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Year : 2011  |  Volume : 54  |  Issue : 2  |  Page : 368-370
Septicemia due to Capnocytophaga canimorsus following dog bite in an elderly male

1 Ramchandra Medical College, Chennai, India
2 Lawrence General Hospital, Lawrence, USA
3 Medical Education Hackensack Medical Center, Hackensack, NJ, USA

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Date of Web Publication27-May-2011


A previously healthy, 67-year-old, man with past medical history of myocardial infarction and hypertension was rushed to the emergency room after sudden onset of fever, chills, severe rigors, hypotension, tachycardia and vomiting. The patient was diagnosed as being in septic shock, and investigations revealed intracellular gram-negative bacilli in polymorphonuclear leukocytes in the peripheral smear. A history of dog contact was elicited after this very unusual and rare finding. Cultures confirmed septicemia due to Capnocytophaga canimorsus, a normal oral and nasal flora inhabitant of cats and dogs that can cause severe and sometimes fatal septicemia in humans. We report this very interesting case because of the common prevalence of dog homeownership and the rarity of C. canimorsus inducing sepsis.

Keywords: Capnocytophaga canimorsus , dog bite zoonotic disease

How to cite this article:
Chary S, Joshi M, Reddy S, Ryan C, Saddi V. Septicemia due to Capnocytophaga canimorsus following dog bite in an elderly male. Indian J Pathol Microbiol 2011;54:368-70

How to cite this URL:
Chary S, Joshi M, Reddy S, Ryan C, Saddi V. Septicemia due to Capnocytophaga canimorsus following dog bite in an elderly male. Indian J Pathol Microbiol [serial online] 2011 [cited 2020 Jul 7];54:368-70. Available from: http://www.ijpmonline.org/text.asp?2011/54/2/368/81642

   Introduction Top

The United States is home to over 72 million pet dogs. [1] Many people believe that a dog's mouth is cleaner than a human's, not realizing that a dog's mouth contains bacteria that are potentially lethal to humans. Capnocytophaga canimorsus, which is a normal constituent bacteria of the gingival flora of cats and dogs, can cause severe and sometimes fatal septicemia in humans. [2],[3],[4],[5],[6] People with predisposing risk factors, such as a compromised immune system, are more susceptible to developing an infection following exposure to this organism. This report presents a case of severe C. canimorsus septicemia in a patient following canine contact. Pet owners, especially those who are immune compromised, should be educated on the risks associated with pet ownership.

   Case Report Top

A 67-year-old man was rushed to the emergency room by his wife, after sudden onset of fever, chills, severe rigors, lightheadedness, and vomiting. He had a history of hypertension and myocardial infarction, for which he was being treated with lisinopril, simvastatin, and atenolol. Emergency room findings confirmed shock with tachycardia, tachypnea, and a systolic blood pressure of 66 mmHg. He presented with severe acrocyanosis, oliguria, pulmonary congestion, and persistent hypotension. Levofloxacin and metronidazole were started pending culture results.

A peripheral smear reviewed in the hospital laboratory revealed bacilli (rods) within polymorphonuclear leukocytes [Figure 1]. This is a highly unusual finding, and with the help of infectious disease consultants, the possibility of an infection due to a dog bite laceration was entertained.
Figure 1: Peripheral smears showing gram-negative bacilli (fusiform shaped rods) in polymorphonuclear leukocytes

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A detailed history, obtained after the findings of bacilli within polymorphonuclear leukocytes, revealed that prior to hospitalization and the development of symptoms, the patient administered cephalosporin to his dog for dermatitis. While doing so his finger rubbed against the dog's teeth and suffered a small laceration. Upon examination, the finger appeared erythematous and sore. The patient's physical examination showed discoloration of the tips of his upper and lower extremities, and ecchymoses where his finger suffered the laceration. His urinalysis and computed tomography (CT) scan of the abdomen and pelvis were normal, with no pelvic abscess or colitis. He was diagnosed with septic shock, and managed accordingly with supportive measures. He also was on dialysis and monitored closely in the intensive care unit. He was placed on meropenem pending identification of the blood culture, and on a combination of ampicillin and sulbactam, 1.5 g every six hours, to cover anaerobic gram-negative rods.

Final blood culture results confirmed C. canimorsus, and the patient recovered with broad-spectrum antibiotic therapy.

   Discussion Top

Capnocytophaga canimorsus , first isolated in 1976, is a gram-negative, non-spore forming bacillus. The genus Capnocytophaga belongs to the family of bacteria known as Flavobacteriaceae. [7] It was formerly classified as Dysgonic Fermenter or DF-2, and it is a normal constituent of the gingival flora of cats and dogs. [2],[3],[4],[5],[6] C. canimorsus is a prominent human pathogen and is implicated in septicemia, meningitis, endocarditis, and ocular infections. [8]

C. canimorsus can induce infection at almost any age, but is gender biased, as it occurs in a greater frequency in men (74%). [2] Those at increased risk include the immunocompromised (5%), and those with conditions such as asplenia (33%), alcoholism (24%), chronic lung disease, hematological malignancies, cirrhosis, and oral ulceration. [2] Infections have been known to occur in those with no predisposing conditions. However, it is important to note that because of its slow growth, low virulence, and susceptibility to antibiotics used for post dog bite prophylaxis, it is more likely to affect those with compromised immune systems and other predisposing risk factors. [3],[5] The patient in this case had a history of hypertension and myocardial infarction, but had no said predisposing risk factors that could pose a threat for the development of infection.

