Enterobacter sakazakii was first described as a new bacterial species in 1980, and over a hundred scientific papers have been written about it. From 1980 to 2007 it was known as Enterobacter sakazakii, but in 2007 there was a proposal to reclassify it into a new genus Cronobacter as Cronobacter sakazakii. (1) For simplicity and for the reasons mentioned later, this discussion will continue to use the original name Enterobacter sakazakii. The proposed alternative classification is given as a section at the end and includes a discussion of the problems and the need for future studies.
Enterobacter sakazakii is a Gram-negative rod-shaped bacterium classified in the family Enterobacteriaceae. It has been isolated from three types of infection — devastating meningitis in very young babies (neonates), bacteremia (blood steam infection) in older babies, and a wide variety of infections (or colonization) in older babies, children and adults. The majority of infections reported in the peer-reviewed literature have described neonates—newborn infants, including premature infants, post-mature infants, and full-term newborns—with sepsis, meningitis, or necrotizing enterocolitis. (2) Although it has been isolated from cases of necrotizing enterocolitis, its causative role is unclear. (3)
Reported outcomes in neonatal meningitis are often severe: seizures; brain abscess; hydrocephalus; developmental delay; and death in as many as 40%–80% of cases. Premature infants are thought to be at greater risk than more mature infants, other children, or adults, and outbreaks have occurred in hospital units for newborns. (3)
Although E. sakazakii can cause illness in all age groups, infants are believed to be at greatest risk of infection and E. sakazakii was first implicated in a case of neonatal meningitis in 1958 (before the organism was given a scientific name). Since that time, around 70 cases of E. sakazakii infection have been reported, but it is likely that is the number of cases is significantly under-reported in all countries and the incidence is probably higher. (4)