Clinical comparison of difco ESP, Wampole isolator, and Becton Dickinson Septi-Chek aerobic blood culturing systems

Abstract

The ESP 80A aerobic blood culture of the ESP automated blood culture system (Difco Laboratories. Detroit, Mich.) was compared with two manual aerobic blood culture systems, the Isolator (Wampole Laboratories, Cranbury, N.J.) and the Septi-Chek (Becton Dickinson, Cockeysville, Md.) systems, for the detection of bloodstream microorganisms from 5,845 blood samples for culture collected from adult patients with suspected septicemia. The bottles were incubated for 7 days, and the sediment from the Isolator tube was inoculated onto solid medium and this medium was incubated for 72 h. A total of 609 microorganisms were recovered from 546 blood cultures. There was no statistically significant difference in the total recovery of microorganisms for the ESP 80A system when compared with that for the Septi-Chek system (P = 0.083); however, the Isolator system recovered significantly more microorganisms overall than either the ESP 80A (P < 0.001) or the Septi-Chek (P < 0.001) system. When assessing individual probable pathogens, the Isolator system detected statistically significantly more Staphylococcus aureus and Candida spp. than either the ESP 80A or the Septi-Chek system (P < 0.05). Similarly, the Isolator system detected statistically significantly more bloodstream infections (septic episodes) caused by S. aureus and Candida spp. than either the ESP 80A or the Septi-Chek system (P < 0.05). In blood culture sets which produced growth of the same probable pathogens in the ESP 80A and the Isolator systems, there was no statistically significant difference in the median times to detection for all pathogens combined (P = 0.067). However, a similar comparison showed the Isolator and the ESP 80A systems to have statistically significantly shorter median detection times for all pathogens combined (P < 0.001) when they were independently compared with the Septi-Chek system. The ESP 80A system had 29 (0.5%) false-positive signals. The ESP system required less processing time than the Isolator system and eliminates the hands-on time for the detection of positive cultures required by the manual systems.