Approximately 54% of cases of infections with C. canimorsus are due to an animal bite, 8.5% are due to scratches, and 27% are due to mere exposure. [3] Therefore, if a patient presents with bacterial sepsis, it is imperative for the examining physician to enquire about any animal contact. Though it usually takes two to three days after contact with the animal for the onset of infection, it has been known in a few occasions to present after as many as four weeks. [3] In this case, the patient suffered a small laceration as his finger rubbed against his dog's teeth, and he presented with infection within 48 h of contact.

Expected clinical signs and symptoms commonly include fever, chills, headache, myalgia, general malaise, and sepsis. Gastrointestinal disturbances such as vomiting, diarrhea, and abdominal pain, respiratory disturbances such as dyspnea, and neurological symptoms such as mental confusion are also relevant clinical findings. [2] Thirteen percent of cases also show a maculopapular rash and gangrenous development at the site of the animal bite. [3] The patient in this case presented with a fever of 101°F, chills, nausea, and vomiting. He developed severe rigors and light headedness, but denied any headaches, abdominal pain, flank pain, or dyspnea. The patient had severe septicemia and went into shock. Ecchymoses was evident at the site of the dog bite, and his upper and lower extremities were discolored.

Accurately diagnosing without delay and providing the proper treatment is imperative for the survival of the patient, considering the high mortality rate associated with C. canimorsus infection. Analysis of a peripheral blood smear allows for timely diagnosis and successful treatment. Neutrophils containing fusiform rods and sometimes even peculiar morphology of these cells allows for confirmatory diagnosis. [2] However, considering the lack of familiarity physicians have with this particular bacteria, many institutions fail to correctly identify C. canimorsus in a peripheral smear. In these cases, polymerase chain reaction (PCR) and 16s ribosomal RNA (rRNA) gene sequencing are other alternatives available for confirmation. [6],[8] C. canimorsus grows slowly on chocolate agar or on heart infusion agar, and therefore treatment should be started before culture results become available. Waiting for culture results could mean the difference between life and death.

This case presents a unique scenario in which the patient developed infection with no predisposing risk factors. A multi-disciplinary approach was therefore crucial in arriving at the diagnosis. Infection due to C. canimorsus was first identified on examination of peripheral smears by the Microbiology department. Subsequently, careful history taking helped to confirm the diagnosis. Without a detailed history, infection caused by C. canimorsus due to exposure of the patient to the oral flora of a dog would not have been entertained. From a community health point of view, because of the increasing population of pet owners, people should be aware of the risks associated with pet ownership. It would behoove pet owners to recognize that domestic pets do possess bacteria that can be potentially lethal to those exposed to them.

   Acknowledgments Top

Authors are very grateful to acknowledge Debra Forbes Morrow, B.S.R.N and Dr. Robert E. Belliveau, MD for their contributions.

   References Top

1.Market Research Statistics - U.S. Pet Ownership and Demographics Sourcebook 2007 [Internet]. American Veterinary Medical Association. c2011- [cited 2011 Jan 11] Available from: http://www.avma.org/reference/marketstats/sourcebook.asp.   Back to cited text no. 1
2.Mirza I, Wolk J, Toth L, Rostenberg P, Kranwinkel R, Sieber SC. Waterhouse-Friderichsen syndrome secondary to Capnocytophaga canimorsus septicemia and demonstration of bacteremia by peripheral blood smear. Arch Pathol Lab Med 2000;124:859-63.  Back to cited text no. 2
3.Tierney DM, Strauss LP, Sanchez JL. Capnocytophaga canimorsus mycotic abdominal aortic aneurysm: Why the mailman is afraid of dogs. J Clin Microbiol 2006;44:649-51.  Back to cited text no. 3
4.Ndon JA. Capnocytophaga canimorsus septicemia caused by a dog bite in a hairy cell leukemia patient. J Clin Microbiol 1992;30:211-3.  Back to cited text no. 4
5.Lion C, Escande F, Burdin JC. Capnocytophaga canimorsus infections in human: Review of the literature and cases report. Eur J Epidemiol 1996;12:521-33.   Back to cited text no. 5
6.Wareham DW, Michael JS, Warwick S, Whitlock P, Wood A, Das SS. The dangers of dog bites. J Clin Pathol 2007;60:328-9.  Back to cited text no. 6
7.Low SC, Greenwood JE. Capnocytophaga canimorsus: Infection, septicaemia, recovery and reconstruction. J Med Microbiol 2008;57:901-3.  Back to cited text no. 7
8.Janda JM, Graves MH, Lindquist D, Probert WS. Diagnosing Capnocytophaga canimorsus infections. Emerg Infect Dis 2006;12:340-2.  Back to cited text no. 8

Correspondence Address:
Megha Joshi
Chief, Department of Pathology, Lawrence General Hospital, 1 General Street, Lawrence, MA 01842
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.81642

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