Antimicrobial resistance patterns and plasmid profiles of Streptococcus suis isolates

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Molecular Epidemiology

Background:

• Streptococcus suis is a significant swine pathogen with zoonotic potential.
• Understanding antimicrobial resistance patterns and plasmid profiles is crucial for disease control.

Purpose of the Study:

• To assess antimicrobial susceptibility and plasmid content of Streptococcus suis isolates.
• To compare isolates from diseased animals in Canada with human cases in Europe.
• To investigate potential links between plasmid DNA and antimicrobial resistance.

Main Methods:

• Antimicrobial susceptibility testing using various agents.
• Plasmid DNA extraction and profiling.
• Colony and Southern blot hybridization using a 5 kb plasmid probe.

Main Results:

• Quebec isolates showed high resistance to clindamycin, erythromycin, and tetracycline; western Canadian isolates were less resistant; European human isolates were more susceptible.
• Over 60% of isolates harbored plasmids (1.5–35 kb), with two common profiles in Canadian animal isolates.
• A 5 kb plasmid band was prevalent in Canadian isolates and hybridized across different plasmid profiles.
• European human isolates had distinct plasmid content compared to Canadian animal isolates.
• A correlation between plasmid presence and antimicrobial resistance was observed, but causality was not established.

Conclusions:

• Geographic location significantly influences Streptococcus suis antimicrobial resistance and plasmid profiles.
• The prevalence of specific plasmids in Canadian isolates suggests potential epidemic strains in swine populations.
• Further research is needed to elucidate the direct role of plasmids in conferring antimicrobial resistance in Streptococcus suis.