What bacteria is in a cat’s mouth?

The great bacterial culprit in the mouth of domestic cats is a bacterium called Pasteurella multocida. It is found in the mouths of between 70-90% of domestic cats and perhaps more importantly between 50-80% of people at the site of a cat bite (Cornell). So, this particular bacterium is the major cause of infections from a cat bite. It is a zoonotic disease because it can be transferred from cat to person.

Bacterium is domestic cat's mouth
Bacterium is domestic cat’s mouth. The central image is by Dr Stannard. If there is a problem with this please contact me via a comment and I will respond quickly. Thanks.
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Pasteurella multocida

Pasteurella multocida is a type of bacteria that is commonly found in the mouths of cats and other animals. It can cause a variety of infections in both animals and humans, including skin infections, respiratory infections, and abscesses. In cats, Pasteurella infections are often associated with bites or scratches, as the bacteria can be transmitted through breaks in the skin. Cats with Pasteurella infections may have symptoms such as swelling, redness, and pain at the site of the infection, as well as fever, difficulty breathing, and loss of appetite. If your cat is showing signs of a Pasteurella infection, it is important to seek veterinary care as soon as possible to prevent the infection from spreading and to help your cat recover.

Cat bites signs of infection – including a possible infection from a scratch

Symptoms and treatment

Infections of your hand from a cat bite in which this bacterium has been ‘injected’ under the skin may develop pain, swelling and redness at the wound site within 24-48 hours. The treatment is straightforward: prompt antibiotic treatment by pills. I did some work on this and listed the best antibiotics to deal with cat bites which may interest you (see link below). That said, you should seek your doctor’s advice.

Best antibiotics for a cat bite

What to do?

I have said it before, the way to deal with cat bites is to watch and wait with vigilance. If there is an infection you must treat it quickly with antibiotics. If you leave it, it’ll get worse and if you are an elderly person, it can even end up killing you, or the hospital that you go to might kill you through neglect! That said most cat bites are not serious and don’t result in a bacterial infection.


In America, CDC state that another species of bacterium called Capnocytophaga is present in the mouths of dogs and cats. Although they do say it is rare for this “germ” to be transmitted to people through bites and scratches. Although, a study published on the National Library of Medicine states that Capnocytophaga canimorsus can be underestimated in its dangers particularly to people suffering from alcohol abuse. The preferred drug of choice in prophylaxis of this infection is amoxicillin with clavulanic acid. That’s according to this study.

Don’t demonize the cat!

We should not demonise the domestic cat because of the bacteria in their mouth. Humans have bacteria in their mouth which is just as toxic and dogs too. I guess the reason why cats are spoken of in the context of bites is because they have long canine teeth and they do like to use them! Normally to kill prey animals but occasionally to bite the lower part of the leg of their owner in play or in perhaps in redirected aggression.


In healthy cats, certain types of bacteria (Porphyromonas, Moraxella, and Fusobacterium) are most common, and among those, the species Capnocytophaga canimorsus is the most prevalent. In cats with oral diseases such as gingivitis or mild periodontitis, different types of bacteria (from the phyla Spirochaetes and Bacteroidetes and the Peptostreptococcaceae family) tend to be more dominant. Another study mentioned in the passage found that a subspecies of Pasteurella multocida called Pasteurella multocida subsp. multocida was more common in diseased cats compared to healthy cats (Source is a study entitled: Characterization of Oral Microbiota in Cats: Novel Insights on the Potential Role of Fungi in Feline Chronic Gingivostomatitis)

Below are some more articles on cat bites.

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