Two cases of acute gastroenteritis occurred in 5-month-old infants hospitalized in a mother-and-child hospital in Queretaro, Mexico, on 24 January 2010. C. sakazakii was recovered from the powdered infant formula (PIF), rehydrated PIF (R-PIF) fed to infants, and their fecal samples. The microorganism was present at levels of 0.33 most probable number (MPN)/g and 24 MPN/ml in PIF and R-PIF, respectively. The total ingested dose for the day before the onset of the diarrheic syndrome ranged between 2,160 and 3,600 MPN/ml. All strains of C. sakazakii recovered from the three sources (R-PIF, PIF, and fecal matter) showed identical biotypes, adhesion and invasiveness factors, and pulsed-field gel electrophoresis profiles. No deaths were observed. Salmonella, Shigella, and enterotoxigenic Escherichia coli were not found in food or fecal samples.