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What is Cronobacter?

Cronobacter multi-species complex (formerly Enterobacter sakazakii) is a group of gram-negative bacteria that exists in the environment and which can survive in very dry conditions. The natural habitat for Cronobacter is not known. It has been found in a variety of dry foods, including powdered infant formula, skimmed milk powder, herbal teas, and starches. It has also been found in wastewater. Cronobacter illnesses are rare, but they are frequently lethal for infants and can be serious among people with immunocompromising conditions and the elderly.

What kinds of illnesses does Cronobacter cause?

Cronobacter can cause several different kinds of infections, and symptoms vary with both the site of infection and the age of the patient.

Infants (<12 months old): In infants, Cronobacter usually causes sepsis or severe meningitis. Some infants may experience seizures. Those with meningitis may develop brain abscesses or infarcts, hydrocephalus, or other serious complications that can cause long-term neurological problems. The mortality rate for Cronobacter meningitis may be as high as 40%.

People of all ages: Cronobacter can cause wound infections or urinary tract infections. People with immunocompromising conditions and the elderly may also develop bloodstream infection due to Cronobacter. Cronobacter has also been isolated from the respiratory secretions of people undergoing mechanical ventilation; in this situation, however, Cronobacter is likely to be colonizing the respiratory tract rather than causing illness. Similarly, Cronobacter has been isolated from the stool of asymptomatic individuals.

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How common is illness due to Cronobacter?

Cronobacter infection is rare. CDC typically receives reports of 4-6 infections in infants per year, although reporting is not required except in one state, Minnesota. As a result, rates of Cronobacter infection in the United States are not well understood. However, a national FoodNet survey in 2002 estimated the annual incidence of invasive Cronobacter infection at one per 100,000 infants aged <1 year and at 8.7 per 100,000 low birth weight infants (<2,500 g [5.5 lbs]). Additionally, more recent, unpublished FoodNet data suggest that infections among older adults are more common, although milder, than infections among infants.

Who is at risk of Cronobacter infection?

Cronobacter infections have been reported in all age groups. However, infants, the elderly, and people with immunocompromising conditions appear to be at greatest risk of Cronobacter infection and can experience more severe symptoms. Meningitis due to Cronobacter occurs almost exclusively among infants in the first 2 months of life.

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How is Cronobacter infection diagnosed?

Cronobacter infection is diagnosed by a laboratory culture. 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, and should be given empiric therapy for sepsis immediately. Antimicrobial sensitivity patterns of Cronobacter isolates should be determined 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 is Cronobacter transmitted?

Cronobacter infections have been associated with consumption of reconstituted powdered infant formula. In several outbreak investigations, Cronobacter has been found in powdered infant formula that had been contaminated in the factory. In other cases, Cronobacter might have contaminated the powdered infant formula after it was opened at home or elsewhere.

Since the bacteria live in the environment, it's possible there are other sources of infection. There have been no confirmed reports of Cronobacter infections spreading vertically or through person-to-person contact. However, other related bacteria commonly spread through person-to-person contact, especially in healthcare facilities when there are lapses in infection control practice.

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 raw materials are used to make the formula, or if the formula powder touches a contaminated surface in the manufacturing environment.

Powdered infant formula can also be contaminated at home or elsewhere after the container is opened. For example, Cronobacter could get into the formula if formula lids or scoops are placed on contaminated surfaces and later touch the formula, or if the formula is mixed with contaminated water or in a contaminated bottle.

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