The in vitro Photoinactivation of Helicobacter pylori by a Novel LED-Based Device

Abstract

The rise of antibiotic resistance is the main cause for the failure of conventional antibiotic therapy of Helicobacter pylori infection, which is often associated with severe gastric diseases, including gastric cancer. In the last years, alternative non-pharmacological approaches have been considered in the treatment of H. pylori infection. Among these, antimicrobial PhotoDynamic Therapy (aPDT), a light-based treatment able to photoinactivate a wide range of bacteria, viruses, fungal and protozoan parasites, could represent a promising therapeutic strategy. In the case of H. pylori, aPDT can exploit photoactive endogenous porphyrins, such as protoporphyrin IX and coproporphyrin I and III, to induce photokilling, without any other exogenous photosensitizers. With the aim of developing an ingestible LED-based robotic pill for minimally invasive intragastric treatment of H. pylori infection, it is crucial to determine the best illumination parameters to activate the endogenous photosensitizers. In this study the photokilling effect on H. pylori has been evaluated by using a novel LED-based device, designed for testing the appropriate LEDs for the pill and suitable to perform in vitro irradiation experiments. Exposure to visible light induced bacterial photokilling most effectively at 405 nm and 460 nm. Sub-lethal light dose at 405 nm caused morphological changes on bacterial surface indicating the cell wall as one of the main targets of photodamage. For the first time endogenous photosensitizing molecules other than porphyrins, such as flavins, have been suggested to be involved in the 460 nm H. pylori photoinactivation.

Microbial Photoinactivation by Visible Light Results in Limited Loss of Membrane Integrity

“…However from the appearance of totally destroyed cells of S. aureus [ 16 ], significant leakage of intracellular substance in A. baumannii [ 27 ] as well as disrupted cell walls, and complete loss of cytoplasmic components at higher doses in C. albicans [ 28 ] , and release of intracellular components of Listeria monocytogenes and P. fluorescens after 4 days of exposure to visible light [ 29 ], it was concluded that membrane permeability must play an important role in photoinactivation processes. Scanning electron microscopy images depicted structures that looked like holes on Helicobacter pylori after 9.3 J/cm 2 [ 57 ].…”

A New High-Throughput-Screening-Assay for Photoantimicrobials Based on EUCAST Revealed Unknown Photoantimicrobials in Cortinariaceae

“…The crucial part of every PhotoMIC assay is the irradiation. Nowadays, dental curing lights ( Nielsen et al, 2015 ) or handmade LED setups ( Morici et al, 2020 ) replaced previously used light bulbs and lasers ( Calin and Parasca, 2009 ). Dental lights – originally designed to polymerize composite fillings – allow only single irradiation and, therefore, limit the throughput.…”

Corynebacterium jeikeium Dormant Cell Formation and Photodynamic Inactivation

“…For example, cyclodextrin with bound porphyrins has been applied for the treatment of Staphylococcus aureus (Hanakova et al, 2014). Endogenous porphyrins were utilized for the killing of pathogenic periodontal bacteria (Cieplik et al, 2014;Hope et al, 2016), skin pathogens St. aureus (Ashkenazi et al, 2003;Lipovsky et al, 2009), Staphylococcus carnosus (Hoenes et al, 2020), Hemophilis parainfluenzae (van der Meulen et al, 1997) and Helicobacter pylori (Hamblin et al, 2005;Morici et al, 2020).…”