Frequently Asked Questions

What is Cronobacter?

Cronobacter is a bacteria that has been found in a variety of dry foods, including powdered infant formula, powdered milk, herbal teas, and starches. It has also been found in water. Cronobacter illnesses are rare, but they can be deadly for infants and can be serious among people with weakened immune systems and people 65 years and older.

Cronobacter multi-species complex (formerly Enterobacter sakazakii) is a group of Gram-negative bacteria that exists in the environment and can survive in very dry conditions. The natural habitat for Cronobacter is not known.

Who is at risk of Cronobacter infection?

Cronobacter infections have been reported in all age groups. However, infants less than 2 months old are most likely to develop meningitis (an inflammation of the membranes that protect the brain and spine) if they are infected with Cronobacter bacteria. Infants born prematurely and those with weakened immune systems are also at risk for severe illness. Visit CDC’s People at Risk page to learn more.

What kinds of illnesses does Cronobacter cause?

Cronobacter can cause several kinds of infections, and symptoms vary with the patient’s age and what part of the body is infected.

  • Infants (<12 months old): In infants, Cronobacter can cause sepsis (a severe bloodstream infection) or meningitis (an infection of the protective membranes that surround the brain). Meningitis due to Cronobacter occurs almost exclusively among infants in the first 2 months of life. Infants with meningitis may develop seizures, brain abscesses or infarcts, hydrocephalus, or other serious complications that can cause long-term neurological problems. A recent report estimates that approximately 20% of infants with meningitis or bloodstream infections due to Cronobacter in the United States have died (Strysko, 2020). Worldwide, approximately 40% of infants reported to have Cronobacter meningitis or bloodstream infections have died (Strysko, 2020).
  • People of all ages: Cronobacter can cause wound infections or urinary tract infections. People who have weakened immune systems due to illnesses or conditions, such as HIV, organ transplants, or cancer, and people who are 65 years and older are more likely to develop bloodstream infection due to Cronobacter. Cronobacter has also been found in the stool (poop) of people who have no symptoms, likely due to colonization. That means the bacteria is found in or on the body, but it does not cause any symptoms or disease. Cronobacter has also been found in the respiratory fluids of people on mechanical ventilators—but in this case, Cronobacter is likely to be colonizing the respiratory tract rather than causing illness.

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How common is illness due to Cronobacter?

Cronobacter infection is rare. CDC typically receives reports of about 2 to 4 infections in infants per year, but Minnesota and Michigan are the only states that require reporting. Because most states do not require reporting, rates of Cronobacter infection in the United States are not well understood. However, a literature review from 1961 to 2018 provides evidence that Cronobacter infections are most common in infants less than 2 months old and often cause death in this age group. Also, infections among older adults may be more common, although milder, than infections among infants.

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How many Cronobacter cases happen every year?

Unlike other foodborne illnesses, Cronobacter sakazakii infection is not a nationally notifiable condition and is not reportable in most states. This means that the true number of annual cases is unknown. Typically, CDC receives 2-4 reports of severe Cronobacter infections in infants annually from health departments and has received reports from 32 states. From January 2002 to July 2022, CDC received 76 reports of severe Cronobacter illnesses among infants. A recent report estimates that approximately 20% of infants with meningitis or bloodstream infections due to Cronobacter in the United States have died (Strysko, 2020). Worldwide, approximately 40% of infants reported to have Cronobacter meningitis or bloodstream infections have died (Strysko, 2020).

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How is Cronobacter transmitted?

Cronobacter infections are often reported among infants who have been fed powdered infant formula. In some cases, Cronobacter has been found in powdered infant formula that was likely contaminated in the factory. In other cases, Cronobacter likely contaminated the powdered infant formula after it was opened at home or elsewhere. There have also been reports of infants getting sick after drinking pumped breast milk. In these cases, Cronobacter contaminated the breast pump parts.

Since Cronobacter bacteria live in the environment, there might be other ways babies can become infected.  It is unknown if Cronobacter infection can be spread from one person to another, but other types of bacteria spread this way, especially in hospitals, if people do not wash their hands well.

