Correlation between antibiotic consumption and resistance of bloodstream bacteria in a University Hospital in North Eastern Italy, 2008-2014

Purpose The spread of multidrug-resistant bacteria is a worrisome problem worldwide. This study investigated the correlation between antibiotic consumption and antimicrobial resistance trends of the most important bacteria causing bacteremia at the University hospital of Trieste, Italy, from 2008 to 2014. Methods Antibiotic consumption (Defined Daily Dose-DDD-per 100 patient/days) and antibiotic resistance (percentage of antibiotic intermediate o resistant isolates) were analyzed independently with linear correlation by year. Potential correlations between antibiotic consumption and bacteria resistance rates were investigated through the Pearson's correlation. Results The overall consumption of antibiotic grew from 80 to 97 DDD 100 patient/days (p = 0.005) during the study period. The increased consumption of amoxicillin/clavulanate and piperacillin/tazobactam was associated with the reduction of MRSA rate from 48.5 to 25.9% (p = 0.007 and p = 0.04, respectively). The increased consumption of piperacillin/tazobactam was associated with the reduction of ESBL-positive Enterobacteriaceae rate from 28.9 to 20.9% (p = 0.01). The increased consumption of carbapenems was associated with the increased rate of carbapenem-resistant Acinetobacter baumannii from 0 to 96.4% (p = 0.03). No carbapenem-resistant Enterobacteriaceae isolates were reported. The consumption of vancomycin grew significantly (p = 0.005). A dramatic spread of vancomycin-resistant Enterococcus faecium occurred in 2014. The consumption of fluoroquinolones and extended-spectrum cephalosporins remained stable. Conclusions An antibiotic stewardship program targeted to limit the consumption of extended-spectrum cephalosporins and fluoroquinolones in favor of amoxicillin/clavulanate and piperacillin/tazobactam correlates with a decreasing rate of MRSA and ESBL-positive Enterobacteriaceae. The analysis of correlations between antibiotic consumption and bacterial resistance rates is a useful tool to orient antimicrobial stewardship policies at local level.