Pseudomonas aeruginosa bacteraemia detected with a new blood culture system Colorbact: a note of caution.

Detection of Pseudomonas aeruginosa bacteraemia by the newly introduced Colorbact blood culture system (Statens Seruminstitut, Copenhagen) was ascertained in a Danish regional department of clinical microbiology. Ten of sixteen bacteraemias (63%, 95% CL: 35-85%) were detected within 24 h; the 48 h figure was 81% (95% CL: 54-96%). The initial bacteriological diagnosis was confounded, however, by the observation of non-motile rods or atypical motility in 8 episodes, including 4 of the 10 episodes with a positive direct microscopy during the first 24 h. This may be an untoward effect of vigorous agitation. In two episodes P. aeruginosa was isolated only from the anaerobic culture bottle, whilst in two other episodes P. aeruginosa grew in aerobic and anaerobic bottles. This observation may reflect a chance distribution of viable bacteria among the bottles in the Colorbact set.