A Case of Intra-abdominal abscess due to Sphingomonas paucimobilis in a patient on Peritoneal dialysis: A case report and review of literature

Introduction

We present the first reported cause of intra-abdominal abscess associated with Sphingomonas paucimobilis PD-related peritonitis. Sphingomonas paucimobilis PD-related peritonitis is also rare with only 13 cases reported in the medical literature before this.

Case History

A 35-year-old male patient on peritoneal dialysis (PD) presented in January 2019 with a 1-day history of abdominal pain and cloudy PD dialysate. He had end-stage kidney disease from chronic glomerulonephritis and was started on automated PD in May 2015. Other medical history included hypertension and a history of inguinal herniorrhaphy. There was an episode of culture-negative peritonitis in 2016. At the time of presentation, his PD regimens consisted of 6 cycles at night, with a fill volume of 2.1 L and last fill of 1.2 L using icodextrin. His daily ultrafiltration volume was around 1.5 L. Two weeks prior to the current presentation, he had an episode of culture-negative peritonitis, which resolved with 2 weeks of intraperitoneal (IP) ampicillin/sulbactam and ceftazidime.

On examination, he was afebrile and blood pressure was 110/70 mmHg. There was periumbilical tenderness but no guarding. Other systemic examination was unremarkable. His PD catheter exit site was normal. PD effluent was turbid, and its white blood cells (WBCs) was 640/μL with 100% neutrophils. Gram stain of the fluid did not show any organism. Empirical IP ampicillin/sulbactam and ceftazidime were started. Three days later, the PD fluid WBC count came down to 350 with 91% neutrophils. At the same time, the PD fluid culture grew Sphingomonas paucimobilis, sensitive only to ciprofloxacin, netilmicin, and co-trimoxazole; but resistant to gentamicin, amikacin, ceftazidime, piperacillin, imipenem, and meropenem. In view of clinical stability, improvement in PD fluid WBC count and the uncertain clinical significance of the organism, the patient was continued on IP ampicillin/sulbactam and ceftazidime.

By day 7, the patient still had abdominal pain and cloudy effluent. Repeat PD fluid was still positive for S. paucimobilis, thus antibiotic was changed to intravenous (IV) ciprofloxacin 200 mg BD. Within 72 h, the PD fluid became clear and WBC count became 0. Despite this, the PD fluid remained positive for S. paucimobilis, possibly because of the presence of biofilm on the catheter. Ultrasound tunnel tract did not reveal any collection. In view of persistent abdominal pain, an ultrasound of the abdomen was done which showed a 13.2 by 10.6 by 10.8 cm loculated abscess around the catheter tip in the pelvis. IV netilmicin 150 mg OD was then added, and the patient underwent PD catheter removal and drainage of the abscess on day 16. Following this, there was marked clinical improvement with resolution of abdominal pain and down trending of his inflammatory markers. He was shifted to hemodialysis via a right internal jugular tunneled dialysis catheter and was discharged well with continuation of IV ciprofloxacin and netilmicin for a total duration of 35 and 19 days, respectively. After completion of the antibiotics, a follow-up ultrasound scan showed total resolution of the intra-abdominal abscess.

Discussion

S. paucimobilis is a yellow-pigmented, aerobic gram-negative bacillus that has a single polar flagellum with slow motility.[1] First isolated in a human infection and named Pseudomonas paucimobilis in 1977,[2] it was then reclassified and renamed as S. paucimobilis in 1990.[3] There are currently more than 30 species in the genus Sphingomonas, with S. paucimobilis considered as the main pathogenic species. Widely distributed in the natural environments in water and soil, the organisms have been isolated in multiple environments—sea ice, river water, mineral water, and other water distribution systems. They are also found in nosocomial environments, such as laboratory instruments, ventilators, and hospital water systems.[4]

Human infections caused by S. paucimobilis are generally rare. S. paucimobilis can cause both sporadic and nosocomial infections. Sporadic infections include infected leg ulcers, urinary tract infection, brain and spleen abscesses. Nosocomial infections include bacteremia caused by contaminated solutions, for example, distilled water, hemodialysis fluid, and sterile drug solutions.[5] Most of the infections are in immunocompromised patients with indwelling devices. No deaths due to infections from this organism have been reported so far. It is a unique organism with low virulence thought to be secondary to the lack of lipid A in its outer membrane; instead there is an atypical lipopolysaccharide sphingoglycolipid.[6] The absence of these components may therefore explain the favorable prognosis observed in the previously reported cases.

Although nosocomial infection with S. paucimobilis has been infrequently reported, PD-related peritonitis with this organism is exceptionally rare. Only 13 cases of S. paucimobilis PD-related peritonitis have been reported prior to ours.[789101112131415161718] Table 1 shows the clinical features of these patients. Vintage on PD ranged from 6 to 72 months. Almost all patients presented with abdominal pain and cloudy dialysate. Only two (14%) patients reported having fever on presentation. Half of them had a recent episode of peritonitis, ranging from 1 week to 7 months before their episodes caused by S. paucimobilis. Table 2 shows their laboratory findings, which vary greatly among the 14 patients. Our case is unique as this is the first reported case of intra-abdominal abscess associated with S. paucimobilis peritonitis. The treatment and outcomes have also been variable as shown in Table 3. Half of the cases were cured with appropriate antibiotics, but the other half required catheter removal, ranging from day 7 to 21 from the day of diagnosis, to eradicate the infection. Most of the latter patients had clinically improved with antibiotics but continued to have positive cultures in their dialysates. This is an exceptionally high treatment failure rate despite the organism's low virulence. This high therapeutic failure rate is partly due to the organism's unpredictable antibiotic sensitivity. None of the case reports have shown any consistent pattern of antibiotic sensitivity. Hence to this date, no definitive guidelines exist for antimicrobial therapy for S. paucimobilis infections. Trimethoprim-sulfamethoxazole, chloramphenicol, ciprofloxacin, and aminoglycosides have all been successfully used to eradicate this bacterium. Among the seven cases that were cured, five used an IP aminoglycoside. Although an aminoglycoside plus a third-generation cephalosporin or a carbapenem alone could effectively treat S. paucimobilis infections,[19] there is insufficient data to comment on the use of monotherapy versus combination therapy. International Society of Peritoneal Dialysis guidelines on the management of peritonitis recommend removing the catheter if there is no clinical improvement within 5 days of appropriate antibiotic therapy. This same criterion should be applied to S. paucimobilis peritonitis.

Our case is unique as firstly the organism was resistant to carbapenem and gentamicin which were both successfully used in previous cases. Secondly, this is the first reported case of intra-abdominal abscess associated with S. paucimobilis PD-related peritonitis. Due to the presence of this intra-abdominal abscess as well as persistent abdominal pain and failure to clear the organism from the effluent, he required PD catheter removal to eradicate the infection.

In conclusion, we report the first case of intra-abdominal abscess associated with S. paucimobilis PD-related peritonitis, which was treated by catheter removal. Despite having low virulence, treatment failure rate of this peritonitis is extremely high, with removal of the catheter in 50% of reported cases. This case adds to the current literature of peritonitis caused by S. paucimobilis.