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Answering parents’ questions about Cronobacter and powdered formula


A 6-month-old boy presented with 2 days of looser-than-normal stools without blood or mucous. Before the onset of diarrhea, he had been fed at least two bottles of an infant formula identified in a national recall. His mom requested testing for Cronobacter sakazakii.

In mid-February, Abbott Nutrition recalled specific lots of powdered formula produced at one Michigan manufacturing facility because of possible Cronobacter contamination. To date, a public health investigation has identified four infants in three states who developed Cronobacter infection after consuming formula that was part of the recall. Two of the infants died.

Dr. Kristina A. Bryant president of the Pediatric Infectious Diseases Society, is a pediatrician at the University of Louisville (Ky.) and Norton Children’s Hospital, also in Louisville.

Dr. Kristina A. Bryant

As media reports urged families to search their kitchens for containers of the implicated formula and return them for a refund, worried parents reached out to pediatric care providers for advice.

Cronobacter sakazakii and other Cronobacter species are Gram-negative environmental organisms that occasionally cause bacteremia and meningitis in young infants. Although these infections are not subject to mandatory reporting in most states, laboratory-based surveillance suggests that 18 cases occur annually in the United States (0.49 cases/100,00 infants).

While early reports in the literature described cases in hospitalized, preterm infants, infections also occur in the community and in children born at or near term. A Centers for Disease Control and Prevention review of domestic and international cases identified 183 children <12 months of age between 1961 and 2018 described as diagnosed with Cronobacter bacteremia or meningitis.1 Of the 79 U.S. cases, 34 occurred in term infants and 50 were community onset. Most cases occurred in the first month of life; the oldest child was 35 days of age at the onset of symptoms. Meningitis was more likely in infants born close to term and who were not hospitalized at the time of infection. The majority of infants for whom a feeding history was available had consumed powdered formula.

Back in the exam room, the 6-month-old was examined and found to be vigorous and well-appearing with normal vital signs and no signs of dehydration. The infant’s pediatrician found no clinical indication to perform a blood culture or lumbar puncture, the tests used to diagnose invasive Cronobacter infection. She explained that stool cultures are not recommended, as Cronobacter does not usually cause diarrhea in infants and finding the bacteria in the stool may represent colonization rather than infection.

The pediatrician did take the opportunity to talk to the mom about her formula preparation practices and shared a handout. Powdered formula isn’t sterile, but it is safe for most infants when prepared according to manufacturer’s directions. Contamination of formula during or after preparation can also result in Cronobacter infection in vulnerable infants.

The mom was surprised – and unhappy – to learn that Cronobacter could be lurking in her kitchen. More than a decade ago, investigators visited 78 households in Tennessee and cultured multiple kitchen surfaces.2C. sakazakii was recovered from 21 homes. Most of the positive cultures were from sinks, counter tops, and used dishcloths. Cronobacter has also been cultured from a variety of dried food items, including powdered milk, herbal tea, and starches.

According to the CDC, liquid formula, a product that is sterile until opened, is a safer choice for formula-fed infants who are less than 3 months of age, were born prematurely, or have a compromised immune system. When these infants must be fed powdered formula, preparing it with water heated to at least 158°F or 70°C can kill Cronobacter organisms. Parents should be instructed to boil water and let it cool for about 5 minutes before using it to mix formula.

While most cases of Cronobacter in infants have been epidemiologically linked to consumption of powdered formula, sporadic case reports describe infection in infants fed expressed breast milk. In one report, identical bacterial isolates were recovered from expressed milk fed to an infected infant and the breast pump used to express the milk.3

Moms who express milk should be instructed in proper breast pump hygiene, including washing hands thoroughly before handling breast pumps; disassembling and cleaning breast pumps kits after each use, either in hot soapy water with a dedicated brush and basin or in the dishwasher; air drying on a clean surface; and sanitizing at least daily by boiling, steaming, or using a dishwasher’s sanitize cycle.

Health care providers are encouraged to report Cronobacter cases to their state or local health departments.

Dr. Bryant is a pediatrician specializing in infectious diseases at the University of Louisville (Ky.) and Norton Children’s Hospital, also in Louisville. She said she had no relevant financial disclosures. Email her at


1. Strysko J et al. Emerg Infect Dis. 2020;26(5):857-65.

2. Kilonzo-Nthenge A et al. J Food Protect 2012;75(8):1512-7.

3. Bowen A et al. MMWR Morb Mortal Wkly Rep. 2017;66:761-2.

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