De-escalation of antimicrobial therapy for bacteraemia due to difficult-to-treat Gram-negative bacilli

Purpose To examine the status and clinical outcome of de-escalating antimicrobial therapy for bacteraemia due to hospital-acquired, Gram-negative bacilli that are difficult to treat. Methods Among 1,610 patients presenting with positive blood cultures collected at our medical centre over a 6-year period, 133 were infected with Serratia, Pseudomonas, Acinetobacter, Citrobacter or Enterobacter sp. (SPACES). We examined the appropriateness of an empiric initial administration of antimicrobials based on in vitro sensitivity, and the success and outcomes of a pathogen-directed de-escalation of therapy. The treatment was considered to be successfully de-escalated when the antimicrobial spectrum was narrowed according to a spectrum ranking or when >= 2 antimicrobials prescribed initially were lowered to one agent. Outcome measures included persistent, recurrent and metastatic infections, infection-related deaths and cost of antimicrobials. Results The treatment was initially appropriate in 79 of 133 patients (59 %), of whom 49 (62 %) were candidates for and 28 (57 %) underwent treatment de-escalation. No treatment failure was observed among these 28 patients, while 2 of 11 patients (18 %) whose treatment was not de-escalated died (p = 0.13). The median cost of antimicrobials was (sic)250/patient lower in the de-escalated than in the non-de-escalated group (p < 0.001). Conclusions Antimicrobial therapy for bacteraemia due to hard-to-treat SPACES was de-escalated in 57 % of candidates, based on the in vitro sensitivity, with no deaths and significantly lower costs of antimicrobial therapy.