Characterization of multi-drug tolerant persister cells in Streptococcus suis

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Antimicrobial Tolerance

Background:

• Persister cells are dormant, non-growing subpopulations exhibiting high tolerance to antibiotics.
• This 'bet-hedging' strategy is vital for microbial survival, especially in pathogenic bacteria.
• Understanding persister cells is key to combating persistent infections.

Purpose of the Study:

• To investigate the formation and characteristics of persister cells in the zoonotic pathogen Streptococcus suis.
• To determine the influence of growth phase on persister cell development in S. suis.
• To explore the genetic and metabolic underpinnings of persister cell formation in S. suis.

Main Methods:

• Culturing Streptococcus suis under varying growth conditions (exponential vs. stationary phase).
• Assessing multi-drug tolerance of identified persister cells against various antibiotics.
• Analyzing gene expression related to metabolic pathways in persister cell mutants.
• Testing for persister cell formation in other S. suis strains and related streptococcal species.

Main Results:

• Streptococcus suis forms multi-drug tolerant persister cells, with higher numbers observed in stationary phase cultures.
• S. suis persister cells exhibit significant tolerance to a range of antibiotics, a trait not heritable through multiple passages.
• A mutation in the arginine deiminase system (involved in metabolic pathways) increased persister cell numbers.
• Persister cell formation was confirmed in other S. suis strains and pathogenic streptococci.

Conclusions:

• This study provides the first evidence of multi-drug tolerant persister cells in the zoonotic pathogen Streptococcus suis.
• Persister cell formation in S. suis is influenced by growth phase and potentially linked to metabolic regulation.
• The findings suggest persister cells are a conserved phenomenon in pathogenic streptococci, impacting treatment strategies.