Targeted photodynamic therapy of established soft-tissue infections in mice

• Published in: Photochemical & photobiological sciences 2004-05, Vol.3 (5), p.451-458
• Main Authors: Gad, Faten, Zahra, Touqir, Francis, Kevin P, Hasan, Tayyaba, Hamblin, Michael R
• Format: Article
• Language: English
• Subjects: Animals; Gram-Negative Bacterial Infections - drug therapy; Male; Mice; Mice, Inbred BALB C; Photochemotherapy; Soft Tissue Infections - drug therapy
• ISSN: 1474-905X; 1474-9092
• DOI: 10.1039/b311901g

The worldwide rise in antibiotic resistance necessitates the development of novel antimicrobial strategies. Although many workers have used photodynamic therapy (PDT) to kill bacteria in vitro, the use of this approach has seldom been reported in vivo in animal models of infection. We have previously described the first use of PDT to treat excisional wound infections by Gram-(-) bacteria in living mice. However, these infected wound models involved a short timespan between infection (30 min) and treatment by PDT. We now report on the use of PDT to treat an established soft-tissue infection in mice. We used Staphylococcus aureus stably transformed with a Photorhabdus luminescenslux operon (luxABCDE) that was genetically modified to be functional in Gram-(+) bacteria. These engineered bacteria emitted bioluminescence, allowing the progress of the infection to be monitored in both space and time with a low light imaging charge-coupled device (CCD) camera. One million cells were injected into one or both thigh muscles of mice that had previously been rendered neutropenic by cyclophosphamide administration. Twenty-four hours later, the bacteria had multiplied more than one hundredfold; poly-L-lysine chlorin e6 conjugate or free chlorin e6 was injected into one area of infected muscle and imaged with the CCD camera. Thirty minutes later, red light from a diode laser was delivered as a surface spot or by interstitial fiber into the infection. There was a light dose dependent loss of bioluminescence (to