Bacterial Biofilm: Bacteria's Dirty Secret

Bacteria have the ability to form communities known as bacterial biofilms. These biofilms can be found in soil, on plants, industrial surfaces, and essentially almost everywhere. In addition to these areas, bacteria can also form biofilms on human tissue, causing a variety of diseases and infections.^[1] The prevalence of biofilms certainly causes concerns in regards to public health. With growing knowledge about the oral and the skin microbiome (the community of bacteria and their byproducts), it is important to discuss how bacterial biofilms affect the skin.

Bacterial Biofilm Formation

Biofilm formation occurs in three stages: adhesion, maturation, and dispersal.^[2]

Adhesion

When bacteria adhere to surfaces in moist environments, they start to secrete a substance that anchors them in place so that they can recruit other bacteria through quorum sensing, a mechanism in which bacteria can communicate with each other through signal molecules. This ability to communicate allows bacteria to form and maintain their biofilm communities. Biofilms may be composed of single or multiple microbial species.

Maturation

During maturation, the bacterial cells produce molecular strands called extracellular polymeric substances (EPS) that hold the biofilm together. The extracellular matrix also consists of proteins and sugars, but a majority of it is composed of water, allowing nutrients to flow and feed the bacteria.

Dispersal

While maturing, the biofilm has the option to disperse. In this stage, bacterial cells will release from the surface and move to a new site where they can form new biofilm communities, thus increasing their virulence.

Effects of Bacterial Biofilm on Human Health

The National Institutes of Health reported that 65% of all microbial infections and 80% of all chronic infections are related to biofilm formation. Biofilms occur on many medical devices such as urinary catheters, pacemakers, and prosthetic joints.^[3] This puts medical device-carrying patients at greater risks for bacterial infection. For example, Porphyromonas gingivalis and Fusobacterium nucelatum can form on tissue in the oral cavity, resulting in an infection known as periodontitis that causes damage to the gums and bones supporting the teeth. In another example, increased biofilm formation by Haemophilus influenzae is associated with otitis media (inflammation of the inner ear) and other invasive diseases.^[4]

Bacterial Biofilm Resistance

Bacterial biofilm resistance poses a huge challenge to clinicians and microbiologists.^[5] In addition to providing structural support, the EPS also offers protection to the biofilm by restricting certain substances from entering the biofilm. As a result, antibodies that are produced by the body’s immune system and antibiotics that are typically used to treat bacterial infections are not very effective in killing all the bacterial cells within the biofilm.^[6] Another contributing factor to biofilm resistance is decreased activity and growth rate. Almost all antibiotics are more effective in killing cells that are active and grow rapidly. However, most of the bacteria in biofilm enter a low energy phase and do not grow as quickly, making them much more resistant to killing.

Treatment of Bacterial Biofilm Infections

Because bacterial biofilms are notorious for being antibiotic and immune resistant, the treatment of bacterial biofilm infections has been a growing area of research. It is almost impossible to eradicate mature biofilms with antibiotics only, so the most efficient treatments attack the biofilm from multiple angles: removal of the infected source (catheter, prosthetic joint, pacemaker, etc.), early use of known effective antibiotics in high dosage and combinations, and administration of agents that inhibit biofilm formation and dispersal.^[7] Additionally when feasible, such as in the case of skin wounds, physical removal of the biofilm may be effective.

Strategies to remove biofilm include

• Removal of the infected source when possible
• Use of effective antibiotics
• Agents that stop bacteria from forming biofilms
• Physical removal of biofilm