Risks of Bacterial Contamination of Infant Formula

Risks of Bacterial Contamination of Infant Formula: French Recommendations Differ from WHO Guidelines. What Are the Health Risks for Newborns?

Lactasource is a breastfeeding information resource, but we feel it is important today to address the topic of bacterial contamination of infant formula (powdered infant formula). Indeed, some breastfed infants may require supplementation with infant formula, or parents may choose a mixed feeding approach: breastfeeding alongside formula use. In light of recent events — including the recall of GUIGOZ Optipro Follow-On Formula (800g tins, lot 52820346AB, for infants from birth to 6 months) and the January 2026 recalls of Picot formulas by Lactalis — we provide a summary of WHO recommendations on the safe preparation of infant formula to minimise this risk.

Powdered infant formula, while sometimes a necessary alternative, is not a sterile product. It may contain bacteria that, if allowed to multiply, pose a risk to infants — particularly the most vulnerable. In the United States, infant formula shortages occurred in 2022 following the closure of a manufacturing plant after concerning illness cases in infants.

The aim is not to cause alarm, but to inform parents about safe preparation practices in order to minimise these risks.

Bacteria in Infant Formula

Cases of contamination of infant formula (powdered infant formula), while rare, occur regularly worldwide. These events ,as illustrated by previous recalls, including the recent case involving a batch of Guigoz formula contaminated with Bacillus cereus, or earlier contaminations by Cronobacter sakazakii in other brands and countries , highlight the critical importance of strict hygiene measures.

• Cronobacter sakazakii: This is the most concerning bacterium in powdered infant formula. It is present in the manufacturing environment. In newborns (particularly preterm infants and those under two months of age) it can cause serious invasive infections such as meningitis or septicaemia.

• Bacillus cereus: Implicated in recent recalls (such as the Guigoz Optipro Follow-On Formula 0–6 months batch), this bacterium causes digestive disturbances, including diarrhoea and vomiting, which can be severe in an infant.

• Salmonella: Another bacterium responsible for significant recalls in the past (notably in the United States). It causes salmonellosis, a serious gastrointestinal infection in infants.

In recent recalls, it is the emetic toxin of B. cereus : cereulide, that is responsible.

These bacteria multiply very rapidly when formula is reconstituted and left at room temperature.

What to Do: French Recommendations vs. WHO (World Health Organization) Guidelines for Formula Preparation

French Recommendations for Infant Formula Preparation

In France, guidelines for bottle preparation are available on the Ameli website and on the 1000 Premiers Jours ("First 1000 Days") website, which states: "Good hygiene is necessary when handling powders, preparing and storing bottles. Sterilisation of bottles and teats is not required: thorough cleaning immediately after each feed is sufficient. Rinse and allow to air-dry. Bottles may be served at room temperature."

Tap water or bottled water may be used without heating.

WHO Recommendations for Infant Formula Preparation

The WHO has published specific guidelines on the preparation, storage, and handling of powdered infant formula to eliminate potentially present bacteria. These recommendations are particularly important for the most vulnerable infants. They are also in effect in the United Kingdom, where the NHS website presents updated 2023 guidance. These recommendations are not limited to developing countries; they apply equally to countries where water is considered safe.

The CDC in the United States has similar recommendations for at-risk infants (born preterm before 37 weeks of gestation or with a compromised immune system), and during the first two months of life.

Step 1: Prepare in a Clean Environment

• Wash your hands thoroughly with soap and water before handling, and dry with a clean towel or disposable paper.

• Clean and disinfect the work surface.

• Clean all equipment: Wash the bottle, teat, ring, and cap with hot soapy water (washing-up liquid) using a bottle brush. Rinse thoroughly with clean water. Leave to air-dry upside down on a clean drying rack. The 2013 guidance recommends sterilising equipment; however, routine sterilisation is generally no longer recommended after 4 months — thorough cleaning is sufficient.

  
  

Step 2: Use Water Above 70°C to Kill Bacteria

This is the most critical step for decontamination. Heat destroys potential bacteria present in the powder.

1. Boil the water (tap water, if suitable and compliant, or low-mineral bottled water suitable for infants) for one minute. Water boils at 100°C; allow it to cool to 70°C before pouring into the bottle.

2. Allow the water to cool in the kettle or saucepan until it reaches at least 70°C. The WHO and NHS state: "To achieve this temperature, do not leave water to stand for more than 30 minutes after boiling." The CDC recommends transferring the water to the bottle after a maximum of 5 minutes' wait to ensure the water remains very hot.

