Anaerobic Bacterial Infections in Dogs

4 min read

Anaerobic infections are those that involve bacteria that 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 from other animals. Anaerobic infection should be suspected when a wound is healing very slowly.

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

Symptoms and Types

Depending on the cause of the anaerobic infection, dogs may display a variety of symptoms. Dogs 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 dogs 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 dog'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 dog's health, onset of symptoms, and possible incidents that might have led to this condition, such as injuries, even slight injuries, fights your dog 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.

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