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Release: Sept. 18, 2000

UI researcher presents progress report from antibiotic-resistance monitoring program

IOWA CITY, Iowa -- University of Iowa researchers play a lead role in tracking the global emergence and spread of antibiotic-resistant bacteria. The SENTRY Antimicrobial Surveillance Program was established in 1997 by investigators at the UI, the Eijkmann-Winkler Institute for Microbiology in Utrecht, the Netherlands and the Women’s and Children’s Hospital in Adelaide, Australia. It is the only global surveillance program monitoring changes in antibiotic resistance among human pathogens. SENTRY, which is sponsored by Bristol-Myers Squibb, covers 33 nations on five continents.

"The program is able to provide a broad snapshot of worldwide rates of antibiotic resistance exhibited by various bacteria," said Daniel J. Diekema, M.D., UI assistant professor of pathology and internal medicine.

At the 40th Interscience Conference on Antimicrobial Agents and Chemotherapy in Toronto on Sunday, Sept. 17, Diekema presented a three-year progress report for the SENTRY program by focusing on news of one problematic organism, Staphylococcus aureus (S. aureus). One of the most virulent human bacterial pathogens, S. aureus is a common cause of bloodstream, lung, skin, bone and joint infections worldwide.

According to the SENTRY data, the fraction of S. aureus strains isolated from bloodstream infections in hospitals in the United States that are resistant to the antibiotic methicillin has risen from 33 to 45 percent in the past three years. Antibiotics related to methicillin have been the drugs of choice for treating S. aureus infections since the late 1950s. In comparison, resistance rates were as low as 2-5 percent in the Netherlands, Canada and Switzerland and higher than 60 percent in some Asian and West Pacific nations.

"In the U.S., there is no uniform approach to methicillin-resistant S. aureus (MRSA). The Netherlands and Canada have much stricter policies for controlling the spread of MRSA," Diekema said. "A patient coming into a Dutch hospital from outside the country may be isolated until they have been checked for resistant S. aureus infection and, if necessary, treated."

Because of global travel, the impact of policies controlling the rates of antibiotic resistance is felt in nations beyond the origin of the bacterial strain. The SENTRY data indicates that community-acquired S. aureus infections, as well as hospital-acquired infections, also showed an increased rate of resistance in the three-year period since 1997. The greater the rates of resistance in community strains, the easier it is for those strains to become regionally wide spread. Most MRSA strains are also resistant to several other antibiotic agents. The SENTRY data shows similar, almost identical strains, across wide geographic regions.

"What we see are unique regional patterns of co-resistance in the MRSA," Diekema said. "If there were more local and regional efforts to keep track of antibiotic-resistance rates, physicians could be more aware of the resistances they were likely to encounter and be better equipped to deal with them."

Despite the concern over the increased rates of antibiotic resistance seen in S. aureus strains worldwide, the SENTRY program also provided some reassurance. Of the more than 15, 000 strains of S. aureus tested none were resistant to the antibiotic vancomycin, which is often considered the last line of defense against this bug. In addition, two new antibiotics were also shown to be effective against almost all the MSRA strains. These two new drugs may be promising alternatives for the treatment of infections due to multiply resistant S. aureus.

"Although we still appear to have a strong defense to fight these bacteria, developing a global strategy to prevent the spread of multiply resistant MRSA strains in both hospitals and communities should be a priority," Diekema said.

Michael A. Pfaller, M.D., UI professor of pathology and epidemiology, and Ronald N. Jones, M.D., UI professor of pathology, directed the research presented by Diekema and other SENTRY collaborators at the Women’s and Children’s Hospital in Adelaide, Australia and the Eijkmann-Winkler Institute of Microbiology in Utrecht, Netherlands.

University of Iowa Health Care describes the partnership between the UI College of Medicine and the UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide.