| Abstract|| |
Sphingomonas paucimobilis, a yellow-pigmented, aerobic, glucose non-fermenting, Gram-negative bacillus, is a rare cause of human infection normally associated with immunocompromised hosts. It has been associated with a few cases of continuous ambulatory peritoneal dialysis (PD) and is notorious for its resistance to the commonly used antibiotics. In half of the cases reported so far, the peritonitis was refractory to treatment, necessitating PD catheter removal. We report a case of Sphingomonas paucimobilis peritonitis in a 50-year-old patient who had been on PD for two years. The patient was successfully treated with intraperitoneal and intravenous antibiotics and the PD catheter was salvaged.
|How to cite this article:|
Mohan D, Railey M. Sphingomonas paucimobilis peritonitis: A case report and review of the literature. Saudi J Kidney Dis Transpl 2015;26:567-71
|How to cite this URL:|
Mohan D, Railey M. Sphingomonas paucimobilis peritonitis: A case report and review of the literature. Saudi J Kidney Dis Transpl [serial online] 2015 [cited 2021 Jun 14];26:567-71. Available from: https://www.sjkdt.org/text.asp?2015/26/3/567/157371
| Introduction|| |
Sphingomonas paucimobilis is a yellowpigmented, gram-negative bacillus that has a single polar flagellum with slow motility.  Although it was first isolated in a human infection and named Pseudomonas paucimobilis in 1977, it was reclassified in 1990 based on phylogenetic data and renamed as S. paucimobilis. , Widely distributed in water and soil, it is a rare cause of infection in human beings. It has been implicated in both sporadic and nosocomial infections, having been recovered from hospital equipment and solutions used in hospitals. It is also an unusual pathogen for peritoneal dialysis (PD) associated peritonitis.
We report a case of PD-associated peritonitis caused by S. paucimobilis that was treated successfully with anti-biogram-based intra-venous meropenem and intraperitoneal tobramycin. This is only the tenth reported case of such peritonitis, and the first from the Arabian Gulf region. We also review the nine other previously reported cases of PD-associated peritonitis caused by this organism.
| Case Report|| |
A 50-year-old Arab lady with end-stage renal disease, who had been receiving continuous ambulatory peritoneal dialysis (CAPD) for 28 months, presented to our hospital with fever, abdominal pain, vomiting and cloudy dialysate for three days. In the past, she had had three episodes of peritonitis, which all responded well to antibiotic therapy.
On examination, her pulse was 104/min, blood pressure was 105/58 mm Hg and temperature was 36.8°C. Her abdomen was diffusely tender with normal bowel sounds and the catheter exit site was unremarkable. Blood investigations revealed hemoglobin 11.4 g/dL, total leukocyte count 15,400/mm 3 (92% neutrophils), creatinine 11.2 mg/dL and urea 117 mg/dL. The peritoneal fluid analysis revealed numerous WBCs, with a neutrophil predominance (80%). The patient was hospitalized and the peritoneal effluent was sent for bacterial culture. She was started on empiric therapy for peritonitis with a single 1 g dose of vancomycin intraperitoneally and ciprofloxacin intravenously.
The gram stain subsequently showed gram negative rods. Vancomycin was discontinued and intraperitoneal tobramycin (4 mg/dL) was added. Peritoneal fluid was inoculated into a BACTEC plus Aerobic/F culture bottle (Becton, Dickinson Diagnostic Instrument Systems, Drogheda, Ireland) and incubated in a BACTEC 9240 Blood Culture System.
On the fourth day of incubation, the culture bottles became positive and subcultures on solid media (5% horse blood agar, chocolate agar, MacConkey agar, Sabouraud's agar and Neomycin blood agar) were performed. Nonhemolytic, convex and yellow-pigmented colonies grew on the blood agar and chocolate agar after 24 h of incubation at 37°C, but no growth was found on MacConkey agar. The bacteria were gram negative, non-fermenting and oxidase and catalase positive. The isolates were identified as S. paucimobilis through the use of the API 20 E (Bio-Mèrieux, MarcyI'Etoile, France) and VITEK 2 (Bio-Mèrieux) biochemical identification systems. The anti-biogram, performed on 5% sheep blood agar by the disk diffusion method, showed sensitivity to cefepime, ceftazidime, amikacin, ciprofloxacin and meropenem.
