Related Experiment Video
Updated: Jul 20, 2026
Influenza Virus Propagation in Embryonated Chicken Eggs
Published on: March 19, 2015
Changes in the virulence of Mycobacterium avium after passage through embryonated hens' eggs
E G Long1, E P Ewing, J H Bartlett
1Division of AIDS, STD and TB Laboratory Research, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
Abstract:
Eight-day-old embryonated hen's eggs were used as a model to study Mycobacterium avium virulence. Strains isolated from human patients caused 20-90% mortality when eggs were infected by injection of bacterial suspensions into the amniotic sac. Virulence of examined strains subsequently decreased with passage through eggs to between 0 and 40% mortality in four passages. Virulence of the egg-attenuated strains could be restored by passage through human peripheral blood mononuclear cells. The site of infection in the egg was usually the mesodermal layer of the chorioallantoic membrane. A few small granulomas containing acid-fast bacteria were seen in the liver, but not in other organs. Death of chicken embryos may have resulted from destruction of the mesodermal layer of the chorioallantoic membrane with consequent respiratory failure. PBMCs infected with less virulent egg-passaged strains of M. avium produced higher levels of tumor necrosis factor-alpha than did peripheral blood mononuclear cells infected with more virulent nonpassaged strains.
Insights
Mycobacterium avium virulence in embryonated eggs decreased with passage but was restored by human cells. Egg passage attenuated M. avium, impacting tumor necrosis factor-alpha production.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Mycobacterium avium is an opportunistic pathogen.
- Understanding M. avium virulence is crucial for disease management.
Purpose of the Study:
- To investigate Mycobacterium avium virulence using an embryonated hen's egg model.
- To assess the effect of serial egg passage on M. avium virulence.
- To evaluate the restoration of virulence by passage through human peripheral blood mononuclear cells (PBMCs).
Main Methods:
- Eight-day-old embryonated hen's eggs were infected with M. avium strains.
- Serial passages of M. avium through eggs were performed.
- Virulence was assessed by embryo mortality.
- Egg-attenuated strains were passaged through human PBMCs.
- Tumor necrosis factor-alpha (TNF-α) production by PBMCs was measured.
Main Results:
- M. avium strains caused 20-90% mortality in eggs.
- Serial egg passage reduced M. avium virulence to 0-40% mortality.
- Passage through human PBMCs restored virulence in egg-attenuated strains.
- Infection site was primarily the chorioallantoic membrane mesodermal layer.
- PBMCs infected with less virulent strains produced higher TNF-α levels.
Conclusions:
- Embryonated hen's eggs serve as a viable model for M. avium virulence studies.
- Serial egg passage attenuates M. avium virulence.
- Human PBMCs can restore virulence to egg-attenuated M. avium strains.
- M. avium infection in eggs may lead to embryo death via respiratory failure.
- Differential TNF-α production by PBMCs correlates with M. avium strain virulence.
