Photoantimicrobials as a potential local approach to geriatric UTIs

Abstract

Aims: To test the efficacy of acceptable photoantimicrobial agents against bacterial pathogens implicated in complicated urinary tract infection (UTI) in comparison with conventionally employed antibacterials. Methods and Results: Toluidine blue (TB), methylene blue (MB), 5‐aminolaevulinic acid (ALA), trimethoprim and levofloxacin were employed in the study against the typical UTI‐implicated pathogens Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Proteus mirabilis. Standard bacterial cell culture was used to assay the activity both in the dark and under 660‐nm LED‐illuminated conditions. TB and MB were highly photoactive across the range and exhibited rapid kill rates, their effects being assayed after 20‐min illumination, rather than the 18‐h incubation employed with the other compounds. Trimethoprim was inactive against all bacteria except Pr. mirabilis, while levofloxacin maintained highly bactericidal activity throughout. ALA required high concentrations for effective action but, for porphyrin production in situ, also required an 18‐h incubation. Conclusions: TB and MB were highly and rapidly photobactericidal in comparison with the remaining agents tested. Significance and Impact of the Study: Ubiquitous catheterization of geriatric patients offers a portal for light delivery to the urinary tract. The photoantimicrobial approach thus offers considerable potential.

A Closer Look at Dark Toxicity of the Photosensitizer TMPyP in Bacteria

“…Using porphyrins or phenothiazines as photosensitizers, the research in the field of PIB has escalated showing first positive results regarding inactivation of different pathogens (17)(18)(19)(20)(21)(22)(23). The porphyrin TMPyP is a potent photosensitizer that preferentially generates singlet oxygen upon light irradiation and is widely used in PIB (24)(25)(26)(27).…”

Photoinactivation Using Visible Light Plus Water-Filtered Infrared-A (vis+wIRA) and Chlorine e6 (Ce6) Eradicates Planktonic Periodontal Pathogens and Subgingival Biofilms

“…The mechanism of aPDT action involves numerous structural and functional inactivations of microbial cells in parallel, making development of resistance against the photodynamic inactivation process much harder to be developed (Wainwright et al, 2010). In addition to their planktonic state, microorganisms exist preferentially as biofilms, where they are embedded in an extracellular matrix and possess different mechanisms to protect themselves against antimicrobials such as antibiotics or disinfectants (Chambless et al, 2006; Flemming and Wingender, 2010).…”

Fast and Effective Photodynamic Inactivation of Multiresistant Bacteria by Cationic Riboflavin Derivatives

“…Using porphyrins or phenothiazins as photosensitizers, the research in the field of PIB has escalated showing first good results regarding inactivation of different pathogens [15] – [21] . However, many photosensitizers show low efficacy when simultaneously applied for different types of bacteria (Gram-positive, Gram-negative) or show moderate toxicity already without light.…”