Case Report

Capnocytophaga canimorsus Associated with Atrial Flutter and Heart Block

Peter T. Lam, M.D. Department of Pathology The Brooklyn Hospital Center Brooklyn, NY 11201

Capnocytophaga canimorsus, for- merly considered dysgonic fermenter (DF-2), is a thin, gram-negative, non spore-forming bacillus. It is a commen- sal of the oral and nasal mucosa of cats and dogs that is transmitted to humans by bites, scratches, or mere contact with the animal. It most frequently causes disease in asplenic patients, alcoholics, and immunocompromised patients (1). Most patients present with septicemia associated with rashes, meningitis, endo- carditis, arthritis, and pleural infections or localized eye infections. The severity ranges from mild to fulminating disease, with shock, respiratory distress, and dis- seminated intravascular coagulation (2). Of the reported cases, ten percent have cardiovascular manifestations with endo- carditis plus one case of tricuspid valve- infected myxoma and another case of myocardial infarction (3). This report describes a patient with atrial flutter and heart block associated with C. canimo rsus.

Case Report A 74-year-old previously healthy male

presented to the hospital emergency room with fever, chills, and rigor for two days. He had an open wound on the hand due to a dog bite five days before. The hand showed an open wound mea- suring 2 cm in diameter. The base of the wound was covered by brown granula- tion tissue and scant yellow exudate. The patient had a hernia repair recently but did not have any complications and denied any cardiac arrhythmia or other symptoms. He had a history of alcohol and cocaine abuse. He stated that he had smoked cocaine a few hours before his admission. On examination, he was febrile (39°C) with associated chills and rigor. His blood pressure was 190/80 mm Hg on initial examination and decreased to 120/80 mm Hg during observation in the emergency room. He also complained of lower back pain and

had a nonproductive cough. An EKG was performed that showed atrial flutter with 3:1/4:1 with a variable ratio. Chest X ray showed cardiomegaly and pul- monary fibrosis with increased mark- ings. Urinalysis showed turbid urine with a large amount of erythrocytes and a mildly elevated protein level. Rapid Plasma Reagin screening test for syphilis was positive and the confirmatory FTA- ABS test was reactive.

Two specimens for blood culture were drawn and inoculated into aerobic and anaerobic blood culture bottles. The patient had not received any antibiotics before collection of blood. The bottles were processed on the BacT/Alert 120 automated blood culture instrument (Organon Teknika Corp., Durham, NC). At two days, the bottles were flagged positive for growth. The Gram stain of the bottle showed gram-negative, curved, slender coccobacillary rods with granules. The broth was subcul- tured to MacConkey agar which was incubated at 35°C, blood and chocolate agars which were incubated in CO2 at 35°C, and blood agar incubated anaerobically.

On the aerobic blood agar plate, multiple, tiny, grey colonies were pre- sent at 24 h that grew into the medium by 48 h. The anaerobic blood agar plate showed small, grey, spreading colonies at 48 h. The chocolate agar medium showed medium, fiat, spreading, grey colonies at 72 h; there was no growth on the MacConkey agar at 48 h. The Gram stain of the colonies revealed the same cellular morphology. The colonies were oxidase-positive, catalase-positive, indole-negative, and non-motile. Identi- fication and antimicrobial susceptibility tests were performed with the Vitek (bioMErieux Vitek, Inc. Hazelwood, MO) Gram Negative Identification panel, but the organism was not identi- fied. The isolate was sent to the city of New York Department of Health Laboratory where the organism was identified as C. canimorsus. The isolate was urease-, ONPG-, and arginine decarboxylase-positive.

The patient was treated with antibi- otics and improved clinically. He was released from the hospital after five days.

