Attachment and entry of Legionella pneumophila in Hartmannella vermiformis

J Infect Dis. 1993 May;167(5):1146-50. doi: 10.1093/infdis/167.5.1146.


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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Bacterial Adhesion
  • Hartmannella / microbiology*
  • Hartmannella / ultrastructure
  • Legionella pneumophila / pathogenicity
  • Legionella pneumophila / physiology*
  • Legionella pneumophila / ultrastructure
  • Microscopy, Electron, Scanning
  • Virulence