title: Transfer of surface-dried Listeria monocytogenes from stainless steel knife blades to roast turkey breast.
abstract: Listeria contamination of food contact surfaces can lead to cross-contamination of ready-to-eat foods in delicatessens. Recognizing that variations in Listeria biofilm-forming ability exist, the goal of this study was to determine whether these differences in biofilm formation would affect the Listeria transfer rate during slicing of delicatessen turkey meat. In this study, six previously identified strong and weak biofilm-forming strains of Listeria monocytogenes were grown at 22 degrees C for 48 h on Trypticase soy agar containing 0.6% yeast extract and harvested in 0.1% peptone. Thereafter, the strains were combined to obtain two 3-strain cocktails, resuspended in turkey slurry, and inoculated onto flame-sterilized AISI grade 304 stainless steel knife blades that were subjected to 6 and 24 h of ambient storage at approximately 78% relative humidity. After mounting on an Instron Universal Testing Machine, these blades were used to obtain 16 slices of retail roast turkey breast. Based on an analysis of the slices by direct plating, Listeria populations decreased 3 to 5 log CFU per slice after 16 slices. Overall, total transfer to turkey was significantly greater for strong (4.4 log CFU total) as opposed to weak (3.5 log CFU total; P < 0.05) biofilm formers. In addition, significantly more cells were transferred at 6 (4.6 log CFU total) than at 24 h (3.3 log CFU total; P < 0.05) with Listeria quantifiable to the 16th slice, regardless of the inoculation level. Increased survival by the strong biofilm formers, as evidenced by viability staining, suggests that these strains are better adapted to survive stressful conditions than their weak biofilm-forming counterparts.
authors.affiliation: Department of Food Science and Human Nutrition, 334A G.M. Trout, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: Keskinen
authors.forename: Ewen C D
authors.initials: EC
authors.lastname: Todd
authors.forename: Elliot T
authors.initials: ET
authors.lastname: Ryser
mesh_terms: D000818:Animals; D018441:Biofilms / Q000254:growth & development; D015169:Colony Count, Microbial; D004866:Equipment Contamination; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D005525:Food-Processing Industry / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D006801:Humans; D008089:Listeria monocytogenes / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D008461:Meat Products / Q000382:microbiology*; D013193:Stainless Steel; D013696:Temperature; D013997:Time Factors; D014422:Turkeys
chemical_list: D013193:Stainless Steel