Treatment of Pneumonia in the Intensive Care Unit in the Setting of Methicillin-Resistant Staphylococcus aureus Surveillance

Background: Methicillin-resistant Staphylococcus aureus (MRSA) pneumonia is a significant cause of morbidity and mortality.  In August 2007, the Illinois government mandated MRSA active surveillance (AS) for high-risk patients including those admitted to intensive care units (ICUs).  While the intent of this measure is for infection control purposes, the impact of AS on clinical decision-making and patient outcomes remains largely unexamined. 

Objective: To determine what effect MRSA AS has on management of pneumonia in ICU patients including correlation of nasal surveillance cultures with respiratory sample microbiology and duration of use of MRSA-active antimicrobial therapy for empiric pneumonia treatment.

Methods: By January 1, 2008, all ICUs at our hospital were performing MRSA AS by nares culture on ICU admission.  All patients with positive respiratory cultures performed in an ICU from January 1, 2008 through December 31, 2008 were evaluated for pneumonia; clinical information obtained from the electronic medical record was reviewed by an expert panel to confirm the presence of pneumonia prior to study inclusion.  MRSA colonization, MRSA bacteremia, and MRSA-active antimicrobial use was compared between patients with MRSA pneumonia and patients with other pathogens.

Results: Of 44 patients with pneumonia included to date, 23 had MRSA pneumonia.  Of these 23, 14 (61%) had evidence of prior MRSA colonization; 11 (48%) had a positive AS culture on the current admission and an additional 3 patients (13%) had evidence of a prior positive surveillance or clinical culture.  No patients with other respiratory pathogens had current or prior MRSA colonization. Of the 23 MRSA pneumonia patients, 9 (39%) had concurrent MRSA bacteremia.  Hospital-onset infections accounted for 55% of the cases in the entire cohort, whereas 48% of the MRSA pneumonias were classified as hospital-onset.  Of the community-onset infections, 14 (70%) had identifiable health-care associations including 10 of the 12 MRSA community-onset cases.  13 of the patients with MRSA pneumonia received MRSA-active antimicrobials in excess of 8 days in contrast to only 1 patient with non-MRSA pneumonia; 6 of these MRSA pneumonia patients had concurrent bacteremia. 17 of 21 patients with non-MRSA pneumonia received 6 days or less of anti-MRSA therapy.

 

Conclusions: In a small sample of patients with pneumonia in the ICU, prior AS cultures positive for MRSA had good correlation with the presence of MRSA pneumonia; however, the sensitivity of AS cultures is not sufficient to exclude MRSA pneumonia. It is unclear that these AS results affected clinical decision-making as most of the patients received MRSA-active agents empirically initially regardless of colonization status, although patients without MRSA in AS or respiratory culture appear to receive fewer days of MRSA-active antimicrobials.