Characterization of three strains of Capnocytophaga canis isolated from patients with sepsis

A Novel 16S rRNA PCR-Restriction Fragment Length Polymorphism Assay to Accurately Distinguish Zoonotic Capnocytophaga canimorsus and C. cynodegmi

The zoonotic bacteria Capnocytophaga canimorsus and C. cynodegmi, the predominant Capnocytophaga species in the canine oral biota, can cause human local wound infections or lethal sepsis, usually transmitted through dog bites. Molecular surveying of these Capnocytophaga species using conventional 16S rRNA-based PCR is not always accurate due to their high genetic homogeneity. In this study, we isolated Capnocytophaga spp. from the canine oral cavity and identified them using 16S rRNA and phylogenetic analysis. A novel 16S rRNA PCR-restriction fragment length polymorphism (RFLP) method was designed based on our isolates and validated using published C. canimorsus and C. cynodegmi 16S rRNA sequences. The results showed that 51% of dogs carried Capnocytophaga spp. Among these, C. cynodegmi (47/98, 48%) was the predominant isolated species along with one strain of C. canimorsus (1/98, 1%). Alignment analysis of 16S rRNA sequences revealed specific site nucleotide diversity in 23% (11/47) of the C. cynodegmi isolates, which were misidentified as C. canimorsus using previously reported species-specific PCR. Four RFLP types could be classified from all the isolated Capnocytophaga strains. The proposed method demonstrates superior resolution in distinguishing C. cynodegmi (with site-specific polymorphism) from C. canimorsus and especially in distinguishing C. canimorsus from other Capnocytophaga species. After in silico validation, this method was revealed to have an overall detection accuracy of 84%; notably, accuracy reached 100% in C. canimorsus strains isolated from human patients. Overall, the proposed method is a useful molecular tool for the epidemiological study of Capnocytophaga in small animals and for the rapid diagnosis of human C. canimorsus infections. IMPORTANCE With the increased number of small animal breeding populations, zoonotic infections associated with small animals need to be taken more seriously. Capnocytophaga canimorsus and C. cynodegmi are part of common biota in the mouths of small animals and can cause human infections through bites or scratches. In this study, C. cynodegmi with site-specific 16S rRNA sequence polymorphisms was erroneously identified as C. canimorsus during the investigation of canine Capnocytophaga by conventional PCR. Consequently, the prevalence of C. canimorsus is incorrectly overestimated in epidemiological studies in small animals. We designed a new 16S rRNA PCR-RFLP method to accurately distinguish zoonotic C. canimorsus from C. cynodegmi. After validation against published Capnocytophaga strains, this novel molecular method had high accuracy and could detect 100% of C. canimorsus-strain infections in humans. This novel method can be used for epidemiological studies and the diagnosis of human Capnocytophaga infection following exposure to small animals.

Putative Novel Species of Genus Capnocytophaga, Capnocytophaga stomatis Bacteremia in a Patient with Multiple Myeloma after Direct Contact with a Cat

Capnocytophaga species are among the typical zoonotic pathogens causing infections following direct contact with animals. Recently, a putative novel species of zoonotic Capnocytophaga, Capnocytophaga stomatis, was reported. We herein report the first case of bacteremia caused by C. stomatis. A woman in her 80s with multiple myeloma who was receiving bortezomib and dexamethasone therapy was admitted to our hospital with a 2-day history of a fever and right calf redness. She was often licked by her cat. On a blood culture, thin, Gram-negative rods were detected, which were identified as C. stomatis by whole-genome sequencing. The patient was successfully treated with ampicillin-sulbactam treatment. Our case highlights the pathogenic potential of the putative novel Capnocytophaga, C. stomatis, in immunocompromised hosts.

Cellulitis and transient bacteremia by Capnocytophaga canis after a cat scratch in an immunocompetent patient

Capnocytophaga canis is still a rare cause of infection. We present a case of an immunocompetent patient admited in the hospital with functional impotence, pain and erythema in his left leg after suffering two scratches from his cat 48 h ago. After obtaining blood and wound cultures, broad-spectrum antimicrobial therapy with intravenous amoxicillin clavulanate was initiated. After 1 day and with a clear improvement of the symptoms the patient was discharged from the hospital with cellulitis and transient bacteremia as diagnosis and completing 1 week of antimicrobial therapy orally. After 80 and 92 h of incubation, both anaerobic flasks were positive. In the Gram-stain Gram-negative rod-shaped bacteria could be observed. Despite subculturing in brucella blood agar, tripticase soy agar with 5 % of sheep blood and chocolate agar, in both anaerobic and microaerophilic conditions, the strain could not be recovered. However, these Gram-negative rods could be identified as C. canis by 16S rRNA sequencing, Capsular typing was performed to study the strain, but none of the studied capsule-types tested positive. C. canis is still a rare cause of human infection, but it must be considered in the differential diagnosis of infections related to bites, scratches and licks from dogs or cats.

