Bacterial biofilms

Biofilms are regarded as one of the most challenging areas of modern biomedicine and they are claimed responsible for a massive proportion (up to 80%) of the antibiotic-tolerant infections (1). They are involved in several chronic diseases such as lung pneumonia of cystic fibrosis patients, otitis media, chronic non-healing wounds and contamination of medical implants. It has been estimated that millions of patients get infected every year and over 23 000 patients die from multiresistant bacterial infections in the EU and in the US (2, 3). Chronic lung infections of cystic fibrosis patients have been related to high production of drug tolerant biofilm populations, persister cells, which makes them nearly impossible to eradicate (4). 

Antimicrobial resistance and -tolerance has become a recognized problem world-wide and has recently been discussed even at United Nations level. There is a need for changes in the use of existing antimicrobials but also a need for alternative therapies to be able to tackle this problem (5). Targeting virulence factors such as quorum sensing (QS) is a strategy that reduces selective pressure on the bacteria to survive and thus limits the development of resistance towards the treatment (6). Another strategy to consider is to use combination therapies and adjuvants to existing antibiotics (7). These alternative treatments are especially of need in therapies for biofilm infections, as there are still no existing antibiofilm drugs available (8, 9). Biofilms are well-structured communities of bacteria enclosed in a self-produced matrix, usually adhered to a surface but can also be aggregated in floating societies. Biofilm bacteria are radically different from single-cell bacterial suspensions and the most crucial difference is their increased chemotolerance (10). The high tolerance has been attributed to various factors; the extracellular polymeric substance layer (EPS, composed of polysaccharides, proteins and extracellular DNA) can restrict antibiotics penetration. The different metabolic states of the bacteria within the biofilm are also of importance; in the core of the community reside bacteria with very low or no metabolic activity. These so called persister cells comprise about 1-5% in both biofilms and planktonic stationary phase cultures (11). Persister cells have been known since the 1940s as a population that is tolerant to antimicrobial treatment but can revive, sometimes slowly, being the main cause of recalcitrance of chronic, biofilm related infections (12).

With the recent recognition of biofilm’s importance as the predominant state for bacterial living instead of the planktonic lifestyle, there has been a progressive shift towards a new era in drug discovery in which searching for antibiofilms is urged to occupy a more prominent place. However, so far, still a very limited repertoire of molecules exists that can selectively act on mature biofilms. Given the reduced interest that antibacterials are attracting to pharmaceutical companies, it is basically up to academic research to provide imperative and innovative ways to drive forward antibiofilm drug discovery.

We have established an assay platform for testing various compound libraries to evaluate the effect on viability, biomass and biofilm matrix (13-16). The platform was established using Staphylococcus aureus and S. epidermidis strains but has also been optimized for Pseudomonas aeruginosa, Burkholderia cenocepacia and Escherichia coli biofilm forming strains. This platform is micro titer well plate based and we can also evaluate the effect on planktonic bacteria simultaneously. Fluorescence microscopy using LIVE/DEAD staining can be added to the platform.

AIR: biofilm platform

We have also optimized a static biofilm method where biofilms are grown on agar plates without the any planktonic bacteria present. Using this method we can study biofilm formation on different surfaces (17, 18). This method is very easy to apply for varoius species and material studies.

Quorum sensing, the communication system of micro organisms, is an important factor in biofilm formation. We have developed a micro well plate based assay platform, using a reporter strain, Chromobacterium violaceum, to efficiently screen for quorum sensing inhibitors that can be further studied on relevant pathogens using the same quorum sensing system (19).

We also have an interest in studying persister bacteria both in planktonic and biofilm cultures. 

At the moment we are also the coordinators of PRINT-AID, a EU-funded Training Network (ETN) for finding better solutions for antimicrobial effects in the development of 3D-printed medical devices. 


1. Moscoso, M., et al., Int Microbiol, 2009. 12(2): p. 77-85.
2. ECDC, Antimicrobial resistance surveillance in Europe. Annual report of the European Antimicrobial Resistance Surveillance Network (EARS-Net). 2014
3. CDC, Antibiotics resistance threats in the United States, 2013. 2013.
4. Mulcahy, L.R., et al., J Bacteriol, 2010. 192(23): p. 6191-9.
5. Czaplewski, L., et al., Lancet Infect Dis, 2016. 16(2): p. 239-51.
6. Starkey, M., et al., PLoS Pathog, 2014. 10(8): p. e1004321.
7. Gill, E.E., et al., Chem Biol Drug Des, 2015. 85(1): p. 56-78.
8. Penesyan, A., et al., Molecules, 2015. 20(4): p. 5286-98.
9. Dharmaprakash, A., et al., Future Microbiol, 2015. 10(6): p. 1035-48.
10. Costerton, J.W., et al., Annu Rev Microbiol, 1995. 49: p. 711-45.
11. Lewis, K., Nat Rev Microbiol, 2007. 5(1): p. 48-56.
12. Wood, T.K., et al., Appl Environ Microbiol, 2013. 79(23): p. 7116-21.
13. Sandberg, M., et al., Int. J. Antimicrob. Agents 32, 233-240 (2008).
14. Sandberg, M.E. et al. J. Microbiol. Methods 78, 104-106 (2009).
15. Skogman, M.E., et al., J. Antibiot. (Tokyo) 65, 453-459 (2012).
16. Skogman ME, et al., J Vis Exp. 2016 Dec 27;(118). doi: 10.3791/54829.
17. Oja T, et al., J Microbiol Methods. 2014 Dec;107:157-60.
18. Hiltunen AK, et al., Int J Pharm. 2016 Mar 30;501(1-2):211-20.
19. Skogman, M.E., et al., Molecules 21,(9) (2016).



Moderated by Malena Skogman, 2017