Applicability of aeration and delayed addition of selenite to the isolation of salmonellae.

The effect of aeration combined with the delayed addition of selenite on the lag period of several strains of salmonellae and other enterobacteria is reported. A procedure has been developed involving shaking of the sample in a basal medium for 4 hr at 37 C, adding selenite and cystine, and continuing shaking for 20 hr. Confirmation by selective plating, biochemical tests, and serology gave results comparable to the standard lactose pre-enrichment method with the saving of 24 hr and elimination of one set of media. Confirmation by fluorescent-antibody tests showed that fewer positive fluorescent stains were obtained from the aerated procedure than from the lactose pre-enrichment procedure. Precautions in the application of this procedure are discussed.