Comparison of rapid testing methods for enzyme production with the germ tube method for presumptive identification of Candida albicans

Abstract

The observation of germ tube production as a method for the presumptive identification of Candida albicans has been in use for many years. Methods have recently been developed for detecting the production of the enzymes L-proline aminopeptidase and ␤-galactosaminidase by yeast isolates grown in culture. Both enzymes are produced by C. albicans; other yeasts may produce either L-proline aminopeptidase or ␤-galactosaminidase but not both enzymes. One hundred thirty-three clinical yeast isolates, including 55 C. albicans, 27 Candida tropicalis, 22 Torulopsis (Candida) glabrata, and 29 other yeast isolates were tested by the germ tube production method and three tests for enzyme production, with the API 20C method used as a "gold standard." All three enzymatic methods evaluated provided more objective and rapid nonmicroscopic alternatives to the germ tube test and may be used to accurately distinguish C. albicans from other yeasts.

Comparison of 12 liquid media for germ tube production of Candida albicans and C. tropicalis

“…Heelan et al. 3 found both the sensitivity and specificity of the GTT 100%, by four drops each of rabbit plasma and TSB. In a study by Kim et al.…”

“…These tests were reported to be more rapid and more sensitive in the diagnosis of C. albicans when compared with the GTT 1,2,9,10,16 . However, GTT is a simple and cheap alternative to other rapid test methods and may therefore be favoured by laboratories trying to work economically 3,13 …”

“…Candida albicans is the fungal pathogen most frequently isolated in humans. The observation of germ tube production is a method for the presumptive identification of C. albicans 3 . This test is based on the observation that yeast cells produce short, slender, tube‐like structures (germ tubes) when incubated in serum at 30–37 °C for 2–4 h. It is a simple, rapid, easy‐to‐perform, cheap and well‐known method 4–6 .…”

“…This test is based on the observation that yeast cells produce short, slender, tube‐like structures (germ tubes) when incubated in serum at 30–37 °C for 2–4 h. It is a simple, rapid, easy‐to‐perform, cheap and well‐known method 4–6 . However, up to 5% of C. albicans isolates were shown to be germ tube negative 2–4,7–11 . It has also been reported that non‐ C. albicans yeasts, i.e.…”

Comparison of the Rapid Yeast Plus Panel with the API20C Yeast System for Identification of Clinically Significant Isolates of Candida Species

“…Conventional methods for the identification of clinically significant yeasts are time-consuming and labor-intensive. Rapid screening methods, including the ability to produce germ tubes (8,13) and production of the enzymes beta-galactosaminidase and L-proline aminopeptidase (2,4,7,11), may be used to presumptively identify C. albicans. Other rapid screening methods involve the use of differential culture media (1,6,10,12).…”