J. Clin. Microbiol. doi:10.1128/JCM.00173-08 1 2 3 4 5 6 ...€¦ · 27/8/2008 · 6 Heather C....
Transcript of J. Clin. Microbiol. doi:10.1128/JCM.00173-08 1 2 3 4 5 6 ...€¦ · 27/8/2008 · 6 Heather C....
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Capnocytophaga cynodegmi in a Rottweiler Dog with Severe Bronchitis and 1
Foreign Body Pneumonia 2
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Running Title: Capnocytophaga cynodegmi in a dog 4
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Heather C. Workman1*, Nathan L. Bailiff2, Spencer S. Jang3, Joe G. Zinkl4 6
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From the Department of Clinical Pathology1, Department of Medicine and 8
Epidemiology2, Microbiology Laboratory3, Department of Pathology, Microbiology 9
and Immunology4, Veterinary Medical Teaching Hospital, School of Veterinary 10
Medicine, University of California-Davis, CA 95616. 11
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*Corresponding author: Heather C. Workman, University of California Davis, 13
Cancer Center 4501 X Street, Suite 3003, Sacramento, CA 95817. Email: 14
[email protected]. Phone: 530.903.2422. 15
16 ACCEPTED
Copyright © 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.J. Clin. Microbiol. doi:10.1128/JCM.00173-08 JCM Accepts, published online ahead of print on 27 August 2008
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Abstract 17
Capnocytophaga cynodegmi is a zoonotic Gram-negative, capnophilic bacterium 18
that is usually seen in people with infections associated with dog or cat bites. The 19
first reported case of C. cynodegmi in a dog is described here. 20
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CASE REPORT 22
A four-year old, male castrated Rottweiler dog initially presented to the University 23
of California, Davis Veterinary Medical Teaching Hospital (VMTH) for a six month 24
history of respiratory distress and suspected pneumonia. Serial thoracic 25
radiographs performed by the primary care veterinarian prior to referral revealed 26
multiple consolidated lung lobes. At the time of referral, radiographs and CT 27
(computed tomography) scan showed consolidation of multiple lung lobes. A 28
CBC (complete blood count) and serum chemistry were performed. A 29
bronchoscopy was done for culture and sensitivity and cytology for each of the 30
following samples: bronchial lavage, bronchial sputum, and biopsy. The sputum 31
was collected from the tracheal tube for intubation/anesthesia. The biopsy was 32
also submitted for histopathology. The CBC at that time showed a mild 33
eosinophilia (4.2 X 103 cells/µl; reference interval, 0.1-1.25 X 103 cells/µµµµl). The 34
cytology of the bronchial lavage and sputum had a marked eosinophilic and 35
moderate pyogranulomatous inflammation with no organisms noted. The biopsy 36
revealed severe, diffuse, chronic eosinophilic bronchitis with eosinophilic 37
granulomas. The cultures of the lavage, sputum, and biopsy tissues were plated 38
on sheep blood agar (Hardy Diagnostics, Santa Maria, CA) for 5 days in 5% CO2. 39
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All cultures were negative. The patient was sent home with fenbendazole, 40
amoxicillin/clavulanic acid, famotidine, sucralfate and glucocorticoids. Follow-up 41
radiographs on a tapering course of glucocorticoids revealed resolution of 42
consolidation but a persistent bronchial pattern. Over the next six months the 43
patient resumed an active lifestyle but had several episodes of acute respiratory 44
signs presumptively diagnosed as bacterial pneumonia secondary to severe 45
bronchiectasis that was treated with variable success with a variety of antibiotics 46
(enrofloxacin, amoxicillin, and amoxicillin/clavulanic acid). He also remained on 47
varying doses of glucocorticoids, as well as gastrointestinal protectants during 48
that time. 49
Due to the recurring episodes, the patient returned to the UC Davis VMTH 50
six months after the initial presentation for a repeat evaluation of his pulmonary 51
disease and possible lung lobectomy. The patient was in good body condition 52
and was severely tachypneic with a respiratory rate of 36 breaths/min. On 53
thoracic auscultation crackles were audible over the right hemi-thorax. Current 54
medications included 20mg (previously on 40mg) prednisone per day, 55
enrofloxacin 136mg BID (owner occasionally giving every 24 hours), amoxicillin 56
800mg TID (owner only giving 400mg every 24 hours) and famotidine once daily. 57
A CBC at that time identified a mild leukocytosis due to mild neutrophilia (17.9 X 58
103 cells/µl; reference interval, 0.3-11.5 X 103 cells/µl) and monocytosis (1.45 X 59
103 cells/µµµµl; reference interval, 0.15-1.35 X 103 cells/µl) with a lymphopenia (0.83 60
X 103 cells/µl; reference interval, 1-4.8 cells X 103 cells/µl) indicative of a 61
glucocorticosteroid leukogram. An arterial blood gas analysis identified 62
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hypoxemia, academia, and hypercapnia that were explained by the patient’s 63
severe pulmonary disease and were consistent with a hypoventilatory condition 64
with associated respiratory acidosis that did not have metabolic compensation. A 65
