Rappaport-Vassiliadis R10 Broth is used for selectively enriching Salmonella from meat and dairy products, feces and sewage-polluted water.
SUMMARY AND EXPLANATION
Rappaport et al. formulated an enrichment medium for Salmonella that was modified by Vassiliadis et al. The Rappaport formulation, designated R25/37°C, recommended incubation at 37°C; the Vassiliadis modification, designated R10/43°C, had a reduced level of malachite green and recommended incubation at 43°C. Later work by Peterz showed that incubation at 41.5° ± 0.5°C for 24 hours improved recovery of Salmonella spp.
Rappaport-Vassiliadis R10 Broth is a selective enrichment medium that is used following pre-enrichment of the specimen in a suitable pre-enrichment medium. It has gained approval for use in analyzing milk and milk products, raw flesh foods, highly contaminated foods and animal feeds.
This medium selectively enriches for salmonellae because bacteria, including other intestinal bacteria, are typically inhibited by malachite green, high osmotic pressure and/or low pH. Salmonella Typhi and S. Paratyphi A are sensitive to malachite green and may be inhibited.
Rappaport-Vassiliadis R10 Broth contains peptone as the carbon and nitrogen source for general growth requirements. Magnesium chloride raises the osmotic pressure in the medium. Malachite green is inhibitory to organisms other than salmonellae. The low pH of the medium, combined with the presence of malachite green and magnesium chloride, helps to select for the highly resistant Salmonella spp.