IMMUNOLOGICAL METHODS FOR THE DETECTION OF STRUCTURAL COMPONENTS AND METABOLITES OF BACTERIA AND FUNGI IN BLOOD

This review compares the clinical usefulness of immunological methods for the detection of structural components and metabolites of bacteria and fungi. Bacterial antigens (especially those of Mycobacterium, Nei sseria, Staphylococcus aureus, Yersinia enterocolitica, Escherichia co li, Salmonella, Chlamydia, and Brucella) are best detected by enzyme-l inked immunosorbent assay. Methods involving antibodies are more expen sive and are effective only when performed in series. The detection of antibodies that recognize S aureus teichoic acid merely confirms the presence of a metastatic complication. Tissue invasion by Candida albi cans is not yet reliably detectable by the presence of a-specific anti gen. Simple, but not completely reliable methods are available such as the latex test for mannans detection and/or agglutination with liposo mes for detecting 48-kDa cytoplasmic protein antigen and an assay for detecting enolase antigen. A latex agglutination test has also been de veloped for the mannans antigen of Aspergillus and for Cryptococcus ne oformans capsular polysaccharide ; the latter test is more cost effect ive. The sensitivity of both tests is improved by serial assays. A neg ative finding with hemmagglutination-based antibody tests rules out C albicans infection, and titers of 1/640 or higher have been associated with disseminated infection by Aspergillus. Concentrations of C albic ans blastopore antigen antibodies higher than 400 IU/ml can be seen in disseminated candidiasis. High concentrations of endotoxin are indica tive of imminent septic shock. Some biological indicators (C reactive protein, angiotensin converting enzyme, fibronectin, elastase-alpha1-a ntitrypsin complex, tumor necrosis factor and interleukin-6) have been used to rule out a bacterial cause of fever. Such methods, when used in combination, appear to be useful only in excluding a microbial caus e of the disease.