It's a bit simplistic to claim that stink is caused by bacteria. When you sweat, you don't just sweat distilled water; you exude salts, oils, and pheromones, too. And yes, for some people, that stinks. Clothes pick it up, too; especially shirts and jackets. If I were riding more than a mile or two, at minimum I'd want to wipe down, powder the pits, and change the shirt.