Automated identification and susceptibility determination directly from blood cultures facilitates early targeted antibiotic therapy

Abstract

Background: The increasing prevalence of antibiotic resistance is challenging established empirical treatments, making early identification and susceptibility determination more important. To avoid time-consuming overnight cultures, a previously published method for the rapid identification and susceptibility testing of blood cultures was instituted at Molde Hospital. The time saved compared to the standard method, and how often the results could have led to a change in the empirical antibiotic treatment compared to Gram stain from cultures, were evaluated. Material and methods: All positive blood cultures with Gram-negative bacilli obtained between March and December 2010 were included in the study (n = 69). Accuracy and turn-around times were compared to those of the standard methods. The empirical antibiotic treatment was recorded when consulting the clinician about the results. Results: Correct identification was obtained in 66/69 (95.7%) of the isolates. Correct susceptibility determination was obtained in 758/759 (99.9%) of the tests. Oral reports to the clinician were given on average 11 h 22 min earlier for identification, and 10 h 51 min earlier for susceptibility determination, compared to the standard methods. With optimal handling we could have managed 17 h 26 min and 16 h 14 min, respectively. In 14/69 cases the empirical treatment included no effective or appropriate antibiotics. 7 of these 14 would not have been changed to working antibiotic treatment based on Gram stain alone. Conclusion: The rapid method was found to be accurate and showed the potential for the initiation of effective antibiotic treatment more than 16 h earlier for 10% of the patients in this small sample.

Keywords::

• Microbiology
• infectious disease
• antimicrobial therapy

Acknowledgements

Garth Tylden of the Department of Microbiology and Infection Control, University Hospital of North Norway is thanked for his assistance of proof reading and developing the manuscript.

Declaration of interests: No funding was received. No commercial relationships or potential conflicts of interest exist.