Early detection of bacterial growth in blood culture by impedance monitoring with a Bactometer model 32

Abstract

A Bactometer model 32 was evaluated for use in early detection of bacterial growth. Experiments with simulated cultures showed that 2 ml of broth introduced into the Bactometer module wells could detect 10(2) and 10(6) CFU/ml in 6 h and 2 h respectively. Both Brain Heart Infusion (BHI) and Fastidious Anaerobic broths supported good growth. Detection of nine of 10 organisms inoculated at approximately 10(6) CFU/ml in BHI were detected within 8.5 h. A culture of Bacteroides fragilis failed to grow under these conditions. Of 189 blood cultures, tested by incubation of 2 ml of BHI, 18 were positive by both conventional and Bactometer methods. False-positive or false-negative specimens were not observed using the Bactometer. Use of the Bactometer enables growth detection at least 12 h earlier than culture methods.