Intra-hospital differences in antibiotic use correlate with antimicrobial resistance rate in Escherichia coli and Klebsiella pneumoniae : a retrospective observational study.

Background: Monitoring antimicrobial use and resistance in hospitals are important tools of antimicrobial stewardship programs. We aimed to determine the association between the use of frequently prescribed antibiotics and the corresponding resistance rates in Escherichia coli and Klebsiella pneumoniae among the clinical departments of a tertiary care hospital.

Methods: We performed a retrospective observational study to analyse the use of nine frequently prescribed antibiotics and the corresponding antimicrobial resistance rates in hospital acquired E. coli and K. pneumoniae isolates from 18 departments of our institution over 9 years (2008-2016). The main cross-sectional analysis assessed the hypothetical influence of antibiotic consumption on resistance by mixed logistic regression models.

Results: We found an association between antibiotic use and resistance rates in E. coli for amoxicillin-clavulanic acid (OR per each step of 5 defined daily dose/100 bed-days 1.07, 95% CI 1.02-1.12; p  = 0.004), piperacillin-tazobactam (OR 2.11, 95% CI 1.45-3.07; p  < 0.001), quinolones (OR 1.52, 95% CI 1.25-1.86; p  < 0.001) and trimethoprim-sulfamethoxazole (OR 1.59, 95% CI 1.19-2.13; p  = 0.002). Additionally, we found a significant association when all nine antibiotics were combined in one analysis. The association between consumption and resistance rates was stronger for nosocomial than for community strains. In K. pneumoniae, we found an association for amoxicillin-clavulanic acid (OR 1.07, 95% CI 1.01-1.14; p  = 0.025) and for trimethoprim-sulfamethoxazole (OR 2.02, 95% CI 1.44-2.84; p  < 0.001). The combined analysis did not show an association between consumption and resistance (OR 1.06, 95% CI 0.99-1.14; p  = 0.07).

Conclusions: We documented an association between antibiotic use and resistance rate for amoxicillin-clavulanic acid, piperacillin-tazobactam, quinolones and trimethoprim-sulfamethoxazole in E. coli and for amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole in K. pneumoniae across different hospital departments. Our data will support stewardship interventions to optimize antibiotic prescribing at a department level.