title: Genetic characterization of Listeria monocytogenes isolates from food processing facilities before and after postcook chiller heat treatment.
abstract: Possible selection for and establishment of stress-resistant Listeria monocytogenes variants as a consequence of heating interventions is of concern to the food industry. Lineage analysis and multilocus variable number tandem repeat analysis (MLVA) was performed on 20 L. monocytogenes isolates, of which 15 were obtained before and 5 were obtained after heat treatment of a postcook meat chiller. The ctsR gene (a class III heat shock gene regulator) from 14 isolates was amplified and sequenced because previous work has indicated that spontaneous mutations can occur in this gene during heat treatment. Heat treatment of the meat chiller did not significantly change the relative abundance of the various L. monocytogenes lineages; lineage II strains (less-heat-resistant isolates) dominated both before and after heat treatment. MLVA typing confirmed that some isolates of L. monocytogenes occur both before and after heat treatment of the chiller. No isolate of L. monocytogenes indicated any likely functionally significant mutations in ctsR. This study indicates the absence of any obvious difference in the profiles of L. monocytogenes strains obtained before and after heat treatment of a meat chiller, based on the characteristics examined. Although this finding supports the effectiveness of heat treatment, the limited number of strains used and characteristics examined mean that further study on a larger scale is required before firm conclusions can be drawn.
authors.affiliation: School of Agriculture and Food Sciences, University of Queensland, St Lucia, Queensland 4072, Australia. s3316807@student.uq.edu.au
authors.forename: Sofroni
authors.initials: S
authors.lastname: Eglezos
authors.forename: Gary A
authors.initials: GA
authors.lastname: Dykes
authors.forename: Bixing
authors.initials: B
authors.lastname: Huang
authors.forename: Mark S
authors.initials: MS
authors.lastname: Turner
authors.forename: Richard
authors.initials: R
authors.lastname: Seale
mesh_terms: D001483:Base Sequence; D005511:Food Handling / Q000379:methods*; D005525:Food-Processing Industry; D014644:Genetic Variation; D006358:Hot Temperature; D008089:Listeria monocytogenes / Q000235:genetics* / Q000302:isolation & purification; D008460:Meat; D018598:Minisatellite Repeats