Discussion C. canimorsus is an uncommon

zoonotic disease transmitted mostly by dog bites and infections are almost always systemic. C. canimorsus infec- tions occur worldwide and cases have been reported from the U.S., Canada, Europe, and Australia. Infection gener- ally occurs two to three days after inoc- ulation by animal bites or scratches, but symptoms can appear after up to four weeks (4). Disease usually affects middle- aged and elderly people. Because of its low virulence, C. canimorsus systemic infections occur more frequently in hosts with impaired host defenses such as asplenic patients, alcoholics, and immunocompromised patients. It should be noted, however, that 40% of the cases occur in healthy individuals. Clinical manifestations are rashes (mac- ular, purpuric, and sometimes, ecchy- motic), cellulitis, peripheral gangrene, meningitis, arthritis, pleural infections, and cardiac abnormalities. Fulminant septicemias are commonly complicated by disseminated intravenous coagulo- pathy, acute renal failure, respiratory distress syndrome, and shock (1).

C. canimorsus is a thin gram-nega- tive, non spore-forming rod. It is a fas- tidious, slow-growing bacterium and subcultures onto enriched media, such as chocolate agar with IsoVitaleX or heart infusion agar with 5% blood (rab- bit or sheep), are necessary and, as rec- ommended by the Centers for Disease Control and Prevention. For a species identification, the important positive reactions are catalase, oxidase, arginine dihydrolase, and ONPG positivity, and production of acid from glucose, mal- tose, lactose, and galactose. Negative reactions are nitrate reduction, urease, gelatin hydrolysis, indole production, lysine decarboxylase, ornithine decar- boxylase, H2S production, and acid pro- duction from sucrose and mannitol (5).

In cellular morphology, C. canimor-

Clinical Microbiology Newsletter 21:21,1999 © 1999 Elsevier Science Inc. 0196-4399/99 (see frontmatter) 173

sus is s imi lar to o ther Capnocytophaga spp. and Fusobacterium spp. The latter is s t r icdy anaerobic and is easi ly ruled

out by no g r o w t h on ae rob ic media . B i o c h e m i c a l react ions that different iate

C. canimorsus f r o m o ther Capnocyto- phaga species are oxidase , catalase, and

arginine d ihydro lase (6). C. canimorsus is h igh ly suscept ib le to a wide range o f an t imicrobia l agents inc luding 13-1actam

agents excep t az t reonam (7,8). In spite this h igh suscept ibi l i ty to mos t anti-

biotics, the morta l i ty rate is 30%. Due to the ser iousness o f sys temic illness,

C. canimorsus should be cons idered as the causa t ive agent in the managemen t o f wounds associa ted with animal bites.

References

1. Pers, C. et al. 1996. Capnocytophaga canimorsus septicemia in Denmark, 1982-1995: Review of 39 cases. Clin. Infect. Dis. 23:71-75.

2. Lion, C., E Escande, and J.C. Burdin. 1996. Capnocytophaga carnimorsus infections in humans: review of literature and report. Eur. J. Epidemiol. 12:521-533.

3. Ehrbar, H.U. et al. 1996. Capnocytophaga canimorsus sepsis complicated by myo- cardial infarction in two patients with normal coronary arteries. Clin. Infect. Dis. 23:335-336.

4. Krol-van Sraaten, M.J., J.E. Landheer, and C.E.M. de Maat. 1990. Capnocyto- phaga canimorsus (formerly DF-2) infections: review of the literature.

Neth. J. Med. 36:304-309.

5. Murray, P.R. et al. 1995. Manual of clinical microbiology. 6th ed., ASM Press, Washington DC., p. 500, 502-503.

6. Pickett, M.J., D.G. Hollis, and E.J. Bottone. 1991. Miscellanous Gram negative bacteria. Manual of clinical microbiology, 5th ed., ASM Press, Washington DC., p. 410-428.

7. Bremmelgaard, A. et al. 1989. Suscepti- bility testing of Danish isolates of Capno- cytophaga and CDC group DF-2 bacteria. APMIS 97:43-48.

8. Verghese, A. et al. 1988. Susceptibility of Dysgonic fermenter-2 to antimicrobial agents in vitro. Antimicrob. Agents Chemother. 32:78-80.

Editors: Mary Jane Ferraro Paul A. Granato Josephine A. More l l o R.J. Zabransky

© 1999 Elsevier Science Inc.

ISSN 0196-4399 CMNEF-J 21(21)169-174, 1999

Elsevier

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