Starvation survival and recovery in serum of Candida albicans compared with Enterococcus faecalis

Abstract

Candida albicans has been a common isolate in posttreatment disease, usually as a monoinfection of the root filled canal. A factor likely to contribute to its pathogenic potential in posttreatment infection is an ability to endure starvation and use serum as a nutritional source. This study evaluated the starvation-survival behavior, growth, and recovery in human serum of C. albicans and compared it with Enterococcus faecalis. Varying cell densities of C. albicans and E. faecalis were suspended in 5% human serum or water for 4-6 months. Starvation recovery was assessed by addition of 50% serum to starved cells. Cell survival was monitored by periodic removal of aliquots and viable counts. Initial cell density was important for starvation survival. Candida albicans and E. faecalis survived starvation in water for 6 months when the starting cell density was >10(5) and >or=10(8) colony-forming units (cfu)/mL, respectively. Both species thrived in 5% serum from low initial densities (>10(2) and >10(4) cfu/mL for C. albicans and E. faecalis, respectively), and starvation-state cells recovered on addition of 50% serum. Candida albicans is well suited for survival in nutrient-limited conditions and can use serum as a source of nutrition and for recovery from starvation. These findings parallel the behavior of E. faecalis, which possesses a similar capacity for starvation survival and growth in serum, traits that are of likely importance for their participation in posttreatment infection.