A Novel Technique for E. coli Testing of Beef and Pork Carcasses

and Implications In January 1997, the USDA-FSIS mandated Escherichia coli (EC) testing in all processing plants to monitor surface contamination of beef, pork, and poultry carcasses. A novel technique that uses membrane filtration (MF) and m-ColiBlue24 (mCB) to determine the amount of EC contamination on a carcass was developed. Sponges from pork carcasses and excision samples from beef carcasses were analyzed using mCB and compared with standard methods. Samples from 77 pork carcasses were plated both on mCB and pour plating on Violet Red Bile (VRB) agar to obtain Total Coliform (TC) counts. There was no significant difference between the counts. The mean values for mCB and VRB agar were 7.4 colony forming units (CFU)/15 cm and 6.1 CFU/15 cm, respectively. The paired t-test revealed a t=0.52 and P=0.61. Excision samples from 57 spiked beef carcasses were used to compare mCB with both TC and EC Petrifilm. The mean TC count on mCB was 1.6 x 10 CFU/cm and 9.3 x 10 CFU/cm on TC Petrifilm. The paired t-test gave a t=2.4 and P=0.02. The mean EC count on mCB was 9.3 x 10 CFU/cm and 3.2 x 10 CFU/cm on EC Petrifilm. The t=3.5 and P<0.01. The new technique that uses mCB detected more TC and EC than both types of Petrifilm. Furthermore, the t values suggest that there is a significant treatment effect.