Identification of Listeria innocua Surrogates for Listeria monocytogenes in Hamburger Patties

Abstract

Listeria innocua M1 has been used by many researchers as a nonpathogenic thermal processing surrogate for Listeria monocytogenes. However, L. innocua M1 has been criticized because its thermal survivability characteristics are not as closely parallel to L. monocytogenes as some would like in a variety of foods and processing conditions. The present study was conducted to compare multiple L. innocua and L. monocytogenes strains to validate L. innocua M1 as the ideal surrogate under high-temperature thermal processing conditions for L. monocytogenes. The D- and z-values of L. innocua M1, L. innocua strain SLCC 5639 serotype (6a), SLCC 5640 (6b), SLCC 2745 (4ab), and L. monocytogenes F4243 (4b) were calculated for raw hamburger patties. Hamburger patties were inoculated with 10(7-8) CFU/g of L. monocytogenes or L. innocua. Samples were heat treated at 4 temperatures (62.5 to 70 degrees C). At each temperature, the decimal reduction time (D-value) was obtained by linear regression of survival curves. The D- and z-values were determined for each bacterium. The D-values of L. innocua and L. monocytogenes serotypes ranged from 3.17 to 0.13 min at 62.5 to 70 degrees C, and the z-values of L. innocua and L. monocytogenes were 7.44 to 7.73 degrees C. Two of the 4 L. innocua serotypes used in this experiment have the potential for use as surrogates in hamburger meat with varying margins of safety. L. innocua M1 should serve as the primary nonpathogenic surrogate with the greatest margin of safety in verifying a new thermal process to destroy L. monocytogenes.

Inactivation of Listeria innocua in brined white cheese by a combination of nisin and heat

“…A stationary-phase culture of a cocktail of three L. innocua strains (ATCC 51742, ATCC 33090, and ATCC 33091) was used to inoculate pasteurized milk that was used to prepare white cheese because cells in this stage are most resistant to preservation stresses (Jydegaard, Gravesen, & Knochel, 2000;Ueckert, ter Steeg, & Coote, 1998). L. innocua was selected for the study as a surrogate alternative for L. monocytogenes to prevent the introduction of the pathogenic organism to the dairy plant and because L. innocua is even more resistant to environmental stresses such as nisin and heat compared to L. monocytogenes strains (Friedly et al, 2008;Kamat & Nair, 1996). Listeria strains were individually cultured into brain heart infusion (BHI) broth (Oxoid, Basingstoke, Hampshire) at 37 C for 24 h, harvested by centrifugation at 4000Âg for 20 min and washed three times with 0.9% saline solution.…”

Evaluation of a bacteriocin-producing strain of Pediococcus acidilactici as a biopreservative for “Alheira”, a fermented meat sausage

“…Therefore L. innocua, considered a valuable surrogate for L. monocytogenes, was used (Friedly et al, 2008;NAC-MCF, 2004). Indeed some researchers report a greater sensitivity of L. monocytogenes towards certain antibacterial compounds than L. innocua (Mataragas, Drosinos, & Metaxopoulos, 2003;Çon, Gökalp, & Kaya, 2001).…”

nfluences of physicochemical stresses on injury and inactivation behaviour of Listeria innocua

“…The similarity of growth properties of both species in a wide range of temperatures, pH and water activity values re-enforces the choice of working with a non-pathogenic species (Begot, Lebert, & Lebert, 1997). The majority of L. innocua strains are more heat resistant than L. monocytogenes, thus providing a margin of safety in the development/design of new thermal processes involving these microorganisms (Friedly et al, 2008). The extreme resistance of Listeria spp.…”