Anaerobic Bacterial Infections in Cats

By PetMD Editorial on Dec. 16, 2009

Anaerobes are a normal part of the body's chemical community, living in symbiosis in the cat's abdomen, vaginal canal, intestines and mouth. However, when something happens to disrupt the balance of bacteria, such as what occurs with deep injuries, surgery or internal infections, these bacteria can invade the tissue, leading to deep infection and tissue death. If left untreated, an anaerobic infection can lead to shock and even death.


The bacteria which cause anaerobic infections are able to grow best in the absence of free oxygen. Consequently, these bacteria often thrive in the mouth around the gums; in deep wounds, such as those caused by puncture to the skin; in wounds caused by fractured bone, where the bone has broken through to the surface; and in deep bite wounds.


Symptoms and Types


Depending on the cause of the anaerobic infection, cats may display a variety of symptoms. Cats that have developed an anaerobic bacterial infection because of a wound, for instance, may display bite marks, have pus oozing from the wound, or open fractures (where bone sticks out). Moreover, wounds infected with anaerobic bacteria will be slow to heal. Other common symptoms of anaerobic bacterial infections in cats include fever, lameness, difficulty eating, and loss of appetite (related to infection of the gums).

There are also several types of bacteria that can lead to infections, including:

  • Bacteroides
  • Fusobacterium
  • Actinomyces
  • Clostridium
  • Peptostreptococcus


The ultimate cause of an anaerobic bacterial infection is the disruption of normal bacterial balance within the cat's body. This can be due to deep injury, trauma, or recent surgical procedures (such as abdominal surgery or when metal implants are placed within the body to support broken bones).



You will need to give your veterinarian a thorough history of your cat's health, onset of symptoms, and possible incidents that might have led to this condition, such as injuries, even slight injuries, fights your cat might have had with another animal, problems eating (which may be related to a mouth infection), and any recent surgeries. Your doctor will need to rule out other causes before making a confirmation of anaerobic infection.


Standard tests include a chemical blood profile, a complete blood count, and a urinalysis, any of which may show a higher than normal white blood cell count, or evidence of a systemic infection. Your veterinarian will be taking samples of any pus along with the tissue (skin/muscle) around the wound to be laboratory cultured (grown) without oxygen. If there is growth, this may be taken as a confirmation that anaerobic bacteria are present.




Your veterinarian will put your cat on long-term antibiotics. While it can be frustrating to give your cat pills for weeks, it is essential to do so for the entire course, even after the symptoms have passed and your cat appears to be better. If even a small amount of the infection remains, it can return worse than before. For especially reluctant cats, many of them will eat pills that have been hidden in a small amount of food that your cat does not normally receive, such as a piece of fresh fish or chicken meat (cooked). If you use this method to give antibiotics to your pet, always be sure that the cat has eaten and swallowed the entire bite of food and that it is not spitting it out in a hidden place (behind a couch, etc.). 


Specific treatment will be dependent on whether the infection is in an easily reachable location. If the infection is in the muscles (of the legs, back, rump, neck, etc.) the veterinarian will open the wound, clean out the dead tissue and expose the tissue to oxygen. If the anaerobic infection is within the body, such as an infected uterus, inside the bones, or in the abdomen, then the veterinarian will have to anesthetize the cat to surgically open and clean and/or drain the wounds. 


Living and Management


These infections are often long-lasting and require long-term antibiotics and monitoring by a veterinarian. It is important to give the antibiotics to your cat on time and as your veterinarian has instructed. If there is bandaging, have your veterinarian go over cleaning and redressing procedures, to ensure that the wound is able to heal. You may need to use am Elizabethan collar, or cone, to keep your cat from getting to the wound.


Be sure to take your cat back for regular follow-up appointments so that wounds may be reopened and cleansed if necessary. Biochemical profiles will also be repeated at follow-up veterinary visits to check on the status of the infection. 


In-between visits, you should call your veterinarian if you notice any changes in your cat's behavior. If the cat seems very tired, has no appetite, or has any redness, swelling or pus at the site of the wound, for example, be sure to consult your veterinarian immediately. 


During the healing process, you may need to limit or prevent your cat's outdoor time, to prevent the infected site from getting dirty, and keep the litter box cleaner than usual (i.e., cleaning after each use) to prevent additional bacteria from entering the wound.

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