Australian Group on Antimicrobial Resistance (AGAR) Australian Gram-negative Surveillance Outcome Program (GnSOP) Bloodstream Infection Annual Report 2024

The Australian Group on Antimicrobial Resistance (AGAR) performs regular period-prevalence studies to monitor changes in antimicrobial resistance in selected enteric gram-negative pathogens. From 1 January 2024 to 31 December 2024, fifty-five hospitals across Australia participated in the Australian Gram-negative Surveillance Outcome Program (GnSOP). A total of 10,340 isolates, comprising Enterobacterales (9,376; 90.9%), Pseudomonas aeruginosa (804; 7.7%) and Acinetobacter species (160; 1.4%), were tested using commercial automated methods. The results were analysed using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints (January 2025). Key resistances reported are to the third-generation cephalosporin ceftriaxone in 14.9% of Escherichia coli and 10.5% of Klebsiella pneumoniae complex isolates. Resistance rates to ciprofloxacin were 15.4% for E. coli; 9.7% for the K. pneumoniae complex; 3.8% for the Enterobacter cloacae complex; and 8.8% for P. aeruginosa. Resistance rates to piperacillin–tazobactam were 7.5%, 10.3%, 25.2%, and 13.6% for the same four species/complexes, respectively. Thirty-nine Enterobacterales isolates from 38 patients were shown to harbour a carbapenemase gene: 21 with a blaNDM gene (blaNDM-5 [8]; blaNDM-1 [7]; blaNDM-7 [6]); eight with blaIMP-4; four with a blaOXA-181-like gene (blaOXA-181 [2]; blaOXA-484 [1]; blaOXA-1205 [1]); three with a blaOXA-48-like gene (blaOXA-48 [2]; blaOXA-244); two with blaKPC-2; and one with blaNDM-5 + blaOXA-484. Carbapenemase genes were also detected in two P. aeruginosa isolates (blaNDM-1 [1]; blaGES-5 [1]).