Comparison of two methods for assessing the bacteriological condition of the water supply in slaughter houses

Abstract

One hundred and five water samples of drinking water quality used in slaughter houses were examined according to The Netherlands' Standard N 3043 (1956) and by the new ‘Differential Hydrobacteriogramme’ (DHB) technique. The latter procedure allows for resuscitation of debilitated cells, uses one single selective enrichment medium and various isolation media and includes confirmation of isolates. Identification of isolates demonstrated that false positives as well as false negatives were frequently obtained by the N 3043 method. Rejection rate of samples by the N 3043 and DHB methods, respectively, was 63 vs. 72 for 81 samples taken from taps, and 4 vs. 10 for 24 samples drawn from wells and mains, Based on these results the DHB technique seems particularly suitable for the monitoring of re-used waters, because it provides more information and has a higher accuracy.