Modified Giolitti and Cantoni Broth (ISO) is used for the detection and enumeration of coagulase- positive staphylococci from food and animal feeding stuffs using the Most Probable Number (MPN) technique according to ISO 6888-3:2003. This medium is not intended for use in the diagnosis of disease or other conditions in humans.
Originally described by Giolitti and Cantoni as a medium for the enrichment of staphylococci from foodstuffs, Mossel later applied the medium to use with samples from dried milk and infant food. Optimized for use in samples where staphylococci may be stressed and/or in low numbers, growth of the target organisms is promoted by sodium pyruvate, Glycine and the high concentration of mannitol. Selectivity is achieved via lithium chloride, which inhibits Gram-negative bacilli, and potassium tellurite, which inhibits Gram-positive organisms other than staphylococci. Further selectivity is achieved by use of anaerobiosis either by pouring a plug of agar/paraffin or by incubation in a jar or incubator under anaerobic conditions. Anaerobiosis particularly inhibits the growth of Micrococcus spp.
The presence of coagulase-positive staphylococci is indicated by the reduction of tellurite, resulting in a blackening of the broth or a black precipitate. Coagulase-positive staphylococci are principally Staphylococcus aureus but may also include the species Staphylococcus intermedius and Staphylococcus hyicus.
