Selective action of inhibitors used in different culture media on the competitive microflora of Salmonella

Abstract

The action of 12 inhibitors employed in the culture media used to detect the presence of Salmonella in food on 24 bacterial strains including contaminating Gram-positive bacteria common in water and food, Gram-negative bacteria, especially Enterobacteriaceae and Pseudomonadaceae, which are components of the competitive microflora, and six Salmonella serotypes was tested. Two liquid culture media (AR 5 and AE 1) were used. Series of tubes containing increasing concentrations of each inhibitor were inoculated with the test strains and incubated at 37 degrees C until growth was verified spectrophotometrically (24-48 h). The results showed that the inhibitors were effective against the Gram-positive contaminating microflora. They did not preferentially inhibit the competitive microflora of Salmonella, chiefly Enterobacteriaceae, and were ineffective against the Pseudomonas strains, which can tolerate concentrations higher than those customarily employed in culture media.