Candida - Antigen (mannan) Detection ..., Antibodies; Molecular diagnosis (PCR).
Mannans are polysaccharides formed by unions mannose molecules. These poliacáridos found in the cell walls of plant cells, forming linear polysaccharide with ? glycosidic linkages (1-4), and in the cell wall of yeasts such as Candida albicans and other species, forming polysaccharides with branched structure a central axis formed by glycosidic linkages ? (1-6) branches and ? (1-2) and ? (1-3). These polysaccharides mannose (mannans) are conjugated proeínas (mannoproteins), and are located in the outermost part of the cell wall. Inside out, in the cell wall of fungi outside of the cytoplasmic membrane, is a layer of chitin [polysaccharide ? (1-4) -acetyl], then out there are several layers of ? (1- 3) -glucan, along with galactomannans [? (1-4) linkages -manano with ? (1-6) galactose, in the case of Aspergillus and some other fungi], and in the cell wall of yeasts such as Candida albicans and other species, is the layer polysaccharides mannose branched structure with a central axis formed by glycosidic linkages ? (1-6) branches and ? (1-2) and ? (1-3). These polysaccharides mannose (mannans) are conjugated with proteins (mannoproteins), and are located in the outermost part of the cell wall.
The existence of these mannoproteins, as a major constituent in the cell wall of Candida cells and releasing polysaccharide mannan, made think that its detection in serum and other biological fluids, could constitute a method of diagnosing infections deep Candida albicans. For this purpose a sandwich ELISA method (mannan sensor system, and conjugate developer) which detects the polysaccharide with ?-glycosidic linkages, forming mannoproteínas Candida spp designed. Some studies showed its utility, while others do not evidenced by low sensitivity (40% of infections by Candida albicans), but had a high specificity (98%). The low sensitivity was due to the reactivity of the monoclonal antibody used was different depending on the species of Candida, and variable expression of the epitope recognized by the monoclonal antibody used. When a monoclonal antibody detecting glycosidic bonds ?-, ?- and, mannose oligosaccharide is used the sensitivity is increased from 69% to 85%, with a specificity of 95%.
Moreover the detection of antibodies, no diagnostic value by the inability to discriminate between antibodies due to colonization or infection, Candida spp. In addition, the circulating mannan antigen, can be withdrawn from circulation to form immunocomplexes with the antibodies. Similarly, antibodies can be withdrawn from circulation to form immunocomplexes with mannan antigen that induced.
For these reasons, the usefulness of detection mananano antigen as diagnostic test for invasive Candida infections is considered controversial. However, this diagnostic test IVAMI provides, alongside conventional diagnostic tests for microscopic examination, cultivation for isolation and molecular methods (PCR).
Tests in IVAMI:
- Antigen detection (mannan), by ELISA.
- Culture for isolation.
- Identification of yeast species by amplification and sequencing of the chromosomal region ITS2.
- PCR in clinical samples for Candida spp.
- Antigen detection: serum, cerebrospinal fluid, urine, etc. (0.5 to 1 mL).
- Cultivation: cerebrospinal fluid (CSF), deep respiratory swab, or other samples.
- Identification of yeast species: crop isolate.
- PCR for detection of Candida spp .: cerebrospinal fluid (CSF), exudate deep breathing, or other samples.
Preservation and shipment of sample:
Refrigerated (preferred) for less than 2 days.
Frozen: over 2 days.
- Detection antibody: 48 to 72 hours.
- Detection of mannan antigen: 48 hours.
- Culture: 48 hours.
- Species identification by molecular methods: 48 to 72 hours.
- PCR for Candida spp. in clinical samples: 48 hours ..
Cost of the test: