Capnocytophaga canimorsus blebitis: case report and review of literature

Abstract

Background
Capnocytophaga canimorsus is a facultative anaerobic, slow-growing, capnophilic, Gram-negative bacillus, that is commonly found in the microflora of canine and feline oral cavities. Capnocytophaga infections are an emerging zoonotic disease that can cause fatal systemic infections in immunocompromised individuals. Localized ocular Capnocytophaga infections, including keratitis, blepharitis, and endophthalmitis, can lead to severe eye threatening situations. To our knowledge, there is currently no documented case of Capnocytophaga canimorsus blebitis with bleb perforation after trabeculectomy.

Case presentation
Our case report and literature review features a novel case of Capnocytophaga blebitis that occurred after trabeculectomy, associated with close dog contact (i.e. face licking). The patient had underwent trabeculectomy 10 years prior and presented with conjunctival injection, perforated bleb, and hypotony. Overall, patient was medically treated subconjunctival vancomycin, gentamicin and moxifloxacin drops. Trabeculectomy revision was performed with good visual outcome. Bacterial cultures grew Capnocytophaga canimorsus .

Conclusions
We discuss the strategies for diagnosis, treatment, and common risk factors for ocular Capnocytophaga infections. At-risk patients with ocular infections should be asked about close contact with dogs and cats; and treated promptly with the proper antibiotic regimen.

