A retrospective study to evaluate the epidemiology, standard of care, outcomes and resource utilization in patients with confirmed or suspected infection by a carbapenem resistant Gram-negative organism in the UK – the CARBAR study - Epidemiology of Gram negative organisms

Antimicrobial resistance is a global threat with potentially devastating consequences and significant costs to society. Carbapenems are customarily reserved for difficult-to-treat Gram-negative (GN) infections, but resistance is increasing; hence WHO classified carbapenem-resistant (CR) strains of Acinetobacter baumannii (CRAB), Pseudomonas aeruginosa (CRPA), and Enterobacteriaceae as critical priority.

CR-GN infections have few effective treatment options, with variable outcomes and scarce clinical trial evidence. In this analysis, we describe the epidemiology of patients infected with CR-GN organisms.

Retrospective chart review from 10 sites in UK. Adult patients admitted to hospital between April 2017-March 2018 were included if they had a confirmed GN bacterial infection and/or positive screening isolate for CR-GN bacteria colonisation. Data collection included microbiological results and patient demographics.

36,078 patients were included, representing 42,310 GN isolates, of which 3,063 (7%) were CR-GN. Mean age was 59.9 years; 60.2% were female.

The most prevalent GN species were E. coli representing 51.8% of all isolates, followed by P. aeruginosa (12.0%), and K. pneumoniae (8.7%).

Within CR-GN isolates CRPA represented 26.6%, E. coli 21.5%, and other bacteria 51.9% (including CRAB and Stenotrophomonas maltophilia).

GN isolates are frequent across the UK, and 7% are CR-GN, representing a small important segment of this population. Understanding the real-world prevalence of GN and particularly CR-GN infections, where there is the highest unmet need, can help optimise antimicrobial stewardship and infection control programmes and ultimately improve overall patient’s and healthcare system’s outcomes, which is the focus of this study’s next phase.