Evaluation of the VITEK® 2 system for testing of Gram-negative bacilli directly from BacT/Alert Fan blood cultures

Abstract number: 1733_1214

Ullberg M., Bergström J.

Objectives: The usefulness of the VITEK 2 system for rapid diagnosis of Gram-negative bacilli in blood cultures was evaluated. The aim was to deliver species identification and susceptibility results to the wards one day earlier than would be feasible using conventional methods.

Methods: Blood cultures were processed by a BacT/ALERT 3D system using FA and FN bottles. Bacteria from cultures showing Gram-negative bacilli on the smears were concentrated by centrifugation in two steps (150g and 2200g for 10 min respectively) and then analysed in the VITEK 2 system. The new colorimetric GN cards were used for identification and AST-N029 cards for antibiotic susceptibility testing. Results were compared with standard procedures using an in-house fermentation system for identification and disc diffusion for susceptibility testing.

Results: A total of 67 Gram-negative cultures were investigated. 96% of the collected strains were correctly identified. Complete susceptibility results were obtained within the time limit of 8 hours for 76% of the strains. Susceptibility results in general correlated well with disc diffusion data. Nineteen of 67 (28%) patients were found to receive an inappropriate antibiotic therapy considering Gram smear and VITEK 2 results. Twelve of those patients would have remained on improper therapy for one more day if standard therapeutic regimen had been applied. These cases included 5 ESBL-producing Klebsiellapneumoniae, 2 multiresistant Escherichia coli, one multiresistant Citrobacter braakii, one Stenotrophomonas maltophilia, one Pseudomonas aeruginosa and 2 Salmonella sp.

Conclusions: The VITEK 2 system proved to be a valuable tool for direct identification and susceptibility testing of Gram-negative bacilli recovered from BacT/ALERT FAN blood cultures. By using the VITEK 2 system, 12 of 67 patients could receive an appropriate antibiotic treatment one day earlier than if standard in-house diagnostic procedures had been implemented.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
Back to top