Staphylococcus lentus peritonitis: a case report.

Abstract

Editor: Peritonitis due to animal bacteria (zoonosis) is an infrequent complication in peritoneal dialysis (PD). We present here a case of peritonitis due to Staphylococcus lentus (S. lentus), a coagulase-negative bacterium of animal origin that rarely affects humans. A non-diabetic 55-year-old man treated with automated PD for 31 months was admitted with abdominal pain and cloudy effluent. Exit site appeared normal. Leukocyte count of the effluent showed 7,640/mm3 with 88.5% polymorphonuclear cells. Gram stain of a sample of turbid peritoneal effluent was negative. Cultures of exit site and effluent were taken. Empiric treatment with intraperitoneal vancomycin and Tobramycin was instituted. Abdominal pain rapidly improved and leukocyte count was lower than 100/mm3 after 4 days of treatment. A Staphylococcus lentus grew on cultures of exit site and abdominal effluent which was sensitive to vancomycin, cloxacillin and Tobramycin. The patient received 15 days of vancomycin (3 doses) with total resolution of peritonitis and without relapse. Tobramycin was stopped on day 5. Since S. lentus is usually an animal pathogen and the patient lives in an urban area, we asked the patient if he had had contact with animals. He reported that he had a horse and rides twice a week. Zoonosis in patients on PD represents 0.03 - 0.54% of total peritonitis episodes (1,2). It has been isolated in less than 15 different microorganisms causing peritonitis of animal origin. The most reported bacterium is Pasteurella multocida, which is mainly transmitted by cats. Since antibiotic sensibility and culture growth rate are quite different in bacteria from animals with respect to common bacteria producing infectious peritonitis, an adequate treatment can be delayed. Zoonosis in PD raises questions concerning the desirability of PD patients having pets or coming into contact with farm animals (2). S. lentus is a coagulase-negative staphylococcus that belongs to the Staphylococcus sciuri group (S. sciuri, S. lentus, and S. vitulinus). Those staphylococci are known animal pathogens and they have been isolated from rodents, chickens, mammals and in farm soil and water (3). S. sciuri may colonize humans and produce serious infections, such as endocarditis septic shock, urinary tract infection, wound infections, endophthalmitis, and pelvic inflammatory disease (4). A case of peritonitis due to S. sciuri has been reported (5) but, to our knowledge, a case of S. lentus in a PD patient has not yet been published. Unlike S. sciuri, S. lentus lacks the Mec A gene, making the S. lentus more susceptible to antibiotics than other members of the S. sciuri group, which are oxacillin-resistant staphylococci, and frequently resistant to other antibiotics (6). The treatment of choice for S. sciuri infections is vancomycin although b-lactam antibiotics are also effective. Due to the diversity of infective agents transmitted by animals, it is impossible to create general antibiotic guidelines for all of them. Positive culture of peritoneal effluent remains the most important factor to determine antibiotherapy. Therefore, we want to emphasize the importance of antibiograms even in coagulase-negative bacteria. Our patient had frequent contact with horses. We can speculate that the S. lentus could have come from the horse through skin contact, perhaps due to inadequate hand washing after riding and before doing his peritoneal exchanges. This case illustrates the need to identify all coagulase-negative staphylococci since they are sometimes a contaminant in asymptomatic patients.