Detection of flagella in 278 Legionella strains by latex reagent sensitized with antiflagellum immunoglobulins.

To determine whether all Legionella species show common flagellum antigen properties, we developed a reagent using latex beads sensitized with flagellin-specific immunoglobulins that could be used in a simple and rapid agglutination reaction to identify Legionella colonies. A total of 278 strains (68 Legionella reference strains and 210 patient and environmental isolates) were tested. The results were compared with those obtained by a direct immunofluorescence assay using an antiflagellum serum and by morphological observations by electron microscopy. The immunological methods based on the use of a flagellum-specific serum have confirmed the presence of a common flagellum antigen for all Legionella species described to date. Flagella were detected for all the legionellae studied except four species: L. oakridgensis, confirmed as a nonflagellate species; L. brunensis; L. cincinnatiensis; and L. longbeachae serogroup 1. However, we noted a remarkable variability in flagellum expression, of greater or lesser degree, according to the species and their origin. A combination of all three methods of flagellum detection revealed that 86.3% of Legionella strains studied were flagellate. The latex test identified 89.6% of these strains, 97.5% of L. pneumophila, and 100% of L. pneumophila serogroup 1.

[Use of cultured epidermis of human origin for demonstrating the acantholytic action of staphylococcal exfoliatin A]. / Emploi d'épidermes de culture d'origine humaine pour mettre en évidence l'action acantholytique de l'exfoliatine A staphylococcique.

Cultured human epithelia obtained from epidermal cells in vitro were used to assay the activity of staphylococcal epidermolytic toxin and develop an in vitro experimental model for the staphylococcal scalded skin syndrome. Human epidermal cells were grown from single epidermal cell suspensions obtained through trypsinization of adult normal skin into multilayered epithelia (with a basal cell layer, several intermediate and one or two upper layers) on mouse 3T3 feeder cells. First passage cultures were incubated with exfoliative toxin A from phage Group II staphylococci at various concentrations in DMEM. They were examined at various time intervals by direct microscopic and histological examination of respectively the culture plates or the epidermal sheets after their detachment from the plates with dispase grad II. A total exfoliation could be obtained at 24 hour at concentrations of Img and 500 micrograms/ml, only local areas of epidermolysis noted at 100 micrograms/ml. The intraepithelial separation was noted to occur between the basal layer and the lowest intermediate layer. No exfoliation could be observed at lower concentrations. Up to 4-5 hours few changes were evident, but at this time small areas of epidermolysis developed. With exfoliatin 100 micrograms/ml, intraepidermal blisters were clearly visible, occurring either between the basal cells and the lowest intermediate layer or between the first two intermediate cell layers. At the ultrastructural level, desmosomes were sparse and altered, with enlargement of the intercellular spaces and condensation of tonofilaments. These data indicate that human epidermal cell cultures, although their differentiation in culture only mimics what occurs in vivo, can be used as an in vitro model of the staphylococcal TEN to further investigate the site of action of such a toxin and the cellular mechanism responsible for the syndrome.