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How widespread is bacterial contamination of powdered infant formula?

Journal of Pediatrics publishes research:  Presence of Soil-Dwelling Clostridia in Commercial Powdered Infant Formulas

Scientific studies on the presence of harmful bacteria in unopened packages of powdered infant formula (PIF) have conclusively shown that powdered infant formula is not a sterile product. Potentially lethal bacteria such as Enterobacter sakazakii (recently renamed Cronobacter) and Salmonella species may be found at low levels in some packages. These bacteria can multiply to dangerous levels once the powder is mixed with warm water to make the feed. 

The World Health Organization and the Food and Agriculture Organization have therefore issued the warning that: "Powdered infant formula is not sterile. It may contain bacteria that can cause serious illness in infants. Correct preparation and handling reduces the risk of illness". This alert is fully explained in their Guidelines on the preparation, storage and handling of powdered infant formula to reduce the risks of infection caused by bacterial contaminants in formula feeding:

The US Food and Drug Administration mandates monitoring for Enterobacter and Salmonella species. However, new research published in January 2010 in the Journal of Pediatrics suggests that these may not be the only bacteria of concern in PIF. After an infant in the UK developed infant botulism caused by infant formula that was contaminated by Clostridium botulinum, researchers in California conducted a two-year series of tests for bacterial contamination of powdered formulas manufactured in the USA.

In the March 2010 issue of the Journal of Pediatrics, the authors of the study on the Presence of Soil-Dwelling Clostridia in Commercial Powdered Infant Formulas explain their procedures for testing the formulas: The Journal of Pediatrics - Volume 156, Issue 3, March 2010, Pages 402-408)

This is the first study of the potential for contamination of powdered infant formula by species of Clostridium. It is important to note that various Clostridia species such as Clostridium difficile have been found in liquid infant formula. 

Clostridium botulinum is one of the spore-producing bacteria in the genus Clostridium and produces the protein toxin botulism, one of the most potent poisons known. Clostridia can multiply in the infant's gut and cause infant botulism, the intestinal toxemia form of botulism: the toxins are absorbed and cause neuromuscular blockade. Honey has been identified as one source of infant botulism and is no longer given to babies under one year of age.

However, although the researchers reported that none of the formula samples tested showed the presence of spores of Clostridium botulinum, 78% of samples of market-purchased formula contained several other species in the genus, notably Clostridium sporogenes and Clostridium butyricum. These close bacterial relatives to Clostridium botulinum are commonly foundin soil and marine sediments and in human and animal excreta, and thus have similar environmental distribution to Clostridium botulinum.

The question can thus be asked whether there is indeed some cause for concern, given that such a wide variety of these species of bacteria can occur in such quantities in cans of PIF with intact factory seals.  Would Clostridium botulinum also be isolated if a larger sample size of cans was examined?

This study was small and concerned only 19 California infants with botulism.  However, the scientists found that five out of thirty samples of the powdered formulas ingested by these infants contained spores of Clostridium (clostridial spores), while seven out of nine samples of unopened packages of formula purchased on the market contained these spores.

The researchers concluded "Neurotoxic clostridial spores have the potential to be present in these products" but that "our finding of soil-dwelling clostridial spores in commercial PIF does not constitute a public health threat". However, given the potential risk to infant health, they recommend "A more extensive study might provide an additional perspective on whether there exists a possible public health hazard from the potentially pathogenic clostridial spores that may be present in commercial formula in the United States".

As the authors of the study state "It has been determined that PIF is not a sterile product and that making it sterile is not feasible". What is of further concern to parents is that the contaminated infant formula products found in the study were manufactured and used in the USA, where conditions of storage and use of powdered infant formula may be of a high standard.  And in those countries where the standard is not so high, and conditions are challenging, there are also no facilities for testing and identifying strains of bacteria that may cause severe illness. So there are at the present time no studies and no data available from these countries.