Comparison of Photodynamic Action by Rose Bengal in Gram‐positive and Gram‐negative Bacteria

Abstract

Abskact-The photodynamic inactivation by illuminated Rose Bengal of a number of bacterial species was compared. The gram-positive species, Bacillus subtilis, Staphylococcus nureus, Streptococcus faecalis and Streptococcus salivarius, were inactivated about 200X more quickly (99% inactivation) than a Salmonella typhimurium wildtype strain. The Salmonella inactivation curve exhibited an initial lag time during which bacteria were not significantly inactivated. The lag time for inactivation of a derivative of the wildtype Salmonelln strain that is deficient in a large portion of its cell wall lipopolysaccharide coat was approximately half of the lag time for the wildtype strain but the subsequent rate of inactivation was approximately the same for the two strains. Dark preincubation of both Salmonella strains with Rose Bengal before illumination shortened the lag time, but did not increase the final rate of inactivation. Dark preincubation prior to illumination did not measurably change the inactivation curve of the gram-positive species. The lag time observed in the inactivation curves for Salmonella bacteria may reflect the time required for penetration of the Rose Bengal anion through the outer portion of the gram-negative cell wall to a critical location within the cell for effective photosensitization.

Rose Bengal-decorated silica nanoparticles as photosensitizers for inactivation of gram-positive bacteria

“…The use of free RB solution in photodynamic inactivation of a number of bacterial species had long been reported in the literature [23, 34]. It was found that some gram-positive bacteria ( Bacillus subtilis , S. aureus , Streptococcus faecalis and Streptococcus salivarius ) were inactivated by free RB dye ~200 times more quickly than the gram-negative Salmonella typhimurium .…”

Exogenous indirect photoinactivation of bacterial pathogens and indicators in water with natural and synthetic photosensitizers in simulated sunlight with reduced UVB

“…In Gram‐negative bacteria, the additional outer membrane may confer some protection against exogenous photoinactivation (Dahl et al . ; Mamone et al . ) that the Gram‐positive bacteria do not have.…”

Phenothiazinium Antimicrobial Photosensitizers Are Substrates of Bacterial Multidrug Resistance Pumps

“…These parameters could have included such variables as membrane structure, DNA and other cellular repair systems, and levels of antioxidant enzymes. RB and light probably kill bacteria by generating extracellular singlet oxygen that destroys the membrane from the outside in (7,8,33), while polycationic polymeric pL-c e6 is probably taken up into bacterial cells by a self-promoted uptake pathway, as described for other polycationic peptides (24). The finding that uptake levels of both MB and TBO by the NorA knockout mutant, wild-type, and overexpressing strains of S. aureus were proportional to levels of NorA expression suggests that the role of the MDRs is to pump out the PS from the cells and thereby lessen the phototoxicity observed upon illumination.…”