Abstract
Purpose. To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. Methods. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic conditions. The inoculum was replaced every 24 hours with a fresh growth medium for up to 10 days to feed the system. Gram staining was done every 24 hours to control the microorganism purity. Biofilms developed under the system were evaluated under the scanning electron microscope (SEM). Results. SEM micrographs demonstrated mushroom-shaped structures, corresponding to a mature E. faecalis biofilm. In the mature biofilm bacterial cells are totally encased in a polymeric extracellular matrix. Conclusions. The proposed in vitro system model provides an additional useful tool to study the biofilm concept in endodontic microbiology, allowing for a better understanding of persistent root canal infections.
Highlights
Contemporary microbiology has demonstrated that microorganisms are organized under specific environmental conditions [1]
Larger structures of wrapped sheets were present and consisted of small numbers of bacteria cells embedded in a matrix of fibers
The E. faecalis biofilm, grown under anaerobic conditions, showed a clump of bacteria cells attached to the dentine surface (Figure 2(a))
Summary
Contemporary microbiology has demonstrated that microorganisms are organized under specific environmental conditions [1]. Planktonic microorganisms are single cells that may float or swim in a liquid medium. Under specific environmental conditions, phenotypic adaptations are expressed as a form of life termed biofilm. It is known that a mature biofilm is able to tolerate antimicrobial concentrations of 10 to 1000 times that required to remove planktonic bacteria [4]. The biofilm concept has changed and it is currently defined as “a bacterial community immersed in a liquid medium, characterized by one or more bacteria that are attached to each other, to a substrate or surface and embedded in an extracellular matrix produced by them, and shows an altered phenotype in the degree of cell proliferation or the expression of their genes” [5]. The study of biofilms has skyrocketed in recent years due to the increased awareness of the pervasiveness and impact of biofilms on natural and industrial systems, as well as human health (chronic bacterial prostatitis, cyst fibrosis, and periodontitis) [5]
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