A new antibiotic may treat skin infections as well as an older pill, a new study finds. The new drug, tedizolid, also did well against drug-resistant infections. It required fewer pills than the older drug as well. The new study included 667 adults. All had cellulitis or other wound infections. People were randomly divided into 2 groups. One group received tedizolid once a day for 6 days. The other got a standard antibiotic, linezolid, twice a day for 10 days. The two drugs worked equally well. Side effects were similar in both groups. New antibiotics are needed because so many types of bacteria now resist older ones. In this study, about one-quarter of the infections were caused by methicillin-resistant Staphylococcus aureus (MRSA). These bacteria are difficult to kill. Linezolid is one of the few antibiotics that works. Tedizolid did as well as linezolid against MRSA infections in this study. Trius Therapeutics Inc. makes the drug. It is not yet approved by the U.S. Food and Drug Administration. The Journal of the American Medical Association published the study. HealthDay News wrote about it February 12.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

We will always need new antibiotics because bacteria can be just one step away from getting the upper hand over our current drugs.

Some strains of bacteria are especially good at changing their structure to make them resistant to antibiotics that killed them in the past. Staph bacteria are a prime example.

Staph is the short name for Staphylococcus aureus. It's a common kind of bacteria that many people carry on their bodies. If it gets under the skin and enters the blood stream, it can be deadly.

When antibiotics were first invented, penicillin could kill this germ. But then it developed resistance to penicillin. That means penicillin could no longer kill it. A newer antibiotic called methicillin was developed that could kill it. But the bacteria developed resistance to methicillin, too.

This newer, resistant strain is called methicillin-resistant Staphylococcus aureus, or MRSA. There are a limited number of antibiotics that reliably kill MRSA. Some can be given only in a vein (by IV). But not everyone with a MRSA infection needs an IV drug.

Most skin-related infections can be treated with a pill. If an infection is likely to be caused by MRSA, doctors often prescribe linezolid. But we won't always be able to rely on linezolid. Already there is some suggestion of MRSA resistance to this drug.

Now researchers are reporting results of a study on a cousin of linezolid. It's called tedizolid. Study results appear in today's issue of the Journal of the American Medical Association.

Some people in the study were diagnosed with a skin-related infection called cellulitis. Others had a skin abscess or an infected wound. All of them required treatment with an antibiotic that could kill MRSA.

Half of the people in the study were treated with linezolid. The other half received tedizolid. Both drugs were given by mouth. The two antibiotics proved to be equally effective in treating complicated skin-related infections.

Tedizolid is a bit easier to take than linezolid. It only needs to be taken once a day. Linezolid must be taken twice a day. Only 6 days of treatment with tedizolid works as well as 10 days of linezolid.

Besides the concern about MRSA becoming resistant to linezolid, it has some other disadvantages. It causes a drop in the platelet count about 5% of the time. Platelets are necessary for normal blood clotting. Linezolid can cause agitation and confusion in people who take some types of antidepressants. Tedizolid appears to have fewer side effects.

It's too early to say that tedizolid will be a better drug than linezolid. This is just one study. We don't know if or when tedizolid will be approved by the Food and Drug Administration (FDA).

What Changes Can I Make Now?

Strains of MRSA originally were found mainly in hospitals. During the last decade, however, strains of MRSA have increasingly been found in the community.

Many people carry MRSA on their skin and in their noses. Usually they don't know it. Most often, it sits there without making them sick.

MRSA is passed from one person to another by touch. If your hands touch an infected area on another person, the bacteria can be passed to you. A person just sitting close to you can't pass MRSA to you.

You can do some simple things to reduce your risk of getting or spreading MRSA. The most important thing you can do is to practice good hygiene.

• Wash your hands often with soap and water, or use an alcohol-based hand cleaner.
• Don't use anyone else's personal items, including towels and razors.
• Don't touch anyone's skin wound, bandages or Band-Aids.
• If you have a cut, scrape or wound, keep the area clean and covered with a bandage. It is much easier for bacteria to enter your body and cause an infection through such wounds.

What Can I Expect Looking to the Future?

If the FDA approves tedizolid, it will be the first approval in what has been called the 10 X 20 initiative. The Infectious Diseases Society of America has set a goal of having 10 new drugs to fight antibiotic-resistant bacteria by the year 2020. It will be quite an achievement if 9 more new drugs are approved within the next 7 years.