'Superbug' breast infections controllable in nursing mothers, researchers find

August 31, 2008

Many nursing mothers who have been hospitalized for breast abscesses are afflicted with the "superbug" methicillin-resistant Staphylococcus aureus, or MRSA, but according to new research by UT Southwestern Medical Center physicians, conservative treatment can deal with the problem.

The study focused on hospitalized women with mastitis, and showed that MRSA was much more likely to be found in those who had both mastitis (an inflammation of the milk glands) and abscesses (pockets of infection).

"The take-home message is that a patient with mastitis does not necessarily need an antibiotic against MRSA," said Dr. George Wendel, professor of obstetrics and gynecology and senior author of the study, which appears in the September issue of the journal Obstetrics and Gynecology. "She will improve with a less specific antibiotic as long as she also empties her breasts, either through feeding or pumping, and if there's an abscess, gets it treated."

The study also showed that if a nursing mother has an abscess, she does not immediately need antibiotics against MRSA, but can be switched to them if tests reveal she has MRSA.

The study was designed to determine which antibiotic treatment is best for severe cases of mastitis, which can be caused by clogged milk ducts with or without infection, and breast abscesses, which are caused by bacterial infections, generally by aureus. There are many strains of staph, one of which is MRSA.

Treating mastitis or breast abscesses immediately with powerful drugs that fight MRSA carries a risk of creating even more antibiotic-resistant strains of staph, Dr. Wendel said.

"The physician can take the time to test the patient to determine what kind of bacteria she has," Dr. Wendel said. "We found that you're not going to put the patient at a disadvantage if you start her on antibiotics while you wait for culture results, then switch her to more powerful medication if she has MRSA."

The study involved 136,459 women who delivered at Parkland Memorial Hospital between 1997 and 2005. Of those, 127 were hospitalized with mastitis, which tends to strike younger women having their first child.

The researchers found that about 59 percent of the women with both mastitis and abscesses had MRSA, while only 2 percent of women with mastitis alone had MRSA. Because the study tracked women who had been hospitalized, there is no way to know whether this proportion is the same in women treated for mastitis on an outpatient basis, Dr. Wendel said.

MRSA is resistant to many antibiotics, but the researchers found that even in cases when the exact cause of the mastitis or abscess had not yet been determined, and the women initially received antibiotics that don't affect MRSA, all eventually recovered completely.

During the study, when tests showed that a woman had MRSA, she was switched to vancomycin, an antibiotic effective against it.

About 2 percent to 10 percent of all nursing mothers develop some sort of breast inflammation such as mastitis, the researchers said. Symptoms of mastitis include unexplained fever and deep soreness or swelling in one breast but not the other.

In contrast to mastitis, an abscess is caused by a localized infection, which causes pain in a specific area that can feel hot to the touch and appear red on the skin.

"Women should seek medical care if they have any symptoms or concerns for breast infections," said Dr. Irene Stafford, resident in obstetrics and gynecology and lead author of the study.

Source: UT Southwestern Medical Center