Photodynamic inactivation of antibiotic resistant strain of Pseudomonas aeruginosa by porphyrins induced by delta-aminolaevulinic acid.
OBJECTIVE
The widespread occurrence of antibiotic resistant strains of Pseudomonas aeruginosa in hospitals is a matter of growing concern. We report the results of a study on photodynamic inactivation of antibiotic resistant strain of P. aeruginosa by delta-aminolaevulinic acid (ALA).


METHODS
Exponentially growing P. aeruginosa cells were incubated in growth medium with ALA for various durations. Subsequently, the cells were washed and resuspended in phosphate buffered saline (PBS). These cells were incubated with different concentrations of glutathione (GSH) in PBS for 15 min. Porphyrins synthesized with and without GSH were detected by fluorescence spectroscopy. The ALA treated cells were irradiated with light at 405 nm with and without subsequent incubation in GSH. Cell survival was measured by colony forming ability.


RESULTS
Incubation of cells in growth medium with ALA led to increased synthesis of protoporphyrins in cells which saturated beyond 4 h. The level of protoporphyrin synthesis increased significantly when ALA treated cells were subsequently incubated with GSH in PBS for 15 min. Irradiation of cells incubated with ALA alone led to weak inactivation. However, substantial cell death was observed in ALA treated cells irradiated in the presence of 15 mM GSH.


CONCLUSIONS
Photodynamic inactivation of P. aeruginosa by ALA induced porphyrins can be enhanced if ALA treated cells are further incubated with GSH and irradiated using 405 nm light. These findings may be useful for inactivation of antibiotic resistant strains of P. aeruginosa causing burn and wound infections in hospitalized patients.
Sharma
Mrinalini
M
Biomedical Applications Section, Center for Advanced Technology, Indore, India.
Bansal
Harsha
H
Gupta
Pradeep Kumar
PK
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D004351:Drug Resistance; D006801:Humans; D008027:Light; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011166:Porphyrins / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology* / Q000528:radiation effects
D017319:Photosensitizing Agents; D011166:Porphyrins; D000622:Aminolevulinic Acid