Clinical impact of inappropriate initial antimicrobial therapy on outcome in bacteremic biliary tract infections

Background: The marked increase in the incidence of biliary tract infections due to antimicrobial-resistant pathogens in recent years is of great concern, as patients infected by these isolates might initially receive antibiotics ineffective against the responsible pathogens. Methods: A retrospective cohort study including 556 episodes of bacteremic biliary tract infection was designed to evaluate the impact of inappropriate initial antimicrobial therapy on the clinical outcomes of patients with biliary tract infections. Results: Of 556 episodes, 257 (46.2%) received inappropriate initial antimicrobial therapy. Although Escherichia coli and Klebsiella species are the most common pathogens, the pathogens that were most frequently associated with inappropriate therapy were Pseudomonas aeruginosa and Enterococcus spp. In multivariable analysis, inappropriate initial antimicrobial therapy was found to be independently associated with increased mortality (odds ratio (OR) 2.25, 95% confidence interval (CI) 1.134.48; p = 0.021), along with pancreaticobiliary tract cancer, liver cirrhosis, Enterobacter infection, and a high Pitt bacteremia score (All p < 0.05). Subgroup multivariate analyses showed that inappropriate initial therapy was not a significant factor associated with mortality in cases where therapeutic decompression or drainage procedures were employed (OR 1.24, 95% CI 0.433.54; p = 0.691) or in cases with appropriate definitive antimicrobial therapy (OR 1.61, 95% CI 0.693.72; p = 0.270) after adjustment for other variables. Conclusions: Our findings suggest that the administration of inappropriate initial antimicrobial therapy might be associated with an adverse outcome in patients experiencing bacteremic biliary tract infections, and that the impact of inappropriate therapy on the outcome may be dependent on therapeutic drainage and appropriate definitive antimicrobial therapy.