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Characterization of MDR and XDR Streptococcus pneumoniae in Canada, 2007-13
Alyssa R Golden1, Margot Rosenthal2, Ben Fultz2
1Department of Medical Microbiology, College of Medicine, Faculty of Health Sciences, University of Manitoba, 727 McDermot Avenue, Winnipeg, Manitoba R3E 3P5, Canada umgoldea@myumanitoba.ca.
Objectives:
The goal of this study was to characterize Streptococcus pneumoniae demonstrating MDR (resistant to three or more antimicrobial classes) or XDR (resistant to five or more classes) phenotypes, collected from Canada during the CANWARD 2007-13 study.
Methods:
From 2007 to 2013 inclusive, S. pneumoniae isolates were collected as a part of the CANWARD surveillance study. MDR and XDR isolates were subjected to PFGE, MLST, molecular detection of pneumococcal pili and macrolide resistance determinants mef(A/E) and erm(B), sequencing of PBPs 1A, 2B and 2X and comparison with Pneumococcal Molecular Epidemiology Network (PMEN) clones.
Results:
Of 2129 S. pneumoniae isolates collected during the CANWARD 2007-13 study, 61 (2.9%) were found to be MDR. Of these MDR isolates, 43 (70.5%) were XDR. The most common serotypes for both MDR and XDR S. pneumoniae were 19A and 19F. Twenty-nine of 61 isolates (48%) demonstrated resistance to clarithromycin, clindamycin, doxycycline, penicillin and trimethoprim/sulfamethoxazole. All isolates possessed at least one macrolide resistance determinant and mutations in PBPs 1A, 2B and 2X. The most common clone was piliated, XDR ST320, an internationally circulating double-locus variant of Taiwan(19F)-14 (ST236).
Conclusions:
Though the rate of MDR S. pneumoniae has remained relatively stable since 2007, XDR strains have emerged in Canada. These strains are virulent, possess resistance determinants and are related to international clones.
Insights
Multidrug-resistant (MDR) and extensively drug-resistant (XDR) Streptococcus pneumoniae strains emerged in Canada between 2007-2013. These virulent XDR strains are linked to international clones and possess key resistance determinants.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, and sepsis.
- Antimicrobial resistance in S. pneumoniae poses a significant public health threat.
- The CANWARD surveillance study monitors antimicrobial resistance trends in Canada.
Purpose of the Study:
- To characterize multidrug-resistant (MDR) and extensively drug-resistant (XDR) Streptococcus pneumoniae isolates collected in Canada.
- To identify the genetic determinants and clonal lineages associated with MDR and XDR phenotypes.
Main Methods:
- Analysis of 2129 S. pneumoniae isolates collected during the CANWARD study (2007-2013).
- Phenotypic characterization of MDR (≥3 classes) and XDR (≥5 classes) resistance.
- Molecular techniques including PFGE, MLST, detection of macrolide resistance genes (mef(A/E), erm(B)), and sequencing of penicillin-binding proteins (PBPs).
- Comparison with Pneumococcal Molecular Epidemiology Network (PMEN) clones.
Main Results:
- 61 (2.9%) isolates were MDR, with 43 (70.5%) classified as XDR.
- Serotypes 19A and 19F were most common among MDR and XDR isolates.
- Common resistance observed to clarithromycin, clindamycin, doxycycline, penicillin, and trimethoprim/sulfamethoxazole.
- All isolates carried macrolide resistance determinants and PBP mutations.
- The predominant clone was a piliated, XDR ST320, a variant of Taiwan(19F)-14 (ST236).
Conclusions:
- While MDR S. pneumoniae rates remained stable, XDR strains have emerged in Canada.
- These emerging XDR strains are virulent and possess significant resistance mechanisms.
- The identified XDR strains are related to internationally circulating clones, highlighting the global nature of antimicrobial resistance.
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