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

Objective: The infrequency of infected aneurysms suggests that either infec tion 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 t o determine whether focal Staphylococcus aureus infection of aortic wall se gments leads consistently to the development of infected aneurysms and to e valuate the segments in which infection did not lead to the infected aneury sm formation. Methods: Twenty pigs were inoculated with 0.1 mi of a Staphyl ococcus aureus inoculum in three segments of the thoracic aorta wall (study group). In another 10 pigs, 0.1 mi of saline solution was injected in thre e segments of the thoracic aorta wall (control group). Study group: histolo gical abnormalities and bacterial culture of the inoculation sites were eva luated at 10 days (n = 5 pigs), 30 days (n = 5 pigs), and 90 days (n = 10 p igs). Control group: histological abnormalities were evaluated at 10 days ( n = 5 pigs) and 90 days (n = 5 pigs). Results: Study group: infected, aneur ysms developed in only two animals killed at 30 days. At 90 days, destructi on of the elastic tissue, scar tissue and neointima formation were found in all the aortic segments studied. Control group: no significant changes wer e found in any of the segments evaluated. Conclusion: In our experimental m odel, 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. (C) 1999 Els evier Science B.V. All rights reserved.