Influence of extracellular bactericidal agents on bacteria within macrophages
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Updated: Sep 27, 2026

Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses
Published on: February 22, 2019
Terri S Hamrick1, Adam H Diaz, Edward A Havell
1Department of Microbiology, Pathology, and Parasitology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
Abstract:
We employed gentamicin-sensitive and -resistant derivatives of Escherichia coli in a macrophage phagocytosis assay that compared lambda bacteriophage and gentamicin as extracellular bactericidal agents. Colony counts and direct microscopic examination of phagocytized E. coli supported the conclusion that gentamicin entered macrophages, even at low concentrations, and contributed to their bactericidal activity. Also, two E. coli strains differing in the ability to express the adhesin of type 1 pili (FimH) were distinguishably different in intracellular survival when lambda was used as the extracellular killing agent but were indistinguishable when gentamicin was employed.
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