Identification of Candida species by direct inoculation of cornmeal tween™ 80 agar from blood culture bottles: Rapid and cost-effective approach

Abstract

Background: This study aimed to compare the accuracy of Candida species identification by direct inoculation of positive blood culture specimens into CornMeal Tween™ (CMT) 80 agar with the conventional methods. Methods: This study was performed in two phases: Phase 1: Inoculation of direct CMT from artificially spiked blood culture bottles with identified Candida species. Phase 2: Direct inoculation of smear-positive bottles on CMT agar for identification. Routine identification method was carried out using urease production, sensitivity to cycloheximide, CMT inoculation, and colony morphology on BiGGY agar. All isolates were also evaluated for sugar assimilation on the biochemical test panel Analytical profile index (API) 20C AUX (BioMerieux). Statistical Analysis Used: The correlation between both methods was determined as percentage agreement rate using kappa score. Results: In the first phase 50 artificially spiked blood culture bottles were included in the study. The sample set consisted of 24% C albicans, 38% C tropicalis, and 22% C glabrata isolates. There was 100% agreement between the directly inoculated and CMT inoculated from colonies at 48 hours. Phase 2: The overall agreement between directly inoculated CMT and conventional method of identification at 72 h was 92%. Conclusion: Direct inoculation of CMT agar can easily differentiate common Candida species microscopically on the basis of chlamydospores, blastopores, and arrangement of pseudo hyphae. However, identification of rare species from specimens containing two different species using direct method is challenging. Therefore, conventional methods including macroscopic/microscopic characteristics and biochemical profile with the aid of API with API 20 AUX would be a better choice for such cases.

Keywords

• API 20 C Aux
• Candida identification
• Candida species
• Corn meal tween 80