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Evolution and molecular characterization of macrolide-resistant Streptococcus pneumoniae in Canada between 1998 and

Aleksandra K Wierzbowski1, James A Karlowsky, Heather J Adam

  • 1Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada.

The Journal of Antimicrobial Chemotherapy
|August 24, 2013
PubMed
Abstract

Insights

Macrolide-resistant Streptococcus pneumoniae (MRSP) in Canada increased significantly from 1998 to 2008. This rise was driven by non-PCV7 serotypes, particularly 19A, which showed increased multidrug resistance and spread.

Area of Science:

  • Clinical Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance Surveillance

Background:

  • Macrolide-resistant Streptococcus pneumoniae (MRSP) poses a significant public health threat.
  • Understanding resistance mechanisms and serotype distribution is crucial for effective treatment and prevention strategies.
  • Surveillance data from 1998-2008 in Canada provides a decade-long perspective on MRSP trends.

Purpose of the Study:

  • To investigate resistance mechanisms, multidrug resistance (MDR), and genetic relatedness of MRSP.
  • To determine serotype distribution and heptavalent pneumococcal conjugate vaccine (PCV7) coverage.
  • To assess the prevalence of pili virulence factors among MRSP isolates.

Main Methods:

  • Analysis of 1518 MRSP isolates from Canadian national surveillance studies (CROSS and CANWARD).
  • Antimicrobial susceptibility testing using broth microdilution.
  • Detection of macrolide resistance genes (mef(A), erm(B)), pili virulence factors, serotyping (Quellung reaction), and genetic relatedness (PFGE).

Main Results:

  • MRSP prevalence increased from 8% to 22% between 1998 and 2008 (P = 0.0001).
  • Dual mef(A)- and erm(B)-positive isolates rose from 3% to 19% (P = 0.001), alongside a decrease in PCV7 serotypes (67% to 31%).
  • Serotype 19A, a non-PCV7 type, increased by 15% and was associated with MDR, dual resistance genes, genetic relatedness, and pili factors.

Conclusions:

  • Significant increase in MRSP respiratory isolates in Canada from 1998-2008.
  • Emergence and spread of non-PCV7 serotypes, particularly 19A, are primary drivers of this increase.
  • Serotype 19A isolates exhibit concerning characteristics including MDR and presence of virulence factors.
Keywords:
piliserotypessurveillancevaccines

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