For my project for the fourth grade science fair, I tested several soaps to see which ones were most effective at keeping your hands clean.
Now, almost 20 years later as a PhD candidate in microbiology, I can’t help thinking: “Ugh, the fourth grade was such an amateur scientist!”
My experiment lacked obvious control groups and ultimately asked the wrong question. Instead of asking which brand of soap was the most “effective” and classifying all bacteria as germs, I should have studied how to prevent the growth and spread of specific pathogenic or pathogenic bacteria.
It is difficult to answer this question. It cannot be said by eye which bacteria that grow inside a Petri dish are the “good guys” compared to those that cause disease, and some pathogenic microbes, such as viruses, cannot be detected inside Agar petri dishes.
However, asking how to prevent the spread of disease-causing pathogens is not only for aspiring microbiologists, but a big question for everyone.
Do we really have a chance to keep our hands clean of germs?
Two punch approach
There are two main strategies.
The first is to reduce the overall biomass of microbes, i.e. to reduce the amount of bacteria, viruses and other types of microorganisms. We do this by foaming with soap and rinsing with water. Soap chemistry helps remove microorganisms from our hands by accentuating the slippery properties of our skin.
Studies have shown that effective washing with soap and water significantly reduces the bacterial load of the bacteria causing diarrhea.
The second strategy is to kill bacteria. We do this by using products with an antibacterial agent such as alcohols, chlorine, peroxides, chlorhexidine or triclosan.
Some academic work has shown that antibacterial soaps are more effective in reducing certain bacteria on dirty hands than soaps without them.
However, there is a problem. Some bacterial cells on our hands may have genes that allow them to be resistant to a certain antibacterial agent. This means that after the antibacterial agent kills some bacteria, the resistant strains that remain on the hands can thrive.
Additionally, the genes that allowed bacteria to be resistant could switch to other bacteria, causing more resistant strains. Together, the “take over” of resistant strains would make the use of the antibacterial agent substantially ineffective.
In addition, long-term use of some antibacterial products can harm health.
For example, animal studies that study the antibacterial agent triclosan, which was present in soaps, toothpastes and deodorants, have been shown to alter the way hormones act in the body.
The Food and Drug Administration has banned the use of over-the-counter antiseptic washing products containing triclosan and many other antibacterial active ingredients.
With that in mind, you may want to stick with simply old soap and water.
To clean our hands, the Centers for Disease Control and Prevention recommend:
- wet hands with clean water.
- apply soap and foam / rub each corner of the hands for 20-30 seconds (about the time to sing “Happy Birthday” twice).
- rinse well with clean running water.
- dry your hands with a clean paper towel or air dry.
I was shocked to read a study which indicated that 93.2 percent of the 2,800 respondents did not wash their hands after coughing or sneezing. In addition, a study showed that in a university setting with 3,749 observations, the average hand wash time was around six seconds!
If soap and water are not available, the CDC recommends using an alcohol-based hand sanitizer that contains at least 60% ethanol. Alcohols have a broad spectrum of antimicrobial activity and are less selective for resistance than other antibacterial chemicals.
However, alcohol-based hand sanitizers may not work on all classes of germs.
Not all microbes are germs
The presence of some bacteria is not necessarily a bad thing.
In the laboratory where I am pursuing my degree thesis, our goal is to understand the complex interactions between animal hosts and bacteria. I would not like to mention that the bacteria that live above or within us are essential for us as guests, especially considering their role in protecting us from pathogens.
We live in a microbial world: trillions of different bacteria colonize our skin, intestines and orifices. Collectively with yeast and viruses, they are called our microbiota.
A plethora of exciting research suggests that associations of animal hosts with their microbiota are not rare events but are in fact of fundamental importance for the biology of the host.
Our microbiota can protect us from germs by training our immune system and resisting colonization): the characteristic of the intestinal microbiota to block the colonization of pathogens.
Although further research is needed to understand the intricate interactions between microbial communities and host cells, coherent work shows that a different population of microbes and a balance of this community are important for our health.
Poor nutrition, lack of sleep, stress and the use of antibiotics can adversely affect our microbiota communities, which in turn can put us at risk of disease.
Indeed, it is becoming clear that our microbiota actively participates in the prevention and sometimes driving of diseases, depending on the state of the microbial communities.
So what is the message to take home?
There is no doubt that washing your hands with water and liquid soap is effective in reducing the spread of infectious microorganisms, including those resistant to antimicrobial agents.
When you don’t have the opportunity to wash your hands after touching questionable surfaces, use an alcohol-based hand sanitizer. Limit the touch of the hands to the mouth, nose and eyes.
In addition, maintaining a healthy microbiota by limiting stress, getting enough sleep and “fertilizing” intestinal microbes with a variety of plant-based foods. It is not only a small world, but also dirty.
Michelle Sconce Massaquoi, PhD student, microbiology, University of Oregon.
A version of this article was first published in December 2017.
This article was republished by The Conversation with a Creative Commons license. Read the original article