Seasonality of bacteremia cases in an emergency department.

OBJECTIVES To assess seasonal variation in episodes of bacteremia. MATERIAL AND METHODS Retrospective cohort study of cases of significant bacteremia found in blood cultures ordered in a hospital emergency department. The incidence, etiology, diagnostic and prognostic yield were analyzed for each season of the year. RESULTS A total of 4384 blood cultures were ordered in 4.1% of the emergency patients attended. The diagnostic yield was 12.2% (incidence, 490 cases per 100 000 cases attended). Cultures were ordered more often in winter (in 4.6% of the patients vs in 3.8% in the other seasons on average, P<.001). The diagnostic yield was lower in winter than in the other seasons (10.2% vs 13%, P=.01), and the contamination rate was higher (4.9% vs 3.8%, P=.02). Escherichia coli was isolated in fewer cultures in winter than in other seasons (36.4% vs 46.9%, P=.03), and Streptococcus pneumoniae was isolated in more (14.5% vs 5.9%, P=.001). CONCLUSION The microbiological profile of blood cultures, their diagnostic yield, and rate of contamination differ greatly in winter.