Novobiocin-brilliant green-glycerol-lactose-agar: further routine evaluation on 5554 human stools and 982 veterinary samples

Abstract

In order to provide a wider evaluation of "Novobiocin-brilliant green-glycerol-lactose" (NBGL) agar, dishes of this medium were added to standard media: Hektoen (H), Salmonella-Shigella agar (SS), at all plating steps for 5554 stool cultures of human medical routine (280 isolates) and 982 samples of veterinary routine (133 isolates). NBGL expectedly missed lactose-glycerol positive strains of the serotype Senftenberg (n = 4), H2S negative strains (n = 1), and strains of the Typhi serotype (n = 7). Otherwise, three strains, of serotype Virchow, were unable to grow on NBGL (0.7% of positive samples). Nevertheless overall sensitivities were increased by approximately 10% in the human routine (H: 70%; SS: 63%; NBGL: 94%; at the direct plating step) (H: 83%; SS: 84%; NBGL: 92%; at the enrichment plating step) and by 48% in the veterinary one (NBGL: 97%; versus usual media: 68%). Positive predictive values of black centred colonies were significantly higher on NBGL in human routine (H: 38%; SS: 40%; NBGL: 89%; at the direct plating step) (H: 20%; SS: 21%; NBGL: 82%; at the enrichment plating step); and in the veterinary one as well (NBGL: 90%; versus usual media: 17%). These data suggest that NBGL agar does improve Salmonella isolation in these kinds of routines, and that growth should be made sure before experiments using given strains.