Bacterial Skin Infections (Pyoderma) in Cats

What Are Bacterial Skin Infections in Cats?

A major function of the skin is to act as a protective barrier against infection. If this barrier is damaged and breached, bacteria can colonize and cause infection.

Bacterial skin infections in cats may be referred to as pyoderma. Both phrases relate to disease of the skin caused by germs. In medical terminology, the prefix “pyo-” means “pus” and the suffix “-derma” refers to the “skin,” forming the definition “pus in the skin.” Bacterial infections of the skin may be caused by an overgrowth of bacteria that normally live on the skin (normal flora) or by bacteria temporarily or not normally found on the skin. Cats develop pyoderma less commonly than dogs do.

If a skin infection is not treated appropriately, the infection can migrate deeper into tissues, causing worsening signs and further discomfort.

Types of Bacterial Skin Infections in Cats

Bacterial infections may be located on the surface of the cat’s skin, extend superficially into the outer layer of the skin (epidermis), or migrate into the deeper layers of the skin (dermis and subcutis).

• Surface: Infection rests on the surface of the skin and may include hot spots, skin fold irritation, and skin redness due to an overgrowth of bacteria.

• Superficial: The infection extends deeper than the skin’s surface into the epidermis and hair follicles. This is commonly caused by Staphylococcus bacteria.

• Deep: This type of infection occurs less commonly, but it is more harmful because it extends into the dermis and can lead to cellulitis or introduce bacteria into the blood. If infections are persistent and do not heal, there may be an underlying immune dysfunction such as feline immunodeficiency virus (FIV) or an atypical mycobacteria infection.

Symptoms of Bacterial Skin Infections in Cats

Signs of bacterial skin infection in a cat may include:

• Excessive scale or dander, especially on the lower back near the tail

• Crusts

• Small, firm bumps on the skin (miliary dermatitis)

• Hair loss

• Redness

• Open sores or ulcers

• Blood and discharge from sores

• Skin odor

• Scratching, licking, or rubbing the skin (itchiness)

Causes of Bacterial Skin Infections in Cats

Bacterial skin infection in cats can be caused by an underlying condition such as allergies, external parasites like fleas, Demodex, or feline chin acne. Areas on the cat’s body that are warm and trap moisture (skin folds) host the perfect conditions for bacteria that can lead to irritation and infection.

Diseases affecting the cat’s immune system such as feline immunodeficiency virus (FIV) or feline leukemia virus (FeLV) can cause an overgrowth of bacteria since a cat’s natural defenses are suppressed.

Injuries such as scratches or bite wounds that compromise the protective function of the skin can allow bacteria to colonize and cause infection, which may progress to an abscess. Endocrine disorders including hyperthyroidism and hyperadrenocorticism (Cushing’s disease) can affect the skin, potentially leading to infection. Inadequate grooming can leave the skin greasy and dirty and cause matting of the hair, which can also irritate the skin.

The most common bacterial strains include:

• Staphylococcus pseudintermedius (usually found on the skin)

• Pasteurella multocida (commonly found in the cat’s mouth and saliva)

How Veterinarians Diagnose Bacterial Skin Infections in Cats

Diagnosing a bacterial skin infection is based on the cat’s history, clinical signs, diagnostic testing, and ruling out other diseases and disorders.

The following diagnostic options may be recommended:

• Skin cytology—Your vet may take samples from the skin lesions and observe them under a microscope to confirm presence or absence of bacteria or white blood cells

• Skin scraping—Skin scrapings are taken to look for mites. This is accomplished by scraping the cat’s skin with a sterile scalpel blade deep enough to cause irritation or some mild bleeding to ensure any mites are included in the sample (Demodex lives deep in the hair follicles)

• Wood’s lamp—Any yellow-green fluorescence observed by lamp may indicate a fungal infection, like ringworm

• Trichogram—Plucked hairs can be examined under a microscope to look for any fungal spores or mites

• Fungal culture—May also be taken to look for fungal growth to help diagnose the cat’s skin condition

• Bacterial culture and sensitivity testing—This will tell the veterinarian what type of bacteria is present and provide direction on the best medication(s) for treatment, especially if the infection is recurrent or does not heal

Treatment of Bacterial Skin Infections in Cats

Successful treatment of a bacterial skin infection is based on the results of the diagnostic testing. 

The most common bacterial skin infection in cats is caused by Staphylococcus pseudintermedius. The most effective systemic antibiotics for treating this type of infection include:

• Clindamycin

• Cephalexin

• Clavamox®

• Trimethoprim sulfa

Topical medications include shampoos, creams, gels, ointments, sprays, wipes, and mousses. These products can be effective for superficial or mild skin infections and the active ingredients can be effective in eliminating bacterial infections. Recommended products include:

• TrizCHLOR® wipes

• Vetoquinol BPO-3™ Shampoo

• Douxo S3 PYO Antiseptic Antifungal Chlorhexidine Dog & Cat Shampoo

• Davis Benzoyl Peroxide Dog & Cat Creme Rinse

• Pet MD Antiseptic & Antifungal Medicated Spray

• Ethyl lactate (10%)

• Sodium hypochlorite (0.005%)

Recovery and Management of Bacterial Skin Infections in Cats

Bacterial skin infections take time to heal, and directions from your veterinarian should be followed precisely. Give the antibiotics exactly as prescribed and make sure your cat finishes all of them. Antibiotics may need to be given daily for three or more weeks. Severe infections may need 8-12 weeks of antibiotic therapy to heal. Superficial infections may be treated until all clinical signs resolve, and then be continued for an extra 7-10 days.

A recurrent or non-healing infection often has an underlying problem that has not been identified and is not being treated correctly. Other reasons an infection hasn’t healed include the antibiotics being stopped too early, the wrong medication being prescribed, or an incorrect dose being used.

Cats with pyoderma may benefit from having their hair clipped, especially long-coated cats. This helps with grooming by removing hair that may trap bacteria, dirt, dead skin cells, and oil. Regular grooming is recommended to help prevent matting of the hair, and it also helps identify any issues before they become a big problem.