Difco) for plate counts ; and Dulcitol Broth, (Difco), Selenite Cysteine Broth (Difco) and
XLD agar for MPN determinations. Results (Fig. 1) showed that the AODC remained
constant, at 10
5 cells per ml, during the study. Counts for FAB and DVC were 0.5 l og
lower than the AODC. All plate counts and MPN estimates, however, exhibited a rapid
decline and became non-culturable on the media employed for enumeration by days 2 and
Figure 1 : Salmonella enteritidis cultures exposed to river water in microcosms. O : Acridine orange Direct
Count, • Fluorescent antibody Count, ■ Direct viable Count, □ Plate Count, Veal Infusion, A Plate
Count, XLD, A MPN-Salmonella Enrichment.
E. coli strain H10407 was introduced at a concentration of 1 x 10 7 cells/ml into a
microcosm containing Chesapeake Bay water (salinity 15 ‰). AODC remained at the
initial concentration (Fig. 2). Over a period of 19 days, viable counts declined only by 0.5
log. Significantly, plate counts on TSA and Eosin Methylene Blue agar (EMB, Difco)
dropped from 10
6 on Day 1 to 10 4 on Day 7, and then to 10 3 cells/ml on Day 14.
510