Transmission of methicillin-resistant Staphylococcus aureus to preterm infants through breast milk.
OBJECTIVE
To determine a potential source of MRSA colonization and infection among preterm infants in a neonatal intensive care unit (NICU) using molecular analysis of breast milk samples.


METHODS
Case report, outbreak investigation.


RESULTS
Preterm triplets were delivered at 26 weeks' gestation via cesarean section when routine active surveillance for MRSA was performed for all infants in a NICU. Surveillance consisted of swabbing the throat, nose, and umbilicus (TNU) weekly. Although infants A and B initially had negative TNU swabs, repeat cultures were positive for MRSA on day of life (DOL) 10 and DOL 18, respectively. Surveillance and clinical cultures for infant C were negative. Infant A developed sepsis, and multiple blood cultures were positive for MRSA beginning on DOL 14. Infant B developed conjunctivitis and a conjunctival exudate culture was positive for MRSA on DOL 70. Both infants were fed breast milk via nasogastric tube. Cultures of breast milk samples for infants A and B dated prior to either infant's first positive surveillance culture were positive for MRSA. All MRSA isolates had identical results on antibiotic susceptibility testing. PFGE demonstrated identical banding patterns for the MRSA isolates from the blood culture of infant A, breast milk for infants A and B, and a surveillance swab from infant B. At no time did the mother develop evidence of mastitis or other local breast infection.


CONCLUSIONS
MRSA can be passed from mother to preterm infant through contaminated breast milk, even in the absence of maternal infection. Colonization and clinical disease can result.
Section of Pediatric Infectious Diseases, University of Chicago, 5841 S. Maryland Avenue MC 5065, Chicago, IL 60637-1463, USA.
Priya
P
Behari
Janet
J
Englund
Grace
G
Alcasid
Sylvia
S
Garcia-Houchins
Stephen G
SG
Weber
D002641:Chicago / Q000453:epidemiology; D004269:DNA, Bacterial / Q000032:analysis; D004196:Disease Outbreaks / Q000517:prevention & control; D004200:Diseases in Twins; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007363:Intensive Care Units, Neonatal / Q000706:statistics & numerical data; D016106:Methicillin Resistance; D008895:Milk, Human / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission*; D014310:Triplets
D004269:DNA, Bacterial