Continuous Ambulatory Peritoneal Dialysis Peritonitis due to Enterococcus cecorum

Abstract

Enterococcus cecorum was isolated as the etiologic agent of a continuous ambulatory peritoneal dialysis peritonitis episode in an alcoholic patient. To date, this is only the third infection due to this bacterium, found in the intestinal tract of many domestic animals, that has been reported in humans.

CASE REPORT

A 44-year-old man with a long history of alcohol abuse developed oliguria after upper gastrointestinal bleeding and a paracentesis for tense ascites due to decompensated alcoholic liver cirrhosis. Despite the correction of his volume status, his renal function did not recover and continuous ambulatory peritoneal dialysis (CAPD) was chosen as the renal replacement modality because of the intractable ascites.

After percutaneous positioning of a two-cuff straight Tenckoff catheter, CAPD treatment was successfully initiated in April 1999 because of hepatorenal syndrome. Eight weeks after initiation of this treatment, the patient developed fever and chills with abdominal discomfort. Clinical examination revealed a severely ill patient with a tender abdomen. The laboratory examination conformed with an inflammatory status. The drain of the dialysate contained 1,500 leukocytes/μl, of which 80% was polymorphonuclear cells. Although the peripheral white blood cell count was not elevated (7,160/μl), C-reactive protein was 13.6 mg/dl. Treatment consisted of cefazolin given at 1,000 mg intraperitoneally in the first exchange, followed by 250 mg in each of the four daily dwells for 5 days and of gentamicin at 60 mg intraperitoneally in one dwell for 5 days. On day 6 and day 10, 1,000 and 500 mg of vancomycin, respectively, was administered. Full recovery from the peritonitis was observed at the follow-up visit at day 10. Antibiotic treatment was stopped after administration of the second dose of vancomycin.

No blood cultures were performed, but a Gram-stained smear of the dialysate revealed numerous white blood cells and gram-positive cocci in chains. Culture on tryptic soy agar plus 5% sheep blood (Becton Dickinson, Erembodegem, Belgium) of the dialysate yielded a pure culture of regular, low-convex, nonhemolytic, partially translucent, and nonpigmented colonies. Growth was enhanced when incubation was performed in air supplemented with 5% CO₂. The API 20 Strep (BioMérieux, Marcy-l'Etoile, France) profile obtained, profile 5672472, gave no identification, but this combination of biochemical reactions, notably, a positive Voges-Proskauer reaction and positivity for ribose, is indicative of the genus Enterococcus, whereas the positive alkaline phosphatase reaction is a unique characteristic that differentiates Enterococcus cecorum from all other enterococci (2). Another important but potentially misleading characteristic is its poor or absent growth on widely used enterococcal selective media containing sodium azide, such as Slanetz and Bartley agar. The negative arginine and l-arabinose reactions and the positive results for β-glucuronidase, d-raffinose, and inulin are typical for the species E. cecorum (1). The phenotypic identification based on growth characteristics and the API 20 Strep result was confirmed by means of tRNA gene (tDNA) PCR and capillary electrophoresis. This PCR-based DNA fingerprinting technique consists of the amplification of the spacer regions between the tRNA genes (6) and yields species-specific fingerprints when the amplified DNA fragments are separated by high-resolution (1-bp) electrophoresis, as is possible on an ABI 310 Prism genetic analyzer (Applied Biosystems, Foster City, Calif.) (5). The fingerprint obtained for this organism consisted of amplified DNA fragments with lengths of 56.2, 63.8, 81.2, 240.9, and 254.7 bp, a pattern observed only for E. cecorum and not for any of the 35 Streptococcus or 13 other Enterococcus species which have been studied by this approach thus far (unpublished data).

MICs determined by the E-test (AB Biodisk, Solna, Sweden) on Mueller-Hinton agar (Becton Dickinson) were 0.75 μg/ml for ceftriaxone, 0.19 μg/ml for penicillin, 0.25 μg/ml for teicoplanin, and 0.50 μg/ml for vancomycin.

Our patient represents the third case of human infection with E. cecorum. A case of septicemia has been described in a patient with morbid obesitas (3), and during the preparation of this manuscript a case of spontaneous peritonitis was described (4). The first case (3) concerned a 44-year-old malnourished female patient, admitted to the hospital for dehydration. The patient also suffered from mucositis, alopecia, diarrhea, and osteoporosis secondary to vitamin deficiency and had undergone numerous surgical procedures for morbid obesity. Seven days after admission, she developed severe sepsis with hypotension, and intravenous epinephrine (4 to 8 μg/min) was begun in order to stabilize the systemic arterial pressure. A gram-positive coccus was cultured from two blood samples taken at day 7. The organism was identified as E. cecorum by means of conventional biochemical tests and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins and was susceptible to ampicillin, ciprofloxacin, imipenem, and vancomycin. The patient was treated intravenously with imipenem for 9 days, followed by ciprofloxacin for 5 more days. Blood samples taken on day 9 after admission from three different intravascular catheters remained sterile, the patient's fever decreased, and thereafter, the hemodynamic variables improved rapidly.

The recently described case (dating from December 1998) (4) concerned a 60-year-old male with a hepatitis B virus-related liver cirrhosis diagnosed 20 years earlier. The infection was also located in the peritoneum but occurred spontaneously in a patient not under CAPD treatment. This infection was bacteremic, and after cefoxitin treatment for 2 weeks the infection relapsed, complicated by fatal septic shock. The organism was identified as E. cecorum with the API Rapid 32 Strep system, which resulted in code 2717 6707 110 and which gives an identification as “Streptococcus cecorum” with the API database, version 1.1, but which results in “no identification, no complementary tests, no related taxa” with the more recent API database, version 3.2.2.

E. cecorum is known as an intestinal commensal organism isolated from chickens, pigs, calves, horses, ducks, cats, dogs, and canaries (1, 2) and might be an inhabitant of the human intestine as well. Its pathogenic importance may be overlooked since its appearance is Streptococcus-like, since it prefers incubation in a CO₂-rich atmosphere, since it does not grow on Enterococcus selective media, and since appropriate phenotypic identification is not obvious.