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

Abstract

In this study, we found that no Candida species other than C. albicans is able to form germ tubes at 39• 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• 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• C, and more than 60% of C. albicans cells formed the germ tubes after 1 h at 39• C. Standard Candida strains (ATCC, CBS), three C. albicans and two C. dubliniensis strains were cultured in serum at 37• C for 2 h and in YEPD at 39 • C for 1 h. All of the three C. albicans formed germ tubes at 39• C. The two C. dubliniensis strains formed germ tubes in serum at 37• C, but grew as a yeast form in YEPD at 39 • C. All of the clinically isolated C. albicans strains in our laboratory formed germ tubes in YEPD at 39• C for 1 h, and none of the clinically isolated Candida species other than C. albicans generated germ tubes in YEPD at 39• C. Thus, the unique germ tube formation of C. albicans induced by high temperature (39 • C) in YEPD could be applied to a protocol for the rapid and convenient identification of C. albicans in clinical laboratories.

Evaluation of Different Media for Germ Tube Production of Candida Albicans and Candida Dubliniensis

“…These morphological transitions often represent a response of the fungus to changing environmental conditions and may permit the fungus to adapt to different biological niches. 8 In the present study, 130 (98.4%) of total C. albicans (132) and 27(90%) of total C. dubliniensis (30) isolates showed germ tube production in trypticase soy broth. In pooled human serum and horse serum, the positivity for germ tube test was noted in 124 (94%) C. albicans.…”

“…In order to investigate the germ tube structure, the elongated daughter cells from the round mother cell without constriction at their origin were referred to as germ tubes, and constriction hyphae at the round mother cell were referred to as pseudohyphae. 8 A criterion for germ tube positivity was observation of minimum five germ tubes in entire wet mount preparation. Negative results were confirmed by examining at least 10 high power fields for the presence of germ tubes.…”

“…Most of the studies on evaluation of media for germ tube production are focused on C. albicans. 8,9,10 Information on efficient media for germ tube testing of C. dubliniensis is limited. The present study was conducted with an aim to evaluate different media like pooled human serum, horse serum, human plasma, egg white, peptone water and trypticase soy broth for germ tube production of C. albicans and C. dubliniensis.…”

Determination of germ tube, phospholipase, and proteinase production by bloodstream isolates of Candida albicans

“…Yeast can be induced to produce GTs, which develop into mycelia. This morphological transition can be induced by changes in a variety of environmental factors and by blocking the host immune response 10 .…”

Surveillance and characterization of Candida bloodstream infections in a Serbian tertiary care hospital

“…Cells were counted in 5 fields per slide, afterwards the percentage of cells that formed germ tubes was calculated. All experiments were done in triplicate and repeated three times [9,10]. Hemolytic activity of Candida isolates was screened on blood agar plates by the method described by Manns et al [11].…”