Serious Bacterial Infection Rare in Neonatal Mastitis

By Lisa Rapaport

July 15, 2021

(Reuters Health) - Few infants with neonatal mastitis develop bacterial infections or experience adverse events, according to a new study that suggests routine testing for bacterial infections may not be needed in many afebrile well-appearing babies.

To assess the prevalence, clinical presentation and outcomes of neonatal mastitis, researchers examined data on 657 infants (median age 21 days) with mastitis who were treated at one of 28 emergency departments in the U.S., Canada, and Spain between 2008 and 2017.

Overall, 641 (98%) of the infants appeared well, while 138 (21%) had a history of fever at home or in the emergency department and 63 (10%) were fussy or feeding poorly.

Doctors obtained blood cultures from 581 infants (88%), urine cultures from 274 (42%), and cerebrospinal fluid cultures from 216 (33%). Pathogens were rare in blood (0.3%), urine (1.1%), and cerebrospinal fluid (0.4%), the study found.

"Most infants with mastitis probably do not require testing for concurrent bacterial infections in the blood, urine or cerebrospinal fluid as long as they do not have fevers and they are otherwise well," said lead study author Dr. Ron Kaplan, an associate professor of pediatrics in the division of emergency medicine at the University of Washington School of Medicine and Seattle Children's Hospital.

Most infants with neonatal mastitis appear to have relatively localized, noninvasive soft tissue infection, and most didn't have signs of fever or systemic illness, Dr. Kaplan said by email.

"Febrile infants should continue to have testing done based on standard recommendations depending on age," Dr. Kaplan said.

In cultures from infection sites of 335 (51%) infants, researchers found pathogens in 77% of cases. The most common pathogens were methicillin-resistant Staphylococcus aureus (54%) and methicillin-susceptible S. aureus (29%).

A total of 591 infants (90%) were admitted to the hospital, including 22 (3.7%) who were admitted to the intensive care unit.

Serious adverse events included 10 (1.5%) infants with sepsis or shock and two infants (0.3%) with severe cellulitis or necrotizing soft tissue infection. No infants died or required vasopressors or endotracheal intubation.

One limitation of the study is that the data came primarily from children's hospitals or facilities with dedicated pediatric emergency department, and it's possible the results may not be generalizable to other settings, the study team notes in Pediatrics.

Even so, the results underscore that mastitis is rare in babies and typically local rather than systemic, said Dr. Howard Faden, a professor of pediatrics and infectious disease at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo in New York.

And when mastitis does happen, it may be seen more in newborns, Dr. Faden, who wasn't involved in the study, said by email.

"Serious bacterial infections occur in infants with mastitis if the infant is within the first month of life," Dr. Faden said.

SOURCE: Pediatrics, online June 29, 2021.