Quickly Matching The Drug With The Bug Saves Lives

June 9, 2005

GAINESVILLE, Fla. — University of Florida researchers are resurrecting an old technology to more quickly and accurately identify potentially deadly bacterial infections in hospital patients.

Speed in identifying these bugs is crucial because bacteria such as E. coli can enter a patient’s bloodstream and almost immediately become life-threatening, said Dr. Ken Rand, the director of clinical pathology at UF’s College of Medicine. He presented his research findings today at the 105th annual American Society for Microbiology general meeting in Atlanta.

“The system we use can cut the time it takes to get a patient on the right antibiotic by 24 to 48 hours,” said Rand, who is also the director of the clinical microbiology laboratory at Shands at UF medical center. “This can save lives and we would like to see it used in every hospital across the country.”

Hospitals currently use a test that requires doctors to guess which antibiotic to use while they await the results of a blood draw and culture.

When doctors make an incorrect guess, patients may be prescribed antibiotics that do not fight the infection because the bacteria are resistant to them, which is like getting no antibiotics at all, Rand said.

To identify a bacterial type under current standard practice, it takes 18 to 24 hours before preliminary results come in and another 24 to 36 hours before the correct antibiotics can be identified. Rand’s work shows that preliminary results gathered between 8 and 18 hours using the 30-year-old manual procedure known as the direct susceptibility method correlate well with final results that otherwise come days later.

If those highly accurate preliminary results are used to check a physician’s initial guess, potential mistakes can be caught earlier and a patient’s treatment can be corrected, he said.

“Not all antibiotics work for all bacteria. Unfortunately, there is no ‘gorilla-micin’ that can be used to attack any bug in the body,” Rand said. “The best we can do is get the right drug to the patient as quickly as possible.”

Looking at past studies, Rand found the mortality rate among patients hospitalized with a gram negative bloodstream infection was about 30 percent to 40 percent when there was a delay in giving the right antibiotic. Among patients who were treated with the right antibiotic from the beginning, the mortality rate fell to 20 percent.

Of the 34 patients Rand evaluated in a new UF study of the direct susceptibility method, 19 had bacterial infections that initially tested completely resistant to the type of antibiotic they were taking. When the final results came in, 17 of those 19 patients — half the cases studied — were confirmed to be infected with bacteria resistant to the prescribed drug.

Working with hospital pharmacists, Rand has developed a system that relies on the preliminary results to get infected patients on the right antibiotics within 18 hours. He said his goal is to cut that time to eight hours.

“In the first nine months of doing this, our mortality rate is just around 20 percent,” Rand said. “So we think we are making a difference, but we know that we have to compare our (study) patients to our own (hospital) patients, not just to what is in the literature. But based on that, right now it looks like we are doing a good job.”

Dr. Gregory Storch, director of the Microbiology Laboratory at the St. Louis Children’s Hospital and a professor of pediatrics, medicine and molecular microbiology in the division of pediatric infectious disease at the Washington University School of Medicine, said the study results are exciting and many U.S. hospitals could immediately adopt the practice.

“In this era of elaborate and very expensive high-tech approaches, it is very nice to see an innovative use of existing technology that has the potential to improve patient outcomes,” Storch said. “Another important component of this work is the close coordination of the microbiology laboratory and the pharmacy, which will help ensure that results generated in the laboratory are acted on without delay. This work may have immediate applicability in many U.S. hospitals.”