The way we wash our hands daily can remove dirt and transient bacteria. However, it's not possible to remove the resident bacteria that naturally live on our hands. For instance, Staphylococcus aureus, commonly known as staph, cannot be washed away. In fact, washing hands may even bring staph to the surface, increasing the risk of transferring it to food. This article will discuss the purpose, meaning, and microbiological aspects of handwashing.
Transient Bacteria and Resident Bacteria
Many people believe that washing hands can rid them of all microbes on the palms. However, this belief is mistaken.
There are two types of bacteria on the palm of the hand. The first type is known as transient bacteria. These are bacteria that adhere to the palms from external sources while walking around in the city. They may include pathogenic bacteria. Such transient bacteria can be washed off with careful hand washing.
However, there is another group of bacteria that resides on the palms, known as resident bacteria. These bacteria naturally live on the human palm, including various types of staphylococci, among which is the food poisoning bacterium, Staphylococcus aureus.
These microorganisms thrive on the palm, utilizing secreted sweat and lipids for nourishment. They inhabit not just the surface of the hand but also deeper areas like hair follicles. Therefore, they are not easily washed off just by hand washing.
Hand Washing Doesn't Eliminate All Bacteria
In my university classes, I conduct an annual experiment with my students where we measure the number of microbes on their hands before and after washing, using the plate culture method. Over 10 years of conducting this experiment, we observed that in some cases, the number of bacteria increases after washing. (Note: The hand washing method used by the students was their usual one, not the thorough cleansing methods recommended in food factories. Therefore, the results may vary depending on the hand washing method, type of soap used, and duration of washing, and cannot be generalized.)
This implies that while washing hands can remove most transient bacteria, the resident bacteria, such as those typically living on the palms, are not easily removed by simply washing with soap. Consequently, washing hands can remove transient bacteria, but it may bring resident bacteria like Staphylococcus aureus to the surface.
Therefore, it's important to understand that washing hands doesn't make them sterile. While hand washing can remove harmful bacteria acquired from the environment, it cannot remove resident bacteria like Staphylococcus aureus.
This is why people involved in food manufacturing or sales should never touch food with bare hands, as resident bacteria from the palms, including Staphylococcus aureus, can transfer to the food.
