Staphylococcal Dermatitis and Staphylococcal Hypersensitivity in Dogs

By Tammy Hunter, DVM; Ernest Ward, DVM

Medical Conditions

What is staph dermatitis?

staph_dermatitis_causes_dog_2018-01Staph dermatitis is an inflammatory skin condition of the skin caused by a group of bacteria called Staphylococcus. This condition is also referred to as Staphylococcal pyoderma or staph pyoderma. Pyoderma is a term used to describe bacterial skin infections.

Does this bacteria always cause dermatitis?

No. Staphylococcus normally reside on the skin of animals and humans without causing any problem. The bacteria are considered opportunistic pathogens. As long as the skin is healthy, these bacteria do not cause problems. But once the skin is irritated, they can invade and rapidly multiply, seizing an opportunity to infect.

What causes this type of skin irritation?

Scratching, licking, and chewing are the most common causes of skin irritation. Any disorder that causes itching or a change in the skin’s environment can create the ideal conditions to allow Staphylococcus to become a problem.

Common causes of itching include fleas, inhalant/seasonal allergy, and food allergy. Other diseases that affect the health of the skin include seborrhea and hormonal imbalances (e.g., hypothyroidism). Irritating chemicals such as flea and tick dips can also cause itching.

How is the condition diagnosed?

There are two typical staphylococcal lesions. One type begins as a red area on the skin with a pimple-like pustule in the center. The other type is a circular, reddish area with a crusty edge and hair loss in the center. The latter can easily be confused with ringworm or yeast skin infection. Finding either of these skin patterns in a dog that is scratching is highly suggestive of staphylococcal dermatitis.

Confirmation can be made with a skin swab or skin biopsy. The swab not only allows confirmation of the identity of the organism, but antibiotic sensitivity testing can also determine the most suitable antibiotic.dog_staph_skin_swab_2018-01

How is the condition treated?

Since the condition is caused by bacteria, it is usually sensitive to several antibiotics. Some infections may require three to six weeks of treatment before the infection is under control. Antibacterial shampoos, sprays, and spot-ons can be helpful in bringing about rapid control of the infection.

"An essential part of treatment is stopping the cycle of itching and scratching."

The other essential part of treatment is stopping the cycle of itching and scratching which may have contributed to the staphylococcal infection. Other tests may be needed to determine the cause of itching. Often, more than one condition contributes to the itching.

Is my dog contagious to me or to other pets?

No. All dogs, cats, and people have Staphylococcus living on the skin as a normal resident. The infection occurs only if the skin is damaged or there is an underlying medical condition.

My dog finished treatment for staphylococcal dermatitis two weeks ago, and now the infection is back. Why is that?

This situation may be caused by an allergy to the staphylococcal bacteria. This is called Staphylococcus hypersensitivity or Staphylococcus allergy.

"The infection may return due to an allergy to the staphylococcal bacteria."

The skin lesions that are caused by hypersensitivity are identical to those of staphylococcal dermatitis. The two diseases are differentiated by recurrence. If the dermatitis is treated properly, the underlying bacterial skin infection with Staphylococcus is eliminated and itching stops. The infection may recur if the itching is not controlled. However, when the dog with staphylococcal hypersensitivity is treated, the skin lesions will often return within a few days or weeks.

Since differentiation of staphylococcal dermatitis and staphylococcal hypersensitivity is based largely on recurrence, it is very important that treatment for dermatitis be continued long enough. This often means a month or more of antibiotics. If not, there will still be a question of which disease is present.

How is staphylococcal hypersensitivity treated?

Treatment begins the same as for staphylococcal dermatitis: oral antibiotics, medicated shampoos, and treatment to stop the itching. In hypersensitivity cases, long-term control is best achieved with periodic routine injections of staphylococcal bacterin. Staphylococcal bacterin is a solution of killed staphylococcal bacteria that is injected into the dog in very tiny amounts.

"In hypersensitivity cases, long-term control is best achieved with periodic routine injections of staphylococcal bacterin."

This is used in an attempt to reprogram or retrain the dog's immune system so it does not overreact to this naturally-occurring bacteria. The treatment begins as a series of daily injections into the skin. After the initial series is completed, the injections are given subcutaneously (just below the skin) on an interval ranging from every three to four days to every two weeks. These injections frequently will give profound improvement when other treatments have failed.

If such a course is prescribed, your veterinarian will teach you to administer these simple injections at home.

How successful is this?

Desensitization therapy or 'allergy shots' are not successful 100% of the time - in dogs or in people. Research has demonstrated that up to 77% of dogs to respond well to this treatment. Most dogs will remain on routine injections for the first one to two years and then less frequent injections may be attempted.

What happens if staphylococcal bacterin desensitization is not successful?

The dog will require periodic treatment with antibiotics and medicated baths. This is not the most desirable approach because Staphylococcus will often develop resistance to the antibiotics. If this occurs, a change in the specific antibiotic used will be necessary. This will also involve more bacteriological tests and antibiotic sensitivity testing in order to establish another appropriate course of treatment.

INSTRUCTIONS

Give the antibiotics according to the instructions on the label. Do not discontinue them even if your dog's skin looks normal. There should be noticeable improvement within one week. Near the end of the course of antibiotic treatment, your veterinarian will need to reexamine your dog to ensure the infection has resolved.

____ Bathe your dog in the medicated shampoo supplied every _____________ days for a total of ___________ baths. Allow the shampoo to remain on your dog's skin for at least five minutes before rinsing thoroughly.

____ An injection was given to stop itching. If this does not occur within twenty-four hours, please contact us. If the injection causes your dog to drink and urinate excessively, please contact us. If this occurs, it will usually stop in a few days. These side effects are dose related. If another injection is needed in the future, we will lower the dose to avoid this side effect.

____ Tablets have been prescribed to control itching. Follow the instructions on the prescription label. Give the first dose ___________________. If these tablets cause your dog to drink or urinate excessively, please contact us. If this occurs, it will stop in a few days. The dosage may be adjusted based on your pet's response.

____ Staphylococcal bacterin is to be given according to the following schedule:

            Dose 1: __________________                      Dose 5: ___________________

            Dose 2: __________________                      Dose 6: ___________________

            Dose 3: __________________                      Dose 7: ___________________

            Dose 4: __________________                      Dose 8: ___________________

Please make an appointment for each of these days.

Following this series you will be shown how to give the injections at home if you prefer.

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