title: Survival Kinetics of Salmonella enterica and Enterohemorrhagic Escherichia coli on a Plastic Surface at Low Relative Humidity and on Low-Water Activity Foods.
abstract: We investigated the survival kinetics of Salmonella enterica and enterohemorrhagic Escherichia coli under various water activity (aw) conditions to elucidate the net effect of awon pathogen survival kinetics and to pursue the development of a predictive model of pathogen survival as a function of aw. Four serotypes of S. enterica (Stanley, Typhimurium, Chester, and Oranienburg) and three serotypes of enterohemorrhagic E. coli ( E. coli O26, E. coli O111, and E. coli O157:H7) were examined. These bacterial strains were inoculated on a plastic plate surface at a constant relative humidity (RH) (22, 43, 58, 68, or 93% RH, corresponding to the aw) or on a surface of almond kernels (aw0.58), chocolate (aw0.43), radish sprout seeds (aw0.58), or Cheddar cheese (aw0.93) at 5, 15, or 25°C for up to 11 months. Under most conditions, the survival kinetics were nonlinear with tailing regardless of the storage aw, temperature, and bacterial strain. For all bacterial serotypes, there were no apparent differences in pathogen survival kinetics on the plastic surface at a given storage temperature among the tested RH conditions, except for the 93% RH condition. Most bacterial serotypes were rapidly inactivated on Cheddar cheese when stored at 5°C compared with their inactivation on chocolate, almonds, and radish sprout seeds. Distinct trends in bacterial survival kinetics were also observed between almond kernels and radish sprout seeds, even though the aws of these two foods were not significantly different. The survival kinetics of bacteria inoculated on the plastic plate surface showed little correspondence to those of bacteria inoculated on food matrices at an identical aw. Thus, these results demonstrated that, for low-awfoods and/or environments, awalone is insufficient to account for the survival kinetics of S. enterica and enterohemorrhagic E. coli .
authors.affiliation: Graduate School of Agricultural Sciences, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Hokunan
authors.affiliation: Graduate School of Agricultural Sciences, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Kento
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Graduate School of Agricultural Sciences, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Graduate School of Agricultural Sciences, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Shuso
authors.initials: S
authors.lastname: Kawamura
authors.affiliation: Graduate School of Agricultural Sciences, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan.
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Koseki
mesh_terms: D015169:Colony Count, Microbial; D054324:Enterohemorrhagic Escherichia coli; D019453:Escherichia coli O157; D005516:Food Microbiology; D006813:Humidity; D007700:Kinetics; D010969:Plastics; D019779:Salmonella enterica; D013696:Temperature; D014867:Water
chemical_list: D010969:Plastics; D014867:Water
keywords: Bacterial pathogen; Desiccation; Inactivation; Low–water activity foods; Weibull model