What are Biofilms?

by Michael_Koger

Biofilms are aggregates of microbial cells on a surface, and they are highly tolerant of antimicrobial drugs.

Biofilms are aggregates of one or several types of microorganisms, and they may occur on any surface. These commonly include plastics, metals, medical implant devices, and environments underground. They especially form when there are moisture and nutrients on the surface. They can coat rocks in streams or rivers, and they tend to excrete a slimy and glue-like material [1, 2].

In humans they will lead to chronic infection. Well-known examples of this are dental plaque and the presence of periodontitis, lung infections in patients with cystic fibrosis, and chronic wounds which have been present for several months. The biofilms adhere as a matrix, and this enables the microorganisms to tolerate a hostile environment which free-floating or planktonic bacteria cannot [1, 2].

Common Biofilm Infections

They may also be responsible for ear infections, sinusitis, tonsillitis, laryngitis, endocarditis, kidney stones, biliary tract infection, urinary tract infection, vaginosis, and osteomyelitis [1].

Biofilms can occur in people who have peripheral vascular catheters, prosthetic heart valves, pacemakers, contact lenses, and vascular grafts.  Tissue fillers such as breast implants are capable of infection acquisition or even an allergic reaction.  Intrauterine devices, voice prostheses, and dialysis catheters can also lead to their formation [1]. 

Management Challenges

Their ability to tolerate the environment and become resistant to large doses of antibiotics makes the clinical management of these clients difficult.  The human immune system will attempt to fight a biofilm, but the usual host defenses are insufficient to resolve the situation [1, 2].

Most biofilms entail a variety of microorganism species such as bacteria, fungi, algae, yeasts, protozoa, and others.  There may also be debris or corrosion products in them.  In some cases, there is only one type of microorganism responsible for it.  Biofilms can form within a matter of hours, and they range from a few cell layers to several inches in thickness [1, 2]. 

Through modern microscopy, scientists have learned a great deal about them.  However, Pasteur and van Leeuwenhoek observed them long ago with simple light microscopy [1, 2]. 

Finally, biofilms pose economic and environmental issues.  For example, they can damage equipment and cause energy loss.  They may contaminate products.  In the United States, they cost billions of dollars each year from these effects [2]. 


Biofilms are a serious environmental and public health problem.  Further research is necessary in order for clinical microbiologists and medical doctors to control them.


  1. Høiby, N., Bjarnsholt, T., Moser, C. et al for the ESCMID Study Group for Biofilms (ESGB) and Consulting External Expert Werner Zimmerli.  (2014).  ESCMID guideline for the diagnosis and treatment of biofilm infections 2014.  Clinical Microbiology and Infection, 21, S1-S25.
  2. Montana State University.  Center for Biofilm Engineering.  (2015).  What are biofilms?  Retrieved June 7, 2015.
  3. The photo is a microscopic view of a bacterial biofilm on a brown recluse spider.  Reprinted with permission from Centers for Disease Control and Prevention/Leah Lowrey/Michael Smith.


The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact their physician for advice.

Updated: 06/10/2015, Michael_Koger
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Sheri_Oz on 06/11/2015

My daughter is doing her PhD on biofilms and their ability to be manipulated for the purposes of purifying sewage waters and producing electricity as a side-effect.

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