Neonatal Mice as Models for Cronobacter sakazakii Infection in Infants

Cronobacter sakazakii is an opportunistic pathogen that has been isolated from powdered infant formulas. C. sakazakii infection can result in serious illnesses such as bacteremia, septicemia, meningitis, and death in at-risk infants who are orally fed contaminated reconstituted powdered infant formulas. The objective of this study was to compare the susceptibilities of BALB/c. C57BL/6, and CD-1 mice to C. sakazakii strain MNW2. We acquired timed-pregnant CD-1 mice and allowed them to give birth naturally. On postnatal day 3.5, each pup was administered a total dose of approximately 10(2) to 10(11) CFU C. sakazakii strain MNW2 in reconstituted powdered infant formula. Mice were observed twice daily for morbidity and mortality. At postnatal day 10.5, the remaining pups were euthanized, and brain, liver, and cecum were excised and analyzed for the presence of C. sakazakii. C. sakazakii was isolated from brains, livers, and ceca in all three mouse strains. The CD-1 mouse strain was the most susceptible of the three, with the lowest infectious dose (10(2) CFU) and the lowest lethal dose (also 10(2) CFU).