A rapid method to determine bacterial contamination on hatching eggs. 3. Use of commercial DNA probe kits for detection of specific pathogens after six hours of incubation

Abstract

The usefulness of commercially available DNA probe kits for the detection of Escherichia coli and Salmonella spp. after only 6 h of incubation, was determined. It was established that the commercially available probe kits used could detect E. coli at initial levels of approximately 4,5 x 10² colony-forming units (cfu) per ml after only 6 h of incubation in nutrient broth (NB). Initial bacterial levels as low as 4,5 /10 cfu/ml could be detected when the NB was incubated for 18 h. Salmonella Enteritidis, at initial levels of 2,86 x 10² cfu/ml could be detected after 6 h of incubation at 37°C in NB, while initial levels as low as 2,86 / 10 cfu/ml could be detected after 18 h at 37°C in both NB and selected media, as specified by the manufacturers of the probe kits. Commercially available DNA probe kits can therefore be used to detect specific pathogens on the surface of hatching eggs and these probes can be used in conjunction with an egg-washing system, which is used to determine total bacterial contamination, although a longer incubation period greatly improves the sensitivity of these tests.