Novobiocin, brilliant green, glycerol, lactose agar: a new medium for the isolation of Salmonella strains

Abstract

We describe a medium, novobiocin, brilliant green, glycerol, lactose (NBGL) agar, for the routine isolation of Salmonella strains from stool samples. The NBGL agar principle involved the use of the antisaprophytic effect of brilliant green and novobiocin. Glycerol and lactose were added in order to distinguish between Citrobacter and Salmonella. NBGL was used in parallel with salmonella-shigella (SS) and Hektoen (H) agar for culturing 2,853 stool samples, of which 184 were confirmed to be salmonellae. NBGL showed a high sensitivity: 94% in direct plating compared to 74% (p < 10(-3)) and 65% (p < 10(-5)) for H and SS, respectively, and 96% in enrichment broth plating vs. 83% (p < 10(-4)) and 86% (p < 10(-3)), respectively, for H and SS. In direct plating using NBGL, 95% of black-centred colonies were confirmed to be salmonellae (vs. 31% and 36%, H and SS). In enrichment plating using NBGL, this figure was 82% (vs. 26% and 28%). The results suggest that NBGL agar is advantageous for the isolation of non-Typhi H2S+ salmonellae.