What false positives / false negatives occur?
A feature of the standard CCA test is that it may derive false positives for coliforms from Aeromonas sp. if present, although these may be associated with severe gastroenteritis in some circumstances (US FDA – The Bad Bug Book). We have not identified any isolates of aeromonas as being present in any of the identification work that has been done in our tests. It appears that in the environmental, food and water samples that we are testing, the genera is very infrequently occurring. In some instances, particular isolates of Citrobacter freundii and Enterobacter sakazaki have been known to turn the CCA medium to white. In the case of the B2P coliform and E. coli products, we have found that these are slower growing than E. coli at 37C and that they will only turn the indicator dye to white after 16 hours (after absolute negatives for E. coli have already been determined). Aeromonas sp. also grow much more slowly at our incubation temperature than at the higher temperatures used in some
