Cronobacter in Two Babies: One Traced to Powdered Formula, One to a Breast Pump

Summary

• Cronobacter sakazakii infections are rare but can cause severe illness and death in infants.
• Whole genome sequencing (WGS) linked one case in a full-term baby to an opened can of powdered infant formula, and an unrelated fatal case in a premature baby to contaminated breast pump equipment.
• Knowing how widespread Cronobacter is in the environment — and preparing and storing formula safely and carefully cleaning and sanitizing pump parts — could prevent devastating infections.

The germ

C. sakazakii is a gram-negative bacterium that can cause meningitis and sepsis — often fatal — in young infants. It is found everywhere in the environment, and survives unusually well in dry conditions. Most reported infant cases have been traced to contaminated powdered formula or to breast milk expressed with a contaminated pump. It has been found in opened formula, pump parts, kitchen sinks, pacifiers, bottles, utensils, vacuum cleaner bags and other foods — and, rarely, in unopened formula and formula factories. Formula scoops can pick it up on counters or in sinks and carry it back into the can.

Baby A: powdered formula (September 2021)

• A full-term boy (born at 40 weeks, 1 day) to a healthy mother after an uncomplicated pregnancy and vaginal birth.
• At 14 days old he had fever, irritability and excessive crying, plus thrush and diaper rash. He had been fed both expressed breast milk and powdered formula.
• C. sakazakii grew from his spinal fluid. After 21 days of IV antibiotics he recovered fully, with no apparent lasting harm.
• C. sakazakii was found in the family's opened powdered formula and in an opened bottled water container used to mix it. Sequencing found two distinct strains: the baby's matched one from the formula exactly (0 SNPs — single-letter genetic differences — apart); a second strain in the same can was closely related to one in the water container (within 4 SNPs). The two strains were unrelated (more than 50,000 SNPs apart).
• Unopened formula from the same lot, tested by federal partners, was negative.

Baby B: breast pump (February 2022)

• A premature boy (born at 30 weeks, 6 days by cesarean for breech position and his mother's worsening preeclampsia), stable in neonatal intensive care, fed expressed breast milk with liquid human milk fortifier, mostly through a tube from mouth to stomach.
• At 20 days old he had pauses in breathing, a slow heart rate and fever, needed breathing support, and seizures began the next day. C. sakazakii grew from his blood and spinal fluid. Despite IV antibiotics and later negative blood cultures, he died 13 days after falling ill.
• The germ was found on the breast pump parts used at home — not in the milk samples, the fortifier, the hospital pump or unopened hospital formula. The home parts had been washed in a household sink, sanitized, and sometimes assembled while still wet. The baby's isolates matched the home pump's (0–1 SNPs apart).

Genetic relationships among isolates from the two babies and their homes. Figure from the CDC report.

What it means

The two cases were unrelated. They show how common the germ is in the home, how much hygiene matters, and how sequencing can pin down a likely source far better than the older methods.

• Very young babies and those born premature are most at risk, perhaps because their immune and digestive systems are immature. Infections are treatable, but nearly 40% of babies with C. sakazakii meningitis die, and many survivors have brain abscesses or hydrocephalus and lasting neurological harm.
• The infection is not nationally notifiable, so its true frequency is unknown; about 18 invasive infant cases are estimated each year in the U.S., mostly isolated contaminations at home rather than outbreaks.
• Limits: the infection isn't reportable in most states; standard lab methods aren't yet routine; and no one visited the homes, so other sources may have been missed.

Protecting babies

• Caregivers: follow safe hygiene, preparation and storage for feeding products.
• Clinicians caring for babies under 2 months, premature, or with weakened immune systems should explain the risk — especially with powdered formula or expressed milk — including alternatives to powdered formula for the highest-risk babies and safe formula preparation and storage.
• Clean and sanitize pump parts thoroughly — see CDC's breast pump cleaning guidance.
• Hospitals caring for premature or critically ill babies might send families home with instructions and a dedicated basin for cleaning feeding supplies.

Sources

Based on Julia C. Haston, Shanna Miko, Jennifer R. Cope and others, "Cronobacter sakazakii Infections in Two Infants Linked to Powdered Infant Formula and Breast Pump Equipment — United States, 2021 and 2022," MMWR, Centers for Disease Control and Prevention (as corrected); a work of the United States government in the public domain.