title: Investigation into Formation of Lipid Hydroperoxides from Membrane Lipids in Escherichia coli O157:H7 following Exposure to Hot Water.
abstract: Although studies have shown antimicrobial treatments consisting of hot water sprays alone or paired with lactic acid rinses are effective for reducing Escherichia coli O157:H7 loads on beef carcass surfaces, the mechanisms by which these interventions inactivate bacterial pathogens are still poorly understood. It was hypothesized that E. coli O157:H7 exposure to hot water in vitro at rising temperatures for longer time periods would result in increasing deterioration of bacterial outer membrane lipids, sensitizing the pathogen to subsequent lactic acid application. Cocktails of E. coli O157:H7 strains were subjected to hot water at 25 (control) 65, 75, or 85 °C incrementally up to 60 s, after which surviving cells were enumerated by plating. Formation of lipid hydroperoxides from bacterial membranes and cytoplasmic accumulation of L-lactic acid was quantified spectrophotometrically. Inactivation of E. coli O157:H7 proceeded in a hot water exposure duration- and temperature-dependent manner, with populations being reduced to nondetectable numbers following heating of cells in 85 °C water for 30 and 60 s (P < 0.05). Lipid hydroperoxide formation was not observed to be dependent upon increasing water temperature or exposure period. The data suggest that hot water application prior to organic acid application may function to increase the sensitivity of E. coli O157:H7 cells by degrading membrane lipids.
authors.affiliation: Department of Nutrition and Food Science, Texas A&M University, College Station, Texas 77843-2253, USA.
authors.forename: Thelma F
authors.initials: TF
authors.lastname: Cálix-Lara
authors.affiliation: Department of Nutrition and Food Science, Texas A&M University, College Station, Texas 77843-2253, USA.
authors.forename: Katie R
authors.initials: KR
authors.lastname: Kirsch
authors.affiliation: Department of Animal Science, Texas A&M AgriLife Research, College Station, Texas 77843-2471, USA; IEH Laboratories and Consulting Group, 15300 Bothell Way N.E., Lake Forest Park, WA 98155, USA.
authors.forename: Margaret D
authors.initials: MD
authors.lastname: Hardin
authors.affiliation: Department of Animal Science, Texas A&M AgriLife Research, College Station, Texas 77843-2471, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Castillo
authors.affiliation: Department of Animal Science, Texas A&M AgriLife Research, College Station, Texas 77843-2471, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Smith
authors.affiliation: Department of Animal Science, Texas A&M AgriLife Research, College Station, Texas 77843-2471, USA. matthew.taylor@agnet.tamu.edu.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Taylor
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents; D002417:Cattle; D015169:Colony Count, Microbial; D019453:Escherichia coli O157; D005511:Food Handling; D005516:Food Microbiology / Q000379:methods*; D006358:Hot Temperature; D019344:Lactic Acid / Q000737:chemistry; D016018:Least-Squares Analysis; D008054:Lipid Peroxides / Q000737:chemistry*; D008460:Meat / Q000382:microbiology; D008563:Membrane Lipids / Q000737:chemistry*; D012107:Research Design; D014867:Water / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D008054:Lipid Peroxides; D008563:Membrane Lipids; D014867:Water; D019344:Lactic Acid