Biofilms – Common and Challenging Sources of a Variety of Pathogens

It’s no exaggeration to say that biofilms are found virtually everywhere, even inside our own bodies (¹). While in many situations they may be beneficial or harmless to our health, biofilms can also be common sources of potentially dangerous microbes[1]. Many members of the genera Legionella, Pseudomonas and Mycobacterium, for example, can thrive in biofilms in water storage and distribution systems causing outbreaks in community and institutional settings (²).

Biofilm development is notoriously difficult to prevent and, once established, they are just as challenging to get rid of. In fact, microbes naturally prefer to adhere to surfaces to initiate their multiplication. In the process, they produce a slimy substance (glycocalyx), which affords them greater protection against antibiotics and microbicides while trapping nutrients (³). Once a biofilm with a pioneering type of microbe gets established, it attracts not only other types of bacteria but fungi, protozoa and bacteriophages as well. Thus, a mature biofilm represents a thriving multi-species or polymicrobial community with an intricate structure of its own. That milieu also allows for regular exchange of enzymatic and genetic material. It would not be unreasonable to assume that complex biofilms represent the origins of higher and multi-cellular forms of life!

Biofilms can often form on implanted medical devices such as heart valves and knee-joints (⁴), and that makes the ensuing bacterial/fungal growth on them highly refractory to antimicrobial therapy, thus needing device replacement. Biofilms can also develop inside reusable medical devices making their cleaning and disinfection difficult (⁵).

One particular source of environmental biofilms is close to home – drinking water storage and distributions systems in domestic and institutional settings (²). In contrast to popular belief that tap water is ‘sterile’, it teams with a variety of biofilm-derived microbes from such systems virtually everywhere. Therefore, municipally-treated potable waters can be sources of many pathogenic microbes (²).

Another wrinkle in the biofilm story is the relatively recent discovery of ‘dry biofilms’ (⁶), and that raises the stakes even higher. In general, dry biofilms are harder to deal with in routine situations and may negate the impact of regular decontamination processes. CREM Co Labs has now established the protocols to develop dry biofilms of relevant microbes on representative environmental surfaces to assess their decontamination by microbicidal chemicals.

Literature cited:

1. Donlan RM. Biofilms: microbial life on surfaces. Emerg Infect Dis. 2002;8(9):881-890. doi:10.3201/eid0809.020063
2. Falkinham JO 3rd, Hilborn ED, Arduino MJ, Pruden A, Edwards MA. Epidemiology and Ecology of Opportunistic Premise Plumbing Pathogens: Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa. Environ Health Perspect. 2015;123(8):749-758. doi:10.1289/ehp.1408692
3. Venkatesan N, Perumal G, Doble M. Bacterial resistance in biofilm-associated bacteria. Future Microbiol. 2015;10(11):1743-1750. doi:10.2217/fmb.15.69
4. Khatoon Z, McTiernan CD, Suuronen EJ, Mah T-F, Alarcon EI. Bacterial biofilm formation on implantable devices and approaches to its treatment and prevention. Heliyon. 2018;4(12):e01067. doi:10.1016/j.heliyon.2018.e01067
5. Lopes LKO, Costa DM, Tipple AF V, et al. Complex design of surgical instruments as barrier for cleaning effectiveness, favouring biofilm formation. J Hosp Infect. 2019;103(1):e53-e60. doi:10.1016/j.jhin.2018.11.001
6. Otter JA, Vickery K, Walker JT, et al. Surface-attached cells, biofilms and biocide susceptibility: implications for hospital cleaning and disinfection. J Hosp Infect. 2015;89(1):16-27. doi:10.1016/j.jhin.2014.09.008.

[1] We understand biofilms better from the pioneering work of researchers such as Prof. Bill Costerton and his colleagues. Costerton’s initial work on biofilms was at the University of Calgary in Alberta, Canada. He then moved to Bozeman, Montana, to head Montana State University’s Center for Biofilm Engineering (CBE). CBE continues to be an international focal point for research, training and standards development on biofilms.