Peritonitis due to Lactococcus cremoris in an automated peritoneal dialysis patient

Olivier Mat1, Camelia Rossi2, Renaud Beauwens1, Françoise Moenens3, Fabienne Mestrez1, Marie-Carmen Muniz1 and Michel Dhaene1

Departments of 1Nephrology, 2Infectious Disease and 3Microbiology R.H.M.S. Baudour Belgium Email: olivier.mat{at}rhms.be

Sir,

Peritonitis is the leading cause of drop-out from peritoneal dialysis (PD) therapy. More than 60% of peritonitis is due to Gram-positive cocci [1]. Potential risk factors for the development of peritonitis have been well identified and include: exit-site infection and nasal carriage of Staphylococcus aureus. As far as we could ascertain, no case of PD peritonitis caused by Lactococcus lactis subsp. cremoris has been reported. It has occasionally caused opportunistic infections in immunodeficient people [2,3] but never in PD.

Case. A 67-year-old male PD patient, of Caucasian origin, was referred to our unit in September 2002 because of abdominal discomfort, fever (37.5°C) and cloudy peritoneal effluent. He had a previous history of arterial hypertension, coronary heart disease, partial thyroidectomy and appendectomy. He experienced APD for 16 months because of nephroangiosclerosis. His usual APD regimen consisted of four 2000 ml exchanges nightly with Dianeal 1.36%. The patient had one episode of bacterial peritonitis in March 2002 due to Gemella morbillorum, which was treated successfully with i.p. cefazolin.

On admission, the clinical picture was dominated by mild diffuse abdominal pain, rebound and normal blood pressure (140/80 mmHg). No tunnel or exit-site infection was present. The laboratory data showed an elevated white blood cell count (13 500/µl with 88.5% neutrophils), normocytic anaemia (haemoglobin 13.0 g/dl), increased inflammatory indice (C-reactive protein 88 mg/l); normal liver and pancreatic enzymes.

PD samples were collected either in blood culture bottles (BACTEC) or centrifuged large volume sterile bottles without transport medium. Analysis of peritoneal effluent demonstrated a WBC count of 1340/µl with 77% neutrophils. Empiric ambulatory antibiotic (once-daily 1.5 g i.p. cefazolin, plus once-daily 120 mg i.p. amikacin) was immediately started [4]. The patient was maintained on APD overnight for the duration of treatment with antibiotics being added to a manual daytime extra exchange. After 24 h, peritoneal culture was positive for Gram-positive cocci, later identified as multisensible L.cremoris. Exit-site sample was contaminated only with Staphylococcus epidermidis. Urine analysis and blood samples were negative. The patient became asymptomatic and effluents progressively cleared within 2 days. On the third day, aminoside was discontinued.

Forty-nine days later, he presented with a second episode of peritonitis. The abdominal investigation by computed tomography (CT) excluded intra-abdominal abscess or tumour. Moreover, 1 year earlier, a double contrast bowel radiography showed no diverticule process. The same multi-sensible pathogen was identified and treated with i.p. vancomycin monotherapy for 14 days [5]. This regimen led to a definitive cure of the infection. Fortunately the patient was transplanted on January 2003 and is doing well.

Microbiology. Lactococcus sp. are catalase-negative Gram-positive cocci closely related to Enterococcus species. Lactococcus sp. form acid in mannitol broth and hydrolyses arginin but fail to form acid from sorbose. Difficulties in distinguishing lactococci from either streptococci or enterococci have probably led to the misidentification of clinical Lactococcus isolates in the past and may have contributed to the paucity of reports concerning the clinical role of these bacteria.

Comments. Intraluminal contamination is known to be the largest source of pathogen in PD-associated peritonitis. Spontaneous bacterial peritonitis is usually due to bacterial (polymicrobial or Gram-negative) translocation from the gut to mesenteric lymph nodes in patients who are submitted to bowel investigation or suffering from liver cirrhosis, cardiac failure or diverticulitis. Our patient does not correspond to this latter condition. Furthermore, posterior inquiry revealed that the patient was a regular consumer of homemade yogurts for a long time. The apparent route of contamination with such a pathogen appears to result from direct intraluminal spreading from contaminated hands. Although technological improvements have reduced the incidence of peritonitis due to touch contamination, Gram-positive agents remain the most common cause of peritonitis [1]. Home-manufactured cheese and yogurt should therefore be considered as a predisposing activity for PD peritonitis. This case report emphasizes once again the importance of pre-dialysis inquiry and careful hand washing to avoid touch contamination.

Conflict of interest statement. None declared.

References

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