Effect of Bacteriophage Infection on the Viability of Escherichia coli and Pseudomonas aeruginosa in Mixed Species Biofilms




Erwin, Thomas C.

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There has been renewed interest in the use of bacteriophage for the treatment of disease. Recent studies have focused on phage infection in single and mixed species planktonic culture. In chronic bacterial disease, however, pathogenic bacteria form biofilms, which facilitates colonization and the development of chronic infection. This study investigated the effect of phage infection on cell survival in Escherichia coli and Pseudomonas aeruginosa mixed species biofilms. In the absence of phages, E. coli and P. aeruginosa were stably maintained during daily serial passage. P. aeruginosa maintained high cell densities in both single-species planktonic and biofilm cultures when infected with its phage, PB-1. Monoculture planktonic and biofilm populations of E. coli were also stable in the presence of its phage, A.W60. In contrast, phage XW60 infection of two-species cultures resulted in the extinction of E. coli in planktonic but not in biofilm populations. In mixed species planktonic and biofilm cultures P. aeruginosa maintained high cell densities when infected with phage PB-1. The increased susceptibility of E. coli to its phage in planktonic culture may be due in part to competition with P. aeruginosa. This is the first report on the effect of bacteriophage infection in a mixed species biofilm and demonstrates the advantage bacterial populations gain by forming biofilm communities.



Bacteriophages, Escherichia coli, Pseudomonas aeruginosa, Biofilms, Microbial ecology, Pathogenic bacteria, Virulence, Microbiology


Erwin, T. C. (2009). <i>Effect of bacteriophage infection on the viability of Escherichia coli and Pseudomonas aeruginosa in mixed species biofilms</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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