Recurrent CAPD peritonitis caused by coagulase-negative staphylococci: re-infection or relapse determined by clinical criteria and typing methods

Abstract Four hundred consecutive episodes of continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis in 105 patients were analysed. Of these episodes 161 (40·25%) were caused by coagulase-negative staphylococci (CNS). Thirty-seven patients developed recurrent attacks (3–10) of peritonitis and CNS accounted for 72 (60%) of these episodes. Classification of reinfection or relapse in 67 of these recurrent episodes of peritonitis was based on clinical criteria alone. This was compared with the results of three typing methods of CNS strains: biotyping plus antibiograms, immunoblotting and 35 S -methionine-labelled protein patterns (radio-PAGE). Radio-PAGE was the most discriminatory method followed by biotyping with antibiograms and then immunoblotting. There was total agreement between clinical diagnosis and the three typing methods in 67·2% of episodes but there was total disagreement between the clinical diagnosis and the three typing methods in 11·9%, suggesting inaccurate clinical diagnosis, and in 20·8% typing by at least one method differed from the clinical criteria. Thus, clinical criteria alone are inadequate for the accurate distinction of reinfection from relapse in recurrent CNS peritonitis. This distinction is desirable for optimal management and accurate assessment of different therapies. We suggest that CNS strains from peritoneal dialysate are stored for future typing should the patient develop repeated episodes of peritonitis, to aid in the diagnosis and management of such patients.