Resistance trends among Enterobacterales from bacteraemias in the UK and Ireland, 2007 - 2017

The British Society for Antimicrobial Chemotherapy (BSAC) Bacteraemia Resistance Surveillance Programme monitors the antimicrobial susceptibility of organisms causing bacteraemias in the UK and Ireland. We review data for Escherichia coli, Klebsiella, Enterobacter, Proteeae, and Serratia collected between 2007-2017.

Consecutive isolates causing clinically significant bacteraemia were tested; participating laboratories (n=24-40) collected 7-20 isolates/species per year. Minimum inhibitory concentrations were determined centrally by BSAC agar dilution.

Rates of resistance in the UK and Ireland remained largely stable over the 11-year period, during which 14,206 isolates were tested [(E. coli, n=5364; Klebsiella, n=3016; Proteeae, n=2423; Enterobacter, n=1819, and Serratia, n=1584)]. A decrease in resistance to piperacillin/tazobactam was noted among all species, except K. aerogenes. A decrease in resistance to ciprofloxacin was seen among E. coli and Enterobacter. Average rates of resistance to ceftolozane/tazobactam ranged from 0.2% (E. coli)to 9.2%(E. cloacae), whereas rates of resistance to ceftobiprole were higher [10% (E. coli) and 20% (E. cloacae)]. Rates of colistin resistance were low among E. coli (0.5%), and Klebsiella (1.2%); however, rates were higher, and increasing among Enterobacter (6.1% in 2011 to 13.4% in 2017). Rates of ESBL production were stable over time; higher among E. coli (9.6%), Enterobacter (10.4%), and Klebsiella (14.7%), compared with <1% among Proteeae and Serratia. Carbapenemase producers remained rare (n=16 over 11 years, without trend).

The largely unchanging or reducing resistance rates among Enterobacterales causing bacteraemia are reassuring and may reflect interventions to reduce inappropriate use of antimicrobials implemented across the countries surveyed.