Biomedical subjects
Publications and source records attributed to E M Elder.
Tatlockia (Legionella) micdadei, the Pittsburgh pneumonia agent, was isolated from a hospital shower. Although it was not possible, at the current time, to establish an epidemiological link to disease acquisition, this information may be significant because it provides further evidence that a water-associated reservoir of this organism exists within the hospital.
Five strains of bacteria (strains 684, 687, U7W, U8W, and MICU-B) that were biochemically and morphologically indistinguishable from Legionella pneumophila were recovered from the environment. Strains U7W, U8W, and MICU-B were antigenically identical to L. pneumophila strain Dallas 1E (serogroup 5), as determined by direct fluorescent antibody staining and immunodiffusion. Although strains 694 and 687 shared antigenic determinants with L. pneumophila Dallas 1E, they could be distinguished by immunodiffusion and differential absorption studies. However, as determined by DNA hybridization, the antigenically distinct strains 684 belong to the same DNA homology cluster as previously described authentic strains of L. pneumophila, whereas strain U7W, U8W, and MICU-B belong to a separate homology group. Therefore, two groups could be identified among these environmental isolates; one represents an antigenic subclass of serogroup 5 L. pneumophila (strains 684, and 687), and the other, although antigenically indistinguishable from serogroup 5 L. pneumophila, probably represents a new Legionella species (strains U7W, U8W, and MICU-B).
Environmental and clinical isolates of Legionella pneumophila obtained from the Pittsburgh Veterans Administration Medical Center were studied for the presence of plasmids and for unique surface antigens. The majority of environmental isolates contained a single 80-megadalton plasmid. After an epidemic of nosocomial Legionnaires disease subsided in the Spring of 1981, plasmid-bearing environmental isolates persisted in the environment. Whereas L. pneumophila could not be reisolated from most sites with plasmidless isolates. During this epidemic the attack rate was highest on wards with plasmidless isolates. All clinical isolates were plasmidless. Strains were serotyped by the indirect immunofluorescence method with serum from a single immunized rat which was used both without absorption and after absorption with various plasmid-bearing and plasmidless isolates. These studies suggested that a plasmid-associated surface antigen was present and that the most common plasmidless environmental serotype was similar to the epidemic clinical serotype.
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