Friends, my shower gets a little funky here in the tropics. Is that bar of soap in the soap dish in my shower an oasis of clean or are there germs, bacteria, virus; mold/mildew/ fungi of any sort? I know I’ll get answers here. Aloha.
I can’t give you an authoritative cite but I was surprised to be awakened from my naivete when I read in a magazine someplace that bars of soap in public bathrooms can transmit germs quite effectively. There’s nothing magically antiseptic about ordinary bar soap that is not made to be antibacterial. As long as it’s wet it can do a fine job of harboring bacteria. I don’t know if the same is true regarding fungus/mold/mildew.
I would also think, however, that your own bar of soap in your own shower would not have any germs that you didn’t bring in there yourself in the first place.
Well I know some bad bacteria can grow on soaps, like Pseudomonas aeruginosa which grows on Quats (quaternary ammonium), which are used to sterilize things, so I’m sure there are things in your soap. Your shower is loaded with Serratia, the orange bacteria you can see growing everywhere, and possibly on your soap. It can cause diseases in rare cases.
Most soaps contain triclosan which inhibits fatty acid biosynthesis, and some bacteria (like Pseudomonas) are resistant to it as well. Wikipedia says those others are Escherichia coli, Staphylococcus aureus and Bacillus, all of which can cause infection.