Salmonella is a gram-negative, facultatively anaerobic, non-sporulating, non-motile rod in the family Enterobacteriaceae. They are widely distributed in animals affecting mainly the stomach and the intestines. These organisms are difficult to differentiate biochemically from Escherichia coli. M-Bismuth Sulphite Broth was formulated by Clark et al (1) and is particularly recommended for detection of Salmonella Typhi from water and various clinical specimens by the membrane filtration technique. Preliminary enrichment on a non-selective medium is not necessary. M-Bismuth Sulphite Broth has a composition similar to Bismuth Sulphite Agar (M027), except Agar. Also in the broth medium, all the constituents are in double concentration.
Peptic digest of animal tissue, beef extract and dextrose provide essential growth nutrients. Ferrous sulphate and bismuth sulphite indicator together act as H2S indicators. Brilliant green acts as selective agent. Luxuriant growth of Salmonella Typhi is obtained after 30 hours incubation at 35°C but metallic sheen and brown-black halo is not developed before 40 hours. The importance of this medium has been repeatedly mentioned for detection of Salmonella Typhi by membrane filter technique (2 - 5).
Storage and Shelf-life:
Store below 30°C in tightly closed container and use freshly prepared medium . Use before expiry date on the label.
References:
1. Clark H. F., Geldreich E. E., Jeter M. L. and Kabler P. W., 1951, Pub l. Hlth. Reports, 66:951.
2. Goets A. and Tsuneishi N., 1951, J. Am. Water Works Assoc., 43:943.
3. Goets A. and Tsuneishi N., 1952, J. Am. Water Works Assoc., 44:471.
4. Goets A. and Tsuneishi N., 1953, J. Am. Water Works Assoc., 45 and 1196.
5. MacFaddin J. F., 1985, Media for Isolation-Identification-Cultivation-Maintenance of Medical Bacteria, Vol. I, Williams and Wilkins, Baltimore.