ABSTRACTA method was developed to rapidly enumerateEscherichia coliin milk, using a Technicon Auto Analyzer II system. The automated system was used to assay for the presence of glutamate decarboxylase (E.C. 4.1.1.15), which is found only inE. coliand a few other bacterial species that are highly unlikely to be found in milk Coliiorms other thanE. coliwere shown not to have this enzyme. This system was capable of detecting as few as 50,000E. coliorganisms/ml. The most probable number (MPN) technique was combined with the automated system to quantitateE. coliin milk With pure cultures it was possible to determine the positive and negative MPN tubes in 8 hr, but a 10‐hr incubation was required for the analysis of milk samples. Since the enzyme is specific forE. coli, the nonselective medium trypticase soy broth and the mildly selective medium lauryl tryptose broth were used in the MPN tubes. It was shown that these media allowed the growth of heat‐injured organisms and the detection of organisms that could not be detected using violet red bide agar. The three advantages of this test over the current violet red bile plating procedure are (1) it is more rapid, (2) it is specific forE. coliand (3) it enumerates process‐injured orga
展开▼
