Direct identification and susceptibility testing of gram-negative bacilli from BACTEC bottles by use of the MS-2 system with updated bacterial identification software.

The Abbott MS-2 system (Abbott Laboratories, Diagnostic Division, Irving, Tex.), equipped with updated bacterial identification software (version 03.02), was used to perform both direct identification and susceptibility tests on gram-negative bacilli from positive BACTEC blood culture bottles. Ninety-eight of 101 Enterobacteriaceae strains, one strain of Acinetobacter calcoaceticus, and two strains of Pseudomonas aeruginosa were correctly identified by following a direct inoculation procedure. One Enterobacter sakazakii isolate was misidentified as Enterobacter cloacae. Ninety-seven percent of 936 direct susceptibility results were identical to the results obtained by using the standard MS-2 susceptibility procedure. Only five tests yielded a sensitive-direct and a resistant-standard MS-2 susceptibility result.