Muller-Kauffmann Tetrathionate-Novobiocin (MKTTn) Broth

Muller-Kauffmann Tetrathionate-Novobiocin Broth is used for the selective and differential isolation of Salmonella spp. in a laboratory setting and is included in ISO 6579:2017. This medium is not intended for use in the diagnosis of disease or other conditions in humans. A selective enrichment medium for the detection of Salmonella spp. in food, animal feed and in environmental samples from the food production area as described in ISO 6579-1:2017. Mueller originally described a tetrathionate broth that inhibited lactose fermenting Enterobacteriaceae but not Salmonella. Kauffmann later modified the formulation to include ox bile and brilliant green to improve selectivity. Finally, Jeffries added Novobiocin to inhibit Proteus species. Meat extract and casein provide a source of nitrogen and amino acids and sodium chloride maintain the osmotic balance. Ox bile and brilliant green act as selective agents against non-target microorganisms. Tetrathionate is generated from the sodium thiosulfate. Iodine and calcium carbonate buffer the sulfuric acid generated from tetrathionate reduction. According to ISO 6579-1:2017 subculture is performed from Buffered Peptone Water (BPW) into MKTTn, followed by subculture onto Xylose-Lysine Deoxycholate (XLD) Agar ISO and second agar. This medium conforms to the performance and formulation requirements of ISO 6579-1:2017.