WASHINGTON (Reuters) - A company that harnesses bacteria-killing viruses said on Saturday it has devised a test that can detect dangerous staph infections within hours.

This could allow doctors to begin treating patients right away with the correct drugs, instead of waiting the usual two to three days for a test that grows the germs in test tubes, the researchers said.

The test detects Staphylococcus aureus bacteria in blood within five hours, Longmont, Colorado-based MicroPhage Inc told a meeting of the American Society for Microbiology and the Infectious Diseases Society of America.

Older tests require a blood culture, in which labs try to grow bacteria in a dish. At least two other companies -- Cepheid and Becton, Dickinson and Co -- had fast tests approved by the U.S. Food and Drug Administration this year.

More than 94,000 life-threatening infections and nearly 19,000 deaths in the United States were caused by drug-resistant staph infections in 2005, according to the U.S. Centers for Disease Control and Prevention.

Bacteria undamaged by the antibiotic methicillin, called methicillin-resistant Staph aureus infections, or MRSA for short, accounted for 63 percent of new hospital-acquired infections in 2004.

“MRSA infections are best treated with broad-spectrum antibiotics, but infections by methicillin-susceptible strains are best treated with narrow-spectrum antibiotics,” MicroPhage said in a statement.

The MicroPhage test requires two test tubes. “One tube determines whether or not the sample contains S. aureus bacteria; the other determines whether the bacteria are antibiotic-resistant or susceptible,” the statement said.