Dose-Dependent Inhibition of Multidrug Resistant Pseudomonas Aeruginosa in Vitro With Combination of Riboflavin and Ultraviolet-A Light
Narrative Responses:
Purpose
To evaluate the effect of increasing doses of riboflavin and ultraviolet a light (UVA) combination on a strain of multi drug resistant Pseudomonas aeruginosa (PA) in vitro.
Methods
Two strains of PA – a quality controlled ATCC-27853 PA sensitive to most antibiotics and a proven multi drug resistant PA (MDR-PA) were inoculated onto plates of Mueller Hinton agar as lawn cultures . Riboflvin (in 0.1% dextran) was then instilled over these plates and these plates were then exposed to a varying period of exposure to UV-A light which was 30, 60 and 90 minutes. All plates were incubated at 37°C between and after the exposures and the zone of inhibition of growth was observed after 18 hours. Digital images of each plate were analysed using image analysis software.
Results
The plate seeded with drug sensitive PA and exposed to combination of riboflavin and UVA showed a clear zone of inhibition of growth in the centre corresponding to the area of exposure, which was measured to be 53.91 mm2. The plate seeded with MDR-PA and treated with single exposure of riboflavin and UVA for 30 minutes showed a faint, barely discernible zone of clearance in the centre. The plates seeded with MDR-PA and subjected to two and three exposures of riboflavin and UVA for 30 minutes each displayed well demarcated zones of clearing measuring 61.67 mm2 and 99.25 mm2 respectively.
Conclusion
There is a definite dose dependent antimicrobial effect of this treatment, even on multi drug resistant bacteria. Elucidation of optimum treatment protocols, customized according to the sensitivity of the causative organism may help define the role of riboflavin and UVA combination treatment in ocular infections due to drug resistant organisms.