Killing mechanism of Listeria monocytogenes in activated macrophages as determined by an improved assay system.
Exposure of Listeria monocytogenes to gentamicin 5 mg/L for 4 h resulted in the killing of most extracellular bacteria, but had no effect on the survival of bacteria inside macrophages. Higher concentrations of gentamicin caused a reduction in the number of intracellular bacteria. This effect was associated with cellular uptake of gentamicin, but was unaffected by activation of macrophages by interferon-gamma and lipopolysaccharide. In experiments in which exposure to gentamicin 5 mg/L for 4 h was used to kill extracellular bacteria, killing by activated macrophages was impaired when O2- production was inhibited by superoxide dismutase, but not when nitric oxide production was blocked by NG-monomethyl-L-arginine. These data suggest that the reactive oxygen intermediates are more important than nitric oxide in the killing of L. monocytogenes, at least in macrophages activated in vitro.
Ohya
S
S
Department of Bacteriology, Niigata University School of Medicine, Japan.
Xiong
H
H
Tanabe
Y
Y
Arakawa
M
M
Mitsuyama
M
M
D000818:Animals; D002474:Cell-Free System; D002478:Cells, Cultured; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects*; D008262:Macrophage Activation; D008264:Macrophages / Q000382:microbiology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D013047:Specific Pathogen-Free Organisms; D013482:Superoxide Dismutase / Q000494:pharmacology; D013997:Time Factors; D019323:omega-N-Methylarginine / Q000494:pharmacology
D005839:Gentamicins; D008070:Lipopolysaccharides; D019323:omega-N-Methylarginine; D007371:Interferon-gamma; D013482:Superoxide Dismutase