271. Diagnosis and Management of Polymicrobial Blood Stream Infections With Multiplex PCR in Hospitalized Children

BACKGROUND: Multiplex PCR (mPCR) can be used to rapidly identify polymicrobial blood stream infections (BSIs) and guide empiric therapy. In addition rapid identification of potential contaminants, may limit unnecessarily broad empiric therapy. The purpose of this study was to describe the use of mPCR to diagnosis polymicrobial BSIs in hospitalized children, and the impact of this technology on antibiotic prescribing. METHODS: We retrospectively identified children at our institution with polymicrobial BSIs diagnosed by mPCR (Film Array Blood Culture Identification Panel, BioFire Diagnostics) from October 2014 to March 2018. A polymicrobial BSI was defined as any blood isolate with ≥1 bacterial or fungal species. Gram stain results, species identification by mPCR, and final species identification via matrix associated laser deionization time of flight (MALDI-TOF) were determined. Antibiotic prescribing for treatment of each BSI was reviewed. RESULTS: Overall, 622 patients experienced 961 blood stream infections. There were 54 patients who experienced 68 polymicrobial BSIs (7%). Of the polymicrobial BSIs, 55 (80.9%) were two organisms and 13 (19.1%) were three or more organisms. Of the 68, 44 (64.7%) had the same Gram stain morphology and 24 (35.3%) had different morphology. Antibiotic therapy was broadened, narrowed, and unchanged in 38 (56%), 16 (24%), 14 (21%) of infections, respectively. Common modifications of therapy included addition of aminoglycoside or meropenem when two Gram-negative bacilli were present, and addition of vancomycin when coagulase negative staphylococci (CoNS) were isolated. CONCLUSION: The use of mPCR commonly led to prompt modification of antibiotic therapy to treat polymicrobial blood stream infections. Identification of CoNS frequently led to broadening of antibiotic therapy, even when other organisms were present. DISCLOSURES: S. Patel, Merck: Grant Investigator, Grant recipient and Research grant. Pfizer: Grant Investigator, Research grant.