4 years ago

Utility of Prior Cultures in Predicting Antibiotic Resistance of Bloodstream Infections Due to Gram-negative Pathogens: A Multicenter Observational Cohort Study

Appropriate empiric antibiotic therapy in patients with bloodstream infections due to Gram-negative pathogens can improve outcomes. We evaluated the utility of prior microbiologic results for guiding empiric treatment in Gram-negative bloodstream infections. Methods We conducted a multi-center observational cohort study, in two large health systems in Canada and the United States, including 1,832 hospitalized patients with Gram-negative bloodstream infection (community, hospital, and ICU acquired) from April 2010 to March 2015. Results Among 1,832 patients with Gram-negative bloodstream infection, 28% (504/1,832) of patients had a documented prior Gram-negative organism from a non-screening culture within the previous 12 months. A most-recent prior Gram-negative organism resistant to a given antibiotic was strongly predictive of the current organism’s resistance to the same antibiotic. The overall specificity was 0.92 (95%CI:0.91-0.93) and positive predictive value was 0.66 (95%CI:0.61-0.70) for predicting antibiotic resistance. Specificities and positive predictive values ranged from (0.77 to 0.98) and (0.43 to 0.78) across different antibiotics, organisms, and patient subgroups. Increasing time between cultures was associated with a decrease in positive predictive value but not specificity. An heuristic based on a prior resistant Gram-negative could have been applied to 1 in 4 patients, and in these patients would have changed therapy in 1 in 5. Conclusions In patients with a bloodstream infection with a Gram-negative organism, identification of a most-recent prior Gram-negative organism resistant to a drug of interest (within the last 12 months) is highly specific for resistance and should preclude use of that antibiotic.

Publisher URL: www.sciencedirect.com/science

DOI: S1198743X17304287

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