Evaluation of Location-Specific MRSA Healthcare-Associated Infections, Data from the New NHSN MDRO and CDAD Module

Background:

A position paper from SHEA/HICPAC suggests that monitoring methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated infections (HAIs) by patient-care area is critically important to identify hospital locations at high risk for transmission of infection.  However, national data on all types of MRSA HAIs by patient location is currently lacking.

Objective:

Describe MRSA HAIs reported from various patient-care locations in a large sample of U.S. hospitals.

Methods:

Data on all MRSA HAIs reported to the National Healthcare Safety Network (NHSN) Multidrug-Resistant Organism (MDRO) and Clostridium difficile-Associated Disease (CDAD) Module in 2009 were analyzed.  Facility users were instructed to report all MRSA HAIs identified within monitored patient locations regardless of device use.  An MRSA HAI incidence rate (MRSA HAIs / 1,000 patient-days) was calculated for each facility-defined patient unit (unit-specific), and data were also summed across all units of the same type for a pooled mean MRSA HAI incidence rate (location-specific).  Differences in type of HAI were also evaluated by select locations.

Results:

A total of 403 facilities performed MRSA infection surveillance in ≥ 1 unit for ≥ 1 month between January and September 2009.  Of these, 197 reported no MRSA HAIs; the remaining reported 915 MRSA HAIs from 317 facility-defined patient units which mapped to 38 different location types.  Most reporting facilities were general hospitals and 54% had ≤ 200 beds.  Of all MRSA HAIs reported, 55% were among males.  Mean patient age was 58 years (range: 0-102).  The median unit-specific MRSA HAI rate was 0, regardless of location type.  The pooled mean MRSA incidence rates and the distributions of specific HAI types varied by location type (Table 1): the highest pooled mean MRSA HAI rate was in surgical intensive care units (ICUs), followed by medical ICUs.  Rates in the medical and medical-surgical ICUs were not remarkably higher than among the select patient wards.  Pneumonia (PNEU) was the most common infection reported in all three ICU types, skin and soft tissue infections (SST) were most common in the medical and medical-surgical wards, and surgical site infections (SSI) represented half of all infections reported from surgical wards (Table 1).

Conclusions:

Bloodstream infections (BSI) represent a minority of the MRSA HAI identified from the select locations evaluated.  Although data are preliminary, hospital wards had MRSA infection incidence rates comparable to the ICUs.  Focusing MRSA surveillance only on BSI in ICUs may overlook a large proportion of the patient population at high risk for MRSA infections.