Coxiella burnetii vascular graft infection.

Abstract

Coxiella burnetii, the causative agent of Q fever, may cause culture-negative vascular graft infections. Very few cases of C. burnetii infection of a vascular graft have been reported. All were diagnosed by serology.
We report the first case of Coxiella burnetii vascular graft infection diagnosed by broad-range PCR and discuss the diagnostic approaches and treatment strategies of chronic C. burnetii infection.
C. burnetii should be considered as etiological agent in patients with a vascular graft and fever, abdominal pain, and laboratory signs of inflammation, with or without exposure history. Broad-range PCR should be performed on culture-negative surgical samples in patients with suspected infection of vascular graft.

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BMC Infectious Diseases
Open Access
Case report
Coxiella burnetii vascular graft infection
Laurence Senn1, Mario Franciolli2, Didier Raoult3, Alexandre Moulin4,
Ludwig Von Segesser5, Thierry Calandra1 and Gilbert Greub*1,6
Address: 1Infectious Diseases Service, Department of Internal Medicine, University Hospital, Lausanne, Switzerland, 2Bellinzona Hospital,
Switzerland, 3Unité des Rickettsies, Université de la Méditerranée, Marseille, France, 4University Institute of Pathology, Lausanne, Switzerland,
5Department of Cardio-vascular Surgery, University Hospital, Lausanne, Switzerland and 6Institute of Microbiology, University of Lausanne,
Bugnon 48, 1011 Lausanne, Switzerland
Email: Laurence Senn - Laurence.Senn@chuv.ch; Mario Franciolli - mario.franciolli@bluewin.ch; Didier Raoult - Didier.Raoult@gmail.com;
Alexandre Moulin - Alexandre.Moulin@chuv.ch; Ludwig Von Segesser - Ludwig.Von-Segesser@chuv.ch;
Thierry Calandra - Thierry.Calandra@chuv.ch; Gilbert Greub* - Gilbert.Greub@chuv.ch
* Corresponding author
Abstract
Background: Coxiella burnetii, the causative agent of Q fever, may cause culture-negative vascular
graft infections. Very few cases of C. burnetii infection of a vascular graft have been reported. All
were diagnosed by serology.
Case presentation: We report the first case of Coxiella burnetii vascular graft infection diagnosed
by broad-range PCR and discuss the diagnostic approaches and treatment strategies of chronic C.
burnetii infection.
Conclusion: C. burnetii should be considered as etiological agent in patients with a vascular graft
and fever, abdominal pain, and laboratory signs of inflammation, with or without exposure history.
Broad-range PCR should be performed on culture-negative surgical samples in patients with
suspected infection of vascular graft.
Background
Infection of synthetic abdominal aortic grafts occurs in
≤1% of patients, with a higher risk (1.5–2%) for grafts that
extend to the femoral location. Vascular graft infection
may result from intra-operative contamination, local
extension from infected adjacent tissue or by hematoge-
nous seeding. The most commonly involved pathogens
are Staphylococcus aureus (30%), Enterobacteriaceae (25%),
coagulase-negative Staphylococci (12%), Enterococci (9%),
Pseudomonas aeruginosa (7%) and Streptococci (5%)[1].
Cultures remain negative in approximately 5% of cases
[1]. C. burnetii account for some of these culture-negative
vascular graft infections. Very few cases of C. burnetii infec-
tion of a vascular graft have been reported [2-5]. All previ-
ously reported cases were diagnosed by serology. The
confirmation of the vascular localization of C. burnetii
infection was obtained after the serological diagnosis of
chronic Q fever by culture [3] and/or DNA amplification
of C. burnetii from vascular graft samples [3-5]. Here, we
report a case of C. burnetii vascular graft infection diag-
nosed by broad-range PCR from a surgical sample of a
para-prosthetic abscess which was confirmed by serology.
To our knowledge, ours is the first case where the diagno-
sis was made by broad-range PCR and suggests that broad-
range PCR should be considered in all cases of culture-
negative vascular graft infections.
