Gram-positive pathogens from Canadian hospitals: 17 years of results from the CANWARD study (2007-23).

Objectives: CANWARD is a Canadian Antimicrobial Resistance Alliance (CARA)/Health Canada partnered national surveillance study established in 2007 to annually assess antimicrobial susceptibilities for bacterial pathogens isolated from patients receiving care in Canadian hospitals. This paper focuses on Gram-positive pathogens.

Methods: In total, 25 897 Gram-positive pathogens were received and 22 132 underwent CLSI broth microdilution testing providing susceptibility data.

Results: 47.9%, 30.2%, 5.7% and 16.2% of isolates tested were from blood, respiratory, urine and wound specimens, respectively; 29.9%, 24.8%, 19.0%, 18.1% and 8.2% of isolates were from patients in medical wards, emergency rooms, intensive care units, hospital clinics and surgical wards. Patient demographics associated with the isolates were: 58.9% male/41.1% female; 13.5% patients aged ≤17 years, 48.5% 18-64 years and 38.0% ≥ 65 years. Of the 25 897 pathogens received, the most common were: Staphylococcus aureus [20.9% (MSSA 16.5%/MRSA 4.4%)], Streptococcus pneumoniae (5.2%) and Enterococcus spp. (Enterococcus faecalis and Enterococcus faecium) (5.0%). MRSA rates (MRSA as a % of all S. aureus tested) decreased significantly during 2007-15 from 26.0% to 19.3% (P < 0.0001); subsequently they increased significantly through study years 2016-23 (16.9%-24.1%; P = 0.002). VRE rates (VRE as a % of all E. faecium tested) ranged from 3.8% to 18.4%, with marked fluctuation year-to-year. Susceptibility rates for MRSA were highest with: 100% ceftobiprole, 99.9% linezolid, vancomycin and daptomycin, 99.8% dalbavancin and 99.4% tedizolid, while susceptibility rates for VRE were 98.4% daptomycin and 86.0% with linezolid.

Conclusions: The CANWARD surveillance study has provided 17 years of reference antimicrobial susceptibility testing data on Gram-positive pathogens.