Scientific article
OA Policy
English

Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy

Publication date2022-08-20
First online date2022-08-20
Abstract

Knowledge of photo-oxidative stress responses in bacteria that survive antimicrobial photodynamic therapy (aPDT) is scarce. Whereas aPDT is attracting growing clinical interest, subsequent stress responses are crucial to evaluate as they may lead to the up-regulation of pathogenic traits. Here, we aimed to assess transcriptional responses to sublethal aPDT-stress and identify potential connections with virulence-related genes. Six Enterococcus faecalis strains were investigated; ATCC 29212, three dental root-canal isolates labelled UmID1, UmID2 and UmID3 and two vancomycin-resistant isolates labelled A1 and A2. TMPyP was employed as a photosensitiser. A viability dose-response curve to increasing concentrations of TMPyP was determined by culture plating. Differential expression of genes involved in oxidative stress responses (dps and hypR), general stress responses (dnaK, sigma-factorVand relA), virulence-related genes (ace, fsrC and gelE) and vancomycin-resistance (vanA) was assessed by reverse-transcription qPCR. TMPyP-mediated aPDT inactivated all strains with comparable efficiencies. TMPyP at 0.015 μM was selected to induce sublethal photo-oxidative stress. Despite heterogeneities in gene expression between strains, transcriptional profiles revealed up-regulations of transcripts dps, hypR as well as dnaK and sigma factorVafter exposure to TMPyP alone and to light-irradiated TMPyP. Specifically, the alternative sigma factorVreached up to 39 ± 113-fold (median ± IQR) (p = 0.0369) in strain A2. Up-regulation of the quorum sensing operon, fsr, and its downstream virulence-related gelatinase gelE were also observed in strains ATCC-29212, A1, A2 and UmID3. Finally, photo-oxidative stress induced vanA-type vancomycin-resistance gene in both carrier isolates, reaching up to 3.3 ± 17-fold in strain A2 (p = 0.015). These findings indicate that, while aPDT successfully inactivates vancomycin-resistant and naïve strains of E. faecalis, subpopulations of surviving cells respond by co-ordinately up-regulating a network of genes involved in stress survival and virulence. This includes the induction of vancomycin-resistance genes in carrier isolates. These data may provide the mechanistic basis to circumvent bacterial responses and improve future clinical protocols.

Keywords
  • Antimicrobial photodynamic therapy
  • Enterococcus faecalis
  • Extra-cytoplasmic function sigma factor V
  • Gene expression
  • Photo-oxidative stress
  • Vancomycin-resistance
Citation (ISO format)
MANOIL, Daniel et al. Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy. In: Journal of photochemistry and photobiology. B, Biology, 2022, vol. 234, p. 112547. doi: 10.1016/j.jphotobiol.2022.112547
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Article (Published version)
Identifiers
ISSN of the journal1011-1344
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Technical informations

Creation31/08/2022 08:58:00
First validation31/08/2022 08:58:00
Update time16/03/2023 07:17:33
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