Relationship between shell structure and movement of Salmonella enteritidis across the eggshell wall.

1. Ultrastructural analyses of the eggshells of one strain of commercial layers indicated that the cuticular layer is rarely present as an even covering over the shell surface and the paired shell membranes are invariably pitted with holes larger than bacterial dimensions. 2. The above conditions pertain irrespective of the age of the laying bird. 3. Bacterial penetration of the eggshell is independent of pore numbers. 4. In the absence of a functional cuticle and with the shell membranes removed, bacteria are checked in their movement by structural modifications in the mammillary layer.     

Automated monitoring system for determining embryo movement and death times following virus infection.

Design and performance information is presented on an automated embryo-monitoring system for intact eggs. The computer-based system has been used successfully for several months to characterize viral pathogenicity in embryonated eggs. Features include electronic sensing of embryo movement, automatic quantification of the amount of movement, and automatic recording of the results on electronic media. The system does not require that eggs be removed from the incubator or that the incubator be opened during the course of an experiment, as is necessary with the manual candling technique. It has greatly improved discrimination of viral pathogenicity effects in fertile eggs because of its sensitivity and reduced intervals between observations. One important potential application involves using the system to measure the effects on virulence of mixing closely related variants of the same strain of virus that differ in pathogenicity, which is the biological scenario most likely approximating a natural disease outbreak.