Published: 07 December 2005
BMC Infectious Diseases 2005, 5:109doi:10.1186/1471-2334-5-109
Received: 07 September 2005
Accepted: 07 December 2005
This article is available from: http://www.biomedcentral.com/1471-2334/5/109
© 2005 Senn et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Case report
A 63-year-old man presented to a regional hospital on
September 8, 2003 with a 2-week history of diffuse
abdominal pain and mild diarrhea, without fever. In
1988, he had received a Dacron aorto-bifemoral graft for
an infra-renal aortic aneurysm. A computerized tomogra-
phy (CT) of the abdomen revealed a para-prosthetic fluid
collection. Blood cultures were sterile in the absence of
any recent antibiotic therapy. Laboratory results showed a
white blood cell count of 5.8 G/l, a CRP of 48 mg/l, no
increase of liver enzymes and a normal serum creatinine
level. Empirical ciprofloxacin and metronidazole therapy
was initiated and abdominal pain improved.
After two months of antibiotic therapy, the patient was
admitted to the University Hospital in Lausanne for
removal of the vascular prosthesis because of presumed
persistent infection, despite two months of antibiotic
treatment. On admission, the patient was afebrile. Clini-
cal examination was normal except for mild periumbilical
tenderness on deep palpation. Laboratory results showed
a normal WBC count (4.9 G/l), a normal CRP (<2 mg/l),
and normal renal and liver functions. At laparotomy,
extensive adhesions and a right para-iliac purulent mass
were found. The prosthetic graft was partially removed,
and replaced by a homograft. Multiple intra-operative
specimens did not grow any microorganisms in culture.
Histopathology showed a chronic inflammatory infiltrate,
ill-formed non-necrotizing granulomas, and degenerative
changes such as calcifications and fibrosis (Figure 1A
&1B). No microorganisms could be identified using Peri-
odic acid-Schiff, Gram, Grocott methenamine silver and
Giemsa stains.
16S rRNA PCR amplification plus sequencing performed
on a fragment of the para-iliac mass was positive for Cox-
iella burnetii, using the BAK11w forward and the PC3mod
reverse primers [6]. The diagnosis of C. burnetii chronic
infection was confirmed by a positive serology performed
at Unité des Rickettsies, Marseille, France: phase I anti-
body titer (IgG): 1600, phase II antibody titer (IgG): 3200.
Antibiotic therapy with doxycycline (100 mg bid orally)
and chloroquine (200 mg tid orally) was started. The dose
of doxycycline was increased to 300 mg daily to reach a
concentration of at least 5 µg/mL [7]. Eighteen months
later (May 2005), the patient was asymptomatic and
serology showed persistence of high levels of phase I IgG
(1600) and phase II IgG (3200).
C. burnetii is a strict intracellular bacterium. It is the caus-
ative agent of Q fever, a worldwide zoonosis mainly trans-
mitted by inhalation of infected particles. There is a wide
animal reservoir, and sheep and cattle are probably the
main source of human infections. Our patient had no
environmental exposure to C. burnetii. Chronic Q fever is
mainly seen in patients with underlying risk factors such
as valvulopathy, pregnancy, and immunosuppression.
Endocarditis accounts for 73% of chronic Q fever cases,
followed by vascular infection (8%), including infections
of aneurysms and vascular grafts [4,8]. Given the signifi-
cant morbidity and mortality of vascular infection, and
given the importance of targeted and prolonged antibiotic
therapy, the diagnosis of C. burnetii infection is crucial to
a successful therapeutic outcome. We report here a rare
case of C. burnetii vascular graft infection. This unexpected
diagnosis was based on broad-range PCR. Q fever is prob-
ably underdiagnosed since the diagnosis will be missed if
it is not systematically looked for in patients with vascular
graft infections of unknown etiology.
Histology of the aortic lesion
Figure 1
Histology of the aortic lesion: A. Chronic inflammatory
infiltrate (yellow arrowhead), fibrosis (black arrowhead), and
ill-formed granuloma (arrow). Hematoxylin-eosin, 100× mag-
nification. B. Closer view of the ill-formed granuloma
(arrow). Hematoxylin-eosin, 400× magnification.

