Direct testing by VITEK^® 2: A dependable method to reduce turnaround time in Gram-negative bloodstream infections

Bloodstream infections pose a major health-care burden worldwide. Routine microbiological methods are time-consuming, thereby delaying appropriate treatment.

The aim of this study is to evaluate the method of direct testing of identification (ID) and antimicrobial susceptibility testing (AST) of positive blood culture bottles by VITEK^®2.

This was a prospective study at a tertiary level hospital.

One hundred positive BACTEC blood culture bottles with monomicrobial Gram-negative organisms on microscopy were tested in parallel by direct ID/AST as well as conventional method. Results obtained by two methods were compared in terms of ID/AST and turnaround time (TAT).

Of the 100 isolates tested, only one was misidentified by the direct method and there was no unidentified isolate. The AST results demonstrated 99.74% categorical and 99.65% essential agreement. Of 1144 organism-antibiotic combinations, there were 0.44% major error, no very major error, or minor error observed.

While conventional method is the gold standard, the direct ID/AST methods have demonstrated that it can be successfully utilized to decrease TAT to the final results by 18-24 h, without sacrificing test accuracy. This technique will help to tailor antimicrobial therapy, thereby reducing patient morbidity, mortality, and antibiotic resistance, as well.