Introduction
1. Occurrence of Enterobacter sakazakii (also called Cronobacter species) infection, rare but potentially life-threatening, among infants (0-12 months old) has aroused concerns in many countries. More and more reports now suggested powdered infant formula is a vehicle for the infection.
E. sakazakii
2. E. sakazakii is a pathogen of emerging public health concern, which generally causes disease only in peoples with weakened immune systems. It is a gram-negative, non-spore-forming rod bacterium with optimum growing temperatures ranging from 37 oC to 43 oC.
3. E. sakazakii can cause invasive infection in all age groups, however, neonates ( ≤ 28 days old) and infants less than 2 months of age, in particular pre-term infants, low-birth-weight infants (< 2.5 kg) and immunocompromised infants, are at greatest risk.
4. As the stomach of newborns, especially of premature babies, is less acidic than that of adults, this may be a possible important factor contributing to the survival of an infection with E. sakazakii in infants.
5. E. sakazakii has been associated with sporadic cases or small outbreaks of blood stream infection and meningitis. Although any infant could develop either disease at any age, E. sakazakii blood stream infection tends to develop in premature infants outside of the neonatal period while E. sakazakii meningitis tends to develop in term infants during the neonatal period. This difference might be related to differences in timing of E. sakazakii exposure rather than susceptibility of the infants.
Occurrence of E. sakazakii
6. Little is known about the ecology of E. sakazakii. However, E. sakazakii is considered to be an environmental organism and is likely to be present in both manufacturing facilities and domestic situations.
7. Although powdered infant formula is not a sterile product, risk of infection can be greatly reduced by correctly preparing and storing it.
Advice to the public
8. The WHO recommends that infants should be exclusively breastfed for the first six months of life to achieve optimal growth, development and health. For mothers who are not breastfed for any reason, caregivers, both at home and in care settings, should always be alerted thatpowdered infant formula is not a sterile product and can be contaminated with pathogens that can cause serious illness. Cleaning and sterilisation of feeding and preparation equipment is an essential prerequisite to the safe preparation of powdered infant formula.
9. According to the Safe preparation, storage and handling of powdered infant formula: guidelines issued by the FAO/WHO, powdered infant formula should be prepared with water that is no cooler than 70 oC in order to kill E. sakazakii (in practice, this means using boiling water that has been left to cool for no more than 30 minutes). Reconstituted powdered infant formula should be then cooled to feeding temperature and consumed immediately. Reconstituted powdered infant formula that has not been consumed within 2 hours should be discarded.
10. Reconstituted milk not for immediate consumption should be cooled immediately and stored under refrigeration at 4 oC or below for up to 24 hours; it should be re-warmed immediately before feeding and for no more than 15 minutes. Re-warmed feed that has not been consumed within two hours should be discarded. However, it is recommended to prepare formula fresh for each feed and avoid storage of reconstituted formula. Feeds that are prepared with water cooler than 70 oC should not be stored for later use.
11. Refrigerated bottle feeds can be re-warmed by placing in a container of warm water with occasional shake or swirl in order to heat evenly; the level of the water should be below the top of the feeding bottle. Never use a microwave oven to prepare or warm-up feeds for infants. It is because microwave ovens heat unevenly and may cause ‘hot spots' in the feed, which may burn the oral mucosa of the infants.
12. For high-risk infants who are not breastfed, caregivers are encouraged to use whenever possible and feasible, commercially sterile liquid formula.
FAO/WHO material:
How to Prepare Powdered Infant Formula in Care Settings
How to Prepare Formula for Bottle-Feeding at Home
How to Prepare Formula for Cup-Feeding at Home
Risk Assessment Section
Centre for Food Safety
October 2008