Successful treatment of peritonitis associated with Campylobacter fetus subspecies fetus in peritoneal dialysis patients: a case report and literature review

Campylobacter fetus subspecies fetus was identified in the peritoneal dialysate of a 42-year-old patient undergoing continuous ambulatory peritoneal dialysis (CAPD). The patient initially received intraperitoneal ceftazidime and cefazolin sodium for 10 days, which led to significant symptom relief. However, bacterial cultures of the peritoneal dialysate remained positive. Further history revealed that the patient frequently dined at her father’s home, where turtles were kept, suggesting that turtle feces might be the source of infection. Subsequently, the treatment regimen was changed to oral amoxicillin-clavulanate potassium for 3 days, and the patient was advised to avoid contact with turtles. One week after discharge, follow-up cultures of the peritoneal fluid showed no bacterial growth. This case, combined with a review of the literature, provides valuable insights into the diagnosis and management of this rare infection.

Clinical trial number

Not applicable.

Introduction

Peritoneal dialysis is an essential kidney replacement therapy for patients with end-stage kidney disease (ESKD). However, peritonitis remains a significant complication of continuous ambulatory peritoneal dialysis (CAPD) [1–3]. The majority of peritonitis cases are caused by gram-positive bacteria, such as Staphylococcus aureus and Streptococcus spp., or gram-negative bacteria, including Escherichia coli and Pseudomonas aeruginosa [4, 5]. In contrast, infections caused by Campylobacter spp. are exceedingly rare [6].

Campylobacter fetus is a gram-negative, microaerophilic bacterium characterized by its curved or spiral shape. This zoonotic pathogen comprises three subspecies: C. fetus subsp. fetus, C. fetus subsp. venerealis, and C. fetus subsp. testudinum [7]. Human infections with C. fetus are often typically foodborne or associated with animal exposure, primarily affecting immunocompromised individuals or those with underlying health conditions [8]. Although peritoneal infections caused by C. fetus are uncommon, they should be considered in patients with specific risk factors, These include contact with reptiles such as turtles, lizards, and snakes, or the consumption of undercooked food, particularly poultry and meat [8, 9].

Case presentation

The patient, a 42-year-old woman, presented with a two-year history of maintenance peritoneal dialysis and a three-day history of abdominal pain. She had a history of hypertension and was initially diagnosed with chronic kidney failure in 2020, with an initial serum creatinine level of 535 µmol/L. She had been diagnosed with chronic kidney disease stage 5 (CKD5) at our hospital in July 2021, with a serum creatinine level of 901 µmol/L. The underlying cause of her kidney disease was not definitively identified, as no kidney biopsy or specific etiological workup was performed. Persistent fluctuations in serum creatinine levels led to the placement of a peritoneal dialysis catheter in January 2022. Her current peritoneal dialysis regimen consisted of four exchanges of 1.5% glucose dialysate and one exchange of 2.5% glucose dialysate daily, with each exchange using 2 L of dialysate. The ultrafiltration volume ranged from 1,800 to 2,200 mL per day, with a daily urine output of 200–400 mL.

Upon admission, laboratory tests revealed a white blood cell count of 7.2 × 10^9/L, a neutrophil count of 5.81 × 10^9/L, hemoglobin level of 105 g/L, C-reactive protein (CRP) level of 129.85 mg/L, procalcitonin level of 0.96 ng/mL, serum albumin level of 35 g/L, and serum potassium level of 3.46 mmol/L. COVID-19 antigen testing was negative. Analysis of peritoneal fluid showed a nucleated cell count of 346/µL, with 80% neutrophils, and the fluid appeared colorless.

On admission, the first bag of peritoneal dialysis fluid collected in the morning was sent for bacterial culture. Based on the preliminary diagnosis, empirical antibiotic therapy with intraperitoneal ceftazidime (1 g/day) and cefazolin sodium (1 g/day) was initiated. A detailed history was taken, focusing on the patient’s dietary habits and exposure history. The patient reported frequent meals at her father’s home, where turtles were kept.

Two days later, routine ascites revealed 279 nucleated cells, with 67% neutrophils and normal fluid color. The patient’s clinical symptoms were significantly improved.

On day four, bacterial culture of the peritoneal dialysis fluid identified Campylobacter fetus subsp. fetus as the causative agent. Antimicrobial susceptibility testing could not be performed. Given the absence of antimicrobial susceptibility results, empirical antibiotic therapy was continued. After 10 days of anti-infective treatment, the patient’s abdominal pain and fever were completely relieved, and the ascites routine examination showed no obvious abnormalities. However, C. fetus subspecies fetus. was still detected in peritoneal fluid culture. The treatment was then switched to oral amoxicillin-clavulanate potassium tablets (375 mg, once daily) for an additional 3 days. On the third day of oral administration of amoxicillin-clavulanate, a repeat bacterial culture of the peritoneal dialysis fluid showed no bacterial growth. The patient was subsequently discharged.

At follow-up 1 week after discharge, the patient remained asymptomatic, with no bacterial growth in the peritoneal fluid culture and no abnormalities in the ascites analysis.

