Objective Third-generation cephalosporins (3GCs) may be susceptible in vitro to Enterobacter spp. and Klebsiella aerogenes. However, treatment with mainly fourth-generation cephalosporins or carbapenems is currently recommended. Diversification of antimicrobial agents in therapy is required to avoid the selection pressure of resistant organisms by broad-spectrum antimicrobial agents. This study investigated the clinical efficacy of 3GC therapy for Enterobacter spp. and Klebsiella aerogenes bacteremia in a multicenter, retrospective, observational study. Methods Patients with Enterobacter spp. or Klebsiella aerogenes detected in blood cultures and treated with a susceptible antimicrobial agent were included in the study. Propensity score matching was performed to align patient background bases, and clinical outcomes between the 3GC and non-3GC groups were compared. Treatment success was defined as having no need for treatment escalation or the addition of other antimicrobial agents, no recurrence, or no death within 30 days. Results The study included 188 cases, of which 57 and 131 were included in the 3GC and non-3GC treatment groups, respectively; 53 patients in each group were matched by propensity score matching. There were no significant differences between groups in rates of switching to a susceptible antimicrobial or adding another agent, relapse within 30 days, or death within 30 days. In the 3GC group, source control was associated with favorable clinical outcomes. Conclusion Definitive 3GC therapy for susceptible Enterobacter spp. and Klebsiella aerogenes bacteremia is as clinically effective and valuable a targeted therapy as non-3GC therapy and can be implemented under conditions in which infection source control measures are in place.
Keywords: Enterobacter; Klebsiella; bacteremia; bacterial drug resistance; beta-lactamases; cephalosporins.