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The diagnosis of Q fever is most frequently made by serol-
ogy. C. burnetii presents a variation of phase (phases I and
II). Antiphase I IgG at titers of ≥1:800 by microimmun-
ofluorescence are indicative of chronic Q fever [9,10]. The
diagnosis has also be made using molecular methods
including 16S rRNA PCR amplification plus sequencing
or a specific C. burnetii PCR. To shorten the diagnostic
delay, Fenollar et al. developed a nested-PCR assay with
serum as a template which showed a sensitivity of 64%
and a specificity of 100% [11]. In the present case, 16s
rRNA PCR amplification plus sequencing was critical for
diagnosis, since Q fever had not been suspected clinically.
Broad-range PCR was also recently shown to be useful for
the diagnosis of blood culture-negative infectious endo-
carditis, identifying an etiological agent in 35.5% of cases
(11/31), including 3 cases due to C. burnetii [12]. The his-
tology of Q fever endocarditis is non-specific and is char-
acterized by fibrosis and
inflammation, and small or absent vegetations. Brouqui et
al. observed a granulomatous inflammation in one third
of cases with Q fever endocarditis, but well formed granu-
loma were not identified. In these cases, degenerative
changes such as valvular calcifications or foreign body
reaction prevented the establishment of a specific associa-
tion between C. burnetii infection and granulomatous
inflammation [13]. The presence of foamy macrophages,
also observed in our case, may suggest a Coxiella infection.
Definite histological diagnosis relies upon immunohistol-
ogy, that may demonstrate the presence of C. burnetii
within the cytoplasm of macrophages [13]. However, this
diagnostic method is less sensitive than PCR [14]. Thus,
immunohistology is unlikely to be a useful tool for the
diagnosis of C. burnetii vascular graft infection. Cell cul-
ture is not widely available as a diagnostic technique as it
requires trained technicians and a biosafety level 3 labora-
tory.
calcifications, mild
Tetracyclines are the antibiotics of choice for acute Q fever
[10]. The bactericidal activity of doxycycline is maximal at
pH 6.6. However, the Coxiella-containing vacuole is
acidic. Therefore, addition of chloroquine that acts as an
alkalinizing agent of the vacuole is essential to improve
the efficacy of doxycycline therapy [15]. Combination of
doxycycline and hydroxychloroquine for at least 18
months is the recommended therapy for Q fever endocar-
ditis [15]. This combined treatment is probably also indi-
cated in case of C. burnetii vascular graft infection. Since
serum doxycycline concentration is correlated with
decrease in levels of phase I antibodies, it is recommended
to adjust the dosage of doxycycline [7]. Patients are con-
sidered cured when phase I IgG antibodies decrease below
1:800, and IgA and IgM antibodies below 1:50 [16]. In
this case, after 18 months of therapy, antiphase I serology
remains strongly positive suggesting persistent infection
most likely due to the fact that the infected prosthesis
could only be partially removed. It also shows how diffi-
cult it is to eradicate C. burnetii and emphasizes the need
for prolonged antibiotic treatment course. Serological fol-
low-up will guide our decision regarding the treatment
duration.
Conclusion
C. burnetii infection should be considered in patients with
a vascular graft and unexplained low-grade fever, abdom-
inal discomfort, laboratory signs of inflammation, and/or
a history of environmental exposure. Broad-range PCR
should be performed on surgical samples in patients with
suspected infection of aneurysm or vascular graft. C. bur-
netii serology and/or specific C. burnetii PCR should also
systematically be performed in cases of culture-negative
vascular graft infection.
Competing interests
The author(s) declare that they have no competing inter-
ests.
Authors' contributions
LS, MF, DR, LVS, TC and GG were involved in patient care.
LS wrote the first draft of the manuscript. AM did the his-
tology and provided the images. All authors improved the
manuscript and approved its final version.
Acknowledgements
We thank Dr Philip E. Tarr for critical reading of the manuscript.
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