Literature review

A systematic search was conducted across multiple databases, including PubMed, Embase, the Chinese National Knowledge Infrastructure (CNKI), WanFang Data and Web of Science (WOS), covering the period from database inception to July 3, 2024. The search terms included “Campylobacter fetus,” “vibrio fetus,” “spirillum serpens,” and “peritonitis.” The search strategy was as follows: (((Campylobacter fetus) OR (vibrio fetus)) OR (spirillum serpens)) AND (peritonitis). The inclusion criteria specified studies involving patients undergoing CAPD and diagnosed with peritonitis caused by Campylobacter fetus. Studies were excluded if they did not focus on peritonitis, Campylobacter fetus infections, or dialysis-related peritonitis. A total of 9 studies involving 9 patients were included, comprising 7 males and 2 females. The mean age of the patients was 53.1 ± 12.2 years [10–18].

Through a review of the literature, we identified various methods for the detection of Campylobacter fetus. Specimens such as peritoneal dialysate, blood, and stool can be inoculated onto multiple media types, including sheep blood agar, chocolate agar, Brucella blood agar, and Campy selective agar. Cultures are incubated under different conditions, such as 35 °C, 5% CO₂, anaerobic, or microaerophilic environments, to observe the morphological and colony characteristics of gram-negative curved bacteria. Two cases reported infections caused by C. fetus subsp. fetus, while one case involved C. fetus subsp. testudinum. For C. fetus subsp. fetus, prolonged incubation of 15 days at 35 °C, compared to the typical 48-hour period reported in other studies, allowed sufficient time for bacterial growth and may have been a key factor in successfully isolating this subspecies. In contrast, the identification of C. fetus subsp. testudinum benefited from the use of diverse culture media and precise molecular biology techniques.

In the nine studies reviewed, abdominal pain and fever were the most frequently reported clinical manifestations, followed by diarrhea and vomiting, which is consistent with the typical presentation of peritonitis (Fig. 1). One case linked C. fetus peritonitis to infectious colitis, while another reported C. fetus translocation into the peritoneal cavity shortly after catheter insertion, likely triggered by the consumption of raw liver. Additionally, one case attributed the infection to contamination at the connection site between the peritoneal dialysis bag and catheter. The remaining studies did not specify potential sources of infection (Table 1).

Fig. 1.

Clinical symptoms in the literature review

Table 1.

Literature review of Campylobacter fetus infections in CAPD

Reported by	Age(y)	Sex	Clinical symptoms	Trigger	Treatment	Route of Administration	Type of subtype	Therapeutic duration	Outcome
Hur, K. [10]	73	Male	Abdominal pain, nausea, vomiting	Infectious Colitis	CEP + QNL	IP	-	2 weeks	improvement
Inoue, K. [11]	55	Male	Fever, lower abdominal pain	Ingestion of raw liver	CARB	IV	-	4 weeks	improvement
Kubota, M. [12]	47	Male	Low-grade fever (37.7 °C), abdominal pain, diarrhea, sore throat, turbid peritoneal effusion, active bowel sounds and no rebound or guarding	-	CEP + QNL	IV + PO	C. fetus subsp. fetus	-	-
Lee, Y. C. [13]	51	Male	Low-grade fever(37.9 °C), abdominal pain, nausea, vomiting, upper abdominal tenderness without peritoneal signs	Catheter contamination	AMG + QNL	IV + IP + PO	-	-	improvement
Meigh, J. A. [14]	58	Female	Abdominal pain, diarrhea, fever (39 °C), abdominal tenderness and alertness, no rebound pain.	-	AMG + VAN	IV + IP	-	-	improvement
Romero Gómez [15]	29	Female	Fever (38 °C), abdominal pain, diarrhea, turbid peritoneal effusion, diffuse abdominal tenderness	-	AMG + VAN	IV	-	2 weeks	improvement
Wens, R. [16]	62	Male	Fever, abdominal pain, diffuse abdominal tenderness	-	AMG + MAC	IV + PO	C. fetus subsp. fetus	3 weeks	Sepsis
Li, H.S. [17]	46	Male	Abdominal pain, turbid peritoneal effusion	-	AMG + MAC	IV + PO	-	4 weeks	improvement
Qiu, W.B. [18]	57	Male	Abdominal pain, diarrhea, turbid peritoneal effusion	-	AMG	-	C. fetus subsp. testudinum	-	-

Note: CEP = Cephalosporins, ONL = Quinolones, CARB = Carbapenem antibiotics, AMG = Aminoglycosides, VAN = Vancomycin, MAC = Macrolides; IP = Intraperitoneal, IV = Intravenous, PO = Per os

In terms of treatment, macrolides plus aminoglycosides, was the predominant approach, with cephalosporins primarily utilized for early empirical treatment. Treatment duration ranged from 2 to 4 weeks, and most patients experienced significant symptom improvement without recurrence. Only one case reported a patient developing sepsis three weeks after treatment initiation (Table 1).

