Cepheid Inc.'s test that can detect drug-resistant staph infections within an hour won clearance for U.S. sale, the company said today.

The test will help doctors determine the correct course of treatment for skin infections more quickly than standard methods that take as long as three days to confirm drug resistance, Sunnyvale, California-based Cepheid said in a statement announcing Food and Drug Administration approval.

About 12 million patients visit doctors and hospitals annually for skin and soft tissue infections, said John Bishop, Cepheid's chief executive officer, in the statement.

The most frequent cause of skin infections in hospital emergency rooms is MRSA, or methicillin-resistant staphylococcus aureus, which can be life-threatening, scientists said in a 2006 report.

"Our clinical trial data show that this new laboratory test makes it possible to accurately detect a staph infection before a patient is released, and it provides information to support treatment choices," said Donna Wolk, chief of clinical microbiology, at the University of Arizona College of Medicine in Phoenix, in the statement.

Cepheid fell $1.30, or 8.9 percent, to $13.30 at 4 p.m. New York time in Nasdaq Stock Market composite trading and has lost 42 percent in the past 12 months.