Rapid detection of simulated bacteremia by centrifugation and filtration

Abstract

A centrifugation-filtration procedure was developed to expedite the recovery of microorganisms from blood. Fresh whole human blood was inoculated with various aerobic and facultatively anaerobic microorganisms (3-18/ml). The seeded blood was carefully overlaid on a Ficoll-Hypaque gradient (density, 1.114 g/ml) and centrifuged (400 .times. g) for 45 min at ambient temperature. The entire gradient (plasma, leukocytes and Ficoll-Hypaque) was removed and filtered through a 0.22-.mu.m membrane filter. The filters were then placed on chocolate agar and incubated at 35.degree. C in humidified air containing 5% CO2. No statistically significant differences were detected between the numbers of microorganisms recovered by filtration and by direct culture of the original inoculum. Most microorganisms were detected within 18 h after filtration. This system has excellent sensitivity and negligible toxicity.