Comparative recovery of bacteria and yeasts from lysis centrifugation and a conventional blood culture system

Blood cultures obtained with a lysis-centrifugation (L-C) system and a conventional two-bottle broth system were compared for the recovery of bacteria and yeasts from 7,000 cultures. The L-C system recovered significantly more total organisms, Escherichia coli, and Candida spp. and detected more patients with bacteremia and fungemia due to members of the family Enterbacteriaceae and yeasts. The broth system recovered significantly more streptococci and detected significantly more low-level Pseudomonas bacteremias. Polymicrobic bacteremia and fungemia were detected equally well by either culture system. Aerobic organisms grew equally well on blood, chocolate, or brain heart infusion agar plates used fr L-C inoculation. A total of 82% of colony counts measured no more than 10 CFU/ml of blood, and it was at least low levels that enhanced detection of organisms by either system was observed. The L-C system isolated organisms and detected yeasts more rapidly than did the broth system. Contaminants occurred in 8.2% of L-C cultures and 1.9% of broth cultures. Low colony counts on L-C plates occurred for both Staphylococcus epidermidis contamination and epticemia.