Objective: Early identification of yeast isolates from blood cultures and establishment of appropriate antifungal therapy may improve clinical outcomes. While the proportion of candidemia caused by non-albicans Candida species continues to increase, Candida albicans still remains as the predominant pathogen. Most of the bloodstream C. albicans isolates remain susceptible to azoles. Thus rapid identification of C. albicans is an important step to guide targeted and cost-effective antifungal strategy in the treatment of bloodstream infections due to C. albicans. The aim of this study was to evaluate the diagnostic accuracy of germ tube test (GTT) performed directly from BacT/Alert® blood culture bottles which were detected as yeast positive by Gram staining.

Materials and Methods: Over a year period (June 2011-July 2012), all positive blood cultures in which yeasts were visualized by Gram staining, were subcultured onto Sabouraud dextrose agar, and a direct GTT was performed. To perform direct GTT, 10-20μl of the blood culture bottle contents were incubated with rabbit serum for 3h at 37ºC. Traditionally, GTT is performed on colonies grown on agar plates after 24-48 h of incubation. All isolates were then completely identified using the API20C AUX (bioMérieux, France) and morphological appearance on corn meal-Tween 80 agar medium.

Results: Among a total of 67 isolates, 32 were identified as C. albicans (47,8%), 14 as C. glabrata (20,9%), 11 as C. parapsilosis (16,4%), five as C. keyfr (7.5%), four as C. krusei (6%), and one as C. tropicalis (1,5%). No false-positive germ tube results were observed for non- albicans Candida isolates. Two C. albicans isolates were GTT negative when tested directly from blood culture bottles but were subsequently found to be GTT positive when the test was performed directly from the colonies. Thus, the calculated sensitivity and specificity of the direct GTT for prospective clinical samples were 94%, and 100%, respectively.

Conclusion: Although not as sensitive as the traditional GTT, direct GTT seemed to be a reliable test in the rapid initial diagnosis of C. albicans species obtained from blood cultures and may contribute to the early and appropriate initiation of the antifungal agent therapy.