Background: Empirical antibiotic use is common in the hospital. Here, we characterize patterns of antibiotic use, infectious diagnoses, and microbiological lab results among hospitalized patients and aim to quantify the proportion of antibiotic use that is potentially attributable to specific bacterial pathogens.
Methods: We conducted an observational study using electronic health records from acute care facilities in the United States Veterans Affairs Healthcare System. From October 2017 to September 2018, 482,381 hospitalizations for 332,657 unique patients that met all criteria were included. At least one antibiotic was administered at 202,037 (41.9%) of included hospital stays. We measured frequency of antibiotic use, microbiological specimen collection, and bacterial isolation by diagnosis category and antibiotic group. A tiered system based on specimen collection sites and diagnoses was used to attribute antibiotic use to presumptive causative organisms.
Results: Specimens were collected at 130,012 (64.4%) hospitalizations with any antibiotic use, and at least one bacterial organism was isolated at 35.1% of these stays. Frequency of bacterial isolation varied widely by diagnosis category and antibiotic group. Under increasingly lenient criteria, 10.2% to 31.4% of 974,733 antibiotic days-of-therapy could be linked to a potential bacterial pathogen.
Conclusions: Overall, the vast majority of antibiotic use could be linked to either an infectious diagnosis or microbiological specimen. Nearly half of antibiotic use occurred when there was a specimen collected but no bacterial organism identified, underscoring the need for rapid and improved diagnostics to optimize antibiotic use.
Keywords: Veterans Affairs; antibiotic stewardship; antibiotics; hospitalization; microbiology.
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