A modification of brilliant green agar for improved isolation of Salmonella.

Five organisms commonly found to be capable of growth on commercial Brilliant Green Agar (BGA) after enrichment in Muller-Kauffman Tetrathionate broth (MKT) were tested for sensitivity to 18 antimicrobial agents. The sensitivities of two Salmonella serotypes to these agents were also tested. A combination of sulphacetamide (at 1.0 mg/ml) and mandelic acid (at 0.25 mg/ml) incorporated into BGA was found to give maximum recovery of salmonellas from MKT broth enrichment whilst giving maximum suppression of contaminating organisms. More importantly, this Antibiotic-enriched Brilliant Green Agar (ABG) gave a lower incidence of false positive results when compared with commercial BGA. Increasing the incubation temperature from 35 to 43°C was found to accentuate the selectivity of ABG without inhibiting the growth of salmonellas. A total of 31 Salmonella serotypes were tested for their ability to grow on ABG at 43°C; all produced typical colonies.