Methods: A retrospective case-control study was conducted in patients with contaminated blood cultures, defined as one of two or more blood cultures with CoNS or VGS, who received antistaphylococcal antibiotics, including vancomycin, daptomycin, and linezolid. Organisms were identified by traditional culture techniques, including use of rapid coagulase tube testing, in the control group (11/12-5/13) and by BCID in the case group (11/13-5/14). A presumptive identification was entered in the record at the time of the coagulase tube and BCID result. Antimicrobial stewardship reviewed potentially contaminated blood cultures during both periods and intervened when necessary. The primary outcome was time from blood culture draw to discontinuation of antibiotics. Secondary outcomes included duration of antibiotic therapy, antibiotic utilization, and clinical outcomes.
Results: At interim analysis, there were 37 patients in the case group and 39 patients in the control group. Demographics were similar between groups, including Charleston co-morbidity scores, intensive care unit admission, and infectious diseases consult. There were more antimicrobial stewardship interventions in the case group but this was not significant (24% vs. 8%, p=0.06). Time from blood culture draw to antibiotic discontinuation was significantly shorter in the case group (2.57 vs. 3.10 days, p=0.03), as was duration of antibiotics (1.97 vs. 2.54 days, p=0.03). No differences in clinical outcomes, including 30-day mortality, 30-day readmission, or Clostridium difficile infection were noted.
Conclusion: BCID was associated with a shorter time to discontinuation of antibiotics and duration of antibiotic therapy for contaminated blood cultures even when compared to rapid coagulase tube testing. Results from rapid diagnostic tests may aid in early cessation of unnecessary antibiotic therapy.