Chromogenic Cronobacter Isolation Agar (CCI) is recommended by ISO 22964 for the isolation and identification of Cronobacter spp. (formerly Enterobacter sakazakii), and is not intended for use in the diagnosis of disease or other conditions in humans. Although rarely causing infections in immunocompetent adults, members of the Cronobacter genus have been implicated in sepsis, meningitis and necrotizing enterocolitis with a high death rate in neonates. These opportunistic pathogens are common in the environment and their ability to survive desiccation presents a significant risk for post-pasteurization contamination and survival in spray dried milk products. Tryptic digest of casein and yeast extract provide a source of nitrogen and essential vitamins. The high content of sodium chloride and the presence of sodium desoxycholate produce a selective and specific medium. Microorganisms that possess α-glucosidase activity appear blue or blue-green due to the presence of the chromogen 5-bromo-4-chloro-3-indolyl-α-D-glucopyranoside. Organisms that reduce the sodium thiosulfate produce a black precipitate due to the presence of thiosulfate and ammonium iron(III) citrate. Cronobacter spp. possess α-D-glucosidase so appear blue to green. Similar Enterobacteriaceae do not express this enzyme thus grow colorless. According to ISO 22964:2017, subculture is performed after selective enrichment in Cronobacter Selective Broth (CSB). This medium conforms to the formulation and performance requirements of ISO 22964:2017.
