Prevalence of and risk factors for antimicrobial resistance in pneumococcal disease in southern Ontario during the PCV13 era.

BACKGROUND

Pneumococcal infections are an important cause of morbidity and mortality, and a major contributor to the burden of antimicrobial resistance (AMR). Multiple factors affect AMR in pneumococci.

METHODS

The Toronto Invasive Bacterial Diseases Network (TIBDN) conducted population-based surveillance for invasive pneumococcal disease (IPD) and hospitalization due to non-bacteremic pneumococcal pneumonia (NBPP) in Toronto/Peel Region, Ontario. Laboratories reported sterile site and respiratory isolates of Streptococcus pneumoniae. Patient data were collected by chart review and patient/physician interview. Population data were from Statistics Canada. Antimicrobial susceptibility testing was performed/interpreted per Clinical and Laboratory Standards Institute guidelines and/or by prediction from whole genome sequencing (WGS). Serotyping was performed by Quellung reaction or WGS.

RESULTS

From 2014 to 2024, 3881 episodes of IPD and 887 of NBPP were identified. Resistance was most common to macrolides (31.4%, 1285/4086), tetracyclines (17.4%, 653/3756), penicillin (meningeal breakpoints: 17.2%, 749/4354), clindamycin (12.3%, 472/3823) and trimethoprim-sulfamethoxazole (12.6%, 495/3929); resistance to ceftriaxone (meningeal breakpoints) and levofloxacin was <1%. Resistance declined over time for ceftriaxone, fluoroquinolones, and erythromycin but increased for oral penicillin, tetracycline and trimethoprim-sulfamethoxazole. Non-susceptibility to ceftriaxone (meningeal breakpoints) increased. Non-susceptibility to ceftriaxone (OR 3.7, 95%CI 2.6-5.3) and resistance to erythromycin (OR 1.3, 95%CI 1.0-1.5) were more common in NBPP than IPD, and in hospital- versus community-acquired disease (ORs 2.0, 95%CI 1.3-3.0 and 1.9, 95%CI 1.4-2.5, respectively). Levofloxacin non-susceptibility was higher in long-term-care-acquired disease (OR 6.3, 95%CI 2.1-19). Recent antibiotic use was associated with increased resistance to the same antibiotic class. Ceftriaxone and erythromycin resistance were most common in 7-valent pneumococcal conjugate vaccine (PCV7) serotypes. Resistance to any antibiotic was not different in isolates of serotypes included in PCV20 versus PCV21.

CONCLUSIONS

In our population, pneumococcal antimicrobial resistance has remained relatively stable, but changes differ by antibiotic class. Implementation of vaccination programs with PCV20 or PCV21 should reduce AMR by disease prevention.