Bacterial Hypersensitivity to Staph Infections in Dogs

The Staphylococcus bacteria is opportunistic, which means that once the skin becomes irritated or broken, this bacteria has the chance to multiply and infect the body. While easily treated with antibiotics and good hygiene, if left untreated, serious conditions can develop in your dog, including organ infections and blood poisoning, and even death. Since a Staph infection is highly probable whenever the skin is cut, be sure to see your veterinarian to treat the wounds with appropriate antibiotics.

The Staphylococcus bacteria is normally present on human and animal skin, and generally doesn’t cause any harm. Some dog's immune systems contain too many Staph antibodies that can cause a hypersensitivity. While symptoms of a bacterial hypersensitivity and a normal Staph infection are similar, the differentiation is made when the infection is recurrent, even after successful treatment.

Symptoms of a Staph infection can include:

• Itchy skin
• Excessive chewing, scratching and licking
• Red area of skin with a pustule in the center
• Red, circular lesion with a crusty edge and loss of hair inside
• Pus exuding from site of any wounds or broken skin
• Excessive pain at wound site
• Atopic dermatitis
• Fever
• Weakness
• Lethargy
• Abnormal behavior
• Confusion
• Septicemia, or blood poisoning

There is one main cause of a hypersensitivity to a Staph infection, which is an allergy to the Staphylococcus bacteria. This hypersensitivity is more likely to occur if these conditions are present:

• Itching disorder
• Persistent scratching
• Flea allergy
• Inhalant allergy
• Food allergy
• Irritating chemicals
• Hypothyroidism
• Excessively moist skin

Causes of Staph infections in general include:

• Cut, wound or broken skin that has become infected with the bacteria
• Ingestion of infected material
• Infected material entering mucosal membranes, such as eyes, mouth or nose
• Contact with infected medical equipment

If any symptoms of a Staph infection are noticed, take your dog immediately to a veterinary clinic. Since symptoms of a bacterial hypersensitivity and a normal Staph infection are similar, with identical lesions, the differentiation is often made only after appropriate treatment has been followed, but the infection is recurrent. Because of this criteria, treatment of the original infection will need to be long enough to rule out a normal Staph infection, usually for a month or longer. If your dog is hypersensitive to the Staph bacteria, the skin lesions should return within a few days to weeks.

A Staph infection is diagnosed through testing bacterial cultures and skin biopsies, and through microscopic examination of skin samples. Changes that are unique to this condition can be seen in the skin’s blood vessels on the microscopic level. 

Red, circular lesions with crusty edges are also indicative of ringworm or yeast infections, but the presence of excessive scratching leads to the diagnosis of a Staph infection.

Treatment of a Staph allergy will begin the same as treatment for a normal Staph infection. This will include oral and topical antibiotics, baths with medicated shampoos, and itching treatments. Antibiotics will need to be administered for 3 to 6 weeks to be able to eliminate a normal Staph infection, and give the right criteria for a hypersensitive condition to be diagnosed correctly.

Hypersensitive dogs will need long term control of the allergy. This involves periodic Staphylococcal bacterin injections, a solution of dead Staph bacteria that helps to reprogram the immune system. Treatment begins as injections given daily, then every 3 to 4 days, then every 2 weeks. Many dogs will continue this treatment for 1 to 2 years, with less frequent injections. This type of desensitization therapy has shown improvement in 77% of dogs.

Periodic antibiotic treatments and medicated baths can be prescribed in cases where desensitization does not cause improvement. However, the Staph bacteria can become antibiotic resistant, and it may be necessary to change medications.

Controlling the itch will help to stop the cycle of reinfection. Antibacterial shampoos and ointments can help to control the infection. An injection may be given to stop the itching.

If Staphylococcal bacterin injections are being given, veterinary visits may be needed for many weeks, or your veterinarian may teach you how to administer the injections at home.

You will most likely be sent home with antibiotics, topical, oral or both. Be sure to keep using them as directed by your veterinarian, and do not discontinue if symptoms subside. Medication may also be given to control itching. Medicated baths may also be prescribed to help stop the infection and control the itching.