Laboratory diagnosis of invasive candidiasis

Abstract

Severe infections due to Candida species have become more frequent during the past two decades because of the increasing numbers of immunosuppressed patients being treated in our hospitals. Distinguishing colonization from invasive disease requires knowledge of the pathogenetic mechanisms leading to invasion. To assist the clinician in therapeutic decisions, clinical microbiologists should identify to species Candida organisms isolated from immunosuppressed patients. Quantitative or semiquantitative cultures of urine, burn tissues, intravascular catheter tips, and bronchoalveolar lavage specimens may provide useful information. Immunofluorescent staining of certain specimens can enhance diagnostic yield. The lysis-centrifugation blood culture technique offers some advantages over traditional broth techniques in detecting Candida fungemia. Antibody testing is of limited diagnostic value in highly immunosuppressed patients. Developing simple and reliable tests for detecting antigens or metabolites of Candida spp. in the sera of infected patients has proven difficult. Methods for typing Candida albicans are evolving. Typing should prove useful for studying the epidemiology of candidiasis in hospitalized patients.

The Medically Important Yeasts Present in Clinical Specimens

“…The current investigation did not discriminate between the two patient populations. The high incidence of Candida albicans in the various specimens is not unexpected since it is the most virulent of all yeasts, in addition to being a major participant in the normal flora of various body sites [1,3,11,12]. The other species that were encountered in high numbers were Torulopsis glabrata, Candida parapsilosis, C. tropicalis, C. krusei, and Saccharomyces cerevisiae.…”

“…Similar findings were reported by Kiehn et al [8] with slight modification of the order of frequency, perhaps due to the difference in the type of patients investigated. The pathogenicity of C. parapsilosis and C. tropicalis in compromised patients is well established [1,3,11,13]. These two species are considered next to C. albicans as etiologies of candidaemia.…”

Combined detection of mannanaemia and anti-mannan antibodies as a strategy for the diagnosis of systemic infection caused by pathogenic Candida species

“…Diagnosis is generally supported by a compendium of clinical [46], radiological [47][48][49] and mycological evidence [50]. Efforts made to include the results of serological tests in this compendium have generally failed, despite consistent improvements in the sensitivity and specificity of these tests, particularly those detecting candidaderived molecules such as D-arabinitol [26], glucans [25] and mannan [24,51].…”

The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase of Candida albicans is a surface antigen

“…Interestingly, some cytosolic proteins, such as enolase, members of the hsp70 family, and phosphoglycerate kinase, have been described to be bona fide components of C. albicans cell walls (2,3,31). Although some of these moieties have been used as potential marker antigens for antibody detection in invasive candidiasis (20,26,33,35,58), a simple, reliable, and easy-to-perform serological assay for the diagnosis of systemic Candida infections has not yet been developed.…”

“…Blood cultures for Candida species generally exhibit low sensitivity (39), and the tests for determination of marker antigens need further fine-tuning to improve their sensitivity and specificity so that they will be valuable in guiding clinical treatment decisions (38,43,44). Likewise, standard immunological tests to detect antiCandida antibodies usually have low specificity and/or sensitivity, since they mainly recognize antibodies against Candida cell wall mannan, which are ubiquitous in human sera (26,54,58); furthermore, the crude preparations of candidal antigens cannot be standardized enough to allow good test reproducibility among laboratories (26). Despite the considerable heterogeneity of the humoral responses to antigens of C. albicans in humans, several cytosolic antigens have been identified.…”