In vitro activity of nine cyanobacterial and ten microalgal newly isolated or culture collection strains against eight significant food-borne pathogens has been evaluated and compared. Water extracts and culture liquids of Gloeocapsa sp. and Synechocystis sp. demonstrated the widest spectrum of activity with minimal inhibitory concentration (MIC) ranging from 1.56 to 12.5 mg mL À1 . Culture liquid of Anabaena sp. had the highest activity (MIC = 0.39 mg mL À1 ) but only to Gram-positive bacteria. Ethanol extracts and fatty acids from all cyanobacteria and microalgae were active against Streptococcus pyogenes and/or Staphylococcus aureus. The fatty acids of Synechocystis sp. inhibited the growth of Bacillus cereus, Escherichia coli and Candida albicans (MIC values of 2.5-1.25 mg mL À1 , respectively). Exopolysaccharides (EPS) of Gloeocapsa sp. were the sample that exhibited activity against all test pathogens with lowest MIC values (0.125-1 mg mL À1 ). High activity with a narrower range of susceptible targets demonstrated the exopolysaccharides of Synechocystis sp. and Rhodella reticulata. Antimicrobial activity was proven for phycobiliproteins isolated from Synechocystis sp., Arthrospira fusiformis, Porphyridium aerugineum and Porphyridium cruentum, respectively. In conclusion Gloeocapsa sp. and Synechocystis sp. and especially their exopolysaccharides showed the most promising potential against the examined food pathogens.In vitro antimicrobial activity of microalgae H. Najdenski et al. ResultsSamples of all investigated cyanobacterial and microalgal strains were initially evaluated for antimicrobial activity by agar diffusion test. No biological activity of In vitro antimicrobial activity of microalgae H. Najdenski et al. 1539 In vitro antimicrobial activity of microalgae H. Najdenski et al.

No abstract

Visible light-absorbing cationic water-soluble gallium(III) phthalocyanines (GaPcs) peripherally substituted with four and eight methylpyridyloxy groups were synthesized and investigated as antimicrobial photodynamic sensitizers. The inserted large gallium ion in the phthalocyanine ligand is axially substituted by one hydroxyl group which prevents aggregation of the complexes in aqueous solution. The cellular uptake and the photodynamic activity for the representative strains of the Gram positive bacteria methicillin-resistant Staphylococcus aureus(MRSA) and Enterococcus faecalis, of the Gram negative bacterium Pseudomonas aeruginosa and of the fungus Candida albicans in planktonic phase were studied. The tetra-methylpyridyloxy substituted GaPc1 showed lower cellular uptake compared to the octa-methylpyridyloxy substituted GaPc2. The photodynamic activity of the GaPcs was studied in comparison to methylene blue (MB) and a photodynamically active Zn(II)-phthalocyanine with the same substitution (ZnPcMe). Photodynamic treatment with 3.0 μM GaPc1 at mild light conditions (50 J cm(-2), 60 mW cm(-2)) resulted in a high photoinactivation of the microorganisms in the planktonic phase nevertheless the dark toxicity of GaPc1 towards MRSA and E. faecalis. GaPcs against fungal biofilm grown on polymethylmethacrylate (PMMC) resin showed a complete inactivation at a higher concentration of GaPc2 (6.0 μM) and of the referent sensitizer ZnPcMe. However, the bacterial biofilms were not susceptible to treatment of GaPcs with only 1-2 log reduction of the biofilm. The bacterial biofilm E. faecalis was effectively inactivated only with MB. The water-soluble octa-methylpyridyloxy substituted GaPc2 has a potential value for photodynamic treatment of C. albicans biofilms formed on denture acrylic resin.

The Gram-negative Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum are major causative agents of aggressive periodontal disease. Due to increase in the number of antibiotic-resistant bacteria, antimicrobial Photodynamic therapy (aPDT) seems to be a plausible alternative. In this work, photosensitization was performed on Gram-positive and Gram-negative bacteria in pure culture using new-age cationic porphyrins, namely mesoimidazolium-substituted porphyrin derivative (ImP) and pyridinium-substituted porphyrin derivative (PyP). The photophysical properties of both the sensitizers including absorption, fluorescence emission, quantum yields of the triplet excited states and singlet oxygen generation efficiencies were evaluated in the context of aPDT application. The studied porphyrins exhibited high ability to accumulate into bacterial cells with complete penetration into early stage biofilms. As compared with ImP, PyP was found to be more effective for photoinactivation of bacterial strains associated with periodontitis, without any signs of dark toxicity, owing to its high photocytotoxicity.

Antibacterial photodynamic therapy is a pioneering method for the inactivation of pathogenic bacteria. Four tetra alkyl-substituted cationic phthalocyanines with different hydrocarbon chains attached to the pyridyloxy group were synthesized. These photodynamic sensitizers were studied for antibacterial inactivation of a multidrug-resistant strain of Gram-negative bacterium Aeromonas hydrophila. Aeromonas species are recognized as etiological agents of a wide spectrum of diseases in humans and animals. The uptake of phthalocyanines by the bacterial cells decreased with an increase in cell density. Following the phthalocyanine solubility from hydrophilic to hydrophobic complexes, the accumulation capacity increased. Full inactivation was achieved with phthalocyanine with (methoxy) pyridyloxy substitution following a short exposure time, low drug concentration and mild irradiation. Although the phthalocyanine with the longest hydrocarbon chain (C12) has some toxic effect in the absence of light, substantial phototoxic effect was obtained with the optimal combination of drug-irradiation parameters.

No abstract

Metal phthalocyanine complexes with different charges, hydrophobicity and metal ions were synthesized and studied for antimicrobial photodynamic therapy of pathogenic bacterial and fungal model strains. Ten positively charged complexes with the metals Zn ( II ), Al ( III ), Ga ( III ), In ( III ), Si ( IV ) and Ge ( IV ) in the center of the ligand and substituents at the ligand bearing four or eight N-alkylpyridyloxy groups were prepared. In addition, a negatively charged Zn ( II )-phthalocyanine with four sulfophenoxy-groups was synthesized. The absorption spectra showed low intensity of the Soret band in the UV part of the spectrum and the intense Q-band in the red to far red region (λ = 671–697 nm). The fluorescence was determined with quantum yields between 0.1–0.33 and life-times 2.8–4.9 ns in dependence of the kind of metal ion and the substituents. In organic solvents all complexes exist in a monomeric state but in aqueous solution they show aggregation with the exception of Ga ( III ) phthalocyanines. The singlet oxygen quantum yields were evaluated in dependence on the metals, substituents and the media with values between 0.16–0.68. The cationic metal phthalocyanines were taken-up by pathogenic cells in a higher amount as compared to the anionic complex. Three of the studied phthalocyanines namely tetra-N-methylpyridyloxy-phthalocyanine Zn ( II ) and tetra- and octa-N-methylpyridyloxy- Ga ( III ) phthalocyanines showed a high photodynamic efficacy towards most of the studied microorganisms in suspensions.

No abstract