[Non-culture based laboratory diagnosis of sepsis]

Blood culture is clearly the most important diagnostic procedure for sepsis. In the majority of cases, however, it yields negative results when bacterial or fungal sepsis is strongly suspected in view of an excellent response to antibacterial or antifungal medication. This is likely because infecting microbes have already been too seriously damaged in the blood stream to grow in culture media. Therefore, various tests have been devised to detect cellular components of pathogens including endotoxin for gram-negative bacteria, (1-->3)-beta-D-glucan for fungi, a non-mannan heat-labile candida antigen, glucronoxylomannan for Cryptococcus neoformans, and galactomannan for Aspergillus. The first two tests are particularly suitable for screening purposes, because, in addition to their high sensitivity and specificity, they cover a wide range of species in each category, though not as widely as blood culture. The candida antigen detectable by Candi-Tec is probably a complex of immune-related proteins, and appears to be a poor indicator in immunocompromised hosts. Glucronoxylomannan has been established as a useful marker of cryptococcosis, whereas galactomannan, though highly specific for aspergillosis, needs a more sensitive detection system to be useful for diagnostic purposes.