermal resistance in ready-to-heat sauces [8]. Other studies also showed that the exposure of bacteria to sublethal stresses such as acid, heat, and NaCl increased their cross-protection responses, especially following continuous exposure to the stresses [9, 10].…”

New insights in thermal resistance of staphylococcal strains belonging to the species Staphylococcus epidermidis, Staphylococcus lugdunensis and Staphylococcus aureus

“…The exposure to sub-lethal stresses, such as acid, heat, salt, and various preservatives, can modify the response to subsequent other stresses, with a mechanism known as cross-protection or cross-resistance response (Beales, 2004;Koutsoumanis, Kendall, & Sofos, 2003). S. aureus treated in Carbonara and meat sauces at 70 C, after an initial decline (about 3e4 log units), reached a constant concentration throughout all the treatment period, with a higher survival ratio if the cells were NaCl pre-habituated (Park et al, 2012).…”

Effects of sodium chloride on heat resistance, oxidative susceptibility, motility, biofilm and plaque formation of Burkholderia pseudomallei

“…Several studies have shown that exposure to NaCl can influence the adaptive survival and virulence of pathogenic bacteria. The relevance of this has been shown in Salmonella enterica serovar Typhimurium (12) , Staphylococcus aureus (Park et al., ), and Listeria monocytogenes (Garner, James, Callahan, Wiedmann, & Boor, ), whereby bacteria cultured in medium‐containing high NaCl show increased heat tolerance (Park et al., ; Yoon, Park, Oh, Choi, & Yoon, ), antibiotic resistance (Yoon et al., ), and invasion ability into host cells (Garner et al., ; Yoon et al., ). Our previous study also showed that B. pseudomallei grown under salt stress displayed significantly greater resistance to the antibiotic ceftazidime (Pumirat et al., ).…”