A new technique for Escherichia coli testing of beef and pork carcasses

Abstract

A novel technique has been developed to monitor Escherichia coli contamination on carcasses using membrane filtration and m-ColiBlue24 (mCB). mCB is a membrane filtration medium that simultaneously detects total coliforms and E. coli (EC) in a period of 24 ± 4 h. A study was conducted, using a sponge method to obtain samples from pork carcasses and the excision technique to remove samples from beef carcasses, that compared mCB to standard methods. On pork carcasses (n = 77), the mean values for mCB and violet red bile agar were 7.4 CFU/15 cm2 and 6.1 CFU/15 cm2, respectively. The paired t test (P > 0.05) indicated no significant difference between the two methods (t = 0.5; P = 0.6). Samples from beef carcasses (n = 57) were used to compare mCB to both coliform count and EC Petrifilm. Of these samples, 27 were artificially inoculated with cattle manure. The mean total coliform count was 4.2 log CFU/cm2 and 4.0 log CFU/cm2 on mCB and coliform count Petrifilm, respectively. The mean EC count on mCB was 4.0 log CFU/cm2 and 3.5 log CFU/cm2 on EC Petrifilm. When comparing mCB to both coliform count (t = 2.4; P = 0.02) and EC (t = 3.5; P < 0.01) Petrifilm, paired t tests (P ≤ 0.05) indicated significant differences.