On the third day of her hospitalization, based on lack of clinical improvement in abdominal pain, ciprofloxacin was discontinued and IV meropenem (500 mg/day) was added. Two days after the initiation of meropenem (and five days of intraperitoneal tobramycin), the patient became asymptomatic and her peritoneal fluid cleared. Peritoneal fluid analysis was repeated after five days of treatment and showed <5 WBCs with no bacterial growth. Treatment with IV meropenem and IP tobramycin were continued for a total duration of three weeks. PD fluid analysis after completion of treatment was sterile. No recurrence of peritonitis occurred during the subsequent three months of follow-up.
| Discussion|| |
S. paucimobilis can cause sporadic infections, including infected leg ulcers, urinary tract infection, abscesses in the brain and spleen and cervical adenopathy. Nosocomial infections include bacteremia/septicemia caused by contaminated solutions, e.g. distilled water, HD fluid and sterile drug solutions.  Most of the infections are associated with immunocompromised hosts or patients fitted with indwelling devices. To date, no deaths have been reported in the literature associated with infections from S. paucimobilis. This organism lacks the lipopolysaccharide components in the outer membrane of the cell wall usually found in Gram-negative organisms, which are associated with endotoxin activity. The absence of these components may therefore explain the favorable prognosis observed in the previously reported cases.  It has also been rarely known to cause PD-associated peritonitis.
The earliest (two) reports of PD-associated peritonitis caused by S. paucimobilis were by Glupcynski et al  in 1984. Thereafter, seven more cases have been reported, with the latest one by Tambawala et al in 2011. ,,,,,, The clinical features, microbiological data and outcomes of these patients, and our patient, are summarized in [Table 1]. Peritonitis due to this organism tends to have a variable outcome, as can be seen from the cases reported so far.
|Table 1: Reported cases (including the present case no. 10) of peritoneal dialysis-associated peritonitis caused by Sphingomonas paucimobilis (data partially taken from 11).|
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As evident from the table, the clinical outcomes in the reported cases have been variable, with six cases, including our patient, being cured after appropriate antibiotic therapy, but the other four patients required catheter removal to eradicate the infection. The organism tends to have unpredictable antibiotic sensitivity, and this has been implicated in the therapeutic failure. None of the case reports have shown any consistent pattern of antibiotic sensitivity. This explains why, to this date, no definitive guidelines exist for antimicrobial therapy for Sphingomonas infections. TMP- SMX, chloramphenicol, ciprofloxacin and aminoglycosides have all been successfully used to eradicate this bacterium.  Imipenem or meropenem alone and an aminoglycoside plus a third-generation cephalosporin have been suggested as suitable antibiotics for the treatment of infections caused by this pathogen. , Among the six cases that were cured, five (including ours) used an intraperitoneal aminoglycoside. There is insufficient data to comment on the use of monotherapy versus combination therapy.
Different from the previous reports, in our patient, the anti-biogram revealed sensitivity to cefipime, ceftazidime, ciprofloxacin and aminoglycoside, in addition to meropenem. However, abdominal pain persisted even after three days of IV ciprofloxacin. Considering the existing experience in the literature with this virulent gram negative organism and its resistance for many antibiotics, we decided to escalate therapy to meropenem, and it succeeded.
The most recent International Society of Peritoneal Dialysis (ISPD) guidelines on the management of peritonitis recommend removing the catheter if no clinical improvement is noted within five days of appropriate antibiotic therapy.  The same criteria may be applied to Sphingomonas-associated peritonitis.
Our patient responded well to the combination of intraperitoneal tobramycin (4 mg/L) and intravenous meropenem, both of which were administered for a duration of three weeks. PD fluid repeated culture after the completion of treatment was sterile.
In summary, a patient with CAPD-associated monomicrobial S. paucimobilis peritonitis infection responded clinically and microbiologically to the anti-biogram-based antibiotic therapy. Because PD-associated S. paucimobilis peritonitis resulted in catheter removal in nearly half the cases reported to date, nephrologists should be aware of the potential virulence of this bacterium. This organism is mostly resistant to the common antibiotics empirically used to treat peritonitis. IV meropenem and intraperitoneal tobramycin were used successfully in our patient to treat the CAPD-associated peritonitis caused by this bacterium.
| Acknowledgment|| |
The authors would like to thank Dr. Anju Nabi of the Department of Microbiology, Dubai Hospital, Dubai for providing the details of identification for S. paucimobilis.
| References|| |
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Dr. Dhanya Mohan
Department of Nephrology, Dubai Hospital, P. O. Box 7272 Dubai
United Arab Emirates