Mobile phones are supposedly 'dirtier than toilet seats', being touched in all situations, multiple times a day. So how often do you disinfect your mobiles, and do you eat finger snacks while using it?
Personally, I take the mobile bump case off for a clean, only now and again...
Why did you come to think that germs that live on glass or metal are going to be harmful to you?
SOME germs might cause diseases and typically only in people who are already immunodepressed. The key to staying healthy is not to fight germs, but rather to... ehm... stay healthy
Your body and all its cavities are perfectly adapted to fight foreign bacteria and that is even before your immune system comes into play. All bacteria that live in your cavities and on your skin are your friends and outcompete "bad bacteria"... it's only when you try to get rid of ALL bacteria from your body that the bad ones are allowed to grow and thrive in the absence of competition, potentially causing disease.
Moral: wash less rather than more and even more importantly, avoid products that claim to kill bacteria and if you can, avoid chemical soaps altogether