Evaluation of a Rapid Impedimetric Procedure for the Quantitative Estimation of Coliforms


  • The authors thank Annikka Rantama from Orio Diagnostica, P.O. Box 19, 00101, Helsinki, Finland, for evaluating our method and contributing her results to this paper.


A selective coliform medium (CM), developed for the impedimetric detection of coliforms, produced better impedance signals than conventional media. The selectivity of CM was better than that of lauryl tryptose broth (LTB) and violet red bile agar (VRBA). The applicability of CM to the quantitative impedimetric detection of coliforms in meat was tested and compared with most probable number and VRBA plate counts. Approximately 90% of the typical VRBA colonies did not produce gas when tested in brilliant green bile broth (BGB). Therefore, the VRBA counts were corrected by the percentage of colonies which produced gas in BGB for each sample. A correlation coefficient of 0.90 was obtained between the impedimetric test and corrected VRBA plate counts using a combined total of 91 meat samples tested by two different laboratories.