Rapid identification and antimicrobial susceptibility testing reduce antibiotic use and accelerate pathogen-directed...

Rapid bacterial identification and susceptibility tests can lead to earlier microbiological diagnosis and pathogen-directed, appropriate therapy. We studied whether accelerated diagnostics affected antibiotic use and patient outcomes.

A prospective randomized clinical trial was performed over a 2-year period. Inpatients were selected on the basis of a positive culture from normally sterile body fluids and randomly assigned to either a rapid intervention arm or the control arm. The intervention arm used the Vitek 2 automated identification and susceptibility testing device, combined with direct inoculation of blood cultures. In the control arm, the Vitek 1 system inoculated from subcultures was used. Follow-up was 4 weeks after randomization.

A total of 1498 patients were randomized: 746 in the intervention arm and 752 in the control arm. For susceptibility testing, the rapid arm was 22 h faster than the control arm, and for identification, it was 13 h faster (P < 0.0001). In the rapid arm, antibiotic use was 6 defined daily doses lower per patient than in the control arm (P = 0.012). Whereas antibiotics were switched more in the rapid group on the day of randomization (P = 0.006), in the control group they were switched more on day two (P = 0.02). Mortality rates did not differ significantly between the two groups (17.6% versus 15.2%).

While rapid bacterial identification and susceptibility testing led to earlier changes and a significant reduction in antibiotic use, they did not reduce mortality.