There are many ways of looking at PAT. Before there were really defined standards, Panasonic would revoke the guarantee on any item that had a PAT test label. If we go back many years, especially the early days of valve amps, there were some lethal products around and the dangers were very real, but the various standards passed in the intervening years mean that equipment itself is very safe.
The venues are another matter, as @Phil Starrhas mentioned. A socket tester is your friend https://www.screwfix.com/p/kewtech-kewcheck-103-13a-socket-tester-230v-ac/45558.
The other point is that your lips are ultra snsitive and a very small elctrostatic charge could be just as likely from a microphone. Perhaps a foam shield? https://www.andertons.co.uk/shure-a58ws-blk-foam-windscreen-for-sm58-beta58a-sm48-and-565sd-mics/ will both protect you from shocks and also protect your mic from saliva.