Bacteriophage Ecology in Escherichia coli and Pseudomonas aeruginosa Mixed-Biofilm Communities

Abstract

Phage therapy is being reexamined as a strategy for bacterial control in medical and other environments. As microorganisms often live in mixed populations, we examined the effect of Escherichia coli bacteriophage W60 and Pseudomonas aeruginosa bacteriophage PB-1 infection on the viability of monoculture and mixed-species biofilm and planktonic cultures. In mixed-species biofilm communities, E. coli and P. aeruginosa maintained stable cell populations in the presence of one or both phages. In contrast, E. coli planktonic populations were severely depleted in coculture in the presence of W60. Both E. coli and P. aeruginosa developed phage resistance in planktonic culture; however, reduced resistance was observed in biofilm communities. Increased phage titers and reduced resistance in biofilms suggest that phage can replicate on susceptible cells in biofilms. Infectious phage could be released from mixed-culture biofilms upon treatment with Tween 20 but not upon treatment with chloroform. Tween 20 and chloroform treatments had no effect on phage associated with planktonic cells, suggesting that planktonic phage were not cell or matrix associated. Transmission electron microscopy showed bacteriophage particles to be enmeshed in the extracellular polymeric substance component of biofilms and that this substance could be removed by Tween 20 treatment. Overall, this study demonstrates how mixed-culture biofilms can maintain a reservoir of viable phage and bacterial populations in the environment.

The Behavior of Staphylococcus aureus Dual-Species Biofilms Treated with Bacteriophage phiIPLA-RODI Depends on the Accompanying Microorganism

“…This may also limit phage-resistance acquisition, which generally confers a loss of competitive ability of the bacteria (30). This seemed to be the case, for example, of dual-species biofilms formed by E. coli and Pseudomonas aeruginosa (22). Here, there were differences in the behaviors of the four accompanying strains studied following antistaphylococcal phage treatments.…”

“…Additionally, phage-encoded proteins, such as endolysins and exopolysaccharide depolymerases, can also be used for biofilm removal (19)(20)(21). Nevertheless, most studies available to date have focused on single-species communities, while only limited work has tackled the elimination of polymicrobial biofilms with phage-based products (22)(23)(24)(25)(26).…”

Using Phage’s to Exterminate Biofilms

“…A study carried out by Tait et al [60]; revealed that using a variety of three phages can entirely destroy a biofilm that's created from single species, nevertheless in the presence of other bacterial species which were insensitive, this technique didn't have much effect. A study by Kay et al [61] also demonstrated that the phages efficiency can be worn off in the clear presence of mixed biofilms. In spite of this, it was reported by Sillankorva et al, the efficiency could be high in model biofilms even in cases like if an individual bacterial species in the biofilm is targeted by the phage, explaining that phages have the ability of killing a specific type of bacterial host even when it dwells in a mixed organization.…”

Experimental approach for bacteriophage susceptibility testing of planktonic and sessile bacterial populations – Study protocol

“…[9][10][11] With this background, bacteriophages have a great unexplored potential, in both preclinical and clinical research.…”