Rapid diagnosis of intravascular catheter-associated infection by direct Gram staining of catheter segments.

We conducted a study to determine the usefulness of the Gram stain in the detection of intravascular catheter-associated infection. A total of 330 intravascular catheters were prospectively collected from adults and children suspected of having such an infection. Semiquantitative solid-agar cultures of the distal catheter tip were correlated with blood cultures. Catheter-associated bacteremia occurred in 34 per cent of cases in which catheter tips were colonized (greater than or equal to 15 colonies per agar plate). There were no cases of catheter-associated bacteremia in patients with uncolonized catheters. Immediately after culture, whole catheter segments were stained by the Gram technique. Gram-negative and gram-positive bacteria and yeast were easily identifiable under oil immersion (X 1000), located predominantly on external catheter surfaces. Any catheter with at least one organism per 20 oil-immersion fields was designated as positive by Gram stain, but the majority of the 41 positive catheters had much larger numbers of organisms. The Gram stain of the catheter tip was 100 per cent sensitive and 96.9 per cent specific for the detection of catheter-tip colonization, with positive and negative predictive values of 83.9 and 100 per cent, respectively. We conclude that a Gram stain of the distal catheter tip is a simple, inexpensive, and accurate test for the rapid diagnosis of intravascular catheter-associated infection.