Evaluation of a new commercial system for the identification of Enterobacteriaceae and non-fermentative bacteria

The performance of a new commercial semi-automatic system (Cobas Micro, Becton Dickinson) for identification of gram-negative fermentative and non-fermentative bacilli was evaluated using strains of clinical origin belonging to 48 different species. Two groups of strains were tested: 510 strains using a long incubation period (21 hours) and 158 strains using a short incubation period (5 hours). The correct identification rate without additional tests was 95.5% and 94.3% for the tests using a long and short incubation period respectively. The findings suggest that the system is highly accurate in the identification of most clinically important gram-negative rods, but shows some shortcomings in the identification of non-fermentative bacteria. The system is easy to use, and with some changes in the database and the inclusion of gram-positive and anaerobic bacteria would offer a valuable alternative to currently available automatic identification systems.