The Incidence of Escherichia coli on Beef Carcasses and Its Association with Aerobic Mesophilic Plate Count Categories During the Slaughter Process

Abstract

An analysis of 535 prefabricated beef carcass samples taken in three processing plants demonstrated an association between the mesophilic aerobic plate count (APC) class and the incidence of obtaining an Escherichia coli-positive sample. Beef carcasses were sampled from three separate plants; one was a fed-beef processing plant and the other two were cow/bull plants. Samples were obtained by sponging and were analyzed for APC and E. coli. When samples were classified into four APC levels or classes (class 1: <2, class 2: ≥2 and <3, class 3: ≥3 and <4, and class 4: ≥4 log CFU/cm2), a trend indicating that samples from higher APC classes were more likely to be positive for E. coli biotype 1 was observed. Of the APC class 4 samples (≥4 log CFU/cm2), 88% were positive for the presence of E. coli, as opposed to 21% in APC class 1 (<2 log CFU/cm2). Univariate chi-square analysis of the resulting contingency tables from reclassified data (class 1: <2, class 2: ≥2 and <3, and class 3: ≥3 log CFU/cm2) indicated a strong association between APC class and the incidence (presence or absence) of an E. coli-positive sample. Using multivariate analysis to account for influences of plant and within plant processing site, the data indicated a strong positive linear trend between the presence of E. coli and the APC class.