Internalization of the PDZ and its photodynamic effect on the growth of ATCC and clinical strains ofE. coliandS. aureus

Abstract

The treatment of bacterial infections has been a challenge after the end of the 'era of antibiotics'. Bacteria are capable of causing many infectious diseases; therefore, with the increasing number of bacteria becoming resistant, development of alternative therapies is needed to minimize, or even eliminate the use of antibiotics. Photodynamic therapy (PDT) is a promising alternative to fight microorganism. In view of the increasing emergence of resistant bacteria and the limitations of conventional treatment, this study evaluated the effect of photodynamic therapy with photodithazine (PDZ) in inactivating bacterial strains of E. coli and S. aureus in vitro, comparing the behavior of clinical and ATCC strains. Confocal microscopy analysis was performed to determine the internalization of the PS and spectrophotometric technique was used to determine the growth of bacteria in vitro. PDT using PDZ was able to reduce the growth of S. aureus strains using the incubation time of 24 h, whereas no satisfactory results were obtained with 15 min incubation. The E. coli strains, tested at two incubation times, did not affectively reduce bacterial growth. Therefore, it is concluded that PDT using PDZ is viable when applied to the S. aureus strains, when suitable incubation times are used.

Efficiency of Antimicrobial Photodynamic Therapy with Photodithazine® on MSSA and MRSA Strains

“…As S. aureus and S. mutans are two Gram-positive bacteria, these results demonstrate that PDZ has a high potential to cause the inactivation of Gram-positive bacteria, which might be explained by the cell wall structure of these microorganisms. Gram-positive bacteria have dense layers of peptidoglycan interspersed with the formation of teichoic acids in their cell wall, which is a porous structure, with low electrical charge and does not represent an obstacle for the passage of small particles [22][23][24].…”

“…PDZ is a Ce6 modified by the addition of N-methyl-D-glucosamine, a solubilizing and stabilizing agent which facilitates its penetration into cells. In addition, it has molecular groups at its ends that may charge the PS, which can be a relevant factor in its interaction with the Gram-positive bacteria [23,25]. The PS aggregation decreases the potential to generate a singlet oxygen since the aggregates contribute to reducing the action time of the singlet and triplet states, affecting the cytotoxic effect responsible for the inactivation of the microorganisms [26].…”