<prompt> What is the most common organism that causes infected abdominal aoic aneurysms AAAs?Escherichia coliBacteroidesSalmonellaPseudomonas aeruginosa  <response>: There are four different causes of an infected aneurysm. 1 Mycotic aneurysms involve a septic embolus from the hea infecting an aery. 2 Microbial aeritis involves bacteria infecting an athero- sclerotic aery to cause aneurysmal degeneration 80 of infected aneurysms. 4 Traumatic pseudoaneurysm that has concomitant bacterial inoculation. Salmonella causes 40 of all aneurysmal infections, with most others being caused by Streptococcus, Staphylococcus, Bacteroides, E. coli, and P. aeruginosa. Blood cultures are positive in only 50 of cases. 