239. Clinical Criteria to Prevent Overtreatment of Coagulase-negative Staphylococcal Positive Blood Cultures
Session: Poster Abstract Session: Antimicrobial Stewardship in Clinical Practice
Friday, October 21, 2011
Room: Poster Hall B1
Background: Coagulase-negative staphylococci (CoNS) are the most common bacteria isolated from blood cultures.  Often a contaminant, CoNS results in overutilization of antibiotics and longer hospital stays.  Few guidelines exist to help differentiate coagulase-negative staphylococcal bacteremia (CoNS-B) and contamination (CoNS-C).  The primary goal was to examine the sensitivity and specificity of a published algorithm (PA) which includes the following variables: number of positive blood cultures, WBC count, temperature, and systolic blood pressure.  A secondary goal was to examine factors that may enhance the PA.

Methods: A retrospective, single-center chart review of 100 randomly selected hospitalized patients who were at least 18 years of age with at least one CoNS in blood culture between September 2009 and September 2010.  An expert panel of infectious diseases physicians reviewed all 100 cases in blinded fashion to determine the significance of CoNS in blood culture (ID).  T-test, Wilcox test, and tests of proportion were used to examine differences between ID and PA.  CART analysis was used to determine significant time to positivity for CoNS-B vs. CoNS-C.

Results: 35% of patients with CoNS positive blood cultures were treated. PA and ID determined 36 and 22 cases of CoNS-B, respectively.  Compared to ID, PA had sensitivity-82%, specificity-78%, PPV-50%, NPV-94%.  Utilization of a published algorithm would have resulted in both overtreatment and undertreatment compared to ID.  PA overtreated 18 cases compared to ID.  Unexpectedly, PA also undertreated 4 patients compared to ID.  The number of positive blood cultures was significantly associated with undertreatment (3±1 vs. 1±0, p<0.01) and overtreatment (1±0 vs. 1.6±0.6, p<0.01).  Factors that may improve the PA may be time to positivity ≥ 19.5 hours, presence of immunosuppression, or presence of concomitant infection.

Conclusion: Utilization of PA did not reduce the total number of misclassifications of CoNS compared to practice.  The PA did not perform as well in practice when only one set of blood cultures were performed.  Incorporating other factors into the decision making process such as time to positivity, presence of immunosuppression, and presence of concomitant infection may enhance the PA. 

Subject Category: J. Clinical practice issues

Jihye Kim, PharmD1, Cinda Christensen, PharmD, BCPS-ID1, Archana Maniar, MD2, Stuart Cohen, MD, FIDSA3 and Hien H. Nguyen, MD2, (1)University of California, Davis Medical Center, Sacramento, CA, (2)Internal Medicine, University of California, Davis Medical Center, Sacramento, CA, (3)University of California at Davis Medical Center, Sacramento, CA


J. Kim, None

C. Christensen, None

A. Maniar, None

S. Cohen, None

H. H. Nguyen, 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.