Title: Thermal Resistance, Biochemical, Serological and Fatty Acid Analysis of Salmonella spp. Isolated from Pasteurized Egg Products Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 13, 2010
Publication Date: August 1, 2010
Citation: Gurtler,J.,Cray,W.Jr.,Hinton,A.Jr.,2010.Thermal Resistance, Biochemical,Serological and Fatty Acid Analysis of Salmonella spp.isolated from Pasteurized Egg products [abstract].International Assn. for Food Protection (IAFP) 97th Annual meeting.Anaheim,CA.p.1. Technical Abstract: Introduction: The Egg Products Inspection Act of 1970 requires that egg products in the U.S. must be pasteurized prior to release into commerce. The USDA Food Safety and Inspection Service (FSIS) is responsible for regulating egg products. Salmonellae are infrequently isolated from pasteurized egg products by food manufacturers or the FSIS and may be present as a result of either pasteurization-resistant bacteria or post-processing contamination. Purpose: The goal of this study was to evaluate twenty strains of Salmonella for variations in thermal resistance, biochemistry, serology, and fatty acid profiles. Methods: Seventeen strains of Salmonella isolated from pasteurized egg products and three heat-resistant strains used in ongoing USDA, ARS/FSIS egg pasteurization studies were compared for thermal resistance in liquid whole egg (LWE) at 60 C, enzymatic profiles with the BBL Crystal Identification System Autoreader, serotyped at the USDA, APHIS, National Veterinary Service Laboratory in Ames, Iowa, and fatty acid analysis was conducted by gas chromatography and FAME MIDI Sherlock software. Results: The D60 values in LWE ranged from 0.30 – 0.50 min, and seven of twenty strains survived pasteurization at 60 C for at least 3.5 min. Isolates serotyped as Heidelberg, Mbandaka, Cerro, Thompson, 4,12:i:-, and Enteritidis (8 isolates). Although some strains exhibited atypical enzymatic activity (e.g., reduction of adonitol, hydrolosis of proline nitroanilide or p-n-p-beta-glucuronide, and nonreduction of melibiose) no differences in biochemical reactions could be correlated with similarity in thermal resistance. FAME analysis revealed that fatty acid profiles may be associated with heat resistance. Significance: This data represents the first steps in determining whether Salmonella contamination in pasteurized egg products may be the result of either thermally-resistant isolates or post-processing contamination. Salmonella isolates are currently being evaluated for PFGE profiles, antimicrobial resistance and more detailed biochemical differences.