P3-68 Influence of Beef Carcass Topography and Surface Composition on the Attachment of Salmonella and Escherichia coli Biotype I

Wednesday, August 6, 2014
Exhibit Hall D (Indiana Convention Center)
Julia Pérez-Montaño, Universidad de Guadalajara, Guadalajara, Mexico
Delia González-Aguilar, Universidad de Guadalajara, Zapopan, Mexico
Carlos A. Campos-Bravo, Universidad de Guadalajara, Guadalajara, Mexico
Adelfo Robles, Rastro Municipal de Zapopan, Zapopan, Mexico
Pablo Torres-Morán, Universidad de Guadalajara, Zapopan, Mexico
Norma Heredia, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Mexico
Elisa Cabrera-Díaz, Universidad de Guadalajara, Guadalajara, Mexico
Introduction: The topography and composition of beef carcasses differ among carcass regions, and some areas of the carcass surface facilitate bacterial adhesion. The attachment properties of Salmonella and E. coli strains proposed as surrogate organisms for validation studies on beef carcasses were compared as affected by carcass tissue.

Purpose: To investigate the attachment properties of Salmonella and E. coli strains proposed as surrogates as affected by the beef carcass topography and surface composition.

Methods: Five rifampicin-resistant Salmonella strains and four ampicillin-resistant E. coli strains were inoculated on beef tissues (1.5 cm2 on muscle, fascia, tendon, fat) and 1.0 cm2 (bone) pieces (0.1-0.5 mm depth). The pieces were individually placed in the inoculum into polystyrene 12-well plates and stored for two different temperature conditions. Temperature conditions included 26.6 ± 2.2°C (RT) for 24h or alternating RT (30 min) -refrigeration (4.8 ± 1.3°C, 24h) -RT (30 min). After incubation time tissues were rinsed and loosely and strongly cells were enumerated on appropriate culture media and Sr value was expressed as percent of bacterial population physically attached to the surface (Sr= #loosely attached cells - #strongly attached cells /#strongly attached cells) .

Results: No differences were observed (P ≥ 0.05) on Sr values for all beef carcass tissues (n = 60). At 26.6 ± 2.2°C, Sr values ranged from 0.47 ± 0.00 to 0.54 ± 0.02 and at alternating temperatures ranged from 0.46 ± 0.01 to 0.54 ± 0.03. No differences were observed (P ≥ 0.05) between Sr values for Salmonella and E. coli on all beef carcass tissues and temperature conditions. The Sr values for Salmonella ranged from 0.52 ± 0.01and for E. coli from 0.52 ± 0.02.

Significance: The topography and superficial composition of tissues did not influence the attachment of bacteria. E. coli strains showed similar attachment properties to Salmonella strains confirming that they may be used as surrogates for validations studies on beef carcasses.