Bacteria and sweat
The amount of bacteria in the shoe will be higher if worn without socks.
Feet, bacteria and smell
Have you noticed that very often, when someone takes off his shoes, a strong stench is released? This strong smell is actually caused by the bacteria and the sweat on our feet. Each of our feet has over 250,000 sweat glands in them. When our feet get warm, they will start to sweat in order to cool down (when the sweat evaporates).
When we wear socks and shoes, the sweat in our feet is unable to escape anywhere. The moist, warm and dark environment in our shoes is perfect for bacteria to multiply and reproduce. The sweat produced by our feet actually does not have any smell r. The smell in fact arises, when the bacteria consumes our sweat for their metabolism. The fatty acid that is produced as a waste product causes the smell in our feet.
The reason some people have more smelly feet than others is because they sweat more. The number of sweat glands and the amount of sweat secreted will differ from person to person, depending on their physiology and body metabolism.
The bacteria should be destroyed before the swabs are discarded. Pour some bleach into the petri dish to kill all the bacteria before disposing in the trash.