PCR and blood culture for detection of Escherichia coli bacteremia in rats - PubMed (original) (raw)

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

A Heininger et al. J Clin Microbiol. 1999 Aug.

Abstract

Critically ill patients often develop symptoms of sepsis and therefore require microbiological tests for bacteremia that use conventional blood culture (BC) techniques. However, since these patients frequently receive early empirical antibiotic therapy before diagnostic procedures are completed, examination by BC can return false-negative results. We therefore hypothesized that PCR could improve the rate of detection of microbial pathogens over that of BC. To test this hypothesis, male Wistar rats were challenged intravenously with 10(6) CFU of Escherichia coli. Blood was then taken at several time points for detection of E. coli by BC and by PCR with E. coli-specific primers derived from the uidA gene, encoding beta-glucuronidase. In further experiments, cefotaxime (100 or 50 mg/kg of body weight) was administered intravenously to rats 10 min after E. coli challenge. Without this chemotherapy, 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 54% of the animals with BC (P, >0.05). Chemotherapy decreased the E. coli detection rate at 25 min and at 55 min after challenge from 100% to 50% with PCR and from 100% to 0% with BC (P, <0.05). Thus, at clinically relevant serum antibiotic levels, PCR affords a significantly higher detection rate than BC in this rat model. The results suggest that PCR could be a useful adjunct tool supplementing conventional BC techniques in diagnosing bacteremia.

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Figures

FIG. 1

FIG. 1

Time course of E. coli detection in experimental bacteremia in rats by PCR, BC, and the direct plating method. (A) Sixteen rats were challenged intravenously with 106 CFU of E. coli at time zero (arrow a) without further intervention. (B and C) Another 10 rats each received 100 mg (B) (arrow b) or 50 mg (C) (arrow c) of cefotaxime/kg of bw 10 min after bacterial challenge. For E. coli detection, blood was collected 5 min before challenge and at the indicated times after challenge. E. coli was detected by PCR (A, B, and C) (filled bars), BC (A, B, and C) (hatched bars), and the direct plating method (A) (open bars). Bars represent the percentages of _E. coli_-positive blood samples. ∗, P < 0.05.

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