Pathogenesis and growth of Listeria monocytogenes in fertile hens' eggs

Abstract

The LD50 for 15-day old chicken embryos inoculated with Listeria monocytogenes into the allantoic sac was determined. The growth cycle of the organism was investigated in different tissues and fluids derived from embryonated eggs following inoculation with a suspension of L. monocytogenes equivalent to the LD50. Eggs receiving doses of 100 and 1000 times the LD50 were used to examine the effect of high doses on the pathogenesis and growth of Listeria in ovo. The pattern of growth of the organism in embryonic blood showed two distinct peaks and correlated with these was the development of large and small pock lesions on the chorioallantoic membrane. Bacterial growth in the internal organs exhibited a single peak. Histological and electron microscopic evidence indicated that the primary cellular damage was due to a soluble haemolysin present prior to the establishment of the organism within the tissues.