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Published on: July 2, 2013
Photodynamic inactivation of methicillin-resistant Staphylococcus aureus by using Giemsa dye as a photosensitizer
Cynthia S A Caires1, Alessandra R Lima2, Thalita H N Lima2
1Instituto de Física, Universidade Federal de Mato Grosso do Sul, 79070-900, Campo Grande, MS CP 549, Brazil; Escola de Saúde, Santa Casa de Campo Grande, Campo Grande, MS 79002-201, Brazil.
Abstract:
The rise of antibiotic-resistant bacteria calls for innovative approaches to combat multidrug-resistant strains. Here, the potential of the standard histological stain, Giemsa, to act as a photosensitizer (PS) for antimicrobial photodynamic inactivation (aPDI) against methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains is reported. Bioassays were performed using various Giemsa concentrations (ranging from 0.0 to 20.0 µM) under 625 nm illumination at a light dose of 30 J cm-2. Remarkably, Giemsa completely inhibited the growth of MSSA and MRSA bacterial colonies for concentrations at 10 µM and higher but exhibited no inhibitory effect without light exposure. Partition coefficient analysis revealed Giemsa's affinity for membranes. Furthermore, we quantified the production of reactive oxygen species (ROS) and singlet oxygen (1O2) to elucidate the aPDI mechanisms underlying bacterial inactivation mediated by Giemsa. These findings highlight Giemsa stain's potential as a PS in aPDI for targeting multidrug-resistant bacteria.
Insights
Giemsa stain shows potential as a photosensitizer for antimicrobial photodynamic inactivation (aPDI). This method effectively inhibited both methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) growth with light activation.
Area of Science:
- Microbiology
- Biochemistry
- Photomedicine
Background:
- Antibiotic resistance is a growing global health threat, necessitating novel therapeutic strategies.
- Traditional antimicrobial treatments are becoming less effective against multidrug-resistant bacteria.
- Innovative approaches are required to combat resistant bacterial infections.
Purpose of the Study:
- To investigate the potential of Giemsa stain as a photosensitizer (PS) for antimicrobial photodynamic inactivation (aPDI).
- To evaluate the efficacy of Giemsa-mediated aPDI against methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA).
- To elucidate the mechanisms of bacterial inactivation by Giemsa-mediated aPDI.
Main Methods:
- Bioassays were conducted using varying Giemsa concentrations (0.0–20.0 µM) under 625 nm illumination (30 J cm⁻²).
- Bacterial growth inhibition was assessed for MSSA and MRSA strains.
- Partition coefficient analysis was used to determine Giemsa's membrane affinity.
- Reactive oxygen species (ROS) and singlet oxygen (¹O₂) production were quantified.
Main Results:
- Giemsa at concentrations of 10 µM and higher completely inhibited MSSA and MRSA growth when combined with light.
- No significant inhibitory effect was observed without light exposure.
- Giemsa demonstrated affinity for bacterial membranes, and ROS/¹O₂ production was confirmed, indicating aPDI mechanisms.
Conclusions:
- Giemsa stain can function as an effective photosensitizer for antimicrobial photodynamic inactivation.
- Giemsa-mediated aPDI offers a promising strategy for combating both MSSA and MRSA infections.
- This study highlights a novel application for a conventional histological stain in fighting antibiotic resistance.
