Factors Determining the Susceptibility of Bacteria to Antibacterial Photodynamic Inactivation

Abstract

Photodynamic inactivation of microorganisms (aPDI) is an excellent method to destroy antibiotic-resistant microbial isolates. The use of an exogenous photosensitizer or irradiation of microbial cells already equipped with endogenous photosensitizers makes aPDI a convenient tool for treating the infections whenever technical light delivery is possible. Currently, aPDI research carried out on a vast repertoire of depending on the photosensitizer used, the target microorganism, and the light delivery system shows efficacy mostly on in vitro models. The search for mechanisms underlying different responses to photodynamic inactivation of microorganisms is an essential issue in aPDI because one niche (e.g., infection site in a human body) may have bacterial subpopulations that will exhibit different susceptibility. Rapidly growing bacteria are probably more susceptible to aPDI than persister cells. Some subpopulations can produce more antioxidant enzymes or have better performance due to efficient efflux pumps. The ultimate goal was and still is to identify and characterize molecular features that drive the efficacy of antimicrobial photodynamic inactivation. To this end, we examined several genetic and biochemical characteristics, including the presence of individual genetic elements, protein activity, cell membrane content and its physical properties, the localization of the photosensitizer, with the result that some of them are important and others do not appear to play a crucial role in the process of aPDI. In the review, we would like to provide an overview of the factors studied so far in our group and others that contributed to the aPDI process at the cellular level. We want to challenge the question, is there a general pattern of molecular characterization of aPDI effectiveness? Or is it more likely that a photosensitizer-specific pattern of molecular characteristics of aPDI efficacy will occur?

Preliminary Studies of Antimicrobial Activity of New Synthesized Hybrids of 2-Thiohydantoin and 2-Quinolone Derivatives Activated with Blue Light

“…For most of the compounds the higher sensitivity is noticed for Gram-positive bacteria and P. aeruginosa . Such an observation is in line with previously reported [ 34 ]. We suspect that the activity of the studied compounds irradiated with blue light might be a result of their binding to the cell membranes of the bacteria.…”

“…The bactericidal effects of blue light radiation have been studied in many bacterial strains, such as Propionibacterium acnes , Helicobacter pylori , Escherichia coli , Staphylococcus aureus , and Pseudomonas aeruginosa [ 30 , 31 , 32 , 33 ]. Gram-positive and Gram-negative bacteria vary significantly in response to ROS sensitive molecules, because of the structural differences of the cell envelopes [ 34 ].…”

Can Gram-Negative Bacteria Develop Resistance to Antimicrobial Blue Light Treatment?

“…The IM is a phospholipid bilayer responsible for, inter alia, transport (D- efflux pumps) and sodium-potassium ions (E) [ 30 ]. The presence of the outer and inner membrane leads to decreased aPDI effectiveness against Gram-negative bacteria [ 31 ].…”

In situ Forming Hyperbranched PEG—Thiolated Hyaluronic Acid Hydrogels With Honey-Mimetic Antibacterial Properties

“…One reason is the different structural composition of gram-positive and gram-negative bacteria: gram-negative bacteria have an outer lipid-based membrane that is additionally decorated with lipopolysaccharides (LPS), while gram-positive bacteria lack this outer lipid bilayer. The peptidoglycans of the outer layer of the gram-positive bacteria have been reported to be significantly more sensitive to oxidation ( Rapacka-Zdończyk et al, 2021 ). In addition, Lee et al showed that the LPS of the gram-negative bacteria have an antioxidant effect and thus eliminate part of the hydrogen peroxide produced and released in situ ( Lee et al, 2017 ).…”