NEW YORK — The rod-shaped bacteria that killed a Missouri infant this month have infected at least 120 infants worldwide since 1958 and have been linked to the use of baby formula in the past, public-health researchers say.
The potential for the bacteria, called Cronobacter, to infect infants through powdered baby formula has only been known since the 1980s, said Kieran Jordan, a microbiologist at the Moorepark Food Research Centre of Ireland’s Agriculture and Food Development Authority, in a telephone interview. Cronobacter ends up in powdered formula because it is well adapted at surviving in very dry environments, he said.
The bacteria may grow rapidly if the powdered product, with even small amounts of Cronobacter, is reconstituted in water that’s not hot enough to kill it, Jordan said. Once in a child, the infection can target the brain and spinal cord, causing swelling of the brain lining, health officials said.
“Once the baby powder is rehydrated it is a very rich environment for the bacteria to grow,” said Jordan, who has published multiple studies on Cronobacter.
The Food and Drug Administration advises boiling water for one minute and then letting it cool before mixing formula. Studies suggest powder needs to be mixed with water heated to at least 158 degrees Fahrenheit to kill off bacteria, the agency says on its website.
Powdered infant formula is “not a sterile product,” said Chris Braden, who heads the Division of Foodborne, Waterborne and Environmental Diseases at the Centers for Disease Control and Prevention in Atlanta.
While formula sold as a liquid typically is pasteurized and “a very low risk,” it’s also more expensive, he said. Powdered formula should be used within a couple of hours of being mixed, and parents should remember to wash hands and equipment like bottles and nipples before preparation.
Not taking safety precautions can lead to permanent damage, Braden said. Even when children survive the infection, they may have neurological deficits, including developmental delays and seizures, he said.
Proving infant formula caused a given case of Cronobacter can be difficult because the bacterium is found “in the kitchen, in soil, even around the house,” Braden said in a telephone interview. It takes a “quite intensive investigation” to prove a cause, he said.
Mead Johnson Nutrition Co.’s Enfamil Newborn was pulled from store shelves by retailers last week after it was learned that a baby from Lebanon, Mo., had taken it before becoming sick and dying. The company’s tests after the death showed no evidence of the bacteria in the same batch of product as that being evaluated by federal regulators, Mead Johnson said in a Christmas Day statement.
State and federal regulators also are analyzing the case of an Illinois newborn given formula who fell sick with the infection during a trip in Missouri, and CDC officials Tuesday confirmed a third Cronobacter infection in an Oklahoma baby who was hospitalized. While the Oklahoma child used powdered formula, it wasn’t the same brand and there’s too little evidence yet to say what caused the illness, Braden said.
Wal-Mart Stores, one of the retailers who pulled the Mead Johnson product from store shelves, said it would await the result of government tests before taking further action.
The CDC in 2009 estimated the number of infants infected with the bacteria and reviewed a 2008 Cronobacter outbreak in which two babies in New Mexico were confirmed with the illness. One of the infants died and the other survived with severe brain damage, according to the CDC’s Oct. 30, 2009, issue of Morbidity and Mortality Weekly Report, an agency publication.
While investigators couldn’t pinpoint the source of the bacteria, infant formula “was the only known risk factor in the two cases,” according to the 2009 paper from the Atlanta-based health agency.
In 2001, a Tennessee baby died following progressive brain damage from Cronobacter infection. The baby was given powdered formula from a batch that was found to contain the bacteria, according to a study in the April 12, 2002, Morbidity and Mortality Weekly Report.
The incident prompted Mead Johnson to voluntarily recall the batch in March 2002, according to the CDC’s report. It also heightened awareness among formula makers, said Susan Ricker, Mead Johnson’s director of global quality services.
“The industry started working with the regulators and the health officials worldwide to make sure that new and effective standards for Cronobacter testing were in place,” Ricker said in a telephone interview.
Mead Johnson now performs 2,300 “quality-control checks” on formula, including tests for nutritional quality and microbiological contamination mandated by U.S. and international standards, according to Ricker. The company samples 300 grams of each batch for Cronobacter contamination, equipment is washed regularly and there’s a system in place to identify “critical control points” whe re bacteria could enter.
“Once we have released a batch, we are stating it is safe for our consumers,” Ricker said.
The Glenview, Ill.-based company also takes steps to educate consumers about safety, said Chris Perille, company spokesman, in an email.
All labels indicate that powdered formulas aren’t sterile and shouldn’t be fed to premature infants or those with immune problems unless under medical supervision, he said. The labels also cover proper hygiene, use and storage.
The bacteria, when found, usually will have infected babies that are premature or have weak immune systems, said Mary Alice Smith, a toxicologist at the University of Georgia.
“It does seem to be the very young infants that are most susceptible to it,” said Smith, who has studied the bacterial infection and has received research funding from Mead Johnson.
The blood brain barrier in newborn babies, as well as parts of the gastrointestinal tract, may not be fully developed, making them more susceptible to the bacteria than older children and adults, Smith said.
Stephanie Armour in Washington contributed to this report..