A 64-year-old man with history of coronary artery disease, hypertension, and hyperlipidemia initially presented to outside hospital with complaint of 6 weeks of fever, weakness, anorexia, and left flank pain. He reported recent illness one month prior with pneumonia which was treated with antibiotic for 10 days. Shortly thereafter, he began to experience loose stool and anorexia. CT abdomen/pelvis in ED revealed a penetrating ulcer at the level of the celiac artery and patient was transferred to our hospital for management.
On admission, patient was afebrile with normal vital signs. Physical exam was unremarkable except for some mild, bilateral pitting edema of his lower extremities. A CT angiogram of abdomen/pelvis confirmed penetrating ulcer along the posterior wall of the thoracoabdominal aorta without periaortic hemorrhage. Blood cultures grew Salmonella enteritidis. Patient was treated with ceftriaxone then ciprofloxacin. Vascular surgery placed rifampin-soaked thoracic endograft. Plan was to remain on antibiotics indefinitely given the aortic repair with hardware.
Salmonella species are known to cause gastroenteritis, bacteremia, and localized infections. Notably, about 20% of bacteremic patients develop focal infections including in the bones, joints, meninges, and skin. Unlike most enteric bacteria, Salmonella species also have the propensity to adhere to vascular endothelium. A study of 105 patients with Salmonella bacteremia revealed 25% of people >50 years also had endothelial infection, reflecting the ability of Salmonella to invade arterial intima. Notably, this was compared to 0% of people <50 years, highlighting another aspect of Salmonella virulence; its preference for areas of abnormality such as atherosclerosis.
In addition to anatomical abnormalities, antibiotics are a known predisposing factor for Salmonella infections. This fact has been well established in both clinical review and animal studies. For example, in a review of 129 non-fecal isolates of Salmonella at Boston Massachusetts General Hospital, prior antimicrobial use accounted for 10% of cases. The ability of antimicrobials to alter normal gut flora has also been utilized for the in vivo study of Salmonella virulence in mouse models. In one study, mice were treated with clinically effective doses of streptomycin and vancomycin before oral infection with Salmonella. Subsequent evaluation of intestinal flora revealed the antibiotics altered the microbiota composition, not only rendering the mouse more susceptible to enteric infection, but also resulting in more severe intestinal pathology. Another mouse model study revealed that streptomycin treatment prior to inoculation with Salmonella was also responsible for increased rate of bacterial translocation.
We present a case of Salmonella bacteremia and aortitis a month after treatment with broad spectrum antibiotics for pneumonia. We hypothesize that antibiotic use predisposed the patient to severe Salmonella infection.
To cite this abstract:Evans CA, Horton J. Salmonella: The Heart of the Problem. Abstract published at Hospital Medicine 2016, March 6-9, San Diego, Calif. Abstract 503. Journal of Hospital Medicine. 2016; 11 (suppl 1). https://www.shmabstracts.com/abstract/salmonella-the-heart-of-the-problem/. Accessed July 22, 2019.