Two similar interventions to prevent hospital-associated methicillin-resistant Staphylococcus aureus infections produced opposite results: One yielded dramatic reductions in overall, bloodstream, device-associated, and non–device-associated MRSA, whereas the other showed no effect, according to separate reports in the April 14 issue of the New England Journal of Medicine.
Photo credit: Janice Haney Carr/CDC
Two similar interventions to prevent hospital associated methicillin resistant Staphylococcus aureus managed to improve hospital safety practices, but one actually decreased MRSA (MRSA bacteria shown here) transmission.
Both interventions centered on culture-based active surveillance for resistant organisms, the expanded use of barrier precautions, attention to hand hygiene, and substantial "culture change" among health care providers to take action against resistant infections. And both interventions substantially improved in-hospital safety practices.
But only one intervention actually decreased MRSA transmission, leaving the issue of how to reduce hospital-associated resistant infections as unclear as ever.
In one study, researchers in the STAR*ICU (Strategies to Reduce Transmission of Antimicrobial-Resistant Bacteria in Intensive Care Units) trial compared an infection-control intervention vs. existing, standard safety procedures in 19 adult medical and surgical ICUs during a 6-month period. They analyzed outcomes for 1,356 patients in the intervention group (10 ICUs) and 2,132 patients in the control group (9 ICUs).
The intervention called for obtaining nasal swabs for MRSA cultures and stool or perianal swabs for vancomycin-resistant enterococcus (VRE) cultures within 2 days of admission to the ICU and weekly thereafter, to actively identify patients who carried or were infected with these organisms. Patients who were found to be colonized or infected – along with patients known to have been colonized or infected during the previous year – were assigned to care with contact precautions, which continued for the duration of their ICU stay. All other patients were assigned to care with universal gloving until surveillance cultures were found to be negative, at which time standard ICU practices resumed.
In control ICUs, swabs were taken in an identical manner, but the culture results were not communicated to ICU staff. Standard existing procedures were used to identify patients who were colonized or infected with MRSA or VRE, and they were then treated using contact precautions, said Dr. W. Charles Huskins of the Mayo Clinic, Rochester, Minn., and his associates.
In addition, "intervention ICUs received training in the intervention, door signs describing each category of precautions, and an aggregate report on the providers’ use of universal gloving during the first month of the intervention period."
In all the ICUs, monitors recorded contacts between providers and patients at random times on random dates, and providers’ use of hand hygiene, clean gloves, and gowns was noted.
Patients who carried or were infected with MRSA or VRE were more often identified in the intervention ICUs than in the control ICUs, and thus were more often assigned to expanded barrier precautions (mean, 51% of all patient-days), universal gloving (43%), and either one or the other (92%). In contrast, patients in the control ICUs were assigned to expanded barrier precautions on only 38% of all patient-days, and universal gloving was not used.
A composite measure of caregivers’ hand hygiene and use of clean gloves was nearly twice as high in the intervention ICUs (47% of contacts) as in the control ICUs (25%). In intervention ICUs, clean gloves were used for 82% of contacts, gowns were used in 77%, and hygiene after contact in 69%. In contrast, these proportions were 72%, 59%, and 59%, respectively, in control ICUs.
Nevertheless the primary outcome (ICU-level incidence of new colonization or infection with MRSA or VRE per 1,000 patient-days at risk) was not significantly different between the intervention and control groups, at 40% and 36%, respectively.
This lack of effectiveness was "surprising, given that surveillance cultures identified a sizable subgroup of colonized patients who were not otherwise recognized, and that colonized or infected patients were assigned to either contact precautions or universal gloving for nearly all their ICU patient-days," Dr. Huskins and his colleagues said (N. Engl. J. Med. 2011;364:1407-18).
It is unclear why the intervention failed to reduce the infection rate, but there are several possibilities.
First, the prolonged lag time (an average of 5 days) between admission to the ICU and reporting of the culture results allowed for transmission before the expanded precautions were undertaken. Second, the providers’ use of proper safety measures was greater but still not optimal in the intervention ICUs.
Third, body sites other than those that were cultured – such as the pharynx, open wounds, the skin, respiratory secretions, or the rectum – may have been harboring MRSA or VRE. Fourth, a different route of transmission that wasn’t addressed by this intervention – such as contaminated instruments or colonized care providers – may have been at fault.