title: Attachment and entry of Legionella pneumophila in Hartmannella vermiformis.
abstract: Legionella pneumophila is an intracellular parasite of Hartmannella vermiformis. Attachment to the amebae and entry of L. pneumophila were studied by two quantitative assays: One used plate counts to measure the number of bacteria attaching to amebae at 4 degrees C; the other determined the number of intracellular bacteria by use of transmission electron microscopy (TEM). The attachment assay showed that L. pneumophila are inefficient in attachment to amebae. About 0.05% of the bacteria were bound after 1 h with a 10- to 40-fold increase over the next 11 h. Attachment of both virulent and avirulent strains of L. pneumophila occurred at a similar rate. Uptake of L. pneumophila was measured by counting intracellular bacteria using TEM. Limited numbers of virulent L. pneumophila were found intracellularly before 4 h, but the numbers increased logarithmically after this time. The number of amebae containing virulent L. pneumophila increased linearly during the 12-h co-incubation. Avirulent L. pneumophila were rarely detected within amebae throughout the 12-h incubation. Results indicate that entry, not attachment, of virulent L. pneumophila is the limiting step in infection of axenically grown H. vermiformis.
authors: Respiratory Diseases Branch (Division of Bacterial and Mycotic Diseases), Centres for Disease Control and Prevention, Atlanta, Georgia 30333.
authors: B S
authors: BS
authors: Fields
authors: S R
authors: SR
authors: Fields
authors: J N
authors: JN
authors: Loy
authors: E H
authors: EH
authors: White
authors: W L
authors: WL
authors: Steffens
authors: E B
authors: EB
authors: Shotts
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D006249:Hartmannella / Q000382:microbiology* / Q000648:ultrastructure; D016952:Legionella pneumophila / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D014774:Virulence