Impact of antibiotic susceptibility reporting on broad spectrum antibiotic use in serratia and morganella bacteremia.

To minimize broad-spectrum antibiotic use, our microbiology laboratory changed antibiotic susceptibility reporting for AmpC-beta-lactamase producing Serratia marcescens and Morganella morganii in blood cultures to include results of narrow spectrum 3rd generation cephalosporins. We assessed the impact of this change on broad-spectrum antibiotic use and clinical outcomes. All adult patients with Serratia marcescens or Morganella morganii in blood culture 2 years pre- and post-change of susceptibility reporting were retrospectively reviewed. Exclusion: more than one pathogen isolated in their blood culture, did not receive antibiotics or died within 48 hours of positive blood culture. Outcomes: Rates of broad-spectrum antibiotic use, in-hospital mortality, clinical response and microbiologic success. There were 30 patients pre-change and 46 patients post-change of reporting. Cefepime use (broad-spectrum) decreased from 46.7% to 6.5% (p < 0.001) and 3rd generation cephalosporin (narrow-spectrum) use increased (3.3% vs 34.8%, p = 0.0013) in the post-change cohort. This demonstrates the potential role of selective susceptibility reporting in antimicrobial stewardship.

Outcomes of treating AmpC-producing Enterobacterales bacteraemia with carbapenems vs. non-carbapenems.

INTRODUCTION: AmpC ß-lactamases are found in Enterobacter species, Serratia species, Citrobacter freundii, Providencia species and Morganella morganii ('ESCPM'). Carbapenems are commonly used to treat severe 'ESCPM' infections. Carbapenem-sparing agents are needed because of increasing carbapenem resistance worldwide. Use of cefepime and piperacillin-tazobactam has limited supportive clinical data. We evaluated the efficacy of non-carbapenems vs. carbapenems in 'ESCPM' bacteraemia. METHODS: A retrospective cohort study was conducted on patients with 'ESCPM' bacteraemia. Primary outcome was 30-day mortality. Analyses were performed on patients who received carbapenems vs. piperacillin-tazobactam or cefepime monotherapy as empirical and definitive therapy. Propensity score for carbapenem therapy was adjusted for in multivariate analyses for 30-day mortality. RESULTS: A total of 241 patients were included. The most common bacterium isolated was Enterobacter species (58.1%). Common sources were urinary (22.8%) and vascular lines (22.0%). Carbapenems (28.6%) and piperacillin-tazobactam (28.6%) were the commonest empirical antibiotics. Carbapenems (54.8%) and cefepime (23.7%) were the most common definitive antibiotics. Median Pitt bacteraemia score was 1 (interquartile range [IQR], 0-2). Overall, 30-day mortality was 12.9%. Adjusted multivariate analyses for empirical and definitive antibiotic treatment models yielded risk factors for 30-day mortality, including higher Pitt bacteraemia score (empirical: adjusted OR [aOR] 1.21 for each point increase, 95% confidence interval [CI]:1.01-1.45; definitive: aOR 1.33 for each point increase, 95% CI:1.06-1.69) and age (empirical: aOR 1.04 for each year increase, 95% CI:1.01-1.08). Empirical piperacillin-tazobactam (aOR 0.29, 95% CI:0.07-1.27) and definitive cefepime (aOR 0.65, 95% CI:0.12-3.55) were not associated with 30-day mortality. CONCLUSIONS: Compared with carbapenem therapy, empirical piperacillin-tazobactam and definitive cefepime were not associated with 30-day mortality in 'ESCPM' bacteraemia.