definition
Cronobacter spp., previously known as Enterobacter sakazakii until 2007, are Gram-negative, motile rods measuring 1–3 µm in length. They are facultatively anaerobic, non-spore-forming, thermotolerant, oxidase-negative, and catalase-positive. Belonging to the Enterobacteriaceae family, these bacteria are commonly found in the environment, though some species are opportunistic pathogens.
Cronobacter spp. are primarily responsible for human infections, particularly in neonates, and can cause severe conditions such as infant meningitis, necrotizing enterocolitis, systemic infections, and even death. The first documented human case occurred in 1958. C. sakazakii and C. malonaticus are the primary culprits behind clinical cases across all age groups, while C. turicensis and C. universalis have been implicated in a few isolated cases. Several virulence factors have been identified, including outer membrane proteins (OMPs), enterotoxins, endotoxins, plasminogen activators, and systems for efflux and iron acquisition. These factors enable the bacteria to survive stomach passage, damage intestinal epithelium, persist in macrophages, and cross the blood-brain barrier, potentially leading to fatal systemic infections.
Cronobacter spp. are particularly resilient, with the ability to form biofilms and a high resistance to osmotic stress and desiccation, primarily due to their capsule production. These traits enhance their persistence, especially in dry environments such as powdered milk processing plants. The bacterium can survive for up to two years in dry conditions, with water activity (aw) levels ranging from 0.14 to 0.27 in dry products. Their generation time varies with temperature: 300 minutes at 10°C, 40 minutes at 23°C, and 20 minutes at 37°C. Additionally, they can utilize sialic acid as their sole carbon source, which facilitates growth in breast milk and infant formula.
