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High-throughput Screening of Chemical Compounds to Elucidate Their Effects on Bacterial Persistence
Published on: February 23, 2021
Bactericidal activity of alpha-bromocinnamaldehyde against persisters in Escherichia coli
Qingshan Shen1, Wei Zhou1, Liangbin Hu1
1Department of Food Science, Henan Institute of Science and Technology, Xinxiang, China.
Abstract:
Persisters are tolerant to multiple antibiotics, and widely distributed in bacteria, fungi, parasites, and even cancerous human cell populations, leading to recurrent infections and relapse after therapy. In this study, we investigated the potential of cinnamaldehyde and its derivatives to eradicate persisters in Escherichia coli. The results showed that 200 μg/ml of alpha-bromocinnamaldehyde (Br-CA) was capable of killing all E. coli cells during the exponential phase. Considering the heterogeneous nature of persisters, multiple types of persisters were induced and exposed to Br-CA. Our results indicated that no cells in the ppGpp-overproducing strain or TisB-overexpressing strain survived the treatment of Br-CA although considerable amounts of persisters to ampicillin (Amp) and ciprofloxacin (Cip) were induced. Chemical induction by carbonyl cyanide m-chlorophenylhydrazone (CCCP) led to the formation of more than 10% persister to Amp and Cip in the entire population, and Br-CA still completely eradicated them. In addition, the cells in the stationary phase, which are usually highly recalcitrant to antibiotics treatment, were also completely eradicated by 400 μg/ml of Br-CA. Further studies showed that neither thiourea (hydroxyl-radical scavenger) nor DPTA (Fe3+ chelator to block the hydroxyl-radical) affected the bactericidal efficiency of the Br-CA to kill E. coli, indicating a ROS-independent bactericidal mechanism. Taken together, we concluded that Br-CA compound has a novel bactericidal mechanism and the potential to mitigate antibiotics resistance crisis.
Insights
Alpha-bromocinnamaldehyde (Br-CA) effectively eradicates persister cells, including highly tolerant strains and stationary phase bacteria, in Escherichia coli. This compound shows potential for combating antibiotic resistance by utilizing a novel, ROS-independent bactericidal mechanism.
Area of Science:
- Microbiology
- Bacteriology
- Antimicrobial Resistance
Background:
- Persister cells are a subpopulation of microorganisms exhibiting tolerance to multiple antibiotics, contributing to recurrent infections and treatment failures.
- Understanding and eliminating persister cells is crucial for developing effective antimicrobial strategies against resistant bacterial strains.
Purpose of the Study:
- To investigate the efficacy of cinnamaldehyde derivatives, specifically alpha-bromocinnamaldehyde (Br-CA), in eradicating persister cells in Escherichia coli.
- To elucidate the bactericidal mechanism of Br-CA against various types of persister cells and stationary phase bacteria.
Main Methods:
- Induction of different persister types in Escherichia coli, including ppGpp-overproducing and TisB-overexpressing strains.
- Treatment of induced persister cells and stationary phase cultures with varying concentrations of alpha-bromocinnamaldehyde (Br-CA).
- Assessment of Br-CA's bactericidal activity and investigation of its mechanism through ROS-scavenging and metal-chelating assays.
Main Results:
- Alpha-bromocinnamaldehyde (Br-CA) at 200 μg/ml eradicated all E. coli cells in the exponential phase.
- Br-CA demonstrated complete eradication of ampicillin (Amp) and ciprofloxacin (Cip) persisters, even those chemically induced to high levels (>10%).
- Stationary phase cells and persisters from ppGpp-overproducing and TisB-overexpressing strains were also completely eradicated by Br-CA, with no ROS-independent mechanism observed.
Conclusions:
- Alpha-bromocinnamaldehyde (Br-CA) is a potent agent against diverse persister cell populations and stationary phase bacteria in E. coli.
- Br-CA exhibits a novel bactericidal mechanism independent of reactive oxygen species (ROS).
- Br-CA holds significant potential as a therapeutic agent to address the growing crisis of antibiotic resistance.
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