The Misconception of Disinfectant Resistance: Answering This Question I Received at ISSA 2023
At the annual International Sanitary Supply Association (ISSA) in November, I presented a thought leadership session on sustainability and how eco-conscious disinfectants can be as effective as traditional. Talking to people after my presentation I heard the same question several times: “How often would I have to switch disinfectants to make sure the pathogens don’t become resistant to them the way they become resistant to antibiotics?” Rotating sanitizers is sometimes still practiced in food processing and in pharmacy compounding, but there are different reasons those places may want to do this that don’t apply broadly. While my colleague addressed pathogen resistance to disinfectants in a previous blog, I want to focus on the differences between antibiotic resistance, immune evasion and disinfection resistance.
Antibiotic Resistance, Immune Evasion, Disinfectant Resistance
Because of the COVID-19 pandemic, we have become familiar with news headlines about viruses evolving to evade our immune system. Additionally, we see lots of scary news coverage about antibiotics not working against common bacteria anymore. It is easy to feel like surface disinfectants would be no different.
To help explain antibiotic resistance, immune evasion, and disinfectant resistance, first imagine that pathogens are like a house. The house has certain functions: the stove and oven to cook food, the doors and windows have locks to keep bad things out and good things in, the bathroom fixtures and plumbing system to eliminate waste. All these things need to work for the house to do its function.
We have developed ways to prevent bacteria and viruses from performing their functions: our immune systems fight them off, and we have antivirals and antibiotics to help where our immune systems cannot handle it alone. But bacteria and viruses have evolved their own protections as well.
Antibiotic Resistance: Finding a Workaround to Something Broken
Antibiotics work by breaking something crucial for the bacteria’s survival. Bacteria need to be able to make proteins to build their walls, they need to eliminate waste, and they need to process nutrients. Antibiotics come in and break one part of it. But in certain cases, bacteria have evolved resistance to antibiotics that can help them remove or inactivate the drug. This would be like breaking your oven. This would prevent you from making some food. But if you were resistant, you could easily fix the oven or remove whatever was keeping it from working and continue functioning as normal.
Immune Evasion: Like Changing the Locks
During the COVID-19 pandemic, we became familiar with terms like “immune evasion” to describe new variants of COVID-19 that our immune systems could not recognize. The immune system generally recognizes proteins on the outside of a pathogen — things on the surface. Immune cells have receptors that fit the proteins on a virus like a lock and a key. Once the immune cell binds to the virus, it can open it up and get inside, killing the virus. A virus like COVID-19 can easily change the shape of a protein on the surface to avoid the immune system. Basically, the virus can change the locks on the house and the immune system takes a while to make a new key.
Disinfectants Destroy the Whole House
I have now explained how antibiotics work to kill bacteria, and how the immune system works to kill viruses. What both of these have in common is that they are highly specific. The immune system recognizes viruses using very specific receptors, like a lock fits a key. Antibiotics work by targeting very specific pieces of bacterial function — like penicillin prevents bacteria from tying proteins together. Bacteria can evolve mechanisms to break down penicillin, and viruses can evolve their structure so that the immune system key doesn’t fit the lock anymore.
Disinfectants, by contrast, are not specific. They broadly destroy the structures of pathogens and have multiple targets and multiple sites of action. To use the house analogy, a disinfectant will blow holes all over the walls and roof until the whole house collapses. There is no way a pathogen can evolve to protect themselves from that. If you want to learn more about how different types of disinfectant active ingredients work to destroy pathogens, I cover the different mechanisms in this blog.
There Is No Need to Rotate Disinfectants — Follow These 3 Tips to Disinfect Properly
Now to return to the questions I received at ISSA 2023. There is no need to rotate disinfectants to prevent resistance! What is most important is to use a disinfectant properly:
- Follow the instructions for use on the label. Some products require you to pre-clean the surface before disinfecting.
- Choose a disinfectant that can kill the pathogens you are concerned about.
- Leave product visibly wet on the surface long enough to meet the contact time. Products with a contact time of 2 minutes or less make it easier to disinfect without needing to re-wet the surface.