Microbial biofilms are structured communities of bacterial cells enclosed in a self-produced matrix that provides a protective shield for bacteria to thrive and resist damage from many extreme environmental conditions. Biofilm encased microbes are almost universally resistant to disinfectants and antibiotics, which can lead to prolonged and chronic infection, amputation, long-term disability, and death. Conventional antimicrobial drugs were not developed to target bacteria growing as biofilms and therefore are often poorly effective against biofilm containing infections. Biofilms also facilitate the spread of antibiotic resistance.
Major mechanisms of biofilm antibiotic resistance
- Slow, incomplete, or ineffective antibiotic penetration into the biofilm matrix itself.
- Nutrient-limitation-mediated stress response, resulting in a much slower rate of growth and higher resistance to antibiotics.
- Alteration of microenvironments within the biofilm, such as pH gradients, that neutralize the action of antibiotics.1
- A subpopulation of “persister” microbes in biofilms that adopt a highly protected state with substantially reduced level of metabolic activity. If other bacteria in the biofilm become compromised, the persister cells tend to survive, and are then triggered to repopulate the biofilm.1
- Biofilms are breeding grounds for exchange of genetic elements, much of which can be found existing freely outside of cells, in a form known as eDNA.2
According to the National Institutes of Health (NIH), at least 80% of human infections involve bacterial pathogens growing as microbial biofilms.
- Stewart PS and Costerton JW. Antibiotic resistance of bacteria in biofilms. Lancet. 2001;358:135-138.
- Ravaioli S et al. Biofilm extracellular-DNA in 55 Staphylococcus epidermidis clinical isolates from implant infections. Int J Artif Organs. 2011;34:840-846.