Routine laboratory diagnosis of continuous ambulatory peritoneal dialysis peritonitis using centrifugation/lysis and saponin-containing media.

This study examines the application in a routine laboratory of a method for concentrating and lysing leucocytes in continuous ambulatory peritoneal dialysis (CAPD) effluent to diagnose peritonitis. Between November 1986 and April 1990 pathogens from 42 of 82 (51%) CAPD specimens from patients with acute peritonitis failed to grow on horse blood agar (HBA) after direct inoculation. Recovery rates of pathogens were 74% (6 of 82) from a solid medium containing saponin and 89% (73 of 82) after lysing the leucocytes before inoculating HBA. Microbial sequestration in leucocytes was demonstrated in 73% (60 of 82) of specimens, while pathogens from 11% (9 of 82) were grown only from a liquid medium. Thirteen of 17 specimens with < 500 leucocytes/mm3 grew on all three solid media. Gram stain microscopy revealed organisms in 51% (41 of 81) of specimens. The method, using apparatus and media prepared for everyday examination of specimens, is sensitive, specific and yields single colonies of most species within 24 h.