Discussion and conclusions

Epidemiology and pathogenesis of Campylobacter fetus

Campylobacter fetus is a rare but noteworthy zoonotic pathogen in humans, comprising three subspecies: C. fetus subsp. fetus, C. fetus subsp. venerealis, and C. fetus subsp. testudinum. Among these, C. fetus subsp. fetus primarily infects mammals and is typically transmitted through the consumption of contaminated meat or direct contact with livestock [8, 9]. In contrast, C. fetus subsp. testudinum is associated with reptile feces and has increasingly been reported in human infections, particularly in individuals with a history of reptile exposure [7, 19].

The pathogenicity of C. fetus is largely mediated by its surface-layer (S-layer) proteins, which confer resistance to complement-mediated lysis and phagocytosis, enhancing the bacterium’s ability to persist within the host [20]. These features contribute to its potential to cause severe systemic infections, including sepsis and meningitis, especially in immunocompromised individuals [21].

Detection methods range from traditional culture techniques under microaerophilic conditions to advanced molecular approaches such as 16S rRNA sequencing, qPCR, MALDI-TOF MS, and whole-genome sequencing (WGS), each offering varying degrees of sensitivity and specificity [22–25].

Clinicians should maintain a high index of suspicion for C. fetus infections, particularly in peritoneal dialysis patients with a history of reptile exposure or the consumption of undercooked foods.

Case review and therapeutic implications

Our case represents a rare instance of C. fetus subsp. fetus peritonitis in a peritoneal dialysis patient, likely linked to reptile exposure—specifically, turtles kept in the patient’s household. Initial intraperitoneal administration of ceftazidime and cefazolin led to symptom improvement but persistent positive cultures, prompting a switch to oral amoxicillin-clavulanate, which ultimately achieved pathogen clearance.

While cephalosporins are not routinely used for treating Campylobacter infections, this case suggests they may still offer clinical benefit in the absence of resistance. The subsequent shift to amoxicillin-clavulanate further highlights the importance of treatment flexibility, particularly when antimicrobial susceptibility testing is unavailable.

A literature review of nine similar cases revealed that most patients presented with abdominal pain and fever, and were treated successfully with aminoglycosides, macrolides, or vancomycin, often in combination. Treatment durations typically ranged from 2 to 4 weeks. Notably, cephalosporins were generally reserved for empirical use, aligning with current ISPD recommendations for gram-negative coverage, including third-generation cephalosporins or cefepime [26].

Previous studies have documented cases of C. fetus subsp. testudinum infections associated with reptile exposure. Initially, these isolates were often misidentified as C. fetus subsp. fetus through conventional culture methods. However, subsequent 16S rRNA gene sequencing provided more accurate identification of C. fetus subsp. testudinum. In the present case, the patient’s exposure history supports the hypothesis of reptile-related infection [18]. Unfortunately, further confirmation of the infection source was limited by the patient’s refusal to provide turtle feces for culture.

Prevention and public health considerations

The highlight of this study lies in the significant therapeutic efficacy of cephalosporins in this case, despite their limited use in the treatment of Campylobacter fetus infections in previous literature. Although C. fetus infections are generally manageable, the unique subspecies classification and challenges in identifying the source of infection emphasize the importance of conducting a thorough patient history during diagnosis and treatment. Specifically, tracing potential sources of infection is crucial to prevent recurrence.

This case not only expands the clinical spectrum of C. fetus-related peritonitis but also underscores the importance of patient education in infection prevention. Peritoneal dialysis patients should be advised to: (1) Avoid direct contact with potential animal reservoirs, especially reptiles. (2) Ensure all food is thoroughly cooked, and avoid consuming raw or unpasteurized products. (3) Adhere to strict aseptic techniques during peritoneal dialysis catheter handling and schedule regular catheter replacements [27–29]. From a broader perspective, this report advocates for heightened awareness of rare pathogens among clinicians and microbiologists. Strengthening diagnostic capacity, particularly at the subspecies level, and encouraging the inclusion of zoonotic exposure in patient histories, may facilitate earlier identification and improved outcomes.

Abbreviations

CAPD

Continuous ambulatory peritoneal dialysis

CRP

C-reactive protein

C. fetus

Campylobacter fetus

C. fetus subsp.

Campylobacter fetus Subspecies

Author contributions

YC and XL conceptualized the study. HQ developed the methodology. YC designed the software. QZ, KB and XL performed validation. XL and QZ conducted formal analysis. YC carried out the investigation. XL and KB provided resources. YC curated the data. YC wrote the original draft. YC and KB reviewed and edited the manuscript. KB and HQ created visualizations. KB supervised the research and administered the project. All authors read and approved the final manuscript.

Funding

This study was supported by the Special project of State Key Laboratory of Dampness Syndrome of Chinese Medicine (Nos. SZ2021ZZ02 and SZ2021ZZ36).

Data availability

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding authors.

Declarations

Ethics approval and consent to participate

The studies involving humans were approved by Ethics Committee of Guangdong Provincial Hospital of Chinese Medicine. The studies were conducted in accordance with the local legislation and institutional requirements. The participant provided her written informed consent to participate in this study.

Consent for publication

Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

Competing interests

The authors declare no competing interests.