Persister Cells: Molecular Mechanisms Related to Antibiotic Tolerance

ABSTRACTPersister cells represent a multidrug-tolerant (MDT), physiologically distinct subpopulation of bacteria. The ability of these organisms to survive lethal antibiotic doses raises concern over their potential role in chronic disease, such as recurrent urinary tract infection (RUTI). Persistence is believed to be conveyed through global metabolic dormancy, which yields organisms unresponsive to external stimuli. However, recent studies have contested this stance. Here, various antibiotics that target different cellular processes were used to dissect the activity of transcription, translation, and peptidoglycan turnover in persister cells. Differential susceptibility patterns were found in type I and type II persisters, and responses differed betweenStaphylococcus saprophyticusandEscherichia coliuropathogens. Further, SOS-deficient strains were sensitized to ciprofloxacin, suggesting DNA gyrase activity in persisters and indicating the importance of active DNA repair systems for ciprofloxacin tolerance. These results indicate that global dormancyper secannot sufficiently account for antibiotic tolerance. Rather, the activity of individual cellular processes dictates multidrug tolerance in an antibiotic-specific fashion. Furthermore, the susceptibility patterns of persisters depended on their mechanisms of onset, with subinhibitory antibiotic pretreatments selectively shutting down cognate targets and increasing the persister fraction against the same agent. Interestingly, antibiotics targeting transcription and translation enhanced persistence against multiple agents indirectly related to these processes. Conducting these assays with uropathogenicE. coliisolated from RUTI patients revealed an enriched persister fraction compared to organisms cleared with standard antibiotic therapy. This finding suggests that persister traits are either selected for during prolonged antibiotic treatment or initially contribute to therapy failure.

Download Full-text

In Vitro Studies of Persister Cells

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.00070-20 ◽

2020 ◽

Vol 84 (4) ◽

Author(s):

Niilo Kaldalu ◽

Vasili Hauryliuk ◽

Kathryn Jane Turnbull ◽

Agnese La Mensa ◽

Marta Putrinš ◽

...

Keyword(s):

Immune System ◽

Bacterial Growth ◽

Molecular Mechanisms ◽

Test Tube ◽

In Vitro Studies ◽

Recurrent Infections ◽

Persister Cells ◽

Persistent Infections ◽

Key Aspects

SUMMARY Many bacterial pathogens can permanently colonize their host and establish either chronic or recurrent infections that the immune system and antimicrobial therapies fail to eradicate. Antibiotic persisters (persister cells) are believed to be among the factors that make these infections challenging. Persisters are subpopulations of bacteria which survive treatment with bactericidal antibiotics in otherwise antibiotic-sensitive cultures and were extensively studied in a hope to discover the mechanisms that cause treatment failures in chronically infected patients; however, most of these studies were conducted in the test tube. Research into antibiotic persistence has uncovered large intrapopulation heterogeneity of bacterial growth and regrowth but has not identified essential, dedicated molecular mechanisms of antibiotic persistence. Diverse factors and stresses that inhibit bacterial growth reduce killing of the bulk population and may also increase the persister subpopulation, implying that an array of mechanisms are present. Hopefully, further studies under conditions that simulate the key aspects of persistent infections will lead to identifying target mechanisms for effective therapeutic solutions.

Download Full-text

Molecular Mechanisms of Non-Inherited Antibiotic Tolerance in Bacteria and Archaea

Molecular Biology ◽

10.1134/s0026893319040058 ◽

2019 ◽

Vol 53 (4) ◽

pp. 475-483 ◽

Cited By ~ 1

Author(s):

T. M. Khlebodarova ◽

V. A. Likhoshvai

Keyword(s):

Molecular Mechanisms ◽

Antibiotic Tolerance

Download Full-text

Interference ofPseudomonas aeruginosasignalling and biofilm formation for infection control

Expert Reviews in Molecular Medicine ◽

10.1017/s1462399410001420 ◽

2010 ◽

Vol 12 ◽

Cited By ~ 65

Author(s):

Thomas Bjarnsholt ◽

Tim Tolker-Nielsen ◽

Niels Høiby ◽

Michael Givskov

Keyword(s):

Cystic Fibrosis ◽

Biofilm Formation ◽

Molecular Mechanisms ◽

Antibiotic Tolerance ◽

Chronic Infections ◽

Major Task ◽

Vitro Data ◽

In Vitro Data

Pseudomonas aeruginosais the best described bacterium with regards to quorum sensing (QS), in vitro biofilm formation and the development of antibiotic tolerance. Biofilms composed ofP. aeruginosaare thought to be the underlying cause of many chronic infections, including those in wounds and in the lungs of patients with cystic fibrosis. In this review, we provide an overview of the molecular mechanisms involved in QS, QS-enabled virulence, biofilm formation and biofilm-enabled antibiotic tolerance. We now have substantial knowledge of the multicellular behaviour ofP. aeruginosain vitro. A major task for the future is to investigate how such in vitro data correlate with the in vivo behaviour ofP. aeruginosa, and how to treat chronic infections of this bacterium in patients.

Download Full-text

Macrophage-produced peroxynitrite induces antibiotic tolerance and supersedes intrinsic mechanisms of persister formation

Infection and Immunity ◽

10.1128/iai.00286-21 ◽

2021 ◽

Author(s):

Jenna E. Beam ◽

Nikki J. Wagner ◽

John C. Shook ◽

Edward S.M. Bahnson ◽

Vance G. Fowler ◽

...

