Antimicrobial Resistance in Staphylococcus aureus and Enterococcus spp. Isolates From Bloodstream Infections in Australian Children, 2013–2021

Background: Rising proportions of antimicrobial resistance (AMR) have been observed in both Staphylococcus aureus and Enterococcus spp. isolates. Methods: The Australian Group on Antimicrobial Resistance surveillance program captures clinical and microbiological data of isolates detected in blood cultures across Australia. EUCAST 2022 was used for interpretation and the AMR package in R for data analysis. Results: There were 2091 bloodstream infections (BSIs) with S. aureus and 534 enterococcal BSI episodes in children <18 years old over 9 years. Three quarters of S. aureus BSI episodes were community-onset (78.3%), while more than half of enterococcal BSIs were hospital-onset (56.9%). The median age for S. aureus BSIs was 6 years, while >50% of enterococcal BSIs were in children <12 months old. Fifteen percent of S. aureus isolates were methicillin-resistant. Overall, 85.3% of S. aureus were resistant to penicillin, 12.5% resistant to erythromycin, 10.3% to clindamycin, and 4.7% to ciprofloxacin. Resistance to penicillin decreased over time, while clindamycin resistance increased. Resistance in Enterococcus spp. was almost entirely observed in Enterococcus faecium; only 1 Enterococcus faecalis isolate was ampicillin-resistant, and no E. faecalis isolates were vancomycin or teicoplanin-resistant. Seventy-three percent of E. faecium were resistant to ampicillin, 25.5% to vancomycin (VREfm), and 8.8% to teicoplanin. Conclusions: Significant shifts in the epidemiology and resistance profiles of S. aureus and Enterococcus spp. BSIs in Australian children were observed, making clear the importance of age-stratified reporting in AMR data.