Capnocytophaga canimorsus peritonitis diagnosed by mass spectrometry in a diabetic patient undergoing peritoneal dialysis: a case report

Abstract

Background Bacterial peritonitis is a serious complication of patients undergoing peritoneal dialysis (PD). Although the identification of causative organisms and use of appropriate antibiotics are essential for treatment, rare and fastidious bacteria are sometimes difficult to detect by conventional biochemical assays. Capnocytophaga canimorsus is a fastidious and slow-growing bacterium that forms a part of the normal oral flora of dogs and cats and is extremely rare as a peritonitis-causing organism. This report demonstrates the usefulness of a mass spectrometry-based technique in identifying such a rare organism in PD-related peritonitis and discusses the diagnosis and treatment of C. canimorsus peritonitis. Case presentation A 49-year-old woman with type 2 diabetes mellitus underwent PD for two years. Repeated exit-site infections led to subcutaneous pathway diversion two months ago. She was hospitalized with fever and abdominal pain as well as cloudy dialysis effluent. Laboratory data revealed increased serum C-reactive protein level and white blood cell (WBC) count in the effluent. Her exit site had no sign of infection, leading to the diagnosis of PD-related peritonitis. Initial therapy with intraperitoneal ceftazidime immediately ameliorated her symptoms, and the WBC count in the effluent normalized in five days. Culture test results of the dialysis effluent on admission were negative with no information regarding the infection route. However, mass spectrometry (MALDI Biotyper, Bruker Daltonics) successfully obtained the specific spectral pattern for C. canimorsus . She had four cats in her house and was advised not to allow the cats in the room where the bag exchange took place. Conclusions C. canimorsus is a rare cause of peritonitis in PD patients and is usually susceptible to intraperitoneal third-generation cephalosporins. This mass spectrometry-based bacterial identification method could provide more opportunities to identify uncommon causes and promote appropriate antibiotics therapy in PD-related peritonitis.

Microbial characteristics across different tongue coating types in a healthy population

“…In the Y-thick greasy group of diabetic patients, the Capnocytophaga genus was highly enriched (Figure 4). This potentially pathogenic genus is reported to be related to periodontitis and type 1 diabetes mellitus [49], and it was recently found in a diabetic patient with peritonitis [50]. The species P. melaninogenica was enriched in the healthy population.…”

Detection of Capnocytophaga canimorsus and Capnocytophaga cynodegmi in dogs with periodontal disease of Brazil

“…Both species of Capnocytophaga have slow and fastidious growth (Tanabe et al, 2019), and it is necessary to enrich the environment with 5 to 10% carbon dioxide (CO2) for its isolation, which may result in negative microbiological cultivation in many cases (Sakai et al, 2019).…”

Bacterial peritonitis secondary to Capnocytophaga canimorsus

“…Infections in humans are usually related to contact with these animals and occur mainly in patients with associated risk factors such as immunosuppression and splenectomy (1,2). Although cases of peritonitis caused by this bacterium have been reported in patients on peritoneal dialysis (3,4), this is the first reported case of isolation of C. canimorsus in the ascitic fluid of a patient with liver cirrhosis.…”