89E-24 |
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T. KIM and J. L. Silva. Dept. of Food Science, Nutrition & Health Promotion, Mississippi State Univ., 110 Herzer Bldg., Mailstop 9805, Mississippi State, MS 39762-9805 The majority of methods for quantifying the viable cells in biofilms are by swabbing, shaking or mild sonication, and enumeration in relation to the colonized surface area. However, absence of suitable methods for quantifying the strength of attachment of microorganisms to surfaces has severely restricted further developments in this field. The objective of this study was to measure the in-vitro attachment strength of selected pathogenic microorganism by two novel methods. In blot succession method, glass coverslips were colonized with pathogens in inoculated tryptic soy broth. Colonized coverslips were blotted onto a tryptic soy agar plate and the process was repeated through a succession of agar plates for one minute. The mini-column method used colonized glass beads that were packed in a column. Each column was controlled to collect 600 drops (speed: fraction per 1 min.; volume: 5.6 mL). In all instances, the number of recovered colonies per plate or column decreased exponentially with plate or column succession number, according to the relationship: CFU=A e -kx where CFU is the number of colonies transferred: k is the removal exponent: A is the intercept: x is the plate number. Comparison of removal exponents indicated that the attachment strength on glass coverslips and beads was greatest for Listeria monocytogenes. It was found that both Salmonella Typhimurium and E.coli O157H7 had similar k values. It is our proposition that the removal exponent could be used as a simple and effective measure of the strength of attachment grown under different environmental conditions. These methods will prove useful in the design of treatment regimes for surface hygiene and in the selection of suitable materials.
Session 89E, Food Microbiology: Pathogens
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |