1000. A Multimodal Rapid Diagnostic Testing Approach for the Diagnosis of Staphylococcus aureus Bacteremia at an Academic Acute Care Medical Center: a Strategy for Improving Patient Outcomes
Session: Poster Abstract Session: Diagnostic Microbiology: Staphylococci
Friday, October 9, 2015
Room: Poster Hall

Time to appropriate antimicrobial therapy has been shown to decrease mortality in patients with severe sepsis. Rapid diagnostics are being developed to identify pathogens and specific resistance mechanisms in order facilitate timely and effective treatment decisions. This Institution is a teaching center equipped with an Antimicrobial Stewardship Team which reviews positive blood cultures to ensure appropriate antimicrobial therapy.


This retrospective study reviewed average turn-around-time (aTAT) for blood cultures positive with methicillin resistant Staphylococcus aureus (MRSA) and methicillin susceptible Staphylococcus aureus (MSSA). The pre-rapid diagnostics group involved traditional identification and antimicrobial susceptibility (AST) techniques. Two rapid diagnostic algorithms were utilized: MALDI (Matrix Assisted Laser Desorption Ionization Time-of-Flight) identification with phenotypic AST and a dual group consisting of MALDI plus Biofire FilmArray Blood Culture Panel (BFBCP) with detection of the methicillin resistance gene, mecA.Average length of hospital stay (aLOS) was assessed for each group and measured in days.


Pre-rapid group: aTAT for MSSA (N = 52) was 43.9 ± 17.4 hours (hrs). For MRSA (N = 18), the aTAT was 43.3 ±10.2 hrs. The aLOS was 15 ± 13 days (d) for MSSA and 19 ± 17 d for MRSA positive patients.

MALDI group: aTAT for MSSA (N = 44) was 30.8 ± 14.9 hrs and for MRSA (N = 14) it was 59.5 ± 13.2 hrs. The aLOS was 14 ± 11 d for MSSA and 18 ± 16 d for MRSA cases.

Dual group: MSSA (N = 43) had an aTAT of 33.9 ± 21.2 hrs and MRSA (N = 23) isolates with an aTAT of 20.2 ± 12.1 hrs. The aLOS was 15 ± 10 d for MSSA and 18 ± 13 d for MRSA cases.


In this study, the aTAT was decreased with the implementation of rapid diagnostic testing, especially for MRSA isolates. The multimodal approach did not have an effect on LOS; however, LOS is an indirect marker of clinical improvement and may be impacted by many variables not controlled in this study. A limitation in our study is that cases were not matched between groups and confounding variables not controlled. With the implementation of rapid diagnostics, the Antimicrobial Stewardship Team was able to ensure patient safety through receipt of rapid identification and bacterial resistance for a timely intervention.

Patricia Couto, M.D.1, Michelle Peahota, Pharm.D., BCPS1 and Amity Roberts, Ph.D, D(ABMM)2, (1)Infectious Diseases, Thomas Jefferson University Hospital, Philadelphia, PA, (2)Clinical Microbiology, Sidney Kimmel Medical School at Thomas Jefferson University, Philadelphia, PA


P. Couto, None

M. Peahota, None

A. Roberts, None

Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.