1054. Biofilm Formation Among Escherichia coli Bloodstream Infection Isolates Is Associated With Source of Bacteremia and Bacterial Sequence Type

BACKGROUND: The clinical impact of Escherichia coli biofilm formation is unknown. METHODS: Adults with E. coli bloodstream infections (BSI) were prospectively enrolled from 2002 to 2015. All E. coli isolates were genotyped using Multilocus sequence typing (MLST) and underwent crystal violet biofilm formation assay quantified by absorbance at 540 nm (OD540) in triplicate. Associations between biofilm formation and patient/bacterial characteristics were characterized by t-tests and ANOVA tests. RESULTS: Ninety-eight percent (186) of the 189 isolates formed detectable biofilms. Bacterial sequence type (ST) was associated with biofilm formation (P < 0.001), as ST73 (average OD(540) = 0.017) and ST393 (average OD(540) = 0.016) had higher average biofilm formation while ST69 (average OD(540) = 0.007) and ST405 (average OD(540) = 0.002) had lower biofilm formation. E. coli isolates with non-multidrug-resistant (non-MDR) phenotype were associated with increased biofilm formation (MDR: average OD(540) = 0.006; average non-MDR: OD(540) = 0.01; P = 0.003). BSI isolates arising from pneumonia or urine/pyelonephritis were associated with the highest biofilm production (P = 0.04). No associations were identified between biofilm formation and route of infection, APACHE-II score, mortality, or complications of BSI. CONCLUSION: In this prospective study of E. coli BSI isolates, biofilm formation was associated with ST, non-MDR phenotype, and BSI source. DISCLOSURES: All authors: No reported disclosures.