Bacterial update

December 1, 2005

Philadelphia - The emergence of methicillin-resistant staphylococcus aureus (MRSA) and new approaches to treatment of various bacterial illnesses are capturing the interests of dermatologists.

It used to be a big event when staff cultured MRSA in the hospital because it meant that those infected were capable of spreading this difficult-to-treat bug around to other debilitated people.

"But, in the past, MRSA never meant much to dermatologists. While the bug was resistant, it was not particularly nasty," says Guy F. Webster, M.D., Ph.D., clinical professor, Jefferson Medical College, Philadelphia.

Dr. Webster has seen several patients, each who had giant ulcers, with what looked like an autoimmune process known as pyoderma gangrenosum, but turned out to be due to staph. Antibiotics would clear up these bacterial infections.

"In the days past, we would typically use cephalosporin to treat staph, but many MRSAs are resistant to cephalosporin; so, now we tend to use doxycycline or ciprofloxacin or sulfamethoxazole with trimethoprim," he says.

Researchers do not know the cause of this super MRSA, and the concern is that overuse of antibiotics on the part of everybody, including dermatologists, is making MRSA more likely to proliferate, Dr. Webster says.

Other bugs

Folliculitis is an ongoing problem, especially among atopic patients, according to Dr. Webster.

Connetics Corporation markets a foam erythromycin, which is approved for treatment of acne. Dr. Webster says that it is a convenient, off-label way to treat large areas of folliculitis. He prescribes it for superficial folliculitis, which is not MRSA. For deeper folliculitis, he prescribes an oral antibiotic.

Dermatologists diagnose impetigo clinically. They treat what they see and then do cultures to confirm that they have diagnosed the right bug, according to Dr. Webster.

"You can usually tell strep from staph because strep has a more golden, honey-looking crust and staph is scabbier," he tells Dermatology Times.

Dermatologists might, in rare cases, recommend that patients treat mild impetigo with soap and water, but that is tiptoeing around the edge of undertreatment, according to Dr. Webster.

"Most of us use at least a topical antibiotic and, probably, an oral," he elaborates.

Non-dermatologists have been known to misdiagnose skin redness as erysipelas - a rare, superficial strep infection. They frequently confuse stasis dermatitis - the result of bad venous circulation with leg swelling and erythema - with cellulitis and erysipelas. The problem is compounded by the fact that cultures of erysipelas are usually negative, even when it clearly is a strep infection, according to Dr. Webster.

"So, it ends up being a diagnosis that you treat on suspicion," he says.

More than they did in the past, dermatologists appreciate that the major predisposition of erysipelas and cellulitis is chronic edema. People with conditions that give them a lot of edema - whether it is a post mastectomy arm, a post blood clot leg or just poor vein quality - have a much higher risk of cellulitis, which is usually a strep infection, he says.

Dermatologists are most likely to see the rare condition necrotizing fasciitis (known as flesh eating bacteria in the media) in people who are debilitated - typically diabetics or people who have had a crush injury. It is important to diagnose this mixed infection, which includes strep, early; otherwise it can be deadly. It is treated surgically and with intravenous antibiotics.

Being able to diagnose the bacterial illness early on can take some intuition, Dr. Webster says.