September 4, 2008 — Doctors at the University of Virginia Health System have significantly reduced one type of infection among surgical intensive care patients by using antibiotic cycling, a method of rotating drugs at regular intervals.
In a study published in the Sept. 3 issue of the journal Surgical Infections, U.Va. researchers report that switching between two antibiotics, linezolid and vancomycin, every three months in the surgical intensive care unit decreased the methicillin-resistant Staphylococcus aureus, or MRSA, infection rate from 1.9 to 1.4 patients per 100 admissions. In-hospital mortality from surgical ICU-acquired MRSA infections fell from 3.8 patients per year to none.
Study data spanned six years, including the period before cycling began (1997 to 2001) and the period after it was instituted (2002 to 2003). The study's key focus was resistant gram-positive cocci, a subgroup defined as MRSA and VRE (which is an acronym for vancomycin-resistant Enterococcus).
"Before we began cycling, 67 percent of the Staphylococcus aureus infections in our surgical ICU were caused by MRSA," notes the study's lead author, Dr. Robert Sawyer, a professor of surgery and co-director of U.Va.'s Surgical Trauma Intensive Care Unit. "Cycling reduced MRSA cases to 36 percent of that total."
The U.Va. study is the first to assess the impact of antibiotic cycling on a group of bacteria known as gram-positive cocci. Increasingly problematic in hospitals, these pathogens tend to develop resistance to antibiotics in sterile and contained environments – areas like ICUs – where patients have weakened immune systems due to severe illness, open wounds, surgical incisions, catheters or other implanted medical devices. At U.Va., surgical ICU patients include those who are recovering from trauma, organ transplants or invasive procedures.
According to Sawyer, U.Va.'s findings are important, yet need to be confirmed by similar studies in other ICUs. "If cycling proves effective at other centers, we might be able to turn the tide on antibiotic resistance, at least for MRSA. In the long run, reducing MRSA should decrease the number of deaths among critically ill patients," he said. "However, the problem is very complex and will almost certainly need a variety of interventions to achieve the best outcomes."
While MRSA infection rates fell during cycling, the prevalence of VRE remained virtually unaltered. VRE infection rates rose slightly, from 0.76 to 0.98 patients per 100 admissions. In-hospital mortality from VRE dropped from 2.8 to 2.5 patients per year.
Cycling reduced the surgical ICU's overall gram-positive infection rate from 19.6 to 11.8 patients per 100 admissions. It lowered the rate of infections from resistant gram-positive cocci from 4.6 to 1.7 patients per 100 admissions.