Laboratory automation reduces time to report of positive blood cultures and improves management of patients with bloodstream infection

Giuseppe Vittorio De Socio, Francesco Di Donato, Riccardo Paggi, Chiara Gabrielli, Alessandra Belati, Giuseppe Rizza, Martina Savoia, Antonella Repetto, Elio Cenci, Antonella Mencacci

The impact on time to results (TTR) and clinical decisions was evaluated for mono-microbial positive blood cultures (BC) processed using the BD Kiestra Work Cell Automation (WCA) system. Positive BC were processed by the WCA system by full-automatic subculture on solid media and digital imaging after 8 h of incubation (8-h method) followed by identification (ID) and antimicrobial susceptibility testing (AST). To evaluate the accuracy of the 8-h method, ID and AST from 8-h and overnight incubated colonies were compared for the same organisms. To evaluate its clinical impact, results from 102 BC processed by the 8-h method (cases) were compared with those from 100 BC processed by overnight incubation method (controls) in a comparable period. Identification after 8-h and overnight incubation gave concordant results in 101/102 (99.0%) isolates. Among a total of 1379 microorganism-antimicrobial combinations, categorical agreement was 99.4% (1371/1379); no very major error, 7 major errors, and one minor error were observed. TTR in cases (32.8 h ± 8.3 h) was significantly (p < 0.001) shorter than in controls (55.4 h ± 13.3 h). A significant reduction was observed for duration of empirical therapy (cases 54.8 h ± 23.3 h vs controls 86.9 h ± 34.1 h, p < 0.001) and 30-day crude mortality rate (cases 16.7% vs controls 29.0%, p < 0.037). Automation and 8-h digital reading of plates from positive BC, followed by ID and AST, greatly reduce TTR and shorten the duration of antimicrobial empiric therapy, possibly improving outcome in patients with mono-microbial bloodstream infections.