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United States Department of Agriculture

Agricultural Research Service

Title: Biofilm Formation by Salmonella Spp. on Cantaloupe Surfaces

Authors
item Annous, Bassam
item Solomon, Ethan
item Cooke, Peter

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 9, 2005
Publication Date: August 14, 2005
Citation: Annous, B.A., Solomon, E.B., Cooke, P.H. 2005. Biofilm formation by salmonella spp. on cantaloupe surfaces (abstract). International Association for Food Protection. Pager No. P3-39.

Technical Abstract: In recent years Salmonella spp. have been implicated in numerous outbreaks linked to fresh produce, most notably, cantaloupe melons. Previous research in our laboratory has documented the inability of a variety of sanitizing rinses and other treatments to inactivate Salmonella inoculated onto cantaloupes. In addition, the efficacy of sanitizers decreased significantly when the organism was allowed to reside on the melon surface for more than 24 hours. We speculated that increased contact time allowed for the formation of a bacterial biofilm prior to sanitation. The entrapment of cells of Salmonella within a biofilm is likely responsible for enhanced sanitizer resistance. Therefore, the goal of our research was to demonstrate that cells of Salmonella form biofilms on cantaloupe surfaces. Two outbreak-related strains of Salmonella were utilized in our study. Ten micro-liter of bacteria were spot-inoculated onto melon rinds in pre-marked areas, and melons were held at either 10 or 22 C. Biofilm formation was monitored using scanning electron microscopy (SEM) on excised portions of the melon rind at 2, 24, 48, and 144 hours post-inoculation. Micrographs indicated that biofilm formation occurred rapidly following introduction of cells onto the melon surface. Fibrillar material was visible after just two hours of inoculation, and cells were embedded in extracellular polymeric material within 24 hours of storage at either temperature. These results indicate that Salmonella spp. are capable of rapidly forming biofilms on cantaloupe tissue and that biofilm formation could be the reason for the increased recalcitrance of attached bacteria to aqueous sanitizers.

Last Modified: 4/21/2014
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