Photodynamic inactivation of Klebsiella pneumoniae and E.coli bacteria using two symmetrical substituted zinc (II) phthalocyanines

ROMINA CLEMENTI; MARIANA MIRETTI; MARIA TERESA BAUMGARTNER; TOMAS C. TEMPESTI

Cordoba

Congreso; 3º Congreso bioquímico de Córdoba 2015; 2015

COBICO. Colegio de bioquímicos de la provincia de Cordoba

The widespread occurrence of antibiotic-resistant microorganisms makes clear the need for new antimicrobial treatments.Photodynamic therapy (PDT) as a method utilizes visible or ultraviolet light in combination with a photosensitizing agent toinduce several phototoxic reactions, which results in cell damage or death. Photodynamic reaction involves a light absorption bya photosensitizer to excite the molecule to the excited singlet state. This excited state undergoes intersystem crossing to thelong-lived triplet state, which can react with molecular oxygen inducing reactive species such as singlet oxygen, superoxide, andradicals. These reactive species can oxidize the surrounding bioorganic molecules leading to cell death. Phthalocyanines, whichare characterized with far red wavelength absorption (>670 nm), long triplet life time (~1 ms), and high quantum yields of singletoxygen generation (>0.2), have been studied as drugs in microbial photodynamic inactivation. The positively chargedphthalocyanines can effectively photoinactivate both, gram-positive and gram-negative bacteria. The gram-positive are moresusceptible to photoinactivation than gramnegative due to the morphological characteristics of their membranes. Klebsiellapneumoniae carbapenemase (KPC)-producing bacteria are an emerging group of highly drug-resistant bacteria causinginfections associated with significant morbidity and mortality. The photodynamic activity of two new cationic phthalocyanines(TMZnPc and TMAZnPc) and commercial ZnPc, was evaluated in KPC-producing bacteria and Escherichia coli ATCC 25922bacteria. Both KPC-producing and E. coli ATCC 25922 were incubated with photosensitizers for 30 minutes in the dark at 37°C. The photoinactivation of the microorganism was determinated for different irradiation times (10, 15 and 30 minutes). TheTMZnPC phthalocyanine showed higher antibacterial properties than TMAZnPc phthalocyanine and ZnPC phtalocyanine forKPC-producing bacteria. The results was 3.9 log reduction (i.e. 99.9% cell killing), 2.6 log reduction (i.e. 99.8% cell killing) and1.9 log reduction (i.e. 99.2% cell killing) respectively. For E. coli ATCC 25922 bacteria the results was 2.4 log reduction (i.e. 99.7% cell killing) to ZnPc, 6.1 log reduction (i.e. 100% cell killing) to TMAZnPc and 7.1 log reduction (i.e. 100% cell killing) toTMZnPc. These results suggest that the zinc phthalocyanine cationic presented very interesting properties to be used in futureas a photodynamic therapy in inactivation of bacteria-resistant and sensitive.