March 01, 2023

Biofilm in Acne

Costerton and Cheng first used the term ‘biofilm’ in the 1970s. Although since then, the definition of a biofilm has been changed multiple times, there are three essential components:

The microbial cells
The surface onto which these cells adhere to
Extracellular polymeric matrix – where cells are embedded and can form more prominent communities.

Over the last few years, biofilm research has expanded considerably and revealed that biofilms are probably the most common form of microbial growth in nature and that the planktonic (free-floating) phenotype of microorganisms, the original subject of microbiological research over the last 100 years could be in fact and in vitro artifact.

Dental plaque, one of the oldest known examples of a biofilm, consists of a well-defined surface (which is dental enamel), a matrix of polysaccharides, and microbial cells. However, not all biofilms fit the biofilm definition that easily. For example, there are many types of mucosal biofilms that are found in the lungs.

One of the essential properties of the microbial cells in a biofilm is that they are phenotypically different from their planktonic counterparts. Depending on the micro-environment, microorganisms can regulate the expression of specific genes, allowing them to adapt to changing conditions.

Factors responsible for increased resistance in biofilms include restriction penetration of antimicrobials, decreased growth rate, expression of resistance genes, and the presence of resistant cells.

This increased resistance allows biofilms to survive in various environments (including the human host) and for infection to persist after treatment. Many chronic conditions are now thought to be biofilm related, which would help explain their chronic nature. Antimicrobial therapy kills off a large number of microbial cells so that it can reduce the symptoms. However, the biofilm, in total, may persist and regrow, causing a re-occurrence of the symptoms.

Another vital aspect of biofilms is the ability of microbial cells to communicate with each other using various communication systems. This process is cell density-dependent and allows bacteria to coordinate gene expression by producing signal molecules.

Using this communication system, microorganisms increase their chances of successfully infecting their host by delaying the production of virulence factors until the population has reached a specific threshold density high enough to overwhelm the immune system.

Biofilms are ubiquitous and notoriously difficult to eradicate. Moreover, the formation of biofilms is rapid.

P. acnes biofilm

P. acnes is an aerotolerant anaerobic, gram-positive, and relatively slow-growing commensal of the human skin. It produces extracellular lipases that hydrolyze triglycerides in the sebum into glycerol and fatty acids. P. acnes can use this glycerol as an energy source, and the end product of the fermentation process is propionic acid. This is where we get the name Propionibacterium. In addition, the free fatty acids play a role in the pathogenesis of acne, eliciting an inflammatory response.

Some studies show that P. acnes has several genes relevant to biofilm formation. Some of these genes are responsible for the extracellular polysaccharide matrix, a gene responsible for the production of adhesion proteins.