The Effect of a Cationic Porphyrin on Pseudomonas aeruginosa Biofilms

Abstract

Current studies have indicated the utility of photodynamic therapy using porphyrins in the treatment of bacterial infections. Photoactivation of porphyrins results in the production of singlet oxygen ((1)O(2)) that damages biomolecules associated with cells and biofilms, e.g., proteins, polysaccharides, and DNA. The effect of a cationic porphryin on P. aeruginosa PAO1 biofilms was assessed by exposing static biofilms to 5,10,15,20-tetrakis(1-methyl-pyridino)-21H,23H-porphine, tetra-p-tosylate salt (TMP) followed by irradiation. Biofilms were visualized using confocal laser scanning microscopy (CLSM) and cell viability determined using the LIVE/DEAD BacLight viability assay and standard plate counts. At a concentration of 100 μM TMP, there was substantial killing of P. aeruginosa PAO1 wild-type and pqsA mutant biofilms with little disruption of the biofilm matrix or structure. Exposure to 225 μM TMP resulted in almost complete killing as well as the detachment of wild-type PAO1 biofilms. In contrast, pqsA mutant biofilms that contain less extracellular DNA remained intact. Standard plate counts of cells recovered from attached biofilms revealed a 4.1-log(10) and a 3.9-log(10) reduction in viable cells of wild-type PAO1 and pqsA mutant strains, respectively. Our results suggest that the action of photoactivated TMP on P. aeruginosa biofilms is two-fold: direct killing of individual cells within biofilms and detachment of the biofilm from the substratum. There was no evidence of porphyrin toxicity in the absence of light; however, biofilms pretreated with TMP without photoactivation were substantially more sensitive to tobramycin than untreated biofilms.

Susceptibility of clinical isolates of Candida to photodynamic effects of curcumin

“…According to CV staining assay, CUR-mediated PDT not only reduced the metabolic activity of Candida biofilms, but also decreased the biofilm biomass of all species evaluated. It has previously been suggested that PDT can target bacterial biofilms by killing the cells and disrupting biofilm architecture [41]. Light micrographs performed by Goulart et al [42] showed that PDT was able to detach bacterial cells from the well in which biofilms were formed.…”

Silver Nanoparticles as Potential Antibacterial Agents

“…Several studies have shown that AgNP activity is strongly dependent on the size [46,47]. In fact, the bactericidal activity of AgNPs of smaller dimensions (<30 nm) was found to be optimal against Staphylococcus aureus and Klebsiella pneumoniae [49]. Smaller nanoparticles seem to have a superior ability to penetrate into bacteria.…”

“…Alteration of membrane [28,41,47] Listeria monocytogenes Morphological changes, separation of the cytoplasmic membrane from the cell wall, plasmolysis [47] Micrococcus luteus Alteration of membrane [28] Nitrifying bacteria inhibits respiratory activity [31] Pseudomonas aeruginosa Irreversible damage on bacterial cells; Alteration of membrane permeability and respiration [17,28,32,33,36,[41][42][43][44][48][49][50] Proteus mirabilis Alteration of cell wall and cytoplasm. [43,44] …”

Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

“…Tetracationic porphyrin TMPyP4 was used on Pseudomonas aeruginosa biofilms, and caused direct cell killing as well as detachment of the biofilm after light activation. The enhanced killing of the cells when TMPyP was used in the combination with tobramycin indicates a light-independent mechanism, and it has been suggested that the two mechanisms together could be employed for the treatment of biofilms and infections not easily reachable by light (Collins et al 2010).…”