Photodynamic Inactivation of Antibiotic-Resistant and Sensitive Aeromonas hydrophila with Peripheral Pd(II)- vs. Zn(II)-Phthalocyanines

Abstract

The antimicrobial multidrug resistance (AMR) of pathogenic bacteria towards currently used antibiotics has a remarkable impact on the quality and prolongation of human lives. An effective strategy to fight AMR is the method PhotoDynamic Therapy (PDT). PDT is based on a joint action of a photosensitizer, oxygen, and light within a specific spectrum. This results in the generation of singlet oxygen and other reactive oxygen species that can inactivate the pathogenic cells without further regrowth. This study presents the efficacy of a new Pd(II)- versus Zn(II)-phthalocyanine complexes with peripheral positions of methylpyridiloxy substitution groups (pPdPc and ZnPcMe) towards Gram-negative bacteria Aeromonas hydrophila (A. hydrophila). Zn(II)-phthalocyanine, ZnPcMe was used as a reference compound for in vitro studies, bacause it is well-known with a high photodynamic inactivation ability for different pathogenic microorganisms. The studied new isolates of A. hydrophila were antibiotic-resistant (R) and sensitive (S) strains. The photoinactivation results showed a full effect with 8 µM pPdPc for S strain and with 5 µM ZnPcMe for both R and S strains. Comparison between both new isolates of A. hydrophila (S and R) suggests that the uptakes and more likely photoinactivation efficacy of the applied phthalocyanines are independent of the drug sensitivity of the studied strains.

Applications of Antimicrobial Photodynamic Therapy in Aquaculture: Effect on Fish Pathogenic Bacteria

“…This modification can also alter their photophysicochemical properties for enhanced singlet oxygen generation. Pcs have, as a result, shown aPDT against fish pathogenic bacteria [37][38][39][40][49][50][51]. For example, Mantareva et al reported the inactivation of Aeromonas hydrophila and Flavobacterium hydatis using Pd(II) and Zn(II)-phthalocyanine complexes (activated using a 665 nm light source with an output power of 100 mW cm −2 , and at a light dose of 50 J•cm −2 for 20 min) [37,40].…”

“…Pcs have, as a result, shown aPDT against fish pathogenic bacteria [37][38][39][40][49][50][51]. For example, Mantareva et al reported the inactivation of Aeromonas hydrophila and Flavobacterium hydatis using Pd(II) and Zn(II)-phthalocyanine complexes (activated using a 665 nm light source with an output power of 100 mW cm −2 , and at a light dose of 50 J•cm −2 for 20 min) [37,40].…”

Photodynamic Inactivation of Opportunistic Premise Plumbing Pathogens and Their Biofilms

“…Similarly, complete photoinactivation of MDR and sensitive strains of A. hydrophila was achieved after 48 h using tetra-methylpyridiloxy-substituted Zn(II) phthalocyanine (Zn-PcMe) (5 µM) and red light (665 nm; fluence rate 100 mW/cm 2 ; light dose 50 J/cm 2 ) [175]. Interestingly, the Pd(II) analogue (pPdPc) was less efficient, and PDI with 8 µM of pPdPc resulted in a 5.47-log reduction in the sensitive strain, and a 3.32-log decrease for MDR, although the accumulation of pPdPc was very similar between MDR and sensitive strains [175].…”

Photodynamic Therapy

“…The photoinactivation demonstrated a complete activity with 8 µM pPdPc for antibiotic-sensitive strain and with 5 µM ZnPcMe for both antibiotic-resistant and sensitive strains. These results suggest that the uptakes and photoinactivation efficacy of the applied phthalocyanines are not related to the drug sensitivity of both strains (for more information, see [ 17 ]). In a study by Ramachandran et al, TiO 2 NPs and TiO 2 conjugated with N-GQDs/TiO 2 NCs were synthetized via microwave-assisted synthesis and two-pot hydrothermal method, respectively.…”