Cidália Pina-Vaz
University of Porto, Portugal
Title: Rapid assessement of antimicrobial susceptibility profile directly from positive blood cultures by flow cytometry
Biography
Biography: Cidália Pina-Vaz
Abstract
Positive blood cultures demand rapid initiation of antimicrobial therapy. However, a minimum of 48 hours are needed for susceptibility results. Early administration of appropriate antimicrobials increases patient survival and reduce hospitalization costs. Flow cytometric protocols for assessment of the most relevant antimicrobials versus common microorganisms isolated from biological specimens were developed by FASTinov and patented (WO2011138765A1). Such tests were applied to positive blood cultures (100 gram negative bacilli, 50 gram positive cocci, 20 yeasts) from Hospital S. João, Porto, Portugal, following ethics commission approval. After becoming positive, microscopic examination was performed and microbial cells were separed after centrifugation; 105 organisms/ml were incubated with antimicrobials, according to gram stain, during 1 hour; cells were afterwards stained with the adequate fluorescent probe and submitted to FC analysis. Susceptibility phenotype was defined according previously defined cut-off values; results were compared with routine susceptibility tests - Vitek2 (BioMérieux, France). In case of discrepant results microdilution was used as reference method. The impact of this early susceptibility results on therapeutic decision, direct and indirect costs were evaluated. A time to result of two hours after the blood culture bottle becoming flagged positive was possible, representing considerable time saving (up to 46 hours). Agreement between FC test and routine test was 99%; high clinical and economic impact was - differences between 1-3 days of additional hospitalization days per patient. The use of flow cytometry for susceptibility profile analysis may represent a new paradigm in clinical microbiology and a step forward in targeted, cost-effective antimicrobial therapy.