Keyword(s):

Pure Culture ◽

Host Response ◽

Therapeutic Strategy ◽

Antibiotic Tolerance ◽

Activated Macrophages ◽

Human Pathogen ◽

Persister Cells ◽

Host Interaction ◽

Bacterial Interaction ◽

Antibiotic Failure

Staphylococcus aureus is a leading human pathogen that frequently causes chronic and relapsing infections. Antibiotic tolerant persister cells contribute to frequent antibiotic failure in patients. Macrophages represent an important niche during S. aureus bacteremia and recent work has identified a role for oxidative burst in the formation of antibiotic tolerant S. aureus . We find that host-derived peroxynitrite, the reaction product of superoxide and nitric oxide, is the main mediator of antibiotic tolerance in macrophages. Using a collection of S. aureus clinical isolates, we find that, despite significant variation in persister formation in pure culture, all strains were similarly enriched for antibiotic tolerance following internalization by activated macrophages. Our findings suggest that host interaction strongly induces antibiotic tolerance and may negate bacterial mechanisms of persister formation, established in pure culture. These findings emphasize the importance of studying antibiotic tolerance in the context of bacterial interaction with the host suggest that modulation of the host response may represent a viable therapeutic strategy to sensitize S. aureus to antibiotics.

Download Full-text

The msaABCR Operon Regulates Persister Formation by Modulating Energy Metabolism in Staphylococcus aureus

Frontiers in Microbiology ◽

10.3389/fmicb.2021.657753 ◽

2021 ◽

Vol 12 ◽

Author(s):

Shanti Pandey ◽

Gyan S. Sahukhal ◽

Mohamed O. Elasri

Keyword(s):

Staphylococcus Aureus ◽

Energy Metabolism ◽

Tca Cycle ◽

Antibiotic Tolerance ◽

Atp Content ◽

Persister Cells ◽

Metabolic Genes ◽

Starting Point ◽

Metabolic Activities ◽

Systemic Infections

Staphylococcus aureus is a major human pathogen that causes chronic, systemic infections, and the recalcitrance of these infections is mainly due to the presence of persister cells, which are a bacterial subpopulation that exhibits extreme, yet transient, antibiotic tolerance accompanied by a transient halt in growth. However, upon cessation of antibiotic treatment, a resumption in growth of persister cells causes recurrence of infections and treatment failure. Previously, we reported the involvement of msaABCR in several important staphylococcal phenotypes, including the formation of persister cells. Additionally, observations of the regulation of several metabolic genes by the msaABCR operon in transcriptomics and proteomics analyses have suggested its role in the metabolic activities of S. aureus. Given the importance of metabolism in persister formation as our starting point, in this study we demonstrated how the msaABCR operon regulates energy metabolism and subsequent antibiotic tolerance. We showed that deletion of the msaABCR operon results in increased tricarboxylic acid (TCA) cycle activity, accompanied by increased cellular ATP content and higher NADH content in S. aureus cells. We also showed that msaABCR (through MsaB) represses the ccpE and ndh2 genes, thereby regulating TCA cycle activity and the generation of membrane potential, respectively. Together, the observations from this study led to the conclusion that msaABCR operon deletion induces a metabolically hyperactive state, leading to decreased persister formation in S. aureus.

Download Full-text

Role of Global Regulators and Nucleotide Metabolism in Antibiotic Tolerance in Escherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00144-08 ◽

2008 ◽

Vol 52 (8) ◽

pp. 2718-2726 ◽

Cited By ~ 192

Author(s):

Sonja Hansen ◽

Kim Lewis ◽

Marin Vulić

Keyword(s):

Escherichia Coli ◽

Cell Formation ◽

Nucleotide Metabolism ◽

Flavin Mononucleotide ◽

Formation Mechanisms ◽

Antibiotic Tolerance ◽

Persister Cells ◽

Global Regulators ◽

Persister Cell

ABSTRACT Bacterial populations produce a small number of persister cells that exhibit multidrug tolerance. Persister cells are largely responsible for the antibiotic recalcitrance of biofilm infections. The mechanism of persister cell formation largely remains unknown due to the challenges in identifying persister genes. We screened an ordered comprehensive library of 3,985 Escherichia coli knockout strains to identify mutants with altered antibiotic tolerance. Stationary-state cultures in 96-well plates were exposed to ofloxacin at a concentration which allows only tolerant persister cells to survive. The persister cell level of each culture was determined. A total of 150 mutants with decreased persistence were identified in the initial screen, and subsequent validation confirmed that neither the growth rate nor the ofloxacin MIC was affected for 10 of them. The genes affected in these strains were dnaJ and dnaK (chaperones), apaH (diadenosine tetraphosphatase), surA (peptidyl-prolyl cis-trans isomerase), fis and hns (global regulators), hnr (response regulator of RpoS), dksA (transcriptional regulator of rRNA transcription), ygfA (5-formyl-tetrahydrofolate cyclo-ligase), and yigB (flavin mononucleotide [FMN] phosphatase). The prominent presence of global regulators among these strains pointed to the likely redundancy of persister cell formation mechanisms: the elimination of a regulator controlling several redundant persister genes would be expected to produce a phenotype. This observation is consistent with previous findings for a possible role of redundant genes such as toxin/antitoxin modules in persister cell formation. ygfA and yigB were of special interest. The mammalian homolog of YgfA (methenyltetrahydrofolate synthetase) catalyzes the conversion of 5-formyl-tetrahydrofolate (THF) into the rapidly degraded 5,10-methenyl-THF, depleting the folate pool. The YigB protein is a phosphatase of FMN which would deplete the pool of this cofactor. Stochastic overexpression of these genes could lead to dormancy and, hence, tolerance by depleting the folate and FMN pools, respectively. Consistent with this scenario, the overexpression of both genes produced increased tolerance to ofloxacin.

Download Full-text