PCR and blood culture for detection of Escherichia coli bacteremia in rats

Critically ill patients often develop symptoms of sepsis and therefore requ ire microbiological tests for bacteremia that use conventional blood cultur e (BC) techniques. However, since these patients frequently receive early e mpirical antibiotic therapy before diagnostic procedures are completed, exa mination by BC can return false-negative results. We therefore hypothesized that PCR could improve the rate of detection of microbial pathogens over t hat of BC, To test this hypothesis, male Wistar rats were challenged intrav enously with 10(6) CFU of Escherichia coli. Blood was then taken at several time points for detection off. coli by BC and by PCR with E, coli-specific primers derived from the uidA gene, encoding beta-glucuronidase. In furthe r experiments, cefotaxime (100 or 50 mg/kg of body weight) was administered intravenously to rats 10 min after E, coli challenge. Without this chemoth erapy, the E, coli detection rate decreased at 15 min and at 210 min after challenge from 100% to 62% of the animals with PCR and from 100% to 53% of the animals with BC (P, >0.05), Chemotherapy decreased the E, coli detectio n rate at 25 min and at 55 min after challenge from 100% to 50% with PCR an d from 100% to 0% with BC (P, <0.05). Thus, at clinically relevant serum an tibiotic levels, PCR affords a significantly higher detection rate than BC in this rat model. The results suggest that PCR could be a useful adjunct t ool supplementing conventional BC techniques in diagnosing bacteremia.