Impact of routine intensive care unit surveillance cultures and resultant barrier precautions on hospital-wide methicillin-resistant Staphylococcus aureus bacteremia.

Background: Serial interventions are often used to reduce the risk of health care-associated methicillin-resistant Staphylococcus aureus (MRSA) infections. To our knowledge, the relative impact of these interventions has not previously been ascertained.

Methods: We conducted a retrospective study of 4 major infection control interventions using an interrupted time series design to evaluate their impact on MRSA bacteremia in an 800-bed hospital with 8 intensive care units (ICUs). Interventions were introduced 1 at a time during a 9-year period and involved the promotion of compliance with maximal sterile barrier precautions during central venous catheter placement, the institution of alcohol-based hand rubs for hand disinfection, the introduction of a hand hygiene campaign, and the institution of routine nares surveillance cultures for MRSA in all ICUs for patients on ICU admission and weekly thereafter while in the ICU. Positive cultures resulted in the initiation of contact isolation precautions. Using segmented regression analyses, we evaluated changes in monthly incidence and prevalence of MRSA bacteremia from their predicted values. Methicillin-susceptible Staphylococcus aureus bacteremia was monitored as a control.

Results: Routine surveillance cultures and subsequent contact isolation precautions resulted in substantial reductions in MRSA bacteremia in both ICUs and non-ICUs. In 16 months, the incidence density of MRSA bacteremia decreased by 75% in ICUs (P=.007) and by 40% in non-ICUs (P=.008), leading to a 67% hospital-wide reduction in the incidence density of MRSA bacteremia (P=.002). Methicillin-susceptible S. aureus bacteremia rates remained stable during this time. The other interventions were not associated with a statistically significant change in MRSA bacteremia.

Conclusions: Routine surveillance for MRSA in ICUs allowed earlier initiation of contact isolation precautions and was associated with large and statistically significant reductions in the incidence of MRSA bacteremia in the ICUs and hospital wide. In contrast, no similar decrease was attributable to the other infection control interventions.