No abstract

Furthermore, neonatal fecal samples were enumerated for bifidobacteria by fluorescence in situ hybridization (FISH) and tested for PA ELISA reactivity. All bifidobacteria, except B. infantis and B. adolescentis, showed reactivity 6-to 600-fold higher compared to the controls (i.e., Micrococcus luteus and Propionibacterium freudenreichii, which contain a cell wall lipomannan). Eggerthella lenta showed a 25-fold-higher reactivity. ELISA reactivity was clearly shown to be associated with bacterial lipoglycans containing a ␤-1,5-galactofuranosyl chain. All neonatal feces showed PA ELISA reactivity and associated numbers of bifidobacteria. Since high concentrations of bifidobacteria are present in the human gut, these bacteria or excreted lipoglycan may cause false serum PA ELISA reactivity in selected patient groups, especially neonates.

Aspergillus markers are becoming increasingly important for the early diagnosis of invasive aspergillosis. The kinetics of release of these surrogate markers, however, is largely unknown. We investigated the release of ␤-(1-5)-galactofuranosyl (galf) antigens (Platelia Aspergillus), 1,3-␤-D-glucan (BG) (Fungitell), and DNA (PCR) in an in vitro model of Aspergillus fumigatus. The results showed that release is correlated to the growth phase of the fungus, which depends on available nutrients. Whereas galf antigens and BG are released during logarithmic growth, DNA is released only after mycelium breakdown. During early logarithmic growth, galf antigens seem to be released somewhat earlier than BG. Furthermore, galf antigen concentrations of more than 120,000 times the serum cutoff value (0.5 ng/ml) can be measured, while BG concentrations reach a value only 978 times the serum cutoff value (60 pg/ml). During lytical growth, release of galf antigens further increased to a maximum level, which depended on pH. After that, the concentration of galf antigens stayed high (pH 7.4) or decreased to zero within 4 days (pH 5.0). In contrast to galf antigens, BG concentration decreased after 1 day of growth. The decrease of galf components seems to be due to the enzyme ␤-galactofuranosidase, which is able to destroy galf epitopes and whose activity fluctuates in the culture filtrates in parallel with galf antigen concentration. Fungal DNA seems to be released only due to autolysis caused by nutrient limitation. In conclusion, several factors clearly influence the release of surrogate markers in vitro. These same factors might also play a role at the infection site of Aspergillus disease in humans.Invasive aspergillosis (IA) has become a leading cause of death among immunocompromised hosts, including transplant patients, those treated for hematological malignancy, and those treated with high-dose corticosteroids (41, 49). In addition, IA is increasingly observed in the nonneutropenic phase after hematopoietic stem cell transplantation and in nonclassic settings, such as intensive care units with critically ill patients (13, 16). The high mortality is due partly to the difficulty in establishing a diagnosis at an early stage of infection, since presenting symptoms are nonspecific and sensitivity of cultures is low. Techniques to improve timely diagnosis have focused on the detection of circulating surrogate markers released by the fungus (43,45,50). With the development of nonculture-based methods, such as PCR and antigen detection, circulating markers can be detected at an early stage of infection in patients with invasive disease (12, 27, 28).The commercially available sandwich enzyme-linked immunosorbent assay (ELISA) (Platelia Aspergillus [PA]; Bio-Rad, Marnes-la-Coquette, France) is based on the rat immunoglobulin M monoclonal antibody EB-A2, which binds the ␤-(1-5)-galactofuranosyl (galf) side chains of the Aspergillus galactomannan (GM) molecule (24,50,51). In addition to GM, fungal glycoproteins also react with the EB-...

A paradoxical increase in circulating Aspergillus antigen was observed during treatment with caspofungin in a patient with proven invasive aspergillosis. With the exception of treatment with the echinocandin, no other factors were found that might explain this clinical observation, which was supported by experiments done in vitro.