A Scanning Electron Microscope Study of Bacterial Invasion in Hen's Egg Shell

Abstract Fresh hen's eggs were immersed in a suspension of P. fluorescens. After 3, 4, 7 and 11 days, eggs were removed and shell samples examined by scanning electron microscopy. No bacterial invasion of the shell pores was evident after 3 days exposure to the microorganism, confirming the protective role of the cuticle in closing pores through the calcareous layers. Pores of eggs exposed 4, 7 and 11 days were infected with P. fluorescens. The cuticular barrier was apparently overcome by a digestive process. Invasion of the pores and shell membranes then proceeded very rapidly. Bacteria were found throughout the shell membrane fiber interstices with no particular accumulation at the continuous inner boundary of the inner shell membrane. The appearance of the fibers and the inner boundary was entirely unchanged after infection which suggested an enzymic process was not involved in the breaching of the final barrier protecting the eggs' contents.