ARS | Publication request: Comparison of an automated Most Probable Number (MPN) technique to traditional plating methods for estimating populations of total aerobes, coliforms and E. coli associated with freshly processed broiler chickens

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2010
Publication Date: August 3, 2010
Citation: Line, J.E., Stern, N.J. 2010. Comparison of an automated Most Probable Number (MPN) technique to traditional plating methods for estimating populations of total aerobes, coliforms and E. coli associated with freshly processed broiler chickens. International Association for Food Protection.

Technical Abstract: Traditional microbiological techniques for estimating populations of viable bacteria can be laborious and time consuming. The Most Probable Number (MPN) technique is especially tedious as multiple series of tubes must be inoculated at several different dilutions. Recently, an instrument (TEMPOTM) has been developed to automate the MPN technique and reduce the effort required to estimate some bacterial populations. The purpose of our study was to compare the automated MPN technique to traditional microbiological plating methods or PetrifilmTM for estimating the total viable count of aerobic microorganisms (TVC), total coliforms (CC), and E. coli (EC) populations on freshly processed broiler chicken carcasses (post-chill whole carcass rinse [WCR] samples) and cumulative drip-line samples from a commercial broiler processing facility. Overall, 120 broiler carcasses, 36 pre-chill drip line samples and 40 post-chill drip line samples were collected over 5 separate days (representing 5 individual flocks) and analyzed by the automated MPN and direct agar plating or PetrifilmTM methods. The TVC correlation coefficient between the automated MPN and traditional methods was found to be very high (0.972) for the pre-chill drip samples which had mean Log values of 3.09 and 3.02, respectively. Correlations were, likewise, high between the methods for the pre-chill CC and EC samples with correlation coefficients of 0.812 and 0.880, respectively. The post-chill WCR samples had much lower mean Log TVC values of 1.53 and 1.31, respectively. The estimated number of total aerobes was generally greater than the total number of coliforms or E. coli recovered for all sample types. The automated MPN instrument was easy to utilize and allowed a single operator to perform the three analytical tests in less time than it took 4 trained laboratory technicians to conduct the tests by traditional methods. As a result accurate MPN estimations may be obtained from these sample types with significantly less effort than traditional methods.