Clean first, then disinfect

Cleaning with a microfiber cloth

Cleaning and disinfection have long been routine in any facility. Of course, the COVID-19 pandemic has further highlighted these operations since SARS-CoV-2 can persist on various surface materials for hours or days. Facilities have sought to improve these cleaning and disinfection practices. Therefore, it is imperative that this process be orderly. Therefore, this article addresses the importance of cleaning before disinfecting. Cleaning and disinfection should be a 2-step process to reduce the risk of transmission of environmental infections.

Clean first! Why?

Primum nitidare – “D’abord nettoyer (Clean First)”. It is a book that my coworker, Gaétan Lanthier, wrote in 2019. It is to say that this is not a new subject!

Centers for Disease Control and Prevention (CDC) cites: “cleaning is “the necessary first step of any sterilization or disinfection process” or, more
simply, you must clean first before you can disinfect.”

The CDC adds: “Cleaning is the necessary first step of any sterilization or disinfection process. Cleaning is a form of decontamination that renders
the environmental surface safe to handle or use by removing organic matters, salts, and visible soils, all of which interfere with microbial inactivation.”

It’s in the mechanical action (friction)

As the CDC mentions it: “The physical action of scrubbing with detergents and surfactants and rinsing with water removes large numbers of
microorganisms from surfaces.”

Studies have shown that friction or mechanical action is at the heart of cleaning. This facilitates the effective removal of dirt, debris, microbes and soiling, making a surface ready for disinfection if necessary.

It’s a matter of interference

The CDC defines cleaning as the “necessary first step” in any disinfection process for “at least two” important reasons: it removes any barrier between the disinfectant and the target pathogen, and it removes materials that could potentially inactivate the disinfectant.

In order to effectively kill pathogens, disinfectant chemicals must have direct contact with the pathogen; however, soils, dirt, and debris can coat or
protect microorganisms, essentially serving as a protective barrier between the chemical and the target.

The build-up to biofiolms

Another important reason to clean first before disinfecting has less to do with the immediate action of a disinfectant on a surface. Rather, it is in prevention of a future problem, namely the buildup to biofilms.

Biofilms are populations of microorganisms attached to a solid surface and protected by a “viscous layer”. This layer is an extracellular matrix of polysaccharides and non-cellular materials.

Biofilms can virtually form on any hard surface, from the countertop to the water pipe. They are involved in a range of infectious diseases.

What about touch-free technology?

Comac ULVC Electrostatic Sprayer for Disinfection

Although research has shown that many of these systems, from ultraviolet light (UV-C) to hydrogen peroxide vapor (HPV) to electrostatic sprayers, can reduce microbial contamination, experts caution that they should be used as a complement to standard manual cleaning and disinfection rather than as a replacement.

Organic matters, dirt and grimes are a limiting factor for UV-C technology.
A light or heavy organic load has a significant negative impact on the destructive efficiency of the devices.

In short, clean first with mechanical action (friction) to remove dirt, debris and microbes. The disinfection step is to be done when the interferences are removed by cleaning in order to kill microbes. This reduces the risk of transmission of environmental infections by keeping surfaces clean.

Loose translation of Rubbermaid TWO STEPS FOR A REASON:


An enzyme to destroy biofilms

One can not stop the progress. The discovery of an enzyme capable of preventing the production of a biofilm, this polymeric protective layer produced by bacteria that prevents antibiotics and surface disinfectants from functioning well, could ultimately revolutionize the fight against nosocomial infections.


The team at the McGill University Health Center, which includes Dr. Donald C. Sheppard, has published a study in the journal Proceedings of the National Academy of Sciences (PNAS). Their hope is that this technology will be the subject of human clinical trials in Canada within 5 years and be used in hospitals within 10 years.

From the abstract:

We demonstrate that glycoside hydrolases derived from the opportunistic fungus Aspergillus fumigatus and Gram-negative bacterium Pseudomonas aeruginosa can be exploited to disrupt preformed fungal biofilms and reduce virulence.

What is a biofilm?

