Case Presentation:
An 80 year old man in ESRD receiving peritoneal dialysis who had suffered several days of nausea, vomiting, and diarrhea came to his nephrologist after his dialysate became a yellow, milky color. The nephrologist cultured his peritoneal fluid, and gram positive cocci in clusters were seen on gram stain. He underwent treatment with intraperitoneal vancomycin every three days for two weeks, but his illness progressed with fevers, abdominal pain, and leukocytosis in addition to prior symptoms. Further culture studies demonstrated that the primary pathogen was not S. epidermidis as initially suspected, but Rothia mucilaginosa (formerly Stomatococcus spp.). After the patient was admitted, IV piperacillin-tazobactam was added to his antibiotic regimen. On day 3 of IV antibiotics in-hospital with continued intraperitoneal vancomycin, the patient was converted to hemodialysis due to persistent peritonitis, and vancomycin was administered by IV. After removal, the PD catheter and dialysate were cultured on the day of surgery, and were positive for coagulase negative staphylococcus and Citrobacter koseri. One week after the peritoneal dialysis site was closed and IV antibiotics were continued, the patient’s symptoms and leukocytosis resolved.
Discussion:
R. mucilaginosa is an encapsulated gram positive species native to the oropharynx and upper respiratory tract. The bacterium is catalase positive and coagulase negative, found growing in tetrads or clusters. It was first identified as a human pathogen in a case of endocarditis in 1978. It has since been found in cases of meningitis, pneumonia, and osteomyelitis, particularly in immunodeficient patients1. While previously rarely seen in cases of peritonitis, R. mucilaginosa has become increasingly prevalent in recent years, especially in the setting of immunocompetent patients receiving peritoneal dialysis2.
The majority of cases of peritonitis in PD patients are due to gram positive infections, particularly S. epidermidis. However, due to the eminence of polymicrobial infections with significant gram negative components, 2010 ISPD guidelines for treatment of peritonitis recommend inclusion of a third generation cephalosporin or an aminoglycoside in addition to intraperitoneal or IV vancomycin for adequate coverage3. In 4 case reports reviewing R. mucilaginosa peritonitis since 2005, resolution of infection was seen in treatment strategies adherent to these guidelines.1,2,4,5 However, these are not designed to account for Rothia spp. bacteria, and no true guideline exists for their treatment.
Conclusions: R. mucilaginosa, although generally considered an opportunistic pathogen, has become increasingly problematic in immunocompetent patients receiving peritoneal dialysis. Although delays in identification and a lack of clinical treatment guidelines may complicate treatment, adherence to the recent ISPD guidelines for empiric antibiotics may be sufficient to cover for the bacterium.