Biofilms in marine environments; implications for aquaculture, coral reefs, marine aquariums, and the human pathogen Vibrio cholerae – Part 2


Biofilms have been shown to have a wide variety of roles in bacterial survival and can form on a tremendous range of materials, both in association with hosts, and on abiotic surfaces. Within hosts, pathogenic bacteria have been shown to utilize biofilms as a virulence attribute. The EPS matrix makes the bacteria relatively inaccessible to attachment by antibodies and masks the bacteria from complement attack. The aggressive attack mounted by the host’s immune system to try to clear a biofilm-associated infection may cause additional tissue damage from inflammation. Biofilms also present a dilemma for physicians. Biofilm bacteria have been shown to be 1000-fold more resistant to antibiotics than the same organisms in their planktonic state. These attributes make biofilm bacteria a candidate for chronicity and re-occurrence.
There are several well-known examples of bacteria that utilize biofilms as a mechanism for pathogenesis. One of the best described is Pseudomonas aeruginosa. It is believed that in patients with cystic fibrosis, Pseudomonas aeruginosa infections are associated with mucoid isolates possessing a high level of EPS alginate production and microcolonies that resemble biofilm structures. No direct correlation between biofilms and pathogenesis in C.F. patients has been demonstrated, but it is strongly suspected.

Periodontis is another well-studied biofilm. In this model, there is a progression of bacteria colonizing the tooth surface from diverse genera; Fusobacterium, Porphyromonas, Streptococcus, and others. This leads to a heterogenous mix of bacteria in a biofilm. Quorum sensing, interspecific signaling, and cooperative secretion of proteases and other proteins to interfere with cytokine signaling all lead to increased survivability of the participating species. Because of their ability to colonize abiotic surfaces, patients with implanted medical devices such as valves or indwelling catheters are at significant risk for developing a biofilm infection. For patients with endocarditis associated with biofilm colonization of heart valves face a 70% fatality rate. Even common surfaces such as contact lenses can form biofilms resulting in keratitis.