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. 2022 Feb 5;10(2):384.
doi: 10.3390/biomedicines10020384.

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

Vanya N Mantareva  1 , Vesselin Kussovski  2 , Petya Orozova  3 , Lyudmila Dimitrova  2 , Irem Kulu  4 , Ivan Angelov  1 , Mahmut Durmus  4 , Hristo Najdenski  2
Affiliations

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

Vanya N Mantareva et al. Biomedicines. .

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.

Keywords: Aeromonas hydrophila; antibiogram of bacterial isolates; antimicrobial multidrug resistance (AMR); palladium and zinc phthalocyanines; photodynamic therapy (PDT).

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Conflict of interest statement

The authors declare no conflict of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Synthesis of tetra-methylpyridiloxy-substituted Pd(II)- and Zn(II)-phthalocyanines.
Figure 2
Figure 2
Photodynamic inactivation of A. hydrophila (R and S) planktonic cultured with peripheral Pd(II)-phthalocyanine (pPdPc) and an LED at 665 nm irradiation. * p < 0.005; ** p < 0.008, and *** p < 0.01.
Figure 3
Figure 3
Uptake of Pd(II)-phthalocyanine (pPdPc) in A. hydrophila (R and S) strains as suspensions with different cell densities as obtained by fluorescence measurements.
Figure 4
Figure 4
Photodynamic inactivation of A. hydrophila (R and S) planktonic cultured with Zn(II)-phthalocyanine (ZnPcMe) and an LED at 665 nm irradiation. * p < 0.005; ** p < 0.008, and *** p < 0.01.
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