Cronobacter Selective Broth (CSB) 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. Enzymatic digest of animal tissues and meat extract provide a source of nitrogen and essential vitamins. High levels of sodium chloride and sucrose, the addition of vancomycin and an elevated incubation temperature produce a selective and specific medium. Cronobacter spp. ferment the sucrose in this broth, resulting in a decrease in pH and thus a change of color from purple to yellow or red due to the presence of the pH indicator bromocresol purple. Most other organisms do not grow in this medium, while E. coli are suppressed, resulting in a turbid medium with no changes in color. According to ISO 22964:2017, subculture is performed after pre-enrichment in Buffered Peptone Water (BPW).
