Rapid differentiation of Candida albicans from other Candida species using its unique germ tube formation at 39° C

In this study, we found that no Candida species other than C. albicans is able to form germ tubes at 39 degrees C in serum-free YEPD (1% (w/v) yeast extract, 2% (w/v) peptone and 2% (w/v) dextrose) media, which makes it easy to identify C. albicans from other Candida species. When cultivated in rabbit serum for at least 2 h at 37 degrees C, more than 60% of C. albicans cells generated germ tubes. In YEPD, however, germ tubes began to appear from C. albicans cells within 30 min at 39 degrees C, and more than 60% of C. albicans cells formed the germ tubes after 1 h at 39 degrees C. Standard Candida strains (ATCC, CBS), three C. albicans and two C. dubliniensis strains were cultured in serum at 37 degrees C for 2 h and in YEPD at 39 degrees C for 1 h. All of the three C. albicans formed germ tubes at 39 degrees C. The two C. dubliniensis strains formed germ tubes in serum at 37 degrees C, but grew as a yeast form in YEPD at 39 degrees C. All of the clinically isolated C. albicans strains in our laboratory formed germ tubes in YEPD at 39 degrees C for 1 h, and none of the clinically isolated Candida species other than C. albicans generated germ tubes in YEPD at 39 degrees C. Thus, the unique germ tube formation of C. albicans induced by high temperature (39 degrees C) in YEPD could be applied to a protocol for the rapid and convenient identification of C. albicans in clinical laboratories.