repeat CT scan revealed extensive fluid accumulation in multiple bronchiectic 66
airways and consolidation of the ventral aspect of right and left caudal lung lobes, 67
the right middle, and the entire accessory lung lobe. 68
A thoracotomy was elected by the owner and lung lobectomy of the right 69
middle, accessory and right caudal lobes was performed. Prior to tissue fixation, 70
aseptic technique was used for gross dissection of each lung lobe. A large 71
parenchymal abscess with a plant awn in situ was identified in the accessory 72
lung lobe (Fig. 1). Cytology and culture were performed on both bronchial fluid 73
and the abscess fluid. Cytology of both sites revealed many moderately to 74
markedly degenerate neutrophils and high amounts of mucus in the background. 75
High numbers of a monomorphic population of thin rod to filamentous shaped 76
bacteria were noted. A small clear zone was noted around each organism. Many 77
organisms were present intracellularly in neutrophils and extracellularly 78
throughout the sample (Fig. 2). 79
The histopathology showed a large plant awn within the accessory lobe 80
with associated chronic, severe, suppurative bronchitis and secondary 81
bronchiectasis of the accessory and caudal lung lobes. In addition, there was a 82
severe suppurative bronchopneumonia with fibrosis that was consistent with 83
secondary bacterial infection (Fig. 3) in all lobes submitted. No evidence of the 84
prior eosinophilic inflammation was identified on any sample. 85
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Cultures from the pulmonary tissue sample obtained at biopsy were grown on 86
sheep blood agar in 5% CO2. These samples gave rise to a pure growth of β-87
lactamase positive, Gram-negative rods that was identified by four days 88
incubation, and was suspected to be Capnocytophaga spp. The cultures from 89
bronchial sputum had similar growth. No additional aerobic or anaerobic bacteria 90
were cultured during 5 days of incubation at 5% CO2. 91
16SrRNA sequencing samples were obtained and purified from colonies 92
grown on sheep blood agar using the QiaAmp Tissue Extraction Kit (Qiagen, 93
Inc., Valencia, CA) following the manufacturer’s instructions. Amplification was 94
performed in a thermal cycler (Bio-Rad). PCR products were run on a 1% 95
agarose gel with a low molecular weight DNA ladder. The PCR products were 96
purified using Microcon Kit (Millipore Corp., Bedford, MA) following the 97
manufacturer’s suggestions. Purified product was submitted to Davis Sequencing 98
(University of California, Davis, Davis, CA). Sequence result was 99% to 99
Capnocytophaga cynodegmi. The patient was further treated with enrofloxacin 100
and a low dose of prednisone. 101
------------------------------------------------------------------------------------------------------------ 102
Capnocytophaga cynodegmi, formerly known as CDC dysgonic fermenter-103
2-like, is a fastidious aerobic, capnophilic, Gram-negative, fusiform bacillus that is 104
about 2-4 µm long and can be slightly curved at the end (1, 3, 11, 13, 14, 16, 20). 105
Cynodegmi is derived from the Greek kyno (dog) and degmos (bite). C. 106
cynodegmi has been found in the saliva, gingival crevices and nasal cavity of 107
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16% of dogs and 18% of cats (8, 11, 14, 17, 22), which helps to explain that up to 108
80% of reports of this organism involve dog bites in people (9,13). 109
The patient afflicted with Capnocytophaga infection in this report is a dog, 110
which to the authors’ knowledge has not been reported. Despite this, 111
Capnocytophaga cynodegmi and C. canimorsus (formerly CDC DF-2, a close 112
relative of C. cynodegmi) are rarely isolated from animal bite wounds compared 113
to many other species of bacteria. Some Capnocytophaga spp. infections have 114
been associated with other types of close animal contact raising the concern for 115
zoonotic potential (10, 11, 14, 17, 19, 22). Capnocytophaga cynodegmi typically 116
causes localized cellulitis of varying severity (9, 13, 15, 16, 19). Other local 117
infections such as keratitis can occur (8,14). Systemic infections such as 118
meningoencephalitis and generalized sepsis have been reported in 119
splenectomized patients as well as those with predisposing conditions such as 120
diabetes, alcoholism, and cirrhosis (3, 14, 20). Recently a C. cynodegmi 121
respiratory infection was reported in a cat with underlying pulmonary neoplasia 122
(7). The risk of zoonosis from animals with C. cynodegmi respiratory infections 123
remains unclear at this time. 124
While the oral cavity was suspected to be the origin of the C. cynodegmi in 125
this patient, the reasons for its development into a pathogen in the lungs likely 126
involve the foreign body. Plant awns migrating through the oral cavity into the 127
respiratory tract may pick up and carry organisms to their final destination, 128
serving as both the vehicle and nidus for development of bacterial 129
bronchopneumonia. Factors that could have contributed to this patient’s risk for 130
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an uncommon cause of bacterial pneumonia include generalized 131
