Evaluation of a lysis-centrifugation and biphasic bottle blood culture system during routine use

Abstract

An in-use evaluation of a commercially available lysis-centrifugation blood culture system (Isolator) is presented. The Isolator was compared with biphasic bottles containing trypticase soy broth and agar for the detection of organisms in 3129 paired blood samples. Of 272 potential pathogens recovered, 78% were detected by the Isolator system; 69% were detected by the biphasic bottle. Of these organisms, 31% were detected only by the Isolator; 22% were detected only by the biphasic bottle. The Isolator demonstrated enhanced detection of facultative gram-negative bacilli, anaerobic bacteria and polymicrobial cultures. The biphasic bottle was more effective for the recovery of facultative gram-positive cocci, especially Streptococcus pneumoniae. The 2 systems were equally effective for the recovery of yeasts. Contamination rates were 3% for the Isolator and 3.2% for the biphasic bottle. Thus, the Isolator system performs well in routine clinical use, but it should be complemented by another method to obtain optimal detection of bacteremia. The biphasic bottle provides an acceptable complementary system in terms of utility and performance.