Evaluation of Mueller‐Hinton‐agar as a simple medium for the germ tube production of Candida albicans and Candida dubliniensis

Abstract

Candida albicans is the most frequently isolated yeast species from clinical specimens. A classical rapid presumptive differentiation from non-albicans species is based on its ability to produce germ tubes after incubation in human serum. The only non-albicans Candida species producing germ tubes is Candida dubliniensis. In this study, we evaluated Mueller-Hinton-agar (MH-agar) as a medium for germ tube formation of C. albicans and C. dubliniensis. A total of 859 yeast isolates from stool samples, including 632 strains of C. albicans, 10 C. dubliniensis and 217 other yeast strains from 20 different species, were grown on Sabouraud glucose (2%) agar at 37 degrees C for 24-72 h. Species were identified by standard methods. For the germ tube test (GTT), an inoculum from a single colony was streaked onto a MH-agar plate and covered by a sterile coverslip. After incubation at 37 degrees C for 2 h, the MH plates were examined using a light microscope at x200. The GTT was positive in 578 of 632 C. albicans strains (sensitivity 91.5%), in six of 10 C. dubliniensis strains (sensitivity 60.0%), and in none of the other yeast strains. MH-agar is a suitable medium for the GTT and the presumptive identification of C. albicans. It is safer to use than human serum and is widely available in microbiology laboratories.

Use of Mueller-Hinton Broth and Agar in the Germ Tube Test

“…The quick presumptive differentiation between C. albicans and non- C.albicans species is often done based on the ability of the isolates to produce positive germ tubes in blood serum 8 Nevertheless, there are two other species that share this characteristic: C. dubliniensis and C. africana were able to form the germ tube 9 . In addition, C. tropicalis may produce pseudohyphae which, because of constriction, may make its differentiation more difficult 2 .…”

“…A simple, fast, safe and practical method, which can facilitate laboratory routine, is needed to differentiate C. albicans from other species 1 . In 2007, a new technique using Mueller-Hinton agar to produce the germ tube was described as being allegedly safer than the conventional method, which uses a blood serum pool that might be contaminated with HIV and hepatitis viruses 8 .…”

Phenomena in dermatology

“…The significance of this phenomenon is that it helps to distinguish pathogenic C. albicans and C. dublinensis from other pathogenic strains like C. pseudotropicalis and C. parapsilosis. [72] Epitope spreading phenomenon Epitope spreading phenomenon explains the progressive formation of antibodies against more than one antigenic determinant during the course of an autoimmune disease. As the disease progresses, progressive tissue injury caused by primary antibodies results in the unmasking of neighbouring proteins to which secondary antibody responses are generated.…”

Evaluation Of Mueller-Hinton Agar For Germ Tube Test

“…Benzer bir şekilde, Rimek ve diğerlerinin çalışmasında da, MHA'ın duyarlılığı %91, özgüllüğü ise %100 olarak tanımlanmıştır 9 .…”

“…Bununla birlikte daha fazla sayıda C. dubliniensis ile yapılan çalışmalara ihtiyaç bulunmaktadır. Rimek ve diğerlerinin çalışmasında, tüm suşlar arasında %1,2 oranında bulunan C. dubliniensis sonuçları değerlendirilmiş, MHA'daki GTT duyarlılığı C.albicans için %91,5, C. dubliniensis için %60 olarak bulunmuştur 9 .…”