Peritonitis causes significant morbidity and mortality in PD patients. It can result in death either from sepsis or from ensuing complications. Gram-positive organisms, especially
Staphylococcus epidermidis and
Staphylococcus aureus, are the most common bacteriologic causes of peritonitis. Recently, the incidence of Gram-positive infections has decreased due to newer techniques and improved exit-site care, while the incidence of Gram-negative organisms has remained stable [
2]. Gram-negative organisms now account for 20 to 30 percent of all peritonitis episodes [
3]. Patients with Gram-negative peritonitis have a worse outcome, are more likely to be hospitalized and more likely to die within six months after peritonitis [
2]. In our case report, peritoneal fluid cultures yielded three different organisms consecutively. The first organism was
P. aeruginosa which is one of the most important causes of Gram-negative peritonitis and is identified in 7.1 percent of culture positive cases [
3]. The major risk factors for infection are a history of antibiotic therapy within 30 days and concomitant exit-site infection [
3]. Our patient did not have any risk factors for this infection. The second microorganism was
Stenotrophomonas maltophilia which is an environmental saprophyte that has been rarely reported to cause peritonitis. The annual rate of isolation for this organism is not known since it has only been reported as case reports. It is mainly a nosocomial pathogen and is resistant to multiple antibiotics [
4]. It can be isolated from water, soil, hospital equipment and humans. The major risk factors include prior broad-spectrum antibiotic use, neutropenia, underlying illness and prolonged hospital stay [
4]. The patient described in this case report had risk factors for this organism, such as prolonged antibiotic use and hospital stay. The third microorganism was VRE, which was first described in the 1980 s and has since become increasingly prevalent, causing infections that include PD-associated peritonitis [
5]. However, the annual rate of isolation is not known. Risk factors for VRE include severe underlying disease, immunosuppression, prior use of vancomycin and other antibiotics, abdominal or cardiothoracic surgery and indwelling urinary or central venous catheters [
6]. Patient had multiple risk factors for VRE infection, such as vancomycin use and prolonged hospital stay. The persistent growth of organisms in his peritoneal culture and his lack of response to antibiotic therapy warranted early removal of the catheter. Failure to respond to antibiotic therapy necessitating early catheter removal is common in patients with
S. maltophilia and/or VRE peritonitis. Our patient was repeatedly advised immediate surgical removal of his PD catheter due to the risk of septic shock and death; however, he refused to undergo the procedure despite regular counseling
The majority of patients with peritonitis have cloudy fluid and abdominal pain. The diagnosis is confirmed by a dialysate aspirate leukocyte count exceeding 100 WBC/ml with at least 50 percent polymorphonuclear leukocytes. A small percentage of patients do not have white blood cells in the peritoneal fluid at presentation with cell counts increasing in time; this is called an impaired initial cell reaction [
7]. This delay may be due to slower cytokine response to infection [
7]. Peritonitis episodes with cell counts less than 100 WBC/ml have been reported in the literature [
8,
9]. However, peritonitis without abdominal pain and/or white blood cells in the peritoneal fluid is an extremely rare entity and to the best of our knowledge, this is the first report of a case of peritonitis with a persistently clear aspirate without any white blood cells. The peritoneal fluid cultures of our case report yielded different organisms consecutively, however the peritoneal cell counts were consistently nil. It can be argued that the positive cultures in the absence of increased white blood cell count in the peritoneal fluid could be indicative of colonization or improper culture collection. The method used for peritoneal culture at our center is as follows: sediment obtained after centrifugation of 100 ml of fluid is inoculated into aerobic and anaerobic Bactec bottles, on aerobic and anaerobic blood, chocolate and MacConkey agar plates. Gram and Giemsa stains are also performed. It is highly unlikely that the only three improper cultures collected at our center so far have been in the same patient. A low white blood cell count in peritoneal fluid in the presence of antibiotic use has been reported. However, since the first organism was isolated before the use of any antibiotic therapy and the consecutive organisms were both resistant to the antibiotic therapy administered at that time, it is not possible to explain the absence of white blood cells by prior therapy. Immunosuppression is another possible mechanism for the lack of white blood cells in our case report; however, he did not have any disease, condition or any other laboratory values indicating that he was indeed immunosuppressed.
We believe our case report demonstrates that clear aspirate and the absence of white blood cells in the peritoneal fluid may not rule out the presence of peritoneal infection in patients on PD. Therefore, any patient on PD presenting with evidence of infection (fever, peripheral leukocytosis) without an obvious cause should have aspirate cultures done even if the aspirate is clear and abdominal pain is absent.