Infection, haemorrhagia and death of chick embryos experimentally inoculated with Listeria monocytogenes by the intra-allantoic route.

When allantoic sacs of embryonated (SPF) chicken eggs were inoculated with different doses to investigate the pathogenicity of two strains of Listeria monocytogens (4379 and NCTC 5214), infection resulted which spread rapidly throughout the embryonated eggs. When low doses were used small pock lesions on the chorio-allantoic membrane (CAM), generalized haemorrhage (especially on the head region) and deaths of the embryos with necrotic foci on the liver and heart were observed. Neither the pock lesions nor the haemorrhage were detected in embryos dying from high doses of the bacterium. Bacteria were recovered from the CAM's, allantoic fluids, amniotic fluids and selected organs of the dead embryos. The pathogenicity was shown to be strain dependent, strain 4379 being more pathogenic than strain NCTC 5214. In vitro studies indicated that brain homogenates of uninoculated chicken embryos are not inhibitory to Listeria monocytogenes at 37 degrees C and will increase the viable count.