Introduction: Pasteurella Multiocida is a gram-negative
coccobacillus that is part of the normal oral flora in many animals, and
thus also the etiologic agent in various infectious syndromes after
animal bites (1). While most of the infections caused by P.
Multiocida are superficial wounds and localized abscesses, instances of
aortitis, bacteremia, meningitis, respiratory complications, septic
arthritis, and spontaneous bacterial peritonitis have also been reported
(2). Herein we describe our management in a case of a canine bite
resulting in a P. Multiocida descending thoracic aorta mycotic
pseudoaneurysm.
Case Report: Our patient is a 61-year-old gentleman who was initially
seen in an Emergency Department after a canine bite. He was admitted and
treated with a course of IV antibiotics for P. Multiocidabacteremia and discharged. Three weeks post discharge, he continued to
feel generalized malaise. Work-up with echocardiogram showed no
intracardiac valvular pathology, but CTA was significant for a
descending thoracic aorta mycotic pseudoaneurysm (Figure 1). After a
discussion with the patient, and a multidisciplinary case review, we
elected to intervene surgically. The patient underwent a left posterior
lateral thoracotomy with femoral-femoral cardiopulmonary bypass for
complete pseudoaneurysm resection, replacement with a 24 mm
GelweaveTM graft (Terumo Cardiovascular Group, Ann
Arbor, Michigan) (Figure 2), and local continuous antibiotic irrigation.
Given purulence and gross infection we planned for a staged approach,
with a secondary washout and omental flap for biologic graft coverage
seven days after the index operation. Intraoperative cultures of the
aortic pseudoaneurysm were consistent with P. Multiocida . The
patient progressed well clinically and was discharged at 14 days to
rehabilitation with a six-week intravenous course of antibiotics. At one
year postoperatively, the patient continues to do well and has no
issues.
Comment: Without intervention, the natural progression of mycotic
pseudoaneurysms is uncontrolled sepsis and/or catastrophic rupture and
hemorrhage (3). Ballestra described the survival of a patient that was
treated with antibiotics for medical sterilization, followed by
endovascular exclusion for the pseudoaneurysm (2). While there may be an
argument to utilize that strategy as compassionate use therapy, in our
practice, patients that are viable surgical candidates undergo open
surgery as we believe that the removal of the infectious source is vital
to long-term survival. In our case, we utilized a staged approach prior
to definitive closure. This strategy allowed for interval sterilization
of the infected cavity via two mechanisms, locally with antibiotic
irrigation, and systemically with intravenous antibiotics after the
source infection has been removed. The subsequent evacuation of the
remnant blood in the thorax can help decrease the microorganism
bio-burden as the stagnant blood can act as a robust medium growth.
Additionally, the pedicled omental flap is a safe adjunct in the
management thoracic aortic graft infections (4), providing a
vascularized biologic barrier to combat anastomotic breakdown and reduce
reinfection risk. Thoracic aortic pseudoaneurysms caused by P.
Multiocida are a rare clinical condition. The patient’s clinical course
with subsequent follow-up suggest that complete resection of the mycotic
pseudoaneurysm, followed by omental flap coverage is a viable strategy
to manage mycotic aortic infections with virulent organisms.
Ethics Statement: All of the authors are in agreement with the content
in the manuscript. Each author has contributed to the drafting and
editing of the manuscript. There are no sources of financial support in
the form of grants, equipment, and/or pharmaceutical items for this
research. There are no potential conflicts of interest. The publication
falls under an encompassing IRB that allows review of institution
specific postoperative cardiovascular patients whereby no formal patient
consent is required.