OVERVIEW

Pyoderma is a bacterial infection of the skin. Pyoderma can be divided into surface pyodermas (infection on the skin surface), superficial pyoderma (infection within the skin) or deep pyoderma (infection under the skin).

The health impact from pyoderma can range from mild with superficial pyoderma to severe with deep pyoderma. Superficial and surface pyodermas can cause intense itching leading to discomfort. The underlying cause of the pyoderma may also have a negative health impact on the dog, depending on the disease.

WHAT TO WATCH FOR

Any of these should trigger a visit to your veterinarian:

Red, itchy and painful skin lesions
Pustules (pimples)
Draining sores
DIAGNOSIS
Diagnostic tests may include:

A detailed medical history. Expect to be asked about how long the lesions have been present, what they looked like initially, and whether itching preceded the lesions or appeared after the lesions.

A complete exam of all body systems with particular attention paid to the type and location of lesions present in the skin.

Cytology. A pustule may be opened and the contents examined under a microscope. With a pyoderma, bacteria and neutrophils (a type of white blood cell) are usually seen. Neutrophils without bacteria may suggest another disease.

Culture. Deep pyodermas are typically cultured to identify the exact bacteria that are present and to help select the best medication. Superficial pyoderma lesions are rarely cultured since they almost always grow the same bacteria (Staphylococcus intermedius).

Other tests, such as skin scrapes, allergy tests, complete blood count or blood chemistry analysis, to determine the underlying cause of the pyoderma, especially if the pyoderma recurs after treatment.

Treatment may include:

Antibiotics to help kill the bacteria infection

Antibacterial shampoos and creams containing benzoyl peroxide, ethyl alcohol or chlorhexidine

Treatment to prevent underlying itchy skin diseases or diseases that suppress the immune system for long-term success

Give all medications as instructed. Even if lesions clear up early, antibiotics should be given until all medications are finished. Observe your dog for draining lesions. Some causes of pyoderma are not preventable, but the presence of fleas can worsen pyoderma. The best prevention is to follow a complete flea control program as recommended by your veterinarian. In addition, keep your dog clean and brushed free of mats.

INFORMATION IN-DEPTH

SURFACE PYODERMA

A hot spot (pyotraumatic dermatitis) is a surface pyoderma that is caused by self-trauma due to some itchy problem, often an allergy. It has the appearance of a moist, red lesion with acute loss of hair and is intensely itchy.

Skin fold pyoderma occurs in folds of skin that are moist and difficult for the animal to keep clean. Examples are: facial fold, tail fold, vulvar fold and lip fold pyoderma.

Superficial pyoderma is infection within the skin. The bacterium that is nearly always incriminated in this infection is Staphylococcus intermedius. This form of pyoderma is the most common kind and affected animals have pustules that may rupture leaving a ring of scale that is called an epidermal collarette.

Pustules may or may not be associated with hair follicles. Pyoderma associated with hair follicles causes hair loss (alopecia) as the pustules rupture. Superficial pyoderma rarely is a primary disease, but rather is a symptom of another skin problem. These underlying skin problems can be pruritic (itchy) or be caused by a suppressed immune system.

Pruritus (itching) leads to self-trauma that causes damage to the skin and breakdown of natural defense mechanisms allowing bacteria to penetrate into the epidermis causing pyoderma. Examples are allergy and infestation of parasite like mites or lice.

A suppressed immune system may allow bacteria to establish an infection within the skin. Examples are: hormonal diseases, like Cushing’s disease or hypothyroidism, some infectious diseases, cancer or any disease that suppresses the immune system. Excessive use of corticosteroids like prednisolone can suppress the immune system.

There are some cases of pyoderma that recur after treatment, yet an underlying cause can never be found. This is called idiopathic pyoderma or primary pyoderma.

Superficial pyoderma must be differentiated from other diseases that present with pustules such as autoimmune skin diseases and certain fungal skin diseases.

Deep pyoderma is rare in dogs but is much more severe than the more common forms. Dogs with deep pyoderma have severe bacterial skin infections with open, draining sores and fever. These animals are very sick, are often not eating and are very depressed.

The bacteria that has infected the skin can be any of a number of species of bacteria and more than one species may be present. All dogs with this form of pyoderma are assumed to have suppressed immune systems.

VETERINARY CARE IN-DEPTH

DIAGNOSIS IN-DEPTH

Your veterinarian will take a thorough medical history and examine all body systems. Other medical tests will be necessary to establish the diagnosis.

Microscopic examination. Your veterinarian may open a pustule and apply the material within the pustule to a microscope slide. The slide is then stained and viewed under a microscope. The presence of pyoderma will reveal bacteria with white blood cells, especially neutrophils.

He may also make an impression of the discharge from a draining sore seen with deep pyoderma by pressing a slide to the lesion. This slide can be stained and examined under the microscope.

Culture and antibiotic sensitivity. In cases of deep pyoderma lesions, this test must be done to identify the bacteria responsible and to select the most appropriate antibiotic. Cultures of superficial pyoderma pustules are rarely done, since they nearly always grow Staphylococcus intermedius.

Visualization. Your veterinarian can usually diagnose surface pyoderma by visualization of the lesion. Hot spots have a characteristic appearance of a moist, red skin lesion with sudden hair loss. Skin fold pyoderma is a red, moist lesion associated with a skin fold. Hot spots are triggered by an itchy skin problem. Thus, diagnostics to determine the itchy underlying cause may be necessary, especially with recurrent hot spots. Often, flea allergy is the culprit.

Superficial pyoderma may cause a dog to be itchy. This can cause confusion in the diagnostic process since itching may lead to pyoderma. The veterinarian may ask if your dog's lesions preceded the itching or if the itching preceded the lesions. If the itching came first, then a pruritic underlying cause is suspected. If the lesions appeared first, then immune suppression may be the cause.

If itching is suspected, the following tests may be done to determine the source of the problem:

Examination of the skin and hair with a flea comb for fleas and lice

A skin scraping to look for mites and other microscopic parasites

Fungal cultures to rule out ringworm fungus (dermatophytes). These skin fungi may cause itching and lead to a secondary pyoderma.

Allergy testing or a food trial to rule out food allergy in chronic cases of pyoderma

In cases where superficial pyoderma is suspected to be caused by immune suppression and in all cases of deep pyoderma, tests are needed to look for the cause of the immune deficiency. Examples include:

Thyroid assays to see if the thyroid gland is making enough thyroid hormone

Tests for Cushing’s disease (hyperadrenocorticism), a disease where the adrenal glands make too much of a hormone called cortisol. One effect of the excessive cortisol can be immune suppression.

Severe, chronic illnesses, such as cancer, can suppress the immune system.

FOLLOW-UP

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not improve rapidly.

Most cases of surface and superficial pyoderma respond well to the therapy outlined above and therefore require little follow–up, unless the case is recurrent or never resolves. Deep pyoderma requires regular recheck exams to monitor for progress.

Be sure to administer all prescribed medication as directed, and alert your veterinarian if you are experiencing problems treating your dog. Antibiotics can have side effects that may require the antibiotic to be stopped temporarily or to be changed to a different medication. The most common side effects are related to irritation of the stomach and intestines. Thus, vomiting or diarrhea may occur. More severe drug reactions may occur but are uncommon. Be sure to let your veterinarian know if any new symptoms occur with antibiotic therapy.