The antimicrobial properties of new synthetic porphyrins

Abstract

The antimicrobial activity of new meso-tetrakis(N-methyl-6-quinolinyl)-substituted porphyrins and meso-tetrakis(N-methyl-6-quinolinyl)-substituted chlorins is described. The dark toxicity and photosensitising potentials of free-base (TQP and TQC) and its Sn(IV)-complexes [(TQP)Sn(IV) and (TQC)Sn(IV)] were tested on Gram-positive (Staphylococus aureus), Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and two species of yeasts (Candida albicans and Rhodotorula bogoriensis). The results described in this paper show that TQP and (TQP)Sn(IV) did not inhibit the growth of S. aureus in the dark, but efficiently photosensitize the inactivation of this Gram-positive bacteria. These porphyrins have no appreciable photosensitizing activity towards Gram-negative bacteria. However, (TQP)Sn(IV) shows high dark toxicity against E. coli and P. aeruginosa. The free-base derivatives demonstrated dark activity only in the case of P. aeruginosa. We suppose that these meso-tetrakis(N-methyl-6-quinolinyl)-substituted porphyrins can bind to the Gram-negative bacteria outer membrane receptors that transported vitamin B12. The meso-substituted chlorins TQC and (TQC)Sn(IV) have shown similar efficiency in the dark- and photoinactivation of S. aureus. They revealed a middle level of dark toxicity towards Gram-negative bacteria. The Sn(IV)-complex of chlorin in comparison with free base and metalloporphyrins are more effective in photoinactivation of Gram-negative bacteria. Yeasts, such as Candida albicans and Rhodotorula bogoriensis are more sensitive to photodynamic inactivation as bacterial cells. The effects of (TQP)Sn(IV) and (TQC)Sn(IV) are more expressed than effects of free bases.

Antimicrobial and anti-biofilm effect of a novel BODIPY photosensitizer againstPseudomonas aeruginosaPAO1

“…In the authors' previous studies GD11-mediated PDT was found active against both Gram-positive and Gram-negative bacteria, although the latter were, as expected, less sensitive to the treatment ). Among Gram-negative bacteria, the opportunistic pathogen P. aeruginosa is known to be less sensitive to photoinactivation than the commonly used model bacterium E. coli (Philippova et al 2003;Tegos et al 2006), which is also the case for GD11 mediated PDT. Nevertheless, an approximately 7 log reduction in viable cells of P. aeruginosa was achievable with a modest concentration increase (2.5 vs 1.5 μM) ( Figure S3).…”

“…The GD11 structure was designed in order to make it effective in PDT against Gram-negative bacteria, using E. coli as the target organism . Here, the efficacy of GD11-mediated PDT was tested against P. aeruginosa PAO1, a bacterium reported to be very much less sensitive to PDT than E. coli (Philippova et al 2003;Tegos et al 2006). Since antimicrobial PDT could be used as an anti-biofilm or an anti-biofouling treatment, a further investigation was aimed to assay this technique against P. aeruginosa biofilms grown in microplates and continuous culture flow-cells.…”

Effect of Organic Matter on the In Vitro Photoeradication of Pseudomonas aeruginosa by Means of a Cationic Tetraaryl‐porphyrin†

“…Applying the protocol standardized in this study, we were able to eradicate a particularly resistant microorganism such as Pseudomonas aeruginosa otherwise difficult to photoeradicate (3–6). Our tetracationic mesoaryl‐porphyrin was active at concentrations lower than those used for commercial photosensitizers (7,8).…”

Can microbial cells develop resistance to oxidative stress in antimicrobial photodynamic inactivation?

“…In recent years, many reports about the efficacy of APDI against P. aeruginosa have been published, and it has become clear that P. aeruginosa is particularly tolerant to photodynamically induced oxidative stress [73–75]. The ability of P. aeruginosa to produce pigments, combined with the ability to elicit an oxidative stress response [76], may thus contribute to survival to APDI-induced oxidative stress.…”