Candida albicans is an ubiquitous yeast which, like all Candida species, belongs to the family of yeast-like fungi. Apart from the yeast form which primarily causes superficial infections, so called pseudo mycelia are a further morphologic manifestation of yeast-like fungi. Germ tubes and the development of pseudo mycelia mainly occur in cases of systemic mycosis. Candida ssp. produce and excrete a range of destructive enzymes that enable the facultative pathogen microorganisms to penetrate mucous membrane barriers and blood vessels barriers.
Candida ssp. are primarily transmitted by smear contamination from person to person. The primary portal of entry is the oral cavity. Changes in the fungistatic properties of the skin, which are a consequence of a slightly acidic pH value and the antagonistic bacterial flora, can facilitate the establishment of superficial candidiasis of the skin surface. Systemic mycosis results from colonization of mucous membranes, particularly in the gastrointestinal tract.
Candida ssp. are able to adhere to the epithelia of a variety of mucosal membranes by adherence proteins and other cell surface structures. The schematic below shows hypothetical steps that may lead to disseminated infections in cases of severe underlying conditions. An exact description of the various stages is not practical (Fig. 1).
Candidiasis can generally be classified into two major groups whose main characteristics are listed in the table below.
The diagnosis of candidiasis on the basis of serological methods is not straight forward: On the one hand transient yeast colonization may induce an antibody response, on the other hand systemic Candida mycosis in immunosuppressed patients may only lead to minor changes in antibody activities. Such situations make critical interpretation of serological findings necessary. In addition, systemic Candida-infections may not cause typical symptoms.
Currently it is not possible to conclude that the results of different test systems for anti-Candida antibody detection are comparable or even exchangeable. Specificity of detected antibodies significantly depends on the test system (ELISA or HAT) or on the antigen preparation used. The detection of IgM antibodies with HAT is better than the IgG detection due to higher agglutination properties of IgM molecules. HAT mainly detects antibodies against cell wall antigens of yeast-like fungi which makes serological interpretation even more complex but gives the opportunity for differentiation. Changes in antibody concentrations may be detectable with ELISA but not with HAT, making a combination of the two techniques advantageous, e.g. in case of decreasing IgM antibody activity and simultaneously increasing IgG antibody activity.
Currently no single technique in isolation allows for a definitive serological diagnosis of candidiasis. Surveillance of at risk patients and therapy control requires the use of a variety of methods including serology and antigen detection. The Candida albicans antigen ELISA Kit is of particular help in such situations by detecting Candida specific antigen in patient samples.