COAGULASE MANNITOL BROTH BASE

Description

Coagulase Mannitol Broth Base is used for the isolation of Staphylococcus aureus from clinical specimens and for differentiation of Staphylococcus aureus from other species on the basis of coagulase production and mannitol fermentation. Chapman for the first time introduced medium for selective isolation and differentiation of Staphylococci. Tellurite-glycine media were designed by Zebovitz et al and Marwin for selectively isolating coagulase positive Staphylococcal species. Present medium is based on Esber and Faulconer formulation. Coagulase Mannitol Broth Base simultaneously detects mannitol fermentation and coagulase production by Staphylococci. Coagulase Mannitol Broth Base is a good substrate for Staphylococci as well as other fastidious bacteria. Coagulase production and mannitol fermentation observed in Coagulase Mannitol Broth Base is presumptive identification of pathogenic Staphylococci. Coagulase production is dependent on the presence of a fermentable sugar like mannitol in this case. It is also dependent on the presence of a protein factor in the heart muscle infusion and blood plasma. When mannitol is fermented, the pH of the medium drops. This drop in pH is indicated by the change in colour of the phenol red, which turns yellow, and exhibit yellow medium. An opaque broth due to coagulated plasma forms due to growth of coagulase positive organisms. Staphylococcus epidermidis a coagulase negative and mannitol non-fermenting species, does not change the colour of the medium. Coagulase negative species may ferment mannitol and produce a yellow colour but opacity will not be formed. Production of gas can be determined by placing a small inverted Durham’s tube in the medium tube. Mutant or old cultures of Staphylococcus aureus may be weak coagulase producers. They should be freshly subcultured and rechecked. Escherichia coli ferments mannitol and may be weakly coagulase positive. For the test, use this medium in 2 to 5 ml amounts after adding about 12-15% plasma. Inoculate by adding about 2 drops of test organism and incubate at 37?C and examine after 2-3 hours and also after 4-5 hours of incubation. Un-inoculated control tubes should also be run in parallel with the fermentation tests.