Related Experiment Videos
Selective lethal photosensitization of methicillin-resistant Staphylococcus aureus using an IgG-tin (IV) chlorin e6
Michelle L Embleton1, Sean P Nair, Barry D Cookson
1Department of Microbiology and Cellular Microbiology Research Group, Eastman Dental Institute for Oral Health Care Sciences, University College London, 256 Gray's Inn Road, London WC1X 8LD, UK.
Objectives:
The growing resistance of methicillin-resistant Staphylococcus aureus (MRSA) to conventional antimicrobial agents necessitates the development of alternative approaches to preventing and treating infections. One such approach is photodynamic therapy, whereby target cells are treated with light-activated drugs (photosensitizers). This investigation aimed to determine whether the ability of MRSA to express the IgG-binding protein, protein A, could be exploited to enable selective lethal photosensitization of the organism with a photosensitizer [tin (IV) chlorin e6; SnCe6] linked to IgG.
Methods:
Various strains of MRSA were exposed to light from a helium/neon laser in the presence of an IgG-SnCe6 conjugate and the survivors enumerated by viable counting. Controls consisted of suspensions irradiated in the presence or absence of the conjugate and suspensions kept in the dark in the presence of the conjugate. Similar experiments were also carried out using the unconjugated photosensitizer. The experiments were repeated using a suspension consisting of both EMRSA-16 and Streptococcus sanguis.
Results:
EMRSA-16 was killed by IgG-SnCe6 and SnCe6 in a light-dose- and photosensitizer-dependent manner. Greater kills were achieved with the IgG-SnCe6 than with the unconjugated SnCe6 using the same light energy dose and photosensitizer concentration. Furthermore, the IgG-SnCe6 conjugate, but not SnCe6, was able to kill EMRSA-16 selectively in a suspension that also contained S. sanguis without any reduction in the viable count of the latter.
Conclusion:
These results demonstrate that selective lethal photosensitization of MRSA can be achieved using an IgG-tin (IV) chlorin e6 conjugate. The effectiveness of killing was dependent, in part, on the particular MRSA strain used, with the clinically important EMRSA-16 strain being the most susceptible.
Insights
Researchers developed a targeted photodynamic therapy to combat antibiotic-resistant MRSA. By linking a photosensitizer to IgG, they selectively killed MRSA, showing promise for new infection treatments.
Area of Science:
- Microbiology
- Photochemistry
- Antimicrobial Resistance
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat due to widespread antimicrobial resistance.
- Photodynamic therapy (PDT) offers an alternative treatment strategy using light-activated photosensitizers.
- Targeting specific bacterial components is crucial for enhancing PDT efficacy and selectivity.
Purpose of the Study:
- To investigate the potential of exploiting MRSA's protein A for targeted photosensitization.
- To evaluate the efficacy of an immunoglobulin G (IgG)-conjugated photosensitizer (tin (IV) chlorin e6; SnCe6) against MRSA.
- To determine the selectivity of this targeted approach in mixed bacterial populations.
Main Methods:
- MRSA strains were exposed to laser light in the presence of an IgG-SnCe6 conjugate.
- Viable bacterial counts were used to enumerate survivors after treatment.
- Control experiments included irradiation without the conjugate and incubation in the dark.
- Experiments were also conducted with unconjugated SnCe6 and in mixed cultures with Streptococcus sanguis.
Main Results:
- The IgG-SnCe6 conjugate demonstrated light-dose and photosensitizer-dependent killing of MRSA (EMRSA-16).
- Targeted IgG-SnCe6 achieved greater bacterial reduction compared to unconjugated SnCe6 at equivalent concentrations and light doses.
- The IgG-SnCe6 conjugate selectively eliminated EMRSA-16 in the presence of S. sanguis, without affecting the latter.
Conclusions:
- Targeted photodynamic therapy using an IgG-SnCe6 conjugate is effective for lethal photosensitization of MRSA.
- The efficacy of this approach is strain-dependent, with EMRSA-16 showing high susceptibility.
- This targeted strategy offers a promising avenue for selective MRSA infection treatment.