Photodynamic anti-gram-positive bacterial activity of pharmaceutical-grade rose bengal

Abstract

This invention contemplates combined use of a rose bengal (RB) derivative with irradiation of bacteria with light to treat and kill the irradiated bacteria. In one aspect, Gram-positive bacteria are treated in a method in which the bacteria are contacted with an aqueous pharmaceutical composition containing a rose bengal (RB) compound of Formula I, discussed within, dissolved or dispersed therein at about 0.2 to about 3.1 µg/mL. Those contacted bacteria are contacted with light of the wavelength about 500 nm to about 600 nm for a time period of about 1 to about 10 minutes to provide a light dose of about 0.7 to about 7.2 J/cm2. A similar method is contemplated for treating Gram-negative bacteria that are one or more of Burkholderia, Salmonella, and Proteus using an aqueous pharmaceutical composition containing about 2 to about 15 µM concentration of the RB compound.

1 . A method of treating a Gram-positive bacteria that comprises the steps of:
 a) contacting said Gram-positive bacteria with an aqueous pharmaceutical composition containing a rose bengal (RB) compound of Formula I, below, dissolved or dispersed therein at a concentration of about 0.2 to about 3.1 µg/mL; and   b) irradiating those contacted bacteria with light of the wavelength about 500 nm to about 600 nm for a time period of about 1 to about 10 minutes to provide a light dose of about 0.7 to about 7.2 J/cm 2                           wherein X is oxygen or nitrogen, “n” is zero or 1 such that when X is oxygen, n is zero and R 2  is absent, and when X is nitrogen, n is 1 and R 2  is present;   when X is oxygen, R 1  is selected from the group consisting of hydrogen (H), M +  that is a pharmaceutically acceptable cation, C 1 -C 4  alkyl, and an aromatic ring as defined herein after;   when X is nitrogen, R 1  and R 2  are the same or different and are selected from the group consisting of hydrogen, C 1 -C 4  alkyl, or together with amido nitrogen atom form a 5- or 6-membered ring, and an aromatic ring as defined herein after;   wherein said aromatic ring is a single ring containing 5- or 6-members, or a 5,6- or 6,6-fused aromatic ring system, said aromatic ring or ring system containing 0, 1 or 2 hetero ring atoms that are independently nitrogen, oxygen or sulfur.   
     
     
         2 . The method according to  claim 1 , wherein said RB compound is rose bengal disodium. 
     
     
         3 . The method according to  claim 1 , wherein said Gram-positive bacteria are one or more of drug-susceptible and drug-resistant  S.   aureus ,  S.  epidermis,  E.   faecalis  and  E.   faecium . 
     
     
         4 . The method according to  claim 1 , wherein said Gram-positive bacteria are one or more  Bacillus subtilis ,  Bacillus cereus , and  Streptococcus salivarius . 
     
     
         5 . The method according to  claim 1 , wherein said Gram-positive bacteria are present within or on mammalian cells when contacted. 
     
     
         6 . The method according to  claim 1 , wherein said Gram-positive bacteria are present as a biofilm. 
     
     
         7 . The method according to  claim 1 , wherein said Gram-positive bacteria are irradiated for a time period of about 2 to about 5 minutes to provide a light dose of about 1.4 to about 3.6 J/cm 2 . 
     
     
         8 . The method according to  claim 1 , wherein said aromatic ring substituent is selected from one or more of the group consisting of one or more of 
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       where 
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       
         
           
           
               
               
           
         
       
       providing an ester or a monosubstituted amine, respectively. 
     
     
         9 . A method of treating a Gram-negative bacteria selected from the group consisting of one or more of  Burkholderia ,  Salmonella , and  Proteus  that comprises the steps of:
 a) contacting said Gram-positive bacteria with an aqueous pharmaceutical composition containing a rose bengal (RB) compound of Formula I, below, dissolved or dispersed therein at a concentration of about 2 to about 15 µM; and 
 b) irradiating those contacted bacteria with light of the wavelength about 500 nm to about 600 nm for a time period of about 1 to about 10 minutes to provide a light dose of about 0.7 to about 7.2 J/cm 2   
                     
 wherein X is oxygen or nitrogen, “n” is zero or 1 such that when X is oxygen, n is zero and R 2  is absent, and when X is nitrogen, n is 1 and R 2  is present; 
 when X is oxygen, R 1  is selected from the group consisting of hydrogen (H), M +  that is a pharmaceutically acceptable cation, C 1 -C 4  alkyl, and an aromatic ring as defined herein after; 
 when X is nitrogen, R 1  and R 2  are the same or different and are selected from the group consisting of hydrogen, C 1 -C 4  alkyl, or together with amido nitrogen atom form a 5- or 6-membered ring, and an aromatic ring as defined herein after; 
 wherein said aromatic ring is a single ring containing 5- or 6-members, or a 5,6- or 6,6-fused aromatic ring system, said aromatic ring or ring system containing 0, 1 or 2 hetero ring atoms that are independently nitrogen, oxygen or sulfur. 
 
     
     
         10 . The method according to  claim 9 , wherein said Gram-positive bacteria are present within or on mammalian cells when contacted. 
     
     
         11 . The method according to  claim 9 , wherein said Gram-positive bacteria are irradiated for a time period of about 2 to about 5 minutes to provide a light dose of about 1.4 to about 3.6 J/cm 2 .