Introduction

Definition

Biofilm can be defined as a microbially derived sessile community characterized by cells that are irreversibly attached to a substratum and embedded in a matrix (Rodney & Costerton, 2002). For example, they irreversibly adhere to surfaces of medical devices like prosthetic devices (Donlan, 2001), causing infections which can result in longer hospitalisation and even death (Barie, 1998)

Biofilm formation

Figure 1 illustrates the 5 stages of biofilm formation (Dirckx & Davies, 2002). They can be split into

1) Initial attachment

2) Irreversible attachment

3) Maturation

4) Further Maturation

5) Dispersal

Figure 1: The five stages of biofilm formation

Rationale

Currently, many antimicrobial agents and methods are targeted only towards the planktonic (freely suspended) cells and not biofilms (Donlan et.al, 2002). However, it is found that the form that most bacteria take is in a matrix-encased, biofilm state. Additionally, there have been few studies done on inhibiting biofilms. One study by Plas et. al (2007) have shown that maggot excretions or secretions are effective agents in inhibiting the formation of biofilms of S. aureus and P. aeruginosa.

Objectives

Our objectives of this experiment are to investigate the antibacterial effect different agents have on Gram-positive S. epidermidis and Gram-negative E. coli and P.fluorescens. We alos wish to investigate the effectiveness of different agents in removing formed biofilms and preventing the formation of biofilms of Gram-positive S. epidermidis and Gram-negative E. coli and P. fluorescens.

Hypothesis

Our hypothesis of this experiment is that different agents will exhibit different antibacterial properties and different effectiveness towards removing formed biofilms and inhibiting formation of biofilms of S. epidermidis and E. coli as well as P. fluorescens.