Automated preparation for identification and antimicrobial susceptibility testing: evaluation of a research use only prototype, the BD Kiestra IdentifA/SusceptA system.

OBJECTIVE: The current BD Kiestra™ total laboratory automation (TLA) system automates specimen inoculation, incubation, and digital visualization of cultures prior to initiation of manual or semi-automated identification (ID) and antimicrobial susceptibility testing (AST). The current study aimed to compare the performance, in a clinical setting, of a fully automated research-use-only prototype, BD Kiestra™ IdentifA/SusceptA (automated system), to our current BD Kiestra™ TLA which utilizes manual or semi-automated IDs and ASTs (current system). METHODS: Clinical samples yielding significant growth after processing by the BD Kiestra™ TLA were tested in parallel for ID and AST by both systems. IDs and ASTs were determined by Bruker matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and BD Phoenix, respectively, with data stored and managed in the BD EpiCenter™. The automated system used a common inoculum preparation for both tests, whereas the current system used separate inocula. Results were compared to assess agreement between the systems. RESULTS: On initial testing, 89% of IDs (466/523) and 92.4% of IDs (484/523) for the automated and current ID systems, respectively, yielded acceptable MALDI-TOF log scores of ≥1.7. On repeat testing, the respective acceptable scores were 97.1% (508/523) and 98.1% (513/523). For initial ASTs, the automated and current systems yielded 97.5% categorical agreement for 7325 drug-organism tests. After omitting discrepant MICs that differed by only one dilution and categorical discrepancies that were not reproducible, 0.2% unresolved discrepancies remained thus (99.8% categorical agreement). CONCLUSIONS: The automated prototype is suitable for development into technology that will provide clinical microbiology laboratories with significant advantages such as improved efficiency, standardization, reproducibility, reduced technical error and greater safety.

Failure of the BD GeneOhm StaphSR assay for direct detection of methicillin-resistant and methicillin-susceptible Staphylococcus aureus isolates in positive blood cultures collected in the United States.

Fifty-nine Staphylococcus aureus isolates from one hundred blood cultures containing gram-positive cocci in clusters were identified by conventional methods and the BD GeneOhm StaphSR assay (SR). The SR misidentified three methicillin (meticillin)-resistant S. aureus (MRSA) isolates as methicillin-susceptible S. aureus (MSSA), while one MSSA isolate tested negative for S. aureus. The three MRSA isolates were strains with MREJ types that cannot be detected by the currently available SR.