Evaluation Of Bactalert Fa Blood Culture Bottles And T2candida Assay For Detection Of candida in The Presence Of Antifungals

N. D. Beyda1, J. Amadio1, J. R. Rodriguez2, K. Malinowski2, K. W. Garey1, A. Wanger2, L. Ostrosky-Zeichner2;

Author address: 

1Univ. of Houston Coll. of Pharmacy, Houston, TX, 2UTHlth., Houston, TX

Abstract: 

Objectives: Blood culture is the gold standard for diagnosing candidemia. Antifungal therapy has been shown to negatively impact the performance of some blood culture systems and other serodiagnostics. The objective of this study was to determine the effect of fluconazole (FLU) and caspofungin (CAS) on the performance of the T2Candida assay (T2CA) when compared to BacT/Alert FA blood culture bottles (BCX).Methods: Simulated candidemia samples were prepared by inoculating human whole blood with clinical bloodstream isolates of C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei at 50 CFU/mL and 5 CFU/mL. CAS (8 ug/mL), FLU (20 ug/mL), or 0.85% NS (antifungal negative control) where then added at concentrations achieved after therapeutic doses. Samples were inoculated into either BCX bottles and incubated for up to 5 days or into K2 EDTA tubes for testing by T2CA. The proportion of samples detected by BCX and T2CA was compared. The impact of antifungals on the time to positivity (TTP) of BCX was also assessed.Results: A total of 240 simulated candidemia samples were tested by each method (n=8 for each species, CFU/mL, and antifungal). In the absence of antifungals, overall detection rate for all species combined was 100% for both methods at 50 CFU/mL. At 5 CFU/mL it was 97.5% and 95% for BCX and T2CA respectively (C. parapsilosis not detected in 1 sample for BCX; C. glabrata and C. krusei not detected in 1 sample each for T2CA). For BCX, presence of FLU reduced overall detection rates to 92.5% and 85% at 50 and 5 CFU/mL respectively, while CAS had no impact. CAS or FLU had no impact on T2CA results at either CFU/mL concentration. Compared to no-antifungal controls, presence of CAS and FLU led to a significant increase in TTP of BCX for most species, particularly for C. albicans at 5 CFU/mL (increase of 3.1 ± 1.3 and 66.8 ± 13.4 hrs respectively; p
2016

abstract No: 

MONDAY-087

Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)