How is Cronobacter infection diagnosed?

Cronobacter infection is diagnosed by a laboratory culture. Cronobacter can be detected in the blood or cerebrospinal fluid (CSF) of patients with sepsis or meningitis caused by these bacteria. Cronobacter bacteria grow on routine culture media, and microbiological laboratories can detect Cronobacter from blood or CSF samples.

If a Cronobacter infection is diagnosed by a laboratory culture in an infant, CDC encourages physicians, hospitals, and laboratories to inform their local or state health department.

How is Cronobacter infection managed?

Infants suspected of having Cronobacter sepsis or meningitis should undergo a full clinical evaluation for sepsis, including blood culture, urine culture, and cerebrospinal fluid culture. They should be hospitalized and given empiric antibiotics for sepsis immediately. Antimicrobial susceptibility testing for Cronobacter isolates should be performed because multidrug-resistant strains have been reported. Brain imaging studies of infants with meningitis can help detect brain abscesses and other complications. People with urinary tract infections or serious wound infections should also be treated with antibiotics. If a patient is colonized, rather than infected, with Cronobacter, treatment is not needed.
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How does powdered infant formula become contaminated with Cronobacter?

Powdered infant formula is not sterile. Manufacturers report that, using current methods, it is not possible to produce sterile powdered infant formula. 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, you can accidentally get Cronobacter in powdered infant formula after the container is opened. For example, Cronobacter could get into the formula if:

  • You place formula lids or scoops on contaminated surfaces, like countertops or sinks, and they later touch the formula.
  • You mix the formula with contaminated water or in a contaminated bottle.

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How can I prepare powdered infant formula with hot water if my baby is at higher risk?

In most cases, it is safe to mix powdered infant formula following manufacturer’s instructions on the container. But, if your baby is at higher risk, consider taking these extra steps to prepare your powdered formula with hot water (at least 158°F/70°C):

  1. Wash hands with soap and water before preparing infant formula.
  2. Clean work surfaces such as countertops and sinks with soap and water or use a disinfectant wipe or paper towel sprayed with cleaning product.
  3. Boil water and let it cool for about 5 minutes.
  4. Pour into a clean bottle or feeding cup.
  5. Add the exact amount of formula listed on the container, put a cap on the bottle. Carefully shake the bottle instead of stirring the mixture.
  6. If you plan to use the prepared formula right away, cool the formula to body temperature to ensure it is not too hot before feeding your baby. Run the prepared, 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.
  7. Before feeding your baby, test the formula’s temperature by putting a few drops on the inside of your wrist. It should feel warm, not hot.

Use prepared infant formula within 1 hour from the start of feeding and within 2 hours of preparing it. If your baby does not finish the entire bottle of formula, throw away leftover formula.

If you do not plan to start feeding your baby with the prepared formula right away, put it in the refrigerator immediately. Use formula in the refrigerator within 24 hours. Throw out formula if you can’t remember how long you have kept it in the refrigerator. Do not feed it to your baby.

For more information visit CDC’s Infant Hygiene page.

What is the best way to clean, sanitize, and store infant feeding items?

Help prevent Cronobacter from growing on these items and keep your baby’s milk safe by carefully cleaning, sanitizing, and storing bottles and breast pump parts.

  • Clean surfaces like countertops and sinks with soap and water, or use a disinfectant wipe or paper towel sprayed with cleaning product.
  • Clean and sanitize infant feeding items (such as nipples, caps, rings, and valves) and breast pump parts in a dishwasher or a clean wash basin that you use only for washing these supplies.
    • Take apart bottles and breast pump equipment after use for thorough cleaning.
    • Do not place these items directly in the sink because germs in sinks or drains could contaminate these items.
    • Allow items to air-dry thoroughly and store them in a clean, protected area.
  • Keep powdered formula in the container dry to prevent germs from growing.
    • Avoid getting the formula scoop wet. There is no need to wash the scoop unless it becomes wet or dirty (such as falling on the floor). If the scoop needs to be washed, clean it as carefully as you would your baby’s bottles.
    • The formula scoop must be completely dry before putting it back into the container.