My colleague Rémi Charlebois described biofilms as follows:

Biofilms found on surfaces are often derived from a complex colony of microorganisms producing polymers that allow them to adhere better to the surface and facilitate colony life. In short, a biofilm is like a city for microbes. Man has learned to tame these biofilms and can use them to treat wastewater or produce certain molecules such as natural plastics. However, the presence of unwanted biofilms could be harmful and can lead to infections.

Biofilms are also found on the skin and medical devices. Thus, according to the article of Le Devoir:

Biofilms, a highly sticky matrix of proteins and sugar polymers made by bacteria to protect themselves, are attached to the skin, mucous membranes or the surface of biomedical materials, including catheters, tubing, heart valves and other prostheses Which become preferred entry points for infection.

In the same article, Dr. Sheppard quotes:

Biofilms are produced by molecules that defend against our immune system or against antibiotics with this shell that is 1000 times more resistant than the organisms that produce and proliferate in these biofilms.

An enzyme that acts as a “destructive machine” for biofilms

In short, the enzyme discovered was modified to destroy the biofilms instead of forming them. This is a new strategy that can reduce nosocomial infections in healthcare centers.

Watch this video about biofilms (25 minutes, french)


Biofilms: What you should know.

Biofilms are everywhere

Well hidden or sometimes visible, always disgusting, biofilms, as so well described by my colleague Rémi Charlebois, are defined as follows:

Biofilm is an aggregation of microbial cells, surrounded by a protective layer of extracellular polymeric matrix, which attaches itself to any surface found in the hospital environment and becomes a source of contamination. Formation of complex, multicellular communities by microorganisms is a natural phenomenon which helps bacteria or fungi to survive environmental stress such as cleaning and disinfection.

Warning: Graphic Content Ahead

A Biofilm looks like this:

Kitchen Drain



Sink strainer






Toilet Bowl



How to remove biofilms

Here are 3 methods to eliminate biofilm:

Replace equipment

This mehode is somewhat drastic, probably very expensive certainly mostly impractical. Some industries still proceed that way in 2016. I must say that in some cases it may be the only and best solution. For example pipe sections, filters, etc.

Strong acids and bases

Hydrochloric or Peracetic acids or strong bases such as caustic are sometimes used alternatively. However, corrosivity and danger of these chemicals can damage surfaces, individual protection equipment, storage and handling can also be a challenge . Furthermore, there is always the workplace hazards.

Biofilm: The Next Big Thing in Disinfection


The Next Big Thing in Disinfection: Biofilm

Have you ever wondered what are the main factors affecting the efficacy of disinfection and sterilization in the healthcare facility? U.S. Centers for Disease Control and Prevention lists seven major causes of microbiological persistence on surfaces:

  1. Number of microorganisms
  2. Microbial resistance to biocides
  3. Concentration and Potency of Disinfectants
  4. Duration of Exposure
  5. Chemical and Physical Factors
  6. Presence of Organic or Inorganic Matter
  7. Biofilms

For many experienced healthcare professionals, these factors are well known and often well dealt with. However, did you know the difference between soil (organic and inorganic matter) and biofilm? They both can significantly lower the efficacy of disinfection, but the biofilm is much harder to remove and control.

What is biofilm and how does it form?

Biofilm is an aggregation of microbial cells, surrounded by a protective layer of extracellular polymeric matrix, which attaches itself to any surface found in the hospital environment and becomes a source of contamination. Formation of complex, multicellular communities by microorganisms is a natural phenomenon which helps bacteria or fungi to survive environmental stress such as cleaning and disinfection.

Many pathogens require a presence of conditioning layer made from organic soil to settle and start extracellular matrix synthesis. But there are bacteria which don’t really need much help to start a biofilm community. When pathogens settle down and surround themselves in an extracellular polymeric substance (EPS), they are much harder to kill.

It has been reported that bacteria found in biofilm can be up to 1,000 times more resistant to biocides than their planktonic counterparts.

How to outsmart and fight biofilm?

Despite biofilms’ rigid structure and resistance mechanisms, biofilm cells can still be outsmarted. Since EPS is the ultimate protective barrier and communication route for pathogens, the control of biofilm should start with disruption of the EPS itself, followed by an application of a biocide.