For many weeks my nine-year-old niece has had recurring sores, like infected pimples or boils, show up in many different places on her body. She was diagnosed by a specialist this week with MRSA staph infection in the lining of her nostrils, occasionally being spread to the skin. Her family doctor prescribed a cream to help control the irritation, nothing more. My initial research on the Internet concerns me. I'm wondering if more should be done. Should her parents ask their doctor about vancomycin treatment?

M.

This is an excellent example of the aphorism "a little knowledge is a dangerous thing." Mind you, I'm not putting you down for searching the Internet or asking the question you have asked. You're doing the right thing. However, this is becoming an increasingly common situation: A concerned patient/parent/relative/friend searches the net and pulls up a bit of treatment information that he or she then brings to the doctor. That's not the problem. The problem is that there are more than a few below-average doctors out there who might act on this information. In the example you have provided, acting on the information might be the equivalent of killing a mosquito with a submachine gun.

In answering your question, I am going to assume that the specialist (1) made the correct diagnosis and (2) instructed the family doctor to initiate appropriate treatment. These are hefty assumptions, of course. If this girl's parents have any doubts about these two assumptions, they should seek a second opinion.

Let's first discuss the diagnosis. MRSA stands for methicillin-resistant Staphylococcus aureus. This is a bacterial species (Staphylococcus aureus, or staph, to use a common abbreviation) that has acquired a resistance to most of the drugs that used to kill it. MRSA is potentially deadly. If it is not recognized, a patient could be treated with antibiotics that have no effectiveness, and her infection could develop lethal momentum.

Vancomycin (Vancocin) is one of the very few antibiotics that can kill MRSA. Until this was realized, many unfortunate patients died from MRSA. Why, then, is vancomycin not necessary for your niece?

To answer this, I need to distinguish between invasive infection and colonization. Invasive infection destroys tissue. "Colonization," on the other hand, is a situation in which the infectious agent (MRSA, in this case) lives in a partial state of truce with its host. (Your niece is the host.) Host defenses (the skin, mucous membranes and the immune system) keep the infectious agent at bay, preventing outright invasive infection.

In your niece's case, MRSA is colonizing her nostrils, and she is inadvertently transferring this bacteria to her skin, probably with her fingertips or fingernails. Once there, the bacteria occasionally mount an infection that could best be described as "minimally invasive," since these sores remain confined to one location and do not spread further. Skin infection with Staphylococcus is more commonly known as impetigo, by the way.

If your niece had a weakened immune system -- if she had AIDS or leukemia, for example -- then she would not be able to defend herself against MRSA, and the bacteria could rapidly mount a devastating infection. In such a case, treatment with vancomycin would be necessary and lifesaving. Please bear in mind that until she is effectively treated for this problem, she can infect other individuals with MRSA. She should not be allowed to visit a hospital, and if she has any friends or relatives with weakened immune systems, she must avoid contact with them. This includes infants and elderly people.

Your niece's primary problem is the fact that her nostrils are colonized with MRSA, leading to recurrent skin infections. If the source of the disease is eradicated, she should stop having these skin infections. The appropriate treatment for MRSA colonization of the nostrils is topical application of an antibiotic called mupirocin (Bactroban). After taking a full course of mupirocin, her doctor should culture her nostrils once again to confirm that the MRSA is gone. Once this is done, her parents should ask their doctor whether it is now safe for her to be near people with weakened immune systems.