Rapid identification of Candida glabrata in Candida bloodstream infections

Candida species are the fourth most common cause of bloodstream infection (BSI) in the hospitalized patient. Candida glabrata is the most common non-Candida albicans Candida species in England and Wales with an attributed mortality of 48%. C. glabrata is known to demonstrate reduced susceptibility to fluconazole, resulting in treatment failures when employing this agent for empirical treatment of Candida BSI. The first part of this study demonstrated a technique utilizing a blood culture system commonly used by many laboratories (BACTEC 9240 automated detection system) that reduced the time to identification of this potentially resistant organism by up to 72 h. A presumptive identification was achieved by observing a difference in the duration of incubation required before growth was detected automatically between Lytic Anaerobic and Plus Aerobic culture bottles. Secondly, experiments exploring the growth characteristics of C. glabrata in BACTEC blood culture bottles containing various media were carried out to explore possible reasons underpinning this clinical observation. The detection of yeast in the anaerobic bottle of a blood culture pair consisting of Lytic Anaerobic and Plus Aerobic in a BACTEC 9240 system was found to be highly predictive of the isolation of C. glabrata (positive predictive value 93.3%, negative predictive value 98.3%). The reason for this appeared to be a component of the Lytic Anaerobic blood culture medium enhancing the growth of C. glabrata in that medium.