Antibiotic Resistance and the Risk of Recurrent Bacteremia

Background. Direct health effects of antibiotic resistance are difficult to assess. We quantified the risk of recurrent bacteremia associated with resistance. Methods. We extracted antimicrobial susceptibility testing data on blood isolates from the Dutch surveillance system for antimicrobial resistance between 2008 and 2017. First and first recurrent (4-30 days) bacteremia episodes were categorized as susceptible, single nonsusceptible, or co-nonsusceptible to third-generation cephalosporins without or with carbapenems (Enterobacteriaceae), ceftazidime without or with carbapenems (Pseudomonas species), aminopenicillins without or with vancomycin (Enterococcus-species), or as methicillin-sensitive/-resistant S. aureus (MSSA/MRSA). We calculated risks of recurrent bacteremia after nonsusceptible vs susceptible first bacteremia, estimated the crude population attributable effect of resistance for the Netherlands, and calculated risks of nonsusceptible recurrent bacteremia after a susceptible first episode. Results. Risk ratios for recurrent bacteremia after a single-and co-nonsusceptible first episode, respectively, vs susceptible first episode, were 1.7 (95% confidence interval [CI], 1.5-2.0) and 5.2 (95% CI, 2.1-12.4) for Enterobacteriaceae, 1.3 (95% CI, 0.5-3.1) and 5.0 (95% CI, 2.9-8.5) for Pseudomonas species, 1.4 (95% CI, 1.2-1.7) and 1.6 (95% CI, 0.6-4.2) for Enterococcus species, and 1.6 (95% CI, 1.1-2.4) for MRSA vs MSSA. The estimated population annual number of recurrent bacteremias associated with nonsusceptibility was 40. The risk of nonsusceptible recurrent bacteremia after a susceptible first episode was at most 0.4% (Pseudomonas species). Conclusions. Although antibiotic nonsusceptibility was consistently associated with higher risks of recurrent bacteremia, the estimated annual number of additional recurrent episodes in the Netherlands (40) was rather limited.