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Chapter 66 : Serological and Molecular Diagnosis of Fungal Infections
This chapter reviews the most extensively evaluated or routinely used tests for the serodiagnosis of mycotic infections. Pulmonary aspergilloma occurs when Aspergillus fumigatus or other Aspergillus species colonize preexisting cavities of tuberculosis, sarcoidosis, or bronchiectasis. Systemic candidiasis should be suspected if serial serum specimens show an increase in titer or an increase in the number of reactive bands detected over time. Serologic tests may also be employed to determine the potential clinical significance of Candida species recovered from various body sites. Enolase, a 48-kDa cytoplasmic antigen of Candida albicans, is a potentially useful diagnostic marker of invasive candidiasis. Tests to detect anti-Coccidioides immitis antibodies are of proven usefulness for the diagnosis and management of coccidioidomycosis. Antibody detection is of value for the diagnosis of cryptococcosis during the early stages of the disease, before antibodies are neutralized by the large amount of capsular antigen released during evolution of infection. The Histoplasma polysaccharide antigen EIA (HPA test) is a microtitration plate-based double-antibody sandwich enzyme immunoassay to detect antigenuria and antigenemia in disseminated histoplasmosis. A major diagnostic precipitin is consistently found in the sera of patients with paracoccidioidomycosis, which reacts with a soluble, specific Paracoccidioides brasiliensis antigen. Invasive fungal infections studied included aspergillosis, candidiasis, fusariosis, and trichosporonosis.
Key Concept Ranking
- Central Nervous System Diseases
Examples of immunodiffusion results observed when a seven-well agar gel pattern is used. (A) Band of identity (patient 2); (B) band of partial identity (patient 1); (C) band of nonidentity (patient 3). Ag, reference antigen; Ab, reference antiserum; 1 to 4, patient test sera. A standard reference band is shown midway between the lower antiserum-containing wells and the central antigen-containing wells in all three panels.
Diagram displaying organization of the microtiter plates and results for the complement fixation assay. Percent lysis: solid circles, 100% lysis; shaded circles, 30 to 90%; open circles, 0% lysis. SC, serum control wells receiving buffer in place of antigen; H, column receiving Histoplasma mycelial histoplasmin antigen; Y, column receiving Histoplasma yeast antigen; B, column receiving Blastomyces antigen; C, column receiving Coccidioides coccidioidin antigen; P column receiving Paracoccidioides yeast antigen; CC, cell control. CH66, amount of complement required for 50% lysis of SRBC. (A) Patient plate. Patient 1 demonstrates serum that is positive for Histoplasma antibodies with a 1:16 titer against mycelial histoplasmin antigen and a 1:64 titer against Histoplasma yeast antigen. Patient 2 displays serum that contains an anticomplementary titer of 1:16. However, because antibodies to coccidioidin are present at a titer that is >2 dilutions beyond the anticomplementary titer, the patient CF result is AC 1:16, Coccidioides 1:128. (B) Control plate. Percent lysis symbols as above. Columns 1 to 9 depict the reactivity of the control sera to specific fungal antigens. Columns 10 to 12, rows A to F, depict the results of the back titration of complement in CH66 units (5 through 1.25) in the presence of fungal antigens or the VBD buffer control. Columns 11 and 12, row H, depict the cell control wells that receive SRBC only.
Commercially available antibody detection tests for fungal diseases
Commercially available antigen detection tests for fungal diseases