Use of delayed secondary enrichment for the isolation of Salmonella in poultry and poultry environments.

A conventional method of isolating Salmonella was compared with isolation using novobiocin-supplemented plating media and delayed secondary enrichment (DSE). The DSE greatly increased the ability to isolate Salmonella from poultry and environmental samples. Four hundred sixty-four isolations of Salmonella were made from a total of 4377 cultures (11%). Two hundred sixty-nine (58%) isolations of Salmonella were made following the 24-hour incubation; of these, 43 (9%) isolates were isolated only at this time. In comparison, a total of 421 (91%) Salmonella were isolated by DSE, of which 195 isolates (42%) were isolated only with DSE. The addition of novobiocin to the selective plating medium increased the isolation rate for Salmonella and reduced the level of contaminating bacteria growing on the plate.