Full text

C A S E R E P O R T Open Access
Capnocytophaga canimorsus blebitis: case
report and review of literature
Michael C. Yang, John Ling and Sameh Mosaed
*
Abstract
Background: Capnocytophaga canimorsus is a facultative anaerobic, slow-growing, capnophilic, Gram-negative
bacillus, that is commonly found in the microflora of canine and feline oral cavities. Capnocytophaga infections are
an emerging zoonotic disease that can cause fatal systemic infections in immunocompromised individuals.
Localized ocular Capnocytophaga infections, including keratitis, blepharitis, and endophthalmitis, can lead to severe
eye threatening situations. To our knowledge, there is currently no documented case of Capnocytophaga
canimorsus blebitis with bleb perforation after trabeculectomy.
Case presentation: Our case report and literature review features a novel case of Capnocytophaga blebitis that
occurred after trabeculectomy, associated with close dog contact (i.e. face licking). The patient had underwent
trabeculectomy 10 years prior and presented with conjunctival injection, perforated bleb, and hypotony. Overall,
patient was medically treated subconjunctival vancomycin, gentamicin and moxifloxacin drops. Trabeculectomy
revision was performed with good visual outcome. Bacterial cultures grew Capnocytophaga canimorsus.
Conclusions: We discuss the strategies for diagnosis, treatment, and common risk factors for ocular
Capnocytophaga infections. At-risk patients with ocular infections should be asked about close contact with dogs
and cats; and treated promptly with the proper antibiotic regimen.
Keywords: Capnocytophaga canimorsus, Blebitis, Trabeculectomy, Bleb perforation, Bleb-associated infections, Case
report
Background
Pet ownership has many benefits, with some studies
reporting a lower risk of cardiovascular disease and mor-
tality with dog ownership [1]. This cohabitation also
comes with its own risks; half of all Americans will be
bitten at least once in their lifetime [2]. Capnocytophaga
canimorsus is commonly found in canine oral micro-
flora, and less commonly in cats. In certain studies, C.
canimorsus could be cultured from oral secretions of ap-
proximately 26% of dogs and 18% of cats [3]. Recent re-
ports have shown the prevalence to be up to 74% of
dogs [4]. C. canimorsus can cause a wide variety of infec-
tions, with a majority being systemic infections and less
than 10% being localized infections [5]. Many of these
localized infections have been ocular; reports include
blepharitis, keratitis, and endophthalmitis [6–8]. How-
ever, to our knowledge, there has not yet been a re-
ported case of blebitis linked to C. canimorsus.We
present a case of C. canimorsus blebitis with bleb perfor-
ation, which highlights the virulence of C. canimorsus
and the need for pet owners with predisposing risk fac-
tors to be vigilant of ocular exposures.
Case presentation
An 81-year-old man was referred by an outside ophthal-
mologist with bacterial blebitis and perforated bleb, 10
years after trabeculectomy. Patient’s medical history was
unremarkable. His ocular history includes radial keratot-
omy, penetrating keratoplasty (PKP), and the
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* Correspondence: smosaed@hs.uci.edu
Department of Ophthalmology, Gavin Herbert Eye Institute, University of
California, Irvine, CA 92697, USA
Yang et al. BMC Ophthalmology (2021) 21:59
https://doi.org/10.1186/s12886-021-01823-8
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aforementioned trabeculectomy 10 years prior. Upon
presentation, patient’s exam was notable for significant
conjunctival injection, elevated cystic bleb, positive Sei-
del’s test with significant flow, and intraocular pressure
of 4 mmHg (Fig. 1). Best corrected vision was 20/100.
Corneal exam revealed fine keratic precipitates (KP) and
evidence of PKP with mild haze around the periphery of
the graft. Anterior chamber exam revealed trace cell and
flare. Fundus exam was unremarkable except for cup-to-
disc ratio of 0.85. No cells seen in vitreous. Given exam
findings and concern for infection, patient was given
subconjunctival injection of vancomycin 25 mg and gen-
tamicin 20 mg. Conjunctival samples and scrapings were
sent for fungal and bacterial cultures. Patient was pre-
scribed a prolonged course of moxifloxacin drops; ini-
tially every 1 h and eventually tapered to four times a
day. Prednisolone acetate drops were added, and the pa-
tient was monitored regularly in clinic with improve-
ment to his clinical condition.
Two weeks after initial presentation, trabeculectomy
revision was performed involving closure of the bleb, ex-
cision of necrotic tissue and scleral patch graft (Fig. 2).
Several months after surgery, patient continued to be
Seidel’s negative with normal intraocular pressure, and
best corrected vision was 20/70 (Fig. 3). Per standard
protocol at our institution, samples were plated on sheep
blood, chocolate, Mac Conkey agar, Brucella agar,
phenyl ethyl alcohol agar, split plate (Bacteroides Bile
Esculin, Laked Brucella agar with Kanamycin and
Vancomycin), and thioglycolate. Given initial appearance
as a rare bacillus species, cultures were sent to County
of Orange, Health Care Agency, Public Health
Laboratory for final identification of C. canimorsus spe-
cies. Further details regarding identification and isolation
were unavailable from the Public Health Laboratory —
however, C. canimorsus has been known to grow on 5%
sheep blood or chocolate agar in 5–10% CO
2
at 37 C [5].
The diagnosis of C. canimorsus was initially suggested
by appearance on Gram stain at our institution and final
identification was made at aforementioned laboratory
(Fig. 4). Further confirmation of C. canimorsus was ob-
tained through DNA sequencing from an outside labora-
tory. The diagnosis of Capnocytophaga canimorsus was
also confirmed independently by the referring ophthal-
mologist’s cultures and testing. Fungal cultures were
negative. Upon further questioning, patient revealed that
he had a Dalmatian dog with poor dentition that fre-
quently licked his face.
Discussion and conclusion
Capnocytophaga canimorsus is a Gram-negative bacillus
that is capnophilic, a facultative anaerobe, and belongs
in the Bacteroidetes phylum. It was originally named
CDC group dysgonic fermenter 2 (DF-2), with articles
published in the 1980s referring to Capnocytophaga
canimorsus as DF-2. The first human infection was re-
ported in 1976, and there has only been approximately
500 reported cases worldwide [9]. This is likely an
underreported figure given that C. canimorsus is notori-
ously difficult to culture, and can also result in subclin-
ical infections [10]. C. canimorsus can be transmitted
through bites, scratches, and close animal contact (e.g.
licking) [5].
With recent advances in ribosomal DNA sequencing,
some researchers have proposed splitting Capnocyto-
phaga canimorsus into two different species. The pro-
posed name of the subclinical strain is Capnocytophaga
canis, and maintaining the same name of Capnocyto-
phaga canimorsus for the clinically symptomatic strain.
