Antimicrobial Stewardship Pharmacist Interventions for Coagulase-Negative Staphylococci Positive Blood Cultures Using Rapid Polymerase Chain Reaction

Jordan R Wong PharmD; Karri A Bauer PharmD; Julie E Mangino MD; Debra A Goff PharmD FCCP


The Annals of Pharmacotherapy. 2012;46(11):1484-1490. 

In This Article

Abstract and Introduction


Background: No studies exist regarding the value of pharmacist interventions using rapid identification of coagulase-negative staphylococci (CoNS) by rapid polymerase chain reaction (rPCR) from blood cultures.
Objective: To evaluate the impact of interventions by infectious diseases pharmacists (ID PharmDs) on blood cultures positive for CoNS using rPCR and assess the duration of antistaphylococcal antibiotic therapy, hospital length of stay (LOS), and related costs.
Methods: A quasi-experimental, pre- and postintervention study of patients with positive blood cultures for CoNS, identified using rPCR, was conducted. Patients were included if there was a blood culture for CoNS from January 1, 2011, to March 31, 2011 (preintervention), or October 1, 2011, to January 18, 2012 (postintervention). Exclusion criteria included age younger than 18 years or 89 years or older, neutropenia, incomplete records, and duplicate or mixed blood cultures. The setting was a 1200-bed academic medical center. The ID PharmD intervened on blood cultures identified in the postintervention group as CoNS after notification from the microbiology laboratory. The pre- and postintervention groups were compared to analyze the effect of the intervention. The primary outcome was time to discontinuation of antistaphylococcal antibiotics by the pharmacist intervention in patients with a positive blood culture for CoNS that was determined to be a contaminant.
Results: We analyzed 53 patients (31 preintervention, 22 postintervention) with CoNS blood culture contaminants. In the postintervention group, antistaphylococcal antibiotics were discontinued 32.0 hours sooner from time of rPCR result (median 57.7 vs 25.7 hours; p = 0.005), total antibiotic exposure decreased 43.5 hours (97.6 vs 54.1 hours; p = 0.011), infection-related LOS decreased 4.5 days (10 vs 5.5 days; p = 0.018), and infection-related costs decreased $8338 ($28,973 vs $20,635; p = 0.144). The pharmacist initiated vancomycin in 7 (21.9%) patients with CoNS bloodstream infections.
Conclusions: Timely interventions by ID PharmDs using rPCR are required to impact the outcomes of patients with positive blood cultures for CoNS.


Antimicrobial resistance is a crisis resulting in a "desperate need for effective programs of antibiotic stewardship," as noted by Dr. John Bartlett's A Call to Arms. He states that "there is a well-documented causal relationship between antimicrobial use and misuse and the emergence of antimicrobial-resistant pathogens."[1] Antimicrobial stewardship involves measures to promote the judicious use of antimicrobials to achieve the best clinical outcomes for patients, while limiting toxicity and minimizing bacterial resistance.[2] In concordance with these principles of stewardship, microbiologic diagnostic tests that rapidly identify organisms support optimal antibiotic use and are considered a "game changer" in the field of infectious diseases.[1,3] These rapid diagnostic tests can impact patient care by accelerating the ability of a clinician to initiate or deescalate antibiotic therapy for optimal patient outcomes.

Coagulase-negative staphylococci (CoNS) are common skin flora. CoNS are often considered a blood culture contaminant in the setting of only 1 positive blood culture bottle out of multiple bottles in a patient without fever, chills, or hypotension.[4] CoNS that are determined to be a contaminant do not require antimicrobial therapy. At The Ohio State University Wexner Medical Center (OSUWMC), approximately 30% of all positive blood cultures are identified as CoNS.

Commercially available rapid diagnostic tests use various technologies capable of identifying methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive S. aureus (MSSA), or CoNS. Depending on the rapid diagnostic test, results can be available in 30 minutes to 5.5 hours versus several days with standard identification and susceptibility testing.[5–8] Many institutions have implemented rapid diagnostic testing, but there are few data evaluating the use of an antimicrobial stewardship program's (ASP) intervention on blood cultures positive for CoNS. The OSUWMC ASP evaluated the rapid polymerase chain reaction Xpert MRSA/SA blood culture test (rPCR) in the management of S. aureus, but no infectious diseases pharmacist (ID PharmD) interventions were made for positive CoNS blood cultures.[9] The purpose of this study was to evaluate the clinical and economic impact of an ID PharmD's intervention on positive CoNS blood cultures, using the rPCR Xpert MRSA/SA blood culture (BC) test.