An aim of this work was to compare interactions between bacteria, and to correlate them with increased or decreased biofilm formation. A better understanding of the interactions occurring within biofilms may lead to more effective control strategies. As the strains used in this study were closely related Enteric species, considerable bacteriocin activity occurred. Bacteriocin-producing strains were found to have a competitive advantage over bacteriocin-sensitive strains, both in gaining a foothold into a new community, and discouraging the attachment of potential competitors. Bacteriocins and bacteriocin-producing strains may be used as a novel strategy to control biofilm growth, and discourage the attachment of pathogenic strains. In general, a decrease in biofilm size and stability, and an increase in sensitivity to disinfectants was exhibited by bacteriocin-producing mixed species biofilms. There were, however, exceptions: certain biofilms of <i>Enterobacter agglomerans/Ent </i>when antagonised with a second, competitive strain produced a signal to repress bacteriocin synthesis in the competing strain, leading to a co-operative state. These biofilms were thicker, more stable and demonstrated an increased resistance to disinfectants. There is also the possibility that bacteriophage can be used to control biofilm formation. Studies indicated that small titres of phage were more successful in the removal of <i>Enterobacter cloace/</i>5920 biofilms. However, infection of three phages, φ1.15, Winchburgh and Blackburn phage, was required to completely eradicate the biofilms. The triple-combination of phage was also found to selectively remove a single bacterial species form a mixed species biofilm. The role of EPS in biofilm resistance and the adaptation of biofilms to increasing concentrations of disinfectant were also investigated. While the involvement of EPS was found to be transient, it was thought that repeated exposure to an antimicrobial agent may select for a more resistant phenotype, leading to biofilm resistance. For example, biofilms responded to increasing concentrations of triclosan by producing a triclosan mutant, and it was thought that increasing concentrations of benzalkonium chloride selected for strains utilising increased expression of multi-drug efflux pumps.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662737 |
| Date | January 2000 |
| Creators | Tait, Karen |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13068 |
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