Persister cells and tolerance to antimicrobials

Area of Science:

• Microbiology
• Bacterial Physiology
• Antimicrobial Resistance

Background:

• Bacterial persister cells are dormant subpopulations that survive antibiotic treatment.
• Persisters contribute significantly to biofilm antimicrobial tolerance.
• The biological mechanisms governing persister formation remain largely unknown.

Purpose of the Study:

• To investigate the influence of bacterial growth stage on persister cell formation.
• To elucidate the nature and origin of persister cells in key bacterial species.

Main Methods:

• Assessing ampicillin and ofloxacin tolerance in Escherichia coli at different growth phases.
• Monitoring persister dynamics in Pseudomonas aeruginosa and Staphylococcus aureus.
• Manipulating E. coli growth phase through reinoculation to observe persister levels.

Main Results:

• Persister cell numbers remained stable during lag and early exponential phases.
• A dramatic increase in persister cells was observed during the mid-exponential growth phase.
• Elimination of persisters by maintaining early exponential phase cultures suggested they are not antibiotic-induced.

Conclusions:

• Persister cell formation is dependent on the bacterial growth stage, specifically increasing during mid-exponential phase.
• Persisters are not indicative of a specific cell cycle stage, defective cells, or a direct response to antibiotics.
• Data suggest persisters are specialized bacterial survival cells.