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Release: July 3, 2001

UI project surveys rates of antibiotic resistance in Iowa

IOWA CITY, Iowa -- Recent media coverage has highlighted the dangers posed by rising rates of antibiotic resistance in bacteria that cause human illness. A long-term study based at the University of Iowa is providing important information about the scale and nature of this problem in Iowa. The results of this unique statewide surveillance project may help the health care community come to grips with this difficult health issue.

The Emerging Infections and the Epidemiology of Iowa Organisms (EIEIO): A Prospective, Statewide, Longitudinal Surveillance Study of Antimicrobial Resistance is the only statewide, systematic surveillance program in the nation that tracks emerging antibiotic resistance. The EIEIO project was started in July 1998 by UI researchers in collaboration with 15 Iowa hospitals. The surveillance system covers 71 percent of all in-patient hospital beds in the state.

"Despite some cost to these institutions in terms of time and effort, we have had three years of continuous, high-level commitment to this study," said Gary V. Doern, Ph.D., UI professor of pathology and director of the study. "A tremendous spirit of cooperation that is typical of Iowa has driven the success of this project."

When a patient with an infection is seen at one of the participating hospitals, a sample is taken and analyzed to identify the infection-causing bacteria. The sample is then sent to the UI where it is tested to determine the bacteria's spectrum of antibiotic resistance.

The study has examined the resistance patterns of two groups of bacteria: those commonly associated with hospital infections and those that are primarily the causes of community-acquired infections.

"The most striking findings from this study are that resistance rates of bacteria associated with hospital-based infections in the state of Iowa are consistently and substantially lower than national rates," Doern said. "For example, nationally in 71 percent of bloodstream infections caused by Staphylococcus aureus (S. aureus), the bacteria are resistant to oxacillin, an antibiotic considered a first line of defense. In Iowa that number is 42 percent."

On the downside, rates of resistance for two pathogens that cause respiratory tract infections in the community are higher in Iowa than in the rest of the nation. The more important pathogen, S. pneumoniae, was found to be resistant to penicillin in about a half of all infections in Iowa, compared to about one third in the rest of the country.

"The implication for Iowa is that we are not doing as well as the rest of the country when it comes to controlling antibiotic resistance in bacteria that cause community-acquired infections," Doern said.

According to Doern, the first goal of the EIEIO project was to assess the scope and size of the antibiotic-resistance problem in Iowa. Step two, which is the stage the researchers have reached, is to make sense of the data and try to explain differences in resistance rates. The third step will be to use the information to devise and implement ways to combat this problem. Finally, these approaches will be evaluated to see which ones are successful in curbing and hopefully reversing the trend of rising rates of resistance.

Numerous studies have shown that the single most important factor in both the emergence of antibiotic resistance and the evolution of even higher rates of resistance over time is increased antibiotic usage. Specifically, antibiotic overuse causes bacteria to develop antibiotic resistance. Conversely, Doern explained that a decrease in usage would restore a more normal balance between resistance and non-resistance bacteria, thus reducing rates of resistance.

"The machinery the bugs need in order to be resistant is essentially excess cellular baggage. Resistance is only an evolutionary advantage when the bacteria are under attack from antibiotics," said Doern. "If there is no antibiotic pressure, the nonresistant bacteria will be able to beat out their overloaded cousins."

Doern believes that education is a key to reducing overuse and inappropriate use of antibiotics and that physicians, the public and managed care organizations would all benefit from a better understanding of how antibiotic resistance occurs and how it can be prevented.

In the future, Doern hopes that it will be possible to develop a fast, accurate and simple diagnostic test that will take the guesswork out of diagnosing causes of infection and allow physicians to prescribe antibiotics only when the patient has a treatable bacterial infection. This strategy would reduce inappropriate antibiotic use but these tests may not be available for years.

Current strategies, which are proving effective in curbing the rise of antibiotic resistance, include infection control, whereby the spread of resistant strains of bacteria between people is prevented. It is likely that good infection control practices play an important role in Iowa's success in restraining the rates of antibiotic resistance in hospital-associated bacteria. Another strategy used to defeat antibiotic resistance is prevention of infection. A vaccine designed to prevent infection specifically by antibiotic-resistant bacteria has recently been developed and approved for use in children. So far it has proved to be highly effective.

The final approach that Doern strongly advocates is that it may be time to change the paradigm of only prescribing the least potent antibiotics and leaving the most powerful drugs in reserve.

"That approach was reasonable before antibiotic resistance became such a problem," Doern said. "We no longer have the luxury of using older, cheaper and invariable less potent drugs. Now that antibiotic resistance is so prevalent, I think we should consider using more potent drugs as a first line of defense, not only to provide an effective cure, but also to prevent further emergence of resistance."

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