title: Changes in thermo-tolerance and survival under simulated gastrointestinal conditions of Salmonella Enteritidis PT4 and Salmonella Typhimurium PT4 in chicken breast meat after exposure to sequential stresses.
abstract: This study assessed changes in thermo-tolerance and capability to survive to simulated gastrointestinal conditions of Salmonella Enteritidis PT4 and Salmonella Typhimurium PT4 inoculated in chicken breast meat following exposure to stresses (cold, acid and osmotic) commonly imposed during food processing. The effects of the stress imposed by exposure to oregano (Origanum vulgare L.) essential oil (OVEO) on thermo-tolerance were also assessed. After exposure to cold stress (5°C for 5h) in chicken breast meat the test strains were sequentially exposed to the different stressing substances (lactic acid, NaCl or OVEO) at sub-lethal amounts, which were defined considering previously determined minimum inhibitory concentrations, and finally to thermal treatment (55°C for 30min). Resistant cells from distinct sequential treatments were exposed to simulated gastrointestinal conditions. The exposure to cold stress did not result in increased tolerance to acid stress (lactic acid: 5 and 2.5μL/g) for both strains. Cells of S. Typhimurium PT4 and S. Enteritidis PT4 previously exposed to acid stress showed higher (p<0.05) tolerance to osmotic stress (NaCl: 75 or 37.5mg/g) compared to non-acid-exposed cells. Exposure to osmotic stress without previous exposure to acid stress caused a salt-concentration dependent decrease in counts for both strains. Exposure to OVEO (1.25 and 0.62μL/g) decreased the acid and osmotic tolerance of both S. Enteritidis PT4 and S. Typhimurium PT4. Sequential exposure to acid and osmotic stress conditions after cold exposure increased (p<0.05) the thermo-tolerance in both strains. The cells that survived the sequential stress exposure (resistant) showed higher tolerance (p<0.05) to acidic conditions during continuous exposure (182min) to simulated gastrointestinal conditions. Resistant cells of S. Enteritidis PT4 and S. Typhimurium PT4 showed higher survival rates (p<0.05) than control cells at the end of the in vitro digestion. These results show that sequential exposure to multiple sub-lethal stresses may increase the thermo-tolerance and enhance the survival under gastrointestinal conditions of S. Enteritidis PT4 and S. Typhimurium PT4.
authors.affiliation: Laboratory of Microbial Processes in Foods, Department of Food Engineering, Technology Center, Federal University of Paraíba, João Pessoa 58051900, Brazil.
authors.forename: Adma Nadja Ferreira de
authors.initials: ANF
authors.lastname: Melo
authors.affiliation: Laboratory of Microbial Processes in Foods, Department of Food Engineering, Technology Center, Federal University of Paraíba, João Pessoa 58051900, Brazil.
authors.forename: Geany Targino de
authors.initials: GT
authors.lastname: Souza
authors.affiliation: Department of Food Science, Rutgers, The State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, USA.
authors.forename: Donald
authors.initials: D
authors.lastname: Schaffner
authors.affiliation: Department of Food Science and Technology, State University of Londrina, Londrina, Paraná 86057970, Brazil.
authors.forename: Tereza C Moreira de
authors.initials: TCM
authors.lastname: Oliveira
authors.affiliation: Laboratory of Microbial Processes in Foods, Department of Food Engineering, Technology Center, Federal University of Paraíba, João Pessoa 58051900, Brazil.
authors.forename: Janeeyre Ferreira
authors.initials: JF
authors.lastname: Maciel
authors.affiliation: Laboratory of Food Microbiology, Department of Nutrition, Health Sciences Center, Federal University of Paraíba, João Pessoa, 58051900, Brazil.
authors.forename: Evandro Leite de
authors.initials: EL
authors.lastname: Souza
authors.affiliation: Laboratory of Microbial Processes in Foods, Department of Food Engineering, Technology Center, Federal University of Paraíba, João Pessoa 58051900, Brazil. Electronic address: magnani2@pq.cnpq.br.
authors.forename: Marciane
authors.initials: M
authors.lastname: Magnani
mesh_terms: D000818:Animals; D002645:Chickens / Q000382:microbiology*; D003080:Cold Temperature; D058639:Cold-Shock Response; D005511:Food Handling; D019344:Lactic Acid / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000494:pharmacology; D031341:Origanum / Q000378:metabolism; D009997:Osmotic Pressure / Q000502:physiology; D028321:Plant Preparations / Q000494:pharmacology; D011202:Poultry Products / Q000382:microbiology*; D012480:Salmonella Infections / Q000382:microbiology / Q000517:prevention & control*; D012477:Salmonella enteritidis / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D009822:Oils, Volatile; D028321:Plant Preparations; D019344:Lactic Acid; D012965:Sodium Chloride
keywords: Essential oil; Food processing; Salmonella; Sub-lethal stress; Survival