Last week I spent some time at the Infection Prevention Society (IPS) annual conference in Birmingham which provided a fantastic selection of talks and discussions on current and emerging IPC challenges. One topic which came up time and time again was biofilms…. for example, whether the presence of biofilms provide Candida auris with the ability to persist in the clinical environment for prolonged periods, through to the role of biofilms in reduced susceptibility to disinfectants and antibiotics. It made me revisit an excellent recent review published in Antimicrobial Resistance and Infection Control, which is the topic of today’s blog and tomorrow’s IPC Journal Club (register here).

This review paper is written by one of the world leading authors when it comes to biocides and disinfectants, from efficacy testing to biocide resistance and tolerance (which is another story). Prof Jean-Yves Maillard and Dr Issy Centeleghe tell a wonderful story of how biofilms challenge our understanding of cleaning and disinfection. One of the reasons I feel this review paper is so important is that it explains how cleaning and disinfection (which is already a challenging to get right), is made even harder by the presence of biofilms.

The review details how biofilm resistance to disinfectants is multifactorial which has clear implications for cleaning and disinfection. These factors include:

1. Mechanical quenching/neutralisation
2. Reduced metabolism and growth rate
3. High cell density and quorum sensing
4. Presence of presider cells (metabolically inactive cells)
5. Extracellular enzymatic degradation of antimicrobials
6. Express of specific mechanisms of resistance
7. Acquistion of resistance genes
8. Increased mutation rate

So, biofilms really do make disinfection more of a challenge. The big question for me is how do we convey these challenges to healthcare professionals and domestic teams who are responsible for keeping our clinical environments clean and safe? The work of Prof Maillard and colleagues is crucial to support the scientific understanding behind these challenges but how do we overcome these challenges in practice? More work is needed to understand how disinfectants can work against biofilms (both wet and dry) and to consider factors other than efficacy (as measured by microbial log reduction). What about regrowth and testing the efficacy of disinfectant products in a model to reproduce how disinfectants interact with biofilms?

The review also places an emphasis on understanding the role of dry surface biofilms (DSB) in disinfectant resistance. This is in comparison to their hydrated biofilm counterparts which we seem to know a (little) bit more about. The review demonstrates the challenge of DSBs documenting that more than 90% of healthcare surfaces harbour DSB, as well as withstanding concentrations of 20,000 parts per million bleach. In short they are everywhere (and are difficult to detect) and our most commonly used disinfectant (bleach) doesn’t work at x 20 times the recommended concentration!! The mechanism of DSB resistance to disinfectants is not yet widely studied but the authors highlight low metabolism, respiration and thickness of the EPS as contributing factors. 

I encourage everyone to read the review which is open access and will enhance your understanding of biofilms and leaving you scratching your heads as to how we tackle this challenge in the clinical environment. The authors conclude that ‘’there is no doubt biofilms need to be appropriately controlled, although control may differ depending on the type of biofilm…education of key stakeholders is paramount to understanding the risks associated with biofilms.’’ I think this sums up the next steps perfectly, we need to think differently about how we control biofilms (both wet and dry) in the clinical environment, but it is vital we educate healthcare professionals on why this is so important.