1239. Active surveillance cultures of Methicillin-Resistant Staphylococcus aureus (MRSA) as a tool to predict MRSA ventilator associated pneumonia
Session: Poster Abstract Session: Sepsis and Critical Care
Saturday, October 22, 2011
Room: Poster Hall B1

Ventilator-associated pneumonia (VAP) is one of the most common infections in the intensive care unit (ICU), and methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a common cause of VAP.  We sought to study the performance characteristics of once weekly active surveillance culture (ASC) of MRSA colonization in predicting the development of MRSA VAP.


Prospective observational study at a university affiliated urban teaching hospital, and level 1 trauma and burn center consisting of 89-bed surgical and medical ICUs.  All patients ≥ 16 years old admitted to the ICU on mechanical ventilation ≥ 48 hours who met diagnostic criteria for VAP by quantitative lower respiratory tract cultures obtained via bronchoscopic alveolar lavage (BAL) or brush specimen between January 2008 to October 2010 were included.  Confirmation of VAP was based on quantitative BAL culture with ≥ 10,000 colony forming units (CFU)/ml or brush specimen ≥ 1,000 CFU/ml of organisms.  Surveillance cultures were taken from the nares, oropharynx or trachea, and any open wound routinely upon admission to the ICU, every 7 days afterwards and at ICU discharge. 


Nine hundred twenty four episodes of suspected VAP were evaluated, and 388 patients with BAL-confirmed VAP were included.  Of the 388 patients, 37 (9.5%) had MRSA VAP, and 54 (13.9%) had MRSA colonization documented by ASC prior to the development of VAP.  The sensitivity and specificity of prior MRSA colonization as a predictor for MRSA VAP are 70.3% (95% CI: 52.8-83.6) and 92.0% (95% CI: 88.5-94.5), respectively.  The positive and negative predictive values are 48.1% (95% CI: 34.5-62.0) and 96.7% (95% CI: 94.0-98.3).


In our study, prior MRSA colonization as ascertained by once weekly ASC yielded high specificity and negative predictive value, suggesting that negative ASC can accurately exclude MRSA as an etiology in most patients with VAP and may decrease the need for empiric MRSA coverage when treating suspected VAP. 

Subject Category: J. Clinical practice issues

Jeannie D. Chan, PharmD, MPH1, Timothy H. Dellit, MD2, Julie Choudhuri, RN, MSPH3, Elizabeth McNamara, RN, MN3, Elizabeth Melius, RN, MN, MPH3, Heather Evans, MD, MS4, Joseph Cuschieri, MD4, Saman Arbabi, MD, MPH4 and John B. Lynch, MD2, (1)Pharmacy, Harborview Medical Center, Seattle, WA, (2)Medicine, Division of Infectious Diseases, Harborview Medical Center, Seattle, WA, (3)Harborview Medical Center, Seattle, WA, (4)Surgery, Harborview Medical Center, Seattle, WA


J. D. Chan, None

T. H. Dellit, None

J. Choudhuri, None

E. McNamara, None

E. Melius, None

H. Evans, None

J. Cuschieri, None

S. Arbabi, None

J. B. Lynch, None

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.