Controlled evaluation of the agar-slide and radiometric blood culture systems for the detection of bacteremia and fungemia

Abstract

A commercially available agar-slide blood culture bottle (Septi-Chek; Roche Diagnostics, Div. Hoffman-La Roche, Inc., Nutley, N.J.) was compared with the radiometric blood culture system (BACTEC; Johnston Laboratories, Inc., Towson, Md.) in 8,544 paired blood cultures from adult patients. The systems were inoculated with equal volumes (10 ml) of blood. Overall, there was no statistically significant difference between the two systems in the recovery of clinically important microorganisms, but significantly more members of the family Enterobacteriaceae other than Escherichia coli were detected by the agar-slide system (P < 0.005). The agar-slide system detected more fungi, and the BACTEC detected more anaerobic bacteria; however, small numbers of recovered organisms precluded statistical significance. When microorganisms grew in both systems, their presence was detected one or more days earlier in the BACTEC (P < 0.001). More contaminants grew in the agar-slide system (P < 0.001). Both systems performed well, and either system should provide high yield and prompt detection of positive blood cultures in patients with bacteremia and fungemia if used in an optimal way as recommended by the respective manufacturers.

Should aerobic blood cultures be shaken intermittently or continuously?

“…By comparing a visually read, stationary incubated, conventional 12-tube blood culture system with the agitated, semi-automatic Bactec I' blood culture system, using C 0 2 production for growth detection, we previously found significantly higher yield and shorter detection time using the Bactec" system (1, 9). The same was found by other investigators when comparing their conventional bottle systems with Bactec (2, 8, 10, 1 I , 12). We observed that when the CO?…”

Colorbact, a visually read blood culture system using darkening of haemoglobin in aerobic blood cultures as an early growth indicator, compared with Bactec® 6A and 7A

“…Our combined aerobic and anaerobic system, Colorbact (A +AN), appears to be very promising as it can be more rapid than the Bactec (6A-7A) system, which so far has been one of the 1094 quickest systems on the market (2, 8, 1 I , 16), and as it is simple, practical, laboursaving and cheap to produce. It seems suitable both for large laboratories with many blood cultures and 24 h staff and for small hospitals which can incubate and shake the blood cultures locally before sending them once a day to the laboratory, where the positive cultures often present themselves with darkening already on arrival.…”

Clinical implications of positive blood cultures.

“…The rising incidence of nosocomial fungemia, especially due to Candida species, may be attributable in part to more sensitive blood culture systems (139,344). However, there can be little doubt that it also reflects changing patterns of medical care.…”