immunosuppression from chronic prednisone usage, as well as altered local 132
respiratory tract defense mechanisms seen with chronic bronchitis and 133
bronchiectasis. Additionally, prior antibiotic usage may also have played a role in 134
selecting against other common bacterial organisms, leading to a pure infection 135
of C. cynodegmi. 136
The patient had also been prescribed enrofloxacin during his first 137
admission to the VMTH, prior to the lobectomy. C. cynodegmi is reported to be 138
sensitive to this antibiotic (7, 13), however, absorption of an antibiotic into an 139
encapsulated purulent lesion is restricted and highly reliant on the degree of 140
abscess maturation. Pharmacokinetic data from in vivo studies demonstrate that 141
substantial antibiotic concentrations can be reached within abscesses in humans 142
and animals, provided the appropriate agent is selected and an optimal dosing 143
regimen is followed as suggested. Nevertheless, the efficacy of antibiotics in 144
exudate may be hindered by various factors, such as acidic pH, protein binding 145
and degradation by bacterial enzymes (23). In addition, severe Gram-negative 146
pulmonary infections often need parenteral antibiotics and are sometimes 147
complicated by antibiotic resistance (9). There are no specific guidelines for this 148
organism when using enrofloxacin. Therefore, therapeutic dose was obtained by 149
relying solely on the minimum inhibitory concentration (MIC) result. This result is 150
useful for determining dose to be given, but the actual therapeutic dose range 151
can depend on many factors, such as the type of infection, location, and 152
bioavailability. The patient began to improve only after his lobectomy and 153
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parenteral antibiotics were administered. All together, this evidence suggests that 154
antibiotic resistance and / or persistence of the foxtail nidus were involved in the 155
perseverance of the patient’s disease. 156
Additional complexities in this case involve the differences between the 157
cytological, histopathological and microbiological findings of the first and second 158
evaluation. It was believed that the patient initially suffered from a form of an 159
idiopathic eosinophilic disease previously reported rarely in dogs including 160
Rottweilers (21). While the disease state initially identified could explain the 161
clinical signs and diagnostic findings as sequelae of severe eosinophilic 162
inflammation, the presence of the foreign body and C. cynodegmi infection for 163
the entire duration cannot be ruled out. The eosinophilic inflammation may have 164
been due to a hypersensitivity reaction of initial exposure to the plant awn and 165
some bacterial infections have also been associated with this type of 166
inflammation (4, 12, 18). C. cynodegmi is a fastidious organism and while growth 167
may be detected in as early as 3 days, 7 to 10 days is more common (8, 14). 168
Inadequate duration of culture could lead to a false negative microbiologic 169
investigation for Capnocytophaga. Cultures submitted to UCD VMTH 170
microbiology lab are routinely cultured for 5 days in 5% CO2 unless other 171
conditions are specified. In some cases growth of Capnocytophaga from lesions 172
may be missed due the polymicrobial nature of most infected bites or foreign 173
body lesions as other organisms may grow more quickly (11). As the name 174
implies, the organism is capnophilic, and though there are subtle differences in 175
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reported growth conditions, all sources agree a 5% CO2 enriched atmosphere 176
improves growth (1, 3, 8, 11, 13, 14, 19, 20). 177
Case Follow-Up 178
The patient had an uneventful recovery, returning to the VMTH for follow-up 179
exams. The owner reports the patient’s quality of life to returning to normal, with 180
much increased energy and playfulness. He remained on oral enrofloxacin and 181
glucocorticosteroids for several months following the surgery. Radiographs taken 182
on the first several follow-up exams showed residual bronchiectasis in the lung 183
lobes that were not removed during the lobectomy. One year later, the patient 184
was still alive. 185
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Figure Legends (pictures are in separate power point documents and have 258
been checked by rapid review). 259
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Figure 1 261
Gross image of accessory lung lobe, sectioned just after surgery and prior to 262
fixation. The plant awn is within the abscess that is surrounded by pale 263
parenchymal tissue. Note the exudate in all airways. 264
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Figure 2 266
Cytology of the sputum sample from the canine patient. Wright’s-Giemsa stain. 267
600X. Note the markedly degenerate neutrophils and the monomorphic 268
population of thin rod to filamentous shaped bacteria seen within neutrophils and 269
in the background substance. 270
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Figure 3 272
Hematoxylin and Eosin stain from lung biopsy, 40X. Note the suppurative 273
inflammation in the airway. 274
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