Inhibition Of Microbial Biofilms

Biofilms can be defined as communities of microorganisms attached to a surface (O’Toole et al., 2000). It is enclosed in a matrix of polysaccharide material (Donlan, 2002). Currently, antimicrobial agents and methods are targeted only towards the planktonic (freely suspended) cells and not biofilms. However, it is found that the form that most bacteria take is in a matrix-encased, biofilm state. The genotype and phenotype of bacteria in a biofilm state are different from the planktonic bacteria hence making it much less susceptible to antimicrobial agents.

 

With that said, there have already been several studies on inhibiting the growth of biofilms and degrading established ones. One example is through the excretion/secretion of maggots of Lucilia sericata. Van der Plas et al. (2008) studied the differential effectiveness of maggot excretions/secretions against biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. They assessed the effects of excretion/secretion (ES) on biofilms using microtitre plate assays and found that as little as 0.2 µg of ES prevented the S. aureus biofilm and 2 µg of ES rapidly degraded biofilm, but in contrast for P. aeruginosa, degradation of it started after 10 hours and required ten-fold more ES than S. aureus to do so (Van der Plas et al., 2008). This was interesting as S. aureus was Gram-positive while P. aeruginosa was Gram-negative, and thus was a likely factor in determining the amount of ES required to degrade each type of biofilm. According to a study conducted by Cazander et al. (2010), the strongest biofilms were formed by S. aureus and S. epidermidis on polyethylene and the weakest on titanium. The highest quantity of biofilm formation was achieved within 7 days for both bacteria. The presence of excretions/secretions from maggots reduced biofilm formation on all biomaterials (Cazander et al., 2010).

 

Namasivayam and Roy (2013) investigated the ability of medicinal plant extracts in preventing Escherichia coli biofilm formation. They found out that the aqueous and chitosan coated extracts of Azadirachta indica, Vitex negundu, Tridax procumbens and Ocimum tenuiflorumi showed effect against biofilm formation.