Microbiological aspects of peritonitis in patients undergoing chronic peritoneal dialysis at the dialysis unit of Sri Jayawardenapura General Hospital

Background Peritoneal dialysis (PD) is an established form of therapy in the management of end stage renal disease. Peritonitis is the main complication of PD. Objectives To study the incidence and microbial aetiol­ ogy of peritonitis in patients undergoing chronic PD at the dialysis unit of Sri Jayewardenapura General Hospital (SJGH); to assess the diagnostic value of the Gram's stain; and to study the relationship of the total white cell count of effluent to peritonitis. Design A prospective, study over three months. Setting Dialysis unit of SJGH. Patient population The study involved 18 patients un­ dergoing manual intermittent peritoneal dialysis (IPD), 4 patients undergoing chronic ambulatory peritoneal dialy­ sis (CAPD), and 1 patient undergoing nocturnal intermit­ tent peritoneal dialysis (NIPD). Measurements Clinical presentation of patients with peri­ tonitis; total and differential white blood cell counts of effluent samples; Gram stain and culture of the centrifuged deposit to determine microbial aetiology; incidence of peri­ tonitis in different categories of dialysis. Results 32 samples were examined from patients on IPD, and 17 from patients on CAPD. In IPD most episodes were due to Gram negative organisms whereas in CAPD most episodes were due to Gram positive organisms. Sensitiv­ ity of Gram's stain in relation to culture was 32.4%. 98% of effluent samples had white blood cell counts of >100/ml and none showed neutrophil Counts of <49%. Conclusions The incidence of IPD associated peritonitis was 11.1 episodes per patient year, and the incidence of CAPD associated peritonitis was 14 episodes per patient year. Flavobacterium spp. were the predominant organ­ isms in IPD associated peritonitis, whereas CAPD associ­ ated peritonitis was commonly caused by coagulase nega­ tive staphylococci. Gram's stain was not useful in the ini­ tial identification of the causative agent, but the white cell and neutrophil counts were found to be sensitive indica­ tors of peritonitis. Introduction PD is an established form of therapy in the manage­ ment of end stage renal disease (1,2). In manual intermittent peritoneal dialysis (IPD), dialysis is carried out 2 to 3 times a week intermittently in hospital, and about 20 one litre exchanges are carried out within 24 hours. In continuous ambulatory peritoneal dialysis 2 litre exchanges are carried out continuously 3 to 4 times a day. Chronic cyclic peritoneal dialysis (CCPD) and nocturnal intermittent peritoneal dialysis (NIPD) are automated tech­ niques of dialysis where a cycler is programmed to deliver the fluid and exchanges are done in the night. Peritonitis is the main complication of PD (3,4), and remains a cause of technique failure, hospitalisation and transfer to haemodialysis (HD), with mortality rates vary­ ing from 2 to 25% (5). There are no previous studies in Sri Lanka on peritonitis in chronic PD systems, hence the need for the present study.

Background Peritoneal dialysis (PD) is an established form of therapy in the management of end stage renal disease.Peritonitis is the main complication of PD.
Objectives To study the incidence and microbial aetiol ogy of peritonitis in patients undergoing chronic PD at the dialysis unit of Sri Jayewardenapura General Hospital (SJGH); to assess the diagnostic value of the Gram's stain; and to study the relationship of the total white cell count of effluent to peritonitis.
Design A prospective, study over three months.
Measurements Clinical presentation of patients with peri tonitis; total and differential white blood cell counts of effluent samples; Gram stain and culture of the centrifuged deposit to determine microbial aetiology; incidence of peri tonitis in different categories of dialysis.
Results 32 samples were examined from patients on IPD, and 17 from patients on CAPD.In IPD most episodes were due to Gram negative organisms whereas in CAPD most episodes were due to Gram positive organisms.Sensitiv ity of Gram's stain in relation to culture was 32.4%.98% of effluent samples had white blood cell counts of >100/ml and none showed neutrophil Counts of <49%.

Introduction
PD is an established form of therapy in the manage ment of end stage renal disease (1,2).
In manual intermittent peritoneal dialysis (IPD), dialysis is carried out 2 to 3 times a week intermittently in hospital, and about 20 one litre exchanges are carried out within 24 hours.In continuous ambulatory peritoneal dialysis 2 litre exchanges are carried out continuously 3 to 4 times a day.Chronic cyclic peritoneal dialysis (CCPD) and nocturnal intermittent peritoneal dialysis (NIPD) are automated tech niques of dialysis where a cycler is programmed to deliver the fluid and exchanges are done in the night.
Peritonitis is the main complication of PD (3,4), and remains a cause of technique failure, hospitalisation and transfer to haemodialysis (HD), with mortality rates vary ing from 2 to 25% (5).There are no previous studies in Sri Lanka on peritonitis in chronic PD systems, hence the need for the present study.

