Antimicrobial phage - bacterial biofilm interaction

The pathogenic bacteria responsible for the majority of human infections only intermittently exist in a planktonic state when in the host. The biofilm state can be said to be the normal ecological niche for these organisms as the biofilm offers several advantages in countering host innate and acquired immunity. Leading causes of hospital acquired infections such as Pseudomonas aeruginosa, Staphylococcus aureus, Acinetobacter baumannii and Escherichia coli can all form complex biofilms in human tissue and on prosthetic devices such as catheters and stents. Bacterial cells within the biofilm are refractory to antibiotic treatment and unfortunately from a human health perspective, such bacteria may be exposed to sub-MIC levels of antibiotic promoting the rapid evolution of antibiotic resistance. The major biofilm associated bacteria above have all developed to resistance to almost all antibiotic classes and in some cases strains may have resistance to all antibiotic classes. Bacteriophages have been shown to be highly effective in killing bacteria associated with biofilms. Not only do phages multiply rapidly within host cells but they may actually induce host bacteria to produce enzymes that break down components of the biofilm matrix such as alginate in the case of P. aeruginosa. The targeted induction of such enzymes greatly strengthens the case for the use of phage in treating biofilm disease however little work has been done in this area [1]. In this project we will examine how effective phage (specific for individual, strains / species) are in killing in simple biofilm models for particular species, such as S. aureus and P. aeruginosa and investigate whether synergy exists in using antibiotics alongside phage treatments. As in vivo biofilms are always polymicrobial we will also test targeted phage mixtures against more complex biofilms. Ultimately we wish, in tandem with Biocontrol Ltd, to investigate utilizing phage as a therapeutic agent in infection control, especially for wounds and burns. Whilst phage shows great promise as a therapeutic agent [2], problems remain with regard to stabilizing it in, for example, a wound dressing or topical cream. Wounds, especially chronic wounds can become infected by biofilm forming bacteria, with the biofilm making treatment much more difficult [3]. The latter part of the project will study the encapsulation of phage in both phospholipid - fatty acid vesicles and in fatty acid micelles. The potential utility of this approach is twofold: 1. The encapsulation should improve the stability of the phage over long time periods and 2. This will provide an environment in which encapsulated phage is only released following bacterial toxin interaction and lysis of the vesicle. [4]. The aim in the later stages of the project will be to incorporate such vesicles or micelles into prototype products where the encapsulated phage on release can assist in infection control and healing in wounds. Such products include paraffin / surfactant based creams and simple wound dressings. 1. Meluleni, G. J., Grout, M., Evans, D. J. Pier, G. B. J. Immunology, 155, 2029-2308, (1995). 2. Wright, A.; Hawkins, C.H.; Anggard; E.E. & Harper, D.R. Clinical Otolaryngology 34, 349-357, (2009). 3. James G.A.; Swogger E.; Wolcott R.; Pulcini E.; Secor P.; Sestrich J.; Costerton J.W.; Stewart P.S.. Wound Repair Regen.16, 37-44. (2008). 4. Zhou, J.; Loftus, A. L.; Mulley, G.; Jenkins, A. T. A. J. Amer. Chem. Soc. 132, 6566-6570 (2010).