However, recent case reports have isolated C. canis from
patients with sepsis [11]. The strains that are harmful to
humans all grow in heat-inactivated human serum, de-
glycosylate IgM and are cytochrome-oxidase positive [4].
Healthy, immunocompetent individuals are typically not
susceptible to overt systemic C. canimorsus infections.
However, at-risk individuals (e.g. immunocompromised,
alcoholics, splenectomized patients) can have systemic
C. canimorsus infections like endocarditis, meningitis,
and even fatal bacteremia leading to multi-organ system
failure [12–15].
Localized C. canimorsus infections have been mostly
identified in the eye; keratitis being the most common
presentation. Capnocytophaga keratitis is an aggressive
cornea infection; in a study of ten patients, 50% required
enucleation and 30% required corneal transplant [16].
Given its capnophilic nature, Capnocytophaga has a
Fig. 1 Capnocytophaga blebitis, preoperative clinical image.
Significant injection, cystic bleb, with associated bleb leakage
Yang et al. BMC Ophthalmology (2021) 21:59 Page 2 of 5
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predilection for the deeper layers of the corneal stroma.
Patients often present with corneal edema, endothelial
lesions, ring-shaped infiltrates, and corneal perforation.
Like our presented case, patients with Capnocytophaga
keratitis report frequent and close interactions with dogs
(e.g. face licking) [17]. Patients susceptible to Capnocyto-
phaga keratitis are often immunocompromised—for
Fig. 2 Capnocytophaga blebitis, intraoperative images of trabeculectomy revision. aSeidel positive, indicating bleb leakage. bLimbus dissection.
cFlap closure with 10–0 Prolene suture, interrupted. dPlacement of scleral patch graft secured with 8–0 Vicryl sutures. eConjunctival closure
with 10–0 Vicryl sutures, running. fWatertight closure confirmed with Seidel negative
Fig. 3 Capnocytophaga blebitis, 4 weeks postoperative clinical
image. Status post bleb closure, excision of necrotic tissue and
scleral patch graft. No bleb leakage, dissolving running suture
visualized at limbus
Fig. 4 Capnocytophaga canimorsus Gram stain image. Gram
negative rods, fusiform cells generally 1–3μm in length. Sample
culture image obtained with permission from Microbe-Canvas team
Yang et al. BMC Ophthalmology (2021) 21:59 Page 3 of 5
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example, status post bone marrow transplant, or rituxi-
mab infusions. Professions that are regularly exposed to
canine and feline mouths (i.e. veterinarians) are also at
risk [7]. Topical clindamycin has been used with good
clinical results in some patients [7,16,17]. Some clini-
cians have also used oral clindamycin to achieve higher
levels of antibiotics in the anterior chamber and deeper
layers of the cornea where Capnocytophaga resides.
The reported incidence of bleb-associated infections
(BAI) range from 1.5 to 4.8% at 5 years follow up. BAIs
range from stage I with no cell in the anterior chamber
and little to no visual impairment to stage IIIB with cell
in the anterior chamber and vitreous with an obscured
view of the fundus [18]. Early BAI occurs within the first
post-operative month, and late BAI occurs after the first
month. Our case of Capnocytophaga blebitis is a late
BAI and stage II (cell in anterior chamber, no cell in vit-
reous). Diagnostic workup can include aqueous/vitreous
stain and culture, polymerase chain reaction (PCR),
biome representational in silico karyotyping (BRiSK), or
metagenomic deep sequencing (MDS) [16–18]. The
most commonly isolated microorganisms in early onset
BAI is coagulase negative Staphylococcus, and late onset
BAI is Streptococcus. There is currently no consensus on
the most effective treatment for BAI. However, com-
monly used treatment regimens are fortified aminoglyco-
sides (e.g. tobramycin (14 mg/mL) with vancomycin (q30
min) or 4th generation fluoroquinolone (q1 hour) [19].
These antibiotics broadly cover Gram-negative and
Gram-positive microorganisms. Of note, Capnocytopha-
ga’ssusceptibility to aminoglycosides and vancomycin
varies widely between studies; but is typically susceptible
to clindamycin, penicillin, cephalosporin, imipenem, and
beta-lactamase inhibitor combinations [7,20]. Our pa-
tient was initially treated with subconjunctival vanco-
mycin and gentamicin; and eventually shifted to a
prolonged course of topical moxifloxacin with treatment
success. Subconjunctival antibiotics are not routinely ad-
ministered; however, our patient was elderly and the typ-
ical regimen of q30 min eyedrops of vancomycin and
aminoglycoside was not possible. Additionally, given the
urgency of acute blebitis and the importance of prompt
administration of antibiotics, we opted for a broad
spectrum approach with vancomycin and gentamicin be-
fore culture sensitivities were available. Given its high li-
pophilicity, topical moxifloxacin achieves high
intraocular concentrations in aqueous humor and con-
junctiva. Moxifloxacin covers broadly for Gram-negative,
Gram-positive and atypical pathogens [18].
Capnocytophaga canimorsus is a member of the com-
plex microflora of canine and feline oral cavities. In im-
munocompromised patients, C. canimorsus has been
known to cause severe systemic infections like
bacteremia and multi-organ failure. In rare cases, C.
canimorsus can cause eye-threatening ocular infections
ranging from keratitis to endophthalmitis. Our novel
case of Capnocytophaga blebitis contributes to the
scarce clinical information available regarding ocular
Capnocytophaga infections. At-risk patients with ocular
infections should be asked about close contact with dogs
and cats; and treated promptly with the proper antibiotic
regimen.
Abbreviations
PKP: Penetrating keratoplasty; KPP: Keratic precipitates; CDCP: Centers for
Disease Control; DF-2P: Dysgonic fermenter 2; BAIP: Bleb-associated
infections; PCRP: Polymerase chain reaction; BRiSKP: Biome representational
in silico karyotyping; MDSP: Metagenomic deep sequencing
Acknowledgements
Thank you to Dr. Mosaed and Dr. Ling for all their support. Special thanks to
the team at Microbe-Canvas for the generous contribution of the Gram stain
image of C. canimorsus.
Authors’contributions
MY drafted manuscript and performed literature review of related topics
including: C. canimorsus and blebitis treatment strategies. JL & SM significant
contributions in conception and acquisition of data, revision of manuscript,
as well as direct patient care involved in case. All authors read and approved
the final manuscript.
Funding
No financial support.
Availability of data and materials
Data sharing is not applicable to this article as no datasets were generated
or analyzed during the current study.
Ethics approval and consent to participate
Need for approval from ethics was waived.
Consent for publication
Written consent for the publication of identifying clinical/personal
information and images was obtained from the patient.
Competing interests
The authors declare that they have no competing interests.
Received: 23 December 2019 Accepted: 20 January 2021
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