Evaluation of three different bottles in BACTEC 9240 automated blood culture system and direct identification of Candida species to shorten the turnaround time of blood culture.

OBJECTIVE

Candida spp. are the most common causes of fungemia. Rapid and accurate diagnostic methods are very important for appropriate management of candidemia. At present, blood culture is the essential diagnostic test despite having a long detection time and low sensitivity rate. We aimed to investigate the ways to shorten the turnaround time from blood culture collection to final identification in candidemia.

METHODS

Sixty clinical bloodstream isolates of Candida were included, and Plus Aerobic/F, Peds Plus/F and Mycosis IC/Fbottles were used with a BACTEC 9240 blood culture instrument. Germ tube production, carbohydrate assimilation (API 20C AUX) and peptide nucleic acid fluorescent in situ hybridization yeast traffic light tests were performed directly from positive-signalled bottles.

RESULTS

Time to positivity of blood cultures was affected by species of Candida, fungal load and bottle type. Candidatropicalis had the shortest and Candidaglabrata had the longest time to positivity. Mycosis IC/F culture bottle had a significant superiority in the isolation of yeasts, especially for C. glabrata and if there was a low fungal load in the bottle. Direct germ tube test had 90 % sensitivity and 97.6 % specificity for Candidaalbicans in two hours after signalling. The compliance between direct and classical assimilation tests was 98.3 %. Sensitivity and specificity of peptide nucleic acid fluorescent in situ hybridization were 100 %.

CONCLUSIONS

We think that it is possible to shorten the turnaround time for the identification of Candida in blood culture even with currently available methods.