Case Studies of E. sakazakii infections and powdered infant formulas


Enterobacter sakazakii, a gramnegative rod shaped bacterium, is implicated as the infective organism in a rare but often fatal (mortality rate of 40 to 80 per cent) form of neonatal meningitis. Infection with the highly virulent organisms has been associated with the use of powdered infant formulas contaminated with the E. sakazakii. A number of cases of neonatal deaths related to the infective organism have been reported in the literature. Significantly, this organism is highly resistant to heat treatment and is able to survive high temperatures during the processing of dried powdered infant formulas.



In April 2001, a male infant, delivered prematurely (weight 1.270 kg and 33.5 weeks gestation) by Cesearian section was admitted to the NICU because of respiratory distress. By day 11 the infant had fever, tachycardia, decreased vascular profusion and neurologic abnormalities. Cultures of the spinal fluid grew E. sakazakii. Treatment with intravenous antimicrobials did not halt the progressive neurological damage and the infant died nine days later, diagnosed with meningitis.


To determine the magnitude and the source of the infection, stool and urine samples of 49 infants were examined - ten were identified as E. sakazakii positive. Further analysis determined the only risk factor was the use of the powdered infant formula Portagen - a specialty formula recommended for infants with malabsorption problems – produced by Mead Johnson.


Samples of the Portagen opened cans used in the NICU and product controls of unopened cans with similar batch numbers were cultured. Both the opened and unopened cans produced positive growth of E. sakazakii, whereas the water and culture were negative.


Additionally, product preparation procedures were according to NICU policies and manufacturers instructions.


The batch of Portagen implicated was recalled voluntarily by Mead Johnson on March 29, 2002.


In conclusion, the investigators cautioned health providers as follows: “Clinicians should be aware that powdered infant formulas are not sterile products and might contain opportunistic bacterial pathogens such as those in the Enterobacteriacae family, including E. sakazakii.


Himelright I, et al. Enterobacter sakazakii Infections Associated with the Use of Powdered Infant Formula --- Tennessee 2001, MMWR 51: 298-300, 2002



In 1988 a similar outbreak of E. sakazakii infection was reported in a Memphis, Tennessee, 20-bed NICU. This time the outbreak involved four infants. Three suffered from bloody diarrhea and three had sepsis. Fortunately all four responded to intravenous antibiotics and survived. The outbreak was traced to contaminated powdered infant formula.


Simmons, BP. Et al. Enterobacter sakazakii infections in neonates associated with intrinsic contamination of a powdered infant formula. Infec Control Hosp Epidemiol 10: 398-401, 1989



In 1998, an outbreak of necrotizing enterocolitis involved 12 neonates in Belgium. E sakazakii was isolated from six of the 12 cases. Ten of the 12 cases had been fed the same brand of powdered infant formula. E. sakazakii was isolated from the formula fed to the infants as well as in unopened tins of the formula. No further cases developed when the use of the contaminated formula stopped. Two of the infants who fell sick - twin boys - died as a result of the infection.


van Acker J, et al. Outbreak of necrotizing enterocolitis associated Enterobacter sakazakii in powdered milk formula. J, Clin Microbiol 39: 293-97,




The national University Hospital of Reykjavik, Iceland has reported three cases of neonatal infections caused by E. sakazakii. Two of the infants, born normal and full term survived and are brain damaged, the third infant, born with Down’s Syndrome and severe cardiac malformations, died. The Enterobacter organisms were cultured and grown from several lots of powdered infant formula used in the hospital.


Biering G. et al. Three cases of neonatal meningitis caused by Enterobacter sakazakii in powdered milk. J. Clin Microbiol 27: 2054-56, 1989



Eight cases of neonatal meningitis caused by E. sakazakii over a period of six years were reported in the Netherlands between 1977 and 1983. Two of the cases had both necrotizing enterocolitis and meningitis.  Despite antibiotic treatment, the fatality rate was 75 per cent.


A quality check by the same key researcher, examined 141 powdered infant formula samples collected from 35 countries. The species most frequently isolated were: Enterobacter agglomerans, cloaclae, E. sakazakii and Klebsiella pneumoniae. They note that if any infections with these causative bacteria occur, it is important to check the procedures for preparation and storage of infant formulas.


Muytens H.L. et al. Analysis of eight cases of neonatal meningitis and sepsis due to Enterobacter sakazakii. J. Clin Mocrobiol 18: 115-20, 1983


Muytens HL et al. Quality of powdered substitutes for breast milk with regard to members of the family Enterobacter. J. Clin Mocrobiol 26: 743-46, 1988·



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