They were way down the list, actually. At least at first. Because you could treat gonorrhoea effectively with sulphonamides by WWII, and syphilis with salvarsan (though this took ages).

Oh dear yes, there are all sorts of urban myths about Fleming and the discovery of penicillin: I am rather on the 'Florey/Chain/Heatley actually putting in the slog to make it effectively usable FTW' side.