When it comes to feeding your little one, safety is always top of mind — and even the tiniest germs can feel like a big worry. Here’s what you need to know about Cronobacter, plus simple steps to help keep your baby’s bottle as safe and squeaky-clean as can be.

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Key Takeaways
  • Cronobacter is rare but serious. This germ can live in powdered formula and, while uncommon, can cause severe infections in young infants.
  • Some babies are more vulnerable. Newborns under 2 months, preemies, and babies with weaker immune systems are at higher risk.
  • Powdered formula isn’t sterile. Contamination can happen during manufacturing or at home, often through unclean hands, bottles, or surfaces.
  • Safe prep is key. Good hygiene, using hot water, and proper storage can help keep your baby’s bottle safe and germ-free.

What is Cronobacter?

Cronobacter sakazakii (or Cronobacter for short) is a germ found naturally in the environment and can live in dry foods such as herbal teas, powdered formula or powdered milk. While cases of Cronobacter are rare, infections among infants can be life-threatening. Cronobacter germs can cause a dangerous blood infection (sepsis) or brain and spinal cord infection (meningitis). 

Initial symptoms of Cronobacter infection include:

  • Fever
  • Poor appetite
  • Excessive crying
  • Limpness
  • Low energy

What puts a baby at risk for Cronobacter?

Infants may be at higher risk for Cronobacter infection if they:

  • Are younger than 2 months old 

  • Have a weakened immune system

  • Were born prematurely

Although rare, Cronobacter infections are often linked to powdered infant formula. Practicing good hygiene while preparing and storing powdered infant formula is key to ensuring a healthy feeding experience for your child. 

How does powdered infant formula become contaminated with Cronobacter?

While powdered infant formula manufacturers are required to produce formula that is safe from harmful bacteria like Cronobacter, powdered formulas — unlike liquid formulas — do not receive certain processing treatments that would make them sterile.

At the factory, Cronobacter could get into formula powder if:

  • Contaminated ingredients are used to make the formula

  • The formula powder touches a contaminated surface

In the home, infants can get infected by Cronobacter through multiple pathways including:

  • Inadequately sanitized breast-pump accessories, bottles and other utensils are used for feeding

  • Inadequate handwashing prior to infant formula preparation

  • Formula lids or scoops are placed on contaminated surfaces, like countertops or sinks, and then later touch the formula

  • Contaminated water is used to mix formula

How to safely prepare powdered infant formula

Before preparing powdered infant formula, it is important to keep surfaces, feeding items, and your hands clean to prevent germs that can make your baby sick from getting into the formula container. When preparing formula, make sure not to set the formula scoop on the counter, in the sink or on any other surface. To prevent germs from getting into the formula container, keep lids and scoops clean and completely dry, and close containers of formula as soon as possible after using.

In most cases, it is safe to prepare powdered infant formula following the instructions on the container. But if your baby is at higher risk of getting Cronobacter, consider following these five steps to prepare your powdered formula with hot water (at least 158 degrees Fahrenheit/70 degrees Celsius).  

  1. Boil the water and let it cool for about five minutes (the water should be at least 158 degrees Fahrenheit or 70 degrees Celsius — you can use a clean kitchen thermometer to check the temp). It's important to mix the formula while the water is still very hot so the heat can kill any bacteria.

  2. Pour the water into a clean bottle or feeding cup.

  3. Add the exact amount of formula listed on the container. Then, put a cap on the bottle and shake to mix. Don’t use a spoon or other utensil to stir because this could introduce germs.

  4. Cool the formula to body temperature to ensure it is not too hot before feeding your baby. Hold the capped bottle under cool water or place it in an ice bath. Do not let the cooling water get into the bottle or on the nipple.

  5. Test the formula’s temperature by putting a few drops on the inside of your wrist. It should feel warm, not hot.

What to do after preparing powdered infant formula

After your baby’s formula is prepared, use the formula within one hour from the start of feeding and within two hours of mixing it with water. 

If your baby does not finish the entire bottle of formula, throw away the leftover formula. Don’t refrigerate leftover formula to save it for later. The combination of the formula and your baby’s saliva can lead to bacteria growth.

If you are not planning to feed your baby the prepared formula right away, you should refrigerate it immediately. Remember to use refrigerated prepared formula within 24 hours. 

For more information about infant formula preparation and storage, visit CDC’s webpage on Infant Formula Preparation and Storage.