Breast milk has been identified as the source of the ‘superbug’ known as methicillin resistant Staphylococcus aureus (MRSA) In two outbreaks among newborns in Los Angeles.

Dr. Dawn M Terashita, of the LA County Health Department described the cases in Washington DC at a meeting of the American Society for Microbiology.

Infants in the neonatal intensive care unit are a “vulnerable population,” she told AMN Health.

MRSA outbreaks are common in newborn nurseries, and the main way the infection is spread is thought to be person-to-person via hand contact.

Earlier this year, Terashita and her colleagues investigated two separate MRSA situations in neonatal intensive care units in which they suspected transmission via breast milk.

One case involved a 35-year-old mother who delivered premature quadruplets. One day after delivery, she developed breast inflammation and was treated with an antibiotic. Her breast milk was collected and fed to all four newborns.

Sixteen days after birth, one of the quadruplets died of MRSA infection. The three siblings and the mother were all found to be harboring MRSA. Frozen breast milk samples obtained during the first week after delivery also contained MRSA.

Tests performed on 18 other infants in the unit turned up one additional case of MRSA - a boy who developed MRSA sepsis 8 days after birth. Breast milk from his mother was also MRSA positive.

The role of breast milk in the transmission of MRSA from mother to infant remains unclear, Terashita noted in comments to AMN Health.

Mothers of newborns should be checked for breast inflammation and skin lesions, she recommended. In the neonatal intensive care unit, the staff “should consider culturing breast milk and discarding if it is MRSA positive,” she added. “Lastly, good hand hygiene should always be reinforced to prevent spread to other infants.”