Does focal destruction of the thoracic aorta wall by Staphylococcus aureus lead to the development of infected aneurysms? An experimental study.

OBJECTIVE

The infrequency of infected aneurysms suggests that either infection of segments of the aortic wall is uncommon, or that infections do not always lead top infected aneurysm formation. The purpose of the study was to determine whether focal Staphylococcus aureus infection of aortic wall segments leads consistently to the development of infected aneurysms and to evaluate the segments in which infection did not lead to the infected aneurysm formation.

METHODS

Twenty pigs were inoculated with 0.1 ml of a Staphylococcus aureus inoculum in three segments of the thoracic aorta wall (study group). In another 10 pigs, 0.1 ml of saline solution was injected in three segments of the thoracic aorta wall (control group).

STUDY GROUP

histological abnormalities and bacterial culture of the inoculation sites were evaluated at 10 days (n = 5 pigs), 30 days (n = 5 pigs), and 90 days (n = 10 pigs).

CONTROL GROUP

histological abnormalities were evaluated at 10 days (n = 5 pigs) and 90 days (n = 5 pigs).

STUDY GROUP

infected aneurysms developed in only two animals killed at 30 days. At 90 days, destruction of the elastic tissue, scar tissue and neointima formation were found in all the aortic segments studied.

CONTROL GROUP

no significant changes were found in any of the segments evaluated.

CONCLUSION

In our experimental model, acute local infection by S. aureus caused the development of infected aortic aneurysm in only 10% of the animals. In the remaining 90%, healing of the site of infection followed resolution of the infection.