Inhibition of Multidrug-Resistant Pseudomonas aeruginosa with Rose Bengal Photodynamic Antimicrobial Therapy: In vitro

Abstract

Purpose : Pseudomonas aeruginosa is the leading cause of gram-negative bacterial keratitis and has worse clinical prognosis than other forms of bacterial keratitis. Increased antibiotic resistance makes medical management of these infections challenging. One such example is multidrug-resistant (MDR) Pseudomonas aeruginosa which is resistant to the most common antimicrobials including: resistance to fluoroquinolones (ciprofloxacin, levofloxacin) aminoglycosides (amikacin, gentamicin, tobramycin), cephalosporins (ceftazidime, cefepime) and carbapenems (imipenem, meropenem). Novel therapies are needed to treat these challenging microorganisms. This study will measure the in vitro inhibitory effect of rose bengal photodynamic therapy against recent MDR Pseudomonas aeruginosa isolates from patients with infectious keratitis.

Methods : Five clinical MDR Pseudomonas aeruginosa isolates from patients with confirmed infectious keratitis were isolated and prepared into inoculum of concertation 10E8 CFU/mL. Three Groups were tested: control, 0.1% rose bengal dark, and 0.1% rose bengal green light. Inoculum suspension was mixed with either NaCL (control) or 0.1% rose bengal for a final organism concentration of 10E4 CFU/mL. 1mL aliquots were plated on blood agar plates in triplicate. Agar plates were divided by light condition and relevant groups were exposed to green light irradiation for 15 minutes with a custom-built green light LED array. At 48 hours, agar plates were photographed to measure bacterial growth inside of a centered 47-mm irradiation zone.

Results : Rose Bengal without green light had no impact on the growth of MDR Pseudomonas aeruginosa strains when compared to the control group. Rose Bengal with green light fully inhibited all MDR Pseudomonas aeruginosa strains inside the irradiation zone.

Conclusions : MDR Pseudomonas aeruginosa can be inhibited by rose bengal photodynamic antimicrobial therapy with 0.1% concentrations. The effectiveness of different exposure time, rose bengal concentration, and light energy were not explored but are warranted for further study. The use of rose bengal photodynamic therapy in MDR Pseudomonas is promising as an alternative to current treatments.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1. Growth inhibition results from RB PDAT. (Top) Control plates (Middle) RB without irradiation (Bottom) RB with irradiation.