Hypervirulent and hypermucoviscous strains of Klebsiella pneumoniae challenged by antimicrobial strategies using visible light

• Published in: International journal of antimicrobial agents 2020-07, Vol.56 (1), p.106025-106025, Article 106025
• Main Authors: dos Anjos, Carolina, Sabino, Caetano P., Sellera, Fábio P., Esposito, Fernanda, Pogliani, Fabio C., Lincopan, Nilton
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Antimicrobial photodynamic therapy; beta-Lactamases - metabolism; Disease Models, Animal; Extended-spectrum β-lactamase; Galleria mellonella; Humans; Klebsiella Infections - therapy; Klebsiella pneumoniae - drug effects; Klebsiella pneumoniae - isolation & purification; Klebsiella pneumoniae - pathogenicity; Klebsiella pneumoniae K1; Light; Moths - microbiology; Photoantimicrobials; Photochemotherapy - methods; Virulence; Virulence - drug effects; Virulence Factors
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2020.106025

•Hypervirulent Klebsiella pneumoniae infections are associated with high mortality rates.•Five hypervirulent strains were challenged by methylene blue-antimicrobial photodynamic therapy (MB-aPDT) and blue light photoinactivation.•All strains were effectively inactivated by both light-based antimicrobial platforms.•Hypermucoviscosity phenotype did not confer tolerance to MB-aPDT or blue light.•Photoinactivation could be used to treat localised infections and hospital environments. Introduction: Infections caused by hypervirulent and/or hypermucoviscous Klebsiella pneumoniae (K. pneumoniae) strains are frequently reported worldwide. Since convergence of hypervirulence and drug-resistance emerged as a serious clinical problem, novel therapeutic strategies are worthy of investigation. In this regard, antimicrobial photodynamic therapy and blue light have proven to be effective against a broad-spectrum of clinically relevant pathogens but have never been tested for hypervirulent/hypermucoviscous strains. Thus, this study investigated the influence of hypermucoviscosity and hypervirulence over the photoinactivation efficacy of blue light alone or antimicrobial photodynamic therapy mediated by methylene blue and red light. Methods: Five clinical isolates of K. pneumoniae were screened for hypermucoviscosity by string test and for hypervirulence by a Galleria mellonella model of systemic infection. Strains were then challenged by both photoinactivation methods performed in vitro. All tests also included a non-hypervirulent/hypermucoviscous control strain for comparison. Results: All K. pneumoniae strains were effectively inactivated by both light-based antimicrobial strategies. Hypervirulent/hypermucoviscous strains exposed to photodynamic therapy presented rapid and consistent inactivation kinetics, while blue light led to slower and more variable inactivation kinetics. Conclusion: Hypermucoviscosity and hypervirulence does not confer tolerance in K. pneumoniae against photoinactivation. Antimicrobial photodynamic therapy represents an interesting alternative to treat localised infections because it is a fast procedure with high effectiveness. On the other hand, antimicrobial blue light could be used to decontaminate hospital environments since no photosensitiser administration is required and harmful effects of ultraviolet light are avoided. Therefore, visible light-based strategies present great potential for the development of safe and effective antimicrobial