[Can a difficult-to-treat resistance approach improve cooperation between microbiologists and clinicians?]

We introduce a relatively new difficult-to-treat resistance (DTR) category to specialists. It significantly influences the predictability of morbidity and mortality in patients with invasive infections caused by DTR strains. Therefore, surveillance of DTR is an important tool of antimicrobial stewardship (AMS) and widely contributes to cooperation between microbiologists and clinicians. We also report the prevalence of strains meeting the criteria for the category in a teaching hospital.

This retrospective cohort single center study included invasive isolates of gram-negative rods from patients hospitalized in the General University Hospital in Prague in 2009-2013 and in 2017-2021.

From a total of 1 732 (920 and 812, respectively) unique strains of gram-negative rods isolated from blood cultures in both periods, 6.6 % were carbapenem-resistant in 2009-2013 and 6.0 % in 2017-2021; 3.7 % were identified as DTR in both periods. Most of the DTR strains were A. baumannii (23.1 % and 45.0 %, respectively) and P. aeruginosa (22.2 % and 15.3 %, respectively). We identified no carbapenem-resistant E. coli and therefore no DTR E. coli.

Infections caused by bacterial strains with a DTR phenotype are grave complications and are tricky to manage. The prevalence of severe infections caused by these strains was relatively low in the studied facility. Antibiotics with anti-DTR effects should be considered the last resort, so it is very important to comply with AMS rules and examine the susceptibility of these agents.