Improving the accuracy of coliform detection in meat products using modified dry rehydratable film method

This study was undertaken to improve the detection accuracy for coliform bacteria, by analyzing biochemical properties of false positive and false negative colonies isolated from two dry rehydratable film methods, 3 M™ Petrifilm™ E. coli/Coliform count (PCC) and MC-Media Pad coliform count (MCC). The detection accuracy of PCC and MCC was determined to be 99.4% and 97.9%, respectively, with the detection error being 0.6% and 2.1%, respectively. False positive colonies (red colony without gas) on PCC were identified as Hafnia alvei and Enterobacter cloacae. All false positive colonies on MCC were identified as Aeromonas caviae; this organism gives a positive oxidase test, whereas coliform bacteria are oxidase negative. In conclusion, we propose that for improving detection accuracy of coliform bacteria, the incubation time of PCC should be modified and increased from 24 h to 48 h, and the oxidase test of MCC isolates should be included in the Korea Food Code.