Cats' sharper teeth can penetrate tissue more deeply that the blunter teeth of dogs. They don't necessarily carry more bacteria but they can inject them deeper into tissues through smaller wounds. It's a hazard all right. However, over 45 years of cat ownership and now with cat number seven, I've been bitten many times by my cats, mostly during play. I read stuff on one US website that said that one cat bite victim in three ends up in hospital. Well I don't recognise that at all, you won't be surprised to know. If my cat bites me I wash the wound in warm soapy water and wipe it gently with an antiseptic wipe. That has always done the trick and I've never had an infection, either from scratches or bites, and I've never had to consult a doctor. The only time I've been bitten by a dog, it was by an Alsatian that broke away from its owner across the road and charged towards the unsuspecting seven-year-old me (we took the owner to court). I contend that aggressive dogs that attack people represent a dimension in this discussion that can't be levelled at cats. It isn't great to be bitten by either animal, of course.