There is no evidence linking four ongoing Cronobacter sakazakii infections in infants across four states, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) announced in a joint news release Friday.

Based on their investigation, the agencies see no need for a recall of infant formula. Parents may continue to feed powdered formula to their infants, the news release said.

In a precautionary move, Walmart recalled Enfamil-brand powdered baby formula from its stores nationwide on December 22, after a 10-day old boy died from Cronobacter infection in Missouri. According to Mead Johnson Nutrition, the formula manufacturer, the recalled batch tested negative for the bacteria before it went to stores.

The CDC said it found Cronobacter bacteria in an opened container of infant formula, an opened bottle of nursery water and prepared infant formula provided by the Missouri Department of Health, but was not certain how the foods became contaminated. In a follow-up, the FDA tested factory-sealed containers of formula and nursery water from the same batches and found no Cronobacter.

The other three infections have occurred in Florida, Illinois and Oklahoma. The infant in Florida died.

The CDC found that the Cronobacter bacteria in the Missouri and Illinois cases differ genetically, which suggests they are not related. The agency said it could not obtain bacteria from the Oklahoma or Florida cases to analyze.

After inspecting the facilities that manufactured the formula and nursery water, the FDA said it found no Cronobacter there, either.

The news release described Cronobacter (also referred to as C. sakazakii, and formerly called Enterobacter sakazakii) as “a very rare cause of a severe infection in young infants,” saying that the CDC is typically informed of 4 to 6 cases each year. The agency knows of 12 cases that occurred in 2011.

“Cronobacter needs to be a reportable illness like E. coli and Salmonella,” said Bill Marler, food safety attorney and publisher of Food Safety News. “We then would have a far better understanding of the cause of these clusters or individual cases.”

In a December 27 Food Politics post about the infant illnesses, New York University food studies professor Marion Nestle pointed out that unlike their liquid counterparts, powdered formulas are not sterile. Nestle wrote that in 2002, “the FDA warned pediatricians that powdered milk formulas could be contaminated with Enterobacter sakazakii, a type of bacteria that causes rare but terrible and sometimes fatal infections in infants.”

Nestle went on to point out that in 2001, the CDC determined that 50 to 80 percent of E. sakazakii cases came from powdered formula.

The CDC said that Cronobacter may multiply in formula after the powder is mixed with water, and the agency recommends mixing fresh formula for each feeding session. The agency also recommends breastfeeding whenever possible.

The news release concluded with a number of recommendations for preparing powdered infant formula:

– Wash hands with soap and water before preparation

– Clean all feeding equipment with hot, soapy water

– Prepare only enough formula for one feeding at a time and give it to the baby right away

– Follow the manufacturer’s directions on the printed label