3. Pour the water into the bottle.

4. Add the powder using a correctly levelled scoop (follow the manufacturer's dosage instructions strictly).

5. Close and gently shake to dissolve the powder.

   
   

Step 3: Cooling and Feeding

1. Cool the bottle immediately: Hold the closed bottle under cold running water or place it in a container of cold water. Keep the water flowing until the formula is lukewarm (approximately body temperature, 37°C).

2. Check the temperature by dripping a few drops onto the inside of your wrist.

3. Feed immediately.

   
   

Essential Storage and Usage Rules

• Prepare fresh: Ideally, prepare the bottle just before the feed.

• Maximum storage time: If prepared using the 70°C water method and rapidly cooled:

• At room temperature (after cooling): maximum 1 hour.

• In the refrigerator at 4°C: maximum 24 hours (always label with the preparation time).

• Discard leftovers: Never reuse formula left after a feed. The infant's saliva contains bacteria that rapidly contaminate the remaining formula.

• Powder tin: Store the opened tin tightly closed in a cool, dry place. Never return the scoop to the powder to avoid introducing moisture or contaminants. Discard the tin 3 weeks after opening. If transferring to smaller containers, ensure they are thoroughly clean and disinfected before each use.

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How Effective Are These Measures?

In an experimental study, Beary et al. demonstrated differences in temperature achieved depending on the type of heating vessel and method used (saucepan with or without a lid after boiling, left on the heat source or not; kettle with or without a lid), as well as the impact of transfer to the bottle and the bottle material (glass or plastic).

The authors highlighted heat losses: transferring water to the bottle significantly reduces temperature, particularly when using a glass bottle compared to plastic, or when the bottle is only half-filled (as contact with ambient air accelerates heat loss). Adding powder to the water also causes a temperature drop. Ultimately, in the experiments conducted, temperatures achieved following the CDC method (5 minutes' wait after boiling) ranged between 81.9°C and 58.9°C — the latter being insufficient to inactivate Cronobacter. The authors note that excessively high temperatures (>70°C) can also cause gelling of the formula and lump formation, within which bacteria may be protected from the heat.

Furthermore, in the recent cases of infant formula contamination with cereulide, these measures would be ineffective: the emetic toxin responsible for the intoxication is heat-resistant and can only be destroyed by treatment at 126°C for 90 minutes.

Formula Preparation Machines

The NHS website also addresses formula preparation machines and recommends following the manufacturer's instructions and using a thermometer to verify that the water reaches 70°C. However, the automated bottle-making machines sold in France on childcare websites — such as "Bib'expresso"-type devices — predominantly offer temperatures between 22 and 40°C and, depending on the model, cannot always be programmed to reach higher temperatures in line with WHO recommendations.

Conclusion

Recalls of infant formula batches due to infectious risk by health authorities are recurring events, often triggered after infants have already been affected. This situation highlights a potential gap in the safety chain and in information provided to families.

In a country where exclusive breastfeeding rates remain low, the majority of parents rely on infant formula. National guidelines on formula preparation have historically prioritised simplifying procedures ("making life easier for parents"), sometimes departing from more stringent international standards.

However, this prioritisation of convenience may come at the expense of child health — particularly for the most vulnerable infants (preterm, immunocompromised, or those under two months of age), for whom bacterial infections transmitted through powdered infant formula can have serious consequences.

We believe it is important that national health authorities review and update the official protocols for infant formula preparation.

BIBLIOGRAPHY

• French recommendations

• Infant formula leaflet 2013, accessed 12/12/2025

• 1000 Premiers Jours website, updated 19/09/2025, accessed 12/12/2025

• AMELI website, accessed 12/12/2025

• WHO Guidelines: Safe preparation, storage and handling of powdered infant formula: guidelines. 2012

• CDC: Preventing Cronobacter in Infants, 2025. Accessed 22/01/2026

• NHS 2023 Recommendations

• Baby Brezza machine description

• Maria Amalia Beary, Sarah E. Daly, Jakob Baker, Abigail B. Snyder, Assessing Hot Water Reconstitution Instructions and Labeling of Powdered Infant Formula to Ensure Cronobacter spp. Reduction, Journal of Food Protection, Volume 88, Issue 9, 2025, 100571, ISSN 0362-028X, https://doi.org/10.1016/j.jfp.2025.100571.

• ANSES / Biological hazard description sheet transmitted through food: Bacillus cereus. 2021