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

Abstract

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 Enterobacteriaceae 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 for L-C inoculation. A total of 82% of colony counts measured no more than 10 CFU/ml of blood, and it was at these 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 1.9o of broth cultures. Low colony counts on L-C plates occurred for both Staphylococcus epidermidis contamination and septicemia.

Isolation of Bartonella (Rochalimaea) henselae: effects of methods of blood collection and handling

“…Because of possible delays before being plated on growth media, blood specimens collected in a typical clinical setting may be frozen or may remain at room temperature for many hours. The Isolator system has been effective in isolating certain bacteria and fungi (4,5,7,8). Processing can be done even after blood has remained at room temperature for as long as 16 h (27).…”

Clinical correlations of serial quantitative blood cultures determined by lysis-centrifugation in patients with persistent septicemia

“…Significant isolates were obtained in 476 of these 7,000 cultures. Details of this study have been described previously (12). Colony counts were calculated by dividing total colonies on plates capable of supporting growth by the amount of blood inoculated onto those plates.…”

“…The lysis-centrifugation blood culture method (2, 4) enables colony counts to be determined routinely. During a prospective comparison of the lysis-centrifugation method and standard broth cultures (12), it was our impression that it was sometimes clinically useful to know the colony counts of a patient as well as the fact that his blood cultures were positive. We therefore reviewed the records of all patients studied from whom colony counts were available on at least three different days.…”

Contaminating coagulase‐negative staphylococci isolated in a lysis‐centrifugation (Isolator®) blood culture system

“…Clinically insignificant, supposedly contaminating organisms are isolated with varying frequency. Conventional blood culture systems generally have a rate of less than 39/0 (2,10,12,15,18,19).…”

“…Recently, a different approach, involving lysing of blood cells and followed by centrifugation, has been introduced. This system, Isolator@, generally has better detection power than several conven-tional blood culture systems (2,4,10,11,12,13), but often has a disturbingly high rate, 10-15%, of supposed contaminants, mainly coagulase-negative staphylococci (2, 10, 1 1, 13). In a recent comparative investigation in our laboratory, 1 1% of the cultures in the Isolator@ system grew coagulase-negative staphylococci of doubtful clinical importance, as compared with 1% in our routine 12-tube system (2).…”