WASHINGTON – Community-acquired methicillin-resistant Staphylococcus aureus should be considered in the differential diagnosis of skin and soft tissue infections, as well as neonatal eye infections, Dr. Morven Edwards said at a practical pediatrics meeting sponsored by the American Academy of Pediatrics.
Dr. Edwards, an infectious disease specialist at Texas Children’s Hospital, Houston, said that unlike a decade ago, she now considers community-acquired MRSA as a possible cause "in almost any manifestation of a problem with the skin or soft tissue, even including those entities that we used to think were caused by other microorganisms."
For example, in the past, perianal dermatitis in a young infant "was essentially a pathognomonic presentation for group A strep infection," which did not even require a culture for an accurate diagnosis and appropriate treatment, said Dr. Edwards, who is a professor of pediatrics at Baylor College of Medicine, Houston.
She referred to a small retrospective study of children between the ages of 5 months and 12 years with perianal erythema, which found that the dominant culture results were MRSA and methicillin-sensitive S. aureus (MSSA), some streptococci, and some mixed infections. In the past, staphylococcal skin and soft tissue infections were considered uncommon among healthy term newborns discharged home, "unless it was just a very mild diaper dermatitis," she noted.
In a 2006 study of healthy term babies who returned to the hospital within a month of discharge to Texas Children’s Hospital’s emergency department, cases of MRSA peaked at 8-12 days after discharge. Almost all were skin and soft tissue infections (SSTIs), and some of the babies had mild, pustular skin disease and were treated as outpatients with topical therapy and/or oral antistaphylococcal medications. But almost 40% required admission for incision and drainage and parenteral antibiotic therapy.
Dr. Edwards referred to a case of an SSTI that started with a stubbed toe and progressed to a disseminated staphylococcal infection and endocarditis – illustrating that "even with an apparently limited minor staph infection, it always should go through our minds that this could be one that’s more serious."
The healthy teenage boy had stubbed his toe during a wrestling match, then developed fever, fatigue, and buttock and back pain, along with swelling and pain in the toe 4 days later. A fracture was diagnosed at an urgent care clinic, and he was sent home, but 9 days after the initial injury, symptoms persisted and he was admitted to the hospital for treatment with broad-spectrum antimicrobials, including clindamycin.
On the fourth day in the hospital, he had a fever of 104° F, "massive" facial swelling, bibasilar crackles, a systolic murmur, left lower quadrant pain, and a large parietal abscess seen on MRI. He had vegetations on the anterior leaflet of the mitral valve and multiple microemboli to the brain. The abscess was drained, and he had a vegetectomy, where vegetation was "peeled" off the leaflet, leaving the valve intact. After 6 weeks of intravenous antimicrobial treatment, he did well and was discharged.
"The lesson is that a seemingly innocuous SSTI always has the potential to disseminate," Dr. Edwards said, adding that while this is very uncommon, especially in a healthy child, "it’s always something to keep in mind."
Transmitted by direct contact, risk factors for community-acquired MRSA include chronic skin conditions, participation in sports teams that involve close contact with other players, and a history of such infections in family members, she noted.
In infants, MRSA infection also should be included in the differential diagnosis of ophthalmia neonatorum, Dr. Edwards said. She described the case of a healthy term 4-day-old baby who presented with eye swelling and purulent discharge, but no other systemic findings. The mother’s pregnancy had been uncomplicated; maternal tests were negative for group B streptococcus, chlamydia, and Neisseria gonorrhoea; and the baby had been discharged home by the second day after a normal vaginal birth.
The cause turned out to be community-acquired MRSA infection. "We need to consider this diagnosis with a higher index of suspicion in young infants now," she said, noting that the peak onset is at age 4-6 days, and it is characterized by a purulent discharge not likely to be a gonococcal infection. The baby was admitted to the hospital and treated with parenteral antimicrobial therapy.
Dr. Edwards disclosed that she is a consultant for and has received research funds from Novartis related to the development of a group B streptococcus vaccine.