Cats' mouths are not cleaner than the mouths of humans. According to Keeping it Kleen, felines have hundreds of micro-organisms living in their mouths like humans. A cat's bite is also more likely to foster an infection because they have sharper teeth.
However, cats do clean their coats frequently, which decreases their chances of contracting parasites like lice or ticks. Cats also keep their mouths closed more often than dogs, preventing additional bacteria from getting in the mouth. Keeping it Kleen believes cats are cleaner in regards to bathing habits, when compared to dogs, but dispels the notion of a cat's mouth being cleaner than a person's mouth.
Families.com notes that a cat's tongue contains hair-like tissues called papillae. These little tissues play a role in catching excess fur and dead skin, along with keeping odor at bay. Papillae also hold food and prey into place. A cat's tongue has the same composition as sandpaper, in order to act as a natural comb and brush.
The Nest mentions a cat's saliva as being a natural antiseptic against wounds, bacteria and viruses. Cat saliva contains a variety of antiseptic compounds,, including nitric oxide, lysozyme and lactoferrin. These compounds also prevent bacteria growth. Another element called opiorphin acts as a pain-killing agent.