Can Prolonged Incubation of Negative Blood Cultures Show Fungal Positivity?

Objective: Standard duration of one set blood culture (BC) is a maximum of 5-7 days. The aim of this study was to evaluate “culture-negative” vials with a prolonged incubation (max 30 days) time and to observe any mycological growth. Materials and Methods: Routine BCs optained from adult patients of Balıkesir Atatürk City Hospital for a year period were included. Render BC System BC128 (Render Biotech Co. Ltd., Shenzhen, China) were used. Randomly selected vials were re-incubated for additional three weeks by conventional methods. In case of any growth, identifications were done by PhoenixTM 100 system (Becton Dickinson, MA, USA) with cornmeal tween 80 agar (RTA Laboratories, Kocaeli, Turkey). Antifungal susceptibility testing was applied with CLSI disk diffusion method. Results: A total of 6047 BC sets were obtained and randomly chosen 1040+122 negative sets (A and B groups, respectively) were included. In group A, none of them had fungal growth. In B (ongoing empiric antifungal ≤48h), only 2 sets showed significant fungal growth, which were observed in 7±2 days, and all strains were identified as C.glabrata complex and these patients were on empiric fluconazole (200 mg/day). One isolate was susceptible dose dependent, the other one was resistant for fluconazole. Latter sets of these fungemia patients showed positive signals in routine incubation period. Conclusion: Invasive fungal infections are increasingly encountered and isolation capacity and optimization of BCs are crucial. In this study, it was obviously observed that standard incubation period is satisfactory in order to detect almost all fungemia.