Combination horizontal and vertical prevention efforts can reduce MRSA, VRE, MDR acinetobacter, and other nosocomial infections by 50%.
Although Staphylococcus aureus (S. Aureus) resistance represents a significant challenge in health care, current data support the argument that we have the ability to reduce all nosocomial infections by 50%, including Methicillin Resistant Staphylococcus aureus (MRSA), Vancomycin-Resistant Enterococci (VRE), and multi-drug resistant (MDR) acinetobacter.
How does this resistance occur? During his presentation at the 48th annual IDSA in Vancouver, Richard P. Wenzel, MD, M.Sc, Professor and Former Chairman, Department of Internal Medicine, Medical College of Virginia, Virginia Commonwealth University told the audience that "Resistance patterns arise primarily from horizontal gene transfer.” He also said that the evolution of S. Aureus “is clonal with some strains such as methicillin resistant USA 300, nee penicillin resistant 80/81, being more virulent. They are also able to spread more rapidly than other strains, and hence dominate.”
Focusing on infection control, Wenzel presented a strong argument for horizontal prevention programs and combination horizontal and vertical prevention efforts, citing recently published data from numerous studies. For clarification, a horizontal program reduces all infections at a specific anatomic site, whereas a vertical program targets a single organism at that site.
Using combination programs, data by Vode LGM et al, showed a 60% reduction of S. aureus surgical site infections (SSIs), which was accomplished with screening, chlorhexidine baths, and mupirocin treatment of S. aureus in nasal carriers. Additionally there was a 79% reduction in deep SSIs and a 55% reduction in superficial SSIs.
Another recently published study compared horizontal prevention using chlorhexidine or Povidone iodine in the initial surgical site in six hospitals. The authors reported a 41% reduction in SSIs within 30 days with chlorhexidine. "This was a 41% reduction with a simple switch in the surgical scrub," Wenzel said. "Curiously, 50% of S. aureus SSI infections were prevented with this general horizontal program and without a targeted program for staff." Looking further at these data, Wenzel and colleagues estimated that combining both horizontal and vertical prevention approaches might yield a 50% absolute reduction of all SSIs.
Looking at the increase in antibiotic strains and shortcomings of nasal screening for S. aureus/MRSA, Wenzel pointed out that only about 25% of S. aureus is in throat carriage, and MRSA throat carriage is between 13-15%. Further, community-associated MRSA is present in only 41% of nares. "We miss things if we only look for MRSA in the nares," he said.
The good news is that there's been a decline in invasive MRSA infections, as the CDC population-based surveillance shows. "These declines began before the MRSA-specific programs," Wenzel said. The declines may be due to horizontal programs put in place in the community or some unexplained natural biological trends.
There is also compelling evidence from several studies to suggest that chlorhexidine baths decrease blood stream infections (BSI). Borer et al, (2007) showed an 85% reduction in ICU-related multi-drug resistant Acinetobacter Baumannii colonization and BSI with daily 4% chlorhexidine baths.
Wenzel said that “horizontal prevention programs work because they are population based, and they have the added advantage of preventing the infections you don't know about -- the infections that haven't yet emerged -- because that's what they were designed to do."