Methodology
The PD effluents processed in the study were from patients who had symptoms and signs of peritonitis or cloudy dialysate.49 effluent samples were examined dur ing the 3 months.A white blood cell count was performed on the uncentrifuged sample, and the centrifuged deposit was used to inoculate culture plates and make smears for the Gram's stain and Irishman's stain.

API 20E was used to identify members of the family
Enterobacteriacae.Non-fermenting oxidase positive or ganisms such as Pseudomonas spp., Flavobacterium spp.and Gram positive organisms were identified using stan dard microbial identification procedures (7).The single yeast culture was identified by Gram stain and germ tube tests.Antibiotic sensitivity tests were performed using the modified Kirby Bauer technique.
Patients were considered to have peritonitis if they met at least two of the following criteria (2,6).A cloudy dialysate with a leucocyte count of more than 100/ml.

Results
Of the 49 samples studied, 47 were from patients who had peritonitis and 2 from patients who had cloudy dialysates but did not have peritonitis.Of the 47 effluent samples, 32 were from patients on IPD and 15 from patients on CAPD.The patient on NIPD did not have peritonitis during this period.
Clinical presentation of patients with peritonitis var ied.All patients with symptomatic peritonitis had diffuse abdominal pain (80%).Abdominal tenderness was found in 48%, fever in 36%, vomiting in 14% and diarrhoea in 6%.
Of the samples processed, except for one effluent sample which was not turbid and showed a cell count of < 100/ml, the others were turbid and had white cell counts of >100/ml.94% showed neutrophil counts of >70%, and none showed neutrophil counts of <49%.
The Gram stain was positive in only 12 effluent samples giving a sensitivity of 32.4% compared to culture.The specificity and positive predictive values of Gram stain were 100%, and the negative predictive value 35%.Table 1 and 2 show the microbial aetiology in IPD and CAPD asso ciated peritonitis.In this study 21.2% of cases of peritoni tis were culture negative.Studies have shown that 10 to 50% of clinically infected PD effluents are culture negative (1,4,8).

Discussion
Accurate diagnosis of peritonitis is an important re quirement for a successful dialysis program.Symptoms and signs are an important component of the definition that aid in the diagnosis, and the frequency of different symptoms in the present study was similar to previous studies reported (1,4).
Cell count and Gram stain are also important in the preliminary diagnosis of peritonitis as the clinical presen tation is variable and sometimes patients are asymptom atic.A cell count indicates whether the turbidity of the dialysate is due to the presence of increased number of leucocytes.Since 98% of samples from patients with peri tonitis had leucocyte counts of >10Q/ml and none showed neutrophil counts of <49%, this study indicates that a leu cocyte count of >100/ml and >50% neutrophils are sensi tive indicators of peritonitis.Total 15

Total culture positive
As the sensitivity of the Gram stain was only 32.4%, it is not a sensitive indicator of peritonitis.In other studies reported the sensitivity of Gram stain in relation to culture varies between 10 and 50% (4,5,8,10).The Gram stain though only positive in a low percentage of cases should be per formed routinely because of its simplicity and its value in making a preliminary identification of the organism in a short time to aid in the choice of antibiotics.
The organisms responsible for IPD associated perito nitis were those found in the hospital environment.Flavobacterium spp, the commonest isolate, was isolated from a sink in the dialysis unit.Flavobacterium spp have been increasingly associated with infectious complications in hospital settings, especially in immunocompromised pa tients (11).In a study at the National Hospital of Sri Lanka of complications of acute peritoneal dialysis, 86.7% of cul ture positive peritonitis were due to coliforms and 10% to Staphylococcus aureus (12).
As in previous studies most cases of peritonitis in CAPD patients in the present study were due to skin com mensals, with the predominant isolate being Staphylococ cus epidermidis.
The most likely portal of entry of the causative organ ism in IPD and CAPD associated peritonitis in our study is the lumen of the catheter.In IPD contamination occurs dur ing multiple connections and disconnections of the PD transfer set to the catheter.We observed that there was no adherence to strict sterile conditions during this procedure.As a result the incidence of IPD associated peritonitis was 11.1 episodes per patient year.The incidence of CAPD as sociated peritonitis was 14 episodes per patient year.This is high compared to centres in the West where it occurs on average 1 to 2 episodes per patient year (4,12,13).Poor hy gienic conditions, associated with poor socioeconomic sta tus, compared to patients in the West, as well as inadequate training in CAPD procedure, have contributed to the high incidence of CAPD associated peritonitis.

Conclusions
The incidence of peritonitis in patients undergoing chronic PD at SJGH is high in comparison to that reported from the West.
Flavobacterium spp were the commonest organisms causing peritonitis in patients undergoing IPD, while co agulase negative Staphylococcus was the commonest in CAPD associated peritonitis.Gram stain was not very useful in the initial identification of the causative agent, while the leucocyte count and neutrophil count were sen sitive indicators of peritonitis