A Bite So Bad: Septic Shock Due to Capnocytophaga Canimorsus Following a Dog Bite

Infection by Capnocytophaga canimorsus (C. canimorsus), a Gram-negative rod found in the normal oral flora of canine and feline species and transmitted through bites or scratches, is a rare phenomenon. Infections most commonly occur in alcoholics and immunocompromised patients. In this report, we describe the case of a middle-aged male with a history of alcohol abuse who presented with septic shock and multisystem organ failure following a suspected dog bite. The patient was a 59-year-old Caucasian male with alcohol abuse disorder who initially presented with encephalopathy and lethargy. The patient had scratches and multiple healing wounds, with a mottled appearance on his extremities. According to his wife, the patient had been playing aggressively with his dog at home. On admission, he was febrile, tachycardic, and saturating in the 80s on ambient air. His extremities rapidly developed diffuse purpura and dry gangrene of all digits along with the tip of his nose and genitals. The patient developed septic shock and multisystem organ failure. Blood cultures initially grew Gram-positive cocci and Gram-negative rods for which broad-spectrum antibiotics were initiated. Follow-up blood cultures were positive for C. canimorsus and the antibiotic regimen was adjusted accordingly. His condition continued to deteriorate. His family opted for comfort measures only and he died soon after. Common sequelae of C. canimorsus infection include septic shock with multisystem organ failure, disseminated purpuric lesions, hypotension, encephalopathy, and acute renal failure. As seen in our patient, C. canimorsus infection should be considered in such patients, particularly if there is a recent history of an animal bite. Prompt initiation of appropriate treatment is essential to improve patient prognosis.

Capnocytophaga canimorsus blebitis: case report and review of literature

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.

Capnocytophaga felis sp. nov. isolated from the feline oral cavity

Four strains, KC07070^T, KC07105, 11 025B-8C and 11 026B-8-C, were isolated from the oral cavity of cats in 2007 or 2011 in Japan. These strains were Gram-stain-negative rods, exhibited gliding motility, grew in air with 5 % CO₂ and showed catalase and oxidase activity. The sequences of 16S rRNA genes of the four strains were 100 % identical. Additionally, the sequences of 16S rRNA genes of KC07070^T had identity to those of the type strains of Capnocytophaga canimorsus (97.7 %), Capnocytophaga cynodegmi (97.8 %) and Capnocytophaga canis (97.4 %) and 91.2-93.8% identity to those of other species of the genus Capnocytophaga. The major cellular fatty acids of KC07070^T were iso-C_15 : 0 (56.2 %) and summed feature 11 (14.9 %). The G+C content of the DNA from KC07070^T was 35.6 mol%, and the genome size was 2.88 Mbp. KC07070^T had digital DNA-DNA hybridization (dDDH) values of 26.2-27.6% and average nucleotide identity (ANI) values of 75.4-83.3 % to the type strains of the closest relatives, C. canimorsus, C. cynodegmi and C. canis. These results of phylogenetic analysis of 16S rRNA gene sequence, cellular fatty acids compositions and dDDH and ANI values indicate that strain KC07070^T represents a novel species, for which we propose the name Capnocytophaga felis sp. nov., with type strain KC07070^T (=JCM 32681^T=DSM 107251^T).

Septic shock caused by Capnocytophaga canis after a cat scratch

Capnocytophaga canis is an uncommon cause of septic shock. Only three cases have been previously reported in the literature. In this article, we describe the case of a 70-year-old male admitted to the intensive care unit for septic shock of unknown origin. On day 2, one anaerobic bottle out of the two sets taken at admission turned positive with Gram-negative bacilli. The pathogen was identified by 16S rRNA gene as C. canis. The strain was characterized and compared with other clinical isolates of Capnocytophaga spp.