Biofilms have been secretly colonising the surfaces of healthcare facilities for decades and, for most of that time, cleaning and infection control teams have had no idea what they were dealing with. Understanding them properly requires a fundamental rethink of what it means to clean a surface and why visible cleanliness is not the same as microbial safety.
At a recent ISSA Oceania webinar, leading microbiologists broke down the science in terms that matter to anyone responsible for cleaning outcomes in healthcare environments. The picture they painted was sobering, but also clarifying: the invisible threat has a logic to it, and understanding that logic is the first step to managing it.
What a biofilm actually is
A biofilm is a structured community of microorganisms – typically bacteria but sometimes fungi – that attach to a surface and become encased in a self-produced matrix of sugars, proteins and DNA. Texas State University chair and Regents’ Professor Rodney Rohde describes it simply: “Think of a sticky type of substance that these microbes and these substances are all mixed into, and they create this extracellular polysaccharide matrix.”
That matrix does more than hold the community together by actively shielding the microbes from disinfectants, antibiotics and even the body’s own immune response. Rohde explains that, within the biofilm, dormant ‘persister cells’ are particularly difficult to eliminate: “The drug, or the defence cell, or the disinfectant can’t reach it through a channel – there’s no transport.” Once the threat passes, those cells are primed to rebuild the biofilm from scratch.
The formation process occurs in stages, starting with the initial attachment to a surface, then multiplication, matrix production and eventually a mature, three-dimensional community capable of releasing cells to colonise new areas. Crucially, this entire process is invisible to the naked eye.
Why standard cleaning routinely falls short
Whiteley Corporation executive chairman Professor Greg Whiteley is a pioneer of dry surface biofilm research and has spent decades tracing the gap between cleaning activity and cleaning outcomes. He points to a seminal 2012 study that illustrated just how profound that gap can be. Even after double disinfection with chlorine, researchers found multi-drug-resistant organisms in biofilms on 90 percent of surfaces in a decommissioned ICU (intensive care unit). When those samples were bagged and stored for 12 months, the biofilms simply regrew, and all the bugs were still alive.
Whiteley has traced part of the problem back to the protocols introduced during the HIV pandemic, which standardised the use of neutral detergent without ever defining what a neutral detergent actually was. “None of that was ever defined,” he says. “The bugs are smart about that. They learned how to survive, and they learned how to grow and adapt.”
The distinction between wet and dry biofilms adds another layer of complexity. Wet biofilms thrive in sinks, drains, catheters and tubing, typically harbouring organisms like Pseudomonas and Legionella. Dry surface biofilms, in contrast, are found on bed rails, keyboards, door handles and any high-touch surface with even minimal residual moisture. These can persist for weeks or months, sometimes harbouring multi-drug-resistant organisms including Methicillin-Resistant Staphylococcus aureus (MRSA) and Vancomycin-Resistant Enterococci (VRE).
The challenge of shared resistance
What makes biofilms particularly formidable is their capacity to share resistance traits across different bacterial species within the same community. Rohde says bacteria use pili, tiny hair-like appendages, to touch neighbouring cells and transfer resistance genes horizontally, without waiting for a reproductive mutation event. The practical implication is that a single biofilm can become a reservoir of multiple resistance traits simultaneously.
Whiteley’s research demonstrates this resistance in quantitative terms that should give cleaning professionals pause. In dry surface biofilm conditions, MRSA has shown resistance to 20,000 parts per million of available chlorine, compared with the one part per million sufficient to kill planktonic bacteria in a swimming pool. In layman’s terms, strength of chemicals alone is not the answer. “You’ve got to be very careful,” Whiteley warns, “that you’re not snowed by false test methods.”
For cleaning teams, the message from the science tells us biofilm management demands sustained effort, validated products and an understanding of the difference between cleaning as a process and cleanliness as an outcome.
