STAPHYLOCOCCAL "HYPERSENSITIVITY"
(Staph Pyoderma)

General Information:

Recurrent staphylococcal skin infection (pyoderma) is a commonly seen canine disease in general veterinary practice. The syndrome is difficult to manage and is frustrating for owners and veterinarians alike.

Conventional diagnostic approaches emphasize the search for an underlying systemic disorder that would explain the recurrences. Unfortunately, in many cases there is no identifiable underlying disease present, despite exhaustive diagnostic evaluation.

A variety of explanations have been set forth as to the underlying mechanisms at work in such patients. One hypothesis holds that development of bacterial hypersensitivity is responsible for the severe clinical signs and recurrent nature of at least a subgroup of dogs with chronic staphylococcal infection.

What is Staphylococcal Pyoderma?

Staphylococcal hypersensitivity is best considered a "clinical syndrome" rather than a definitive diagnosis. That is, we recognize that there is a group of dogs that present with recurrent staphylococcal skin disease that is:
  • Superficial;
  • Very itchy;
  • Highly inflammatory; and,
  • Characterized by the presence of circular, reddened, rapidly-spreading lesions termed "epidermal collarettes."
  • Papules, pustules, focal alopecia, and focal crusting are present along with the collarettes.

    The disease is invariably quite antibiotic-responsive, with relief of itching often noted within 2 or 3 days after antibiotics are started and with a return to normal after 3 to 6 weeks of such treatment.

    The problem arises when antibiotic treatment is stopped, for typically the disease can relapse within 1 to 3 weeks following cessation of antibiotics.

    Experimental evidence, clinical appearance, and parallels with a similar syndrome in humans has led to the theory that in dogs, the antibody response to staphylococcal infection may be detrimental in some individuals and result in hypersensitivity and recurrent pyoderma.

    How does Staphylococcal Pyoderma Work?

    Because the immunologic mechanisms underlying recurrent pyoderma related to "staphylococcal hypersensitivity" are not completely defined, there is at present no reliable laboratory test to diagnose this syndrome. Rather, staphylococcal pyoderma is still a clinical syndrome which can be suspected on the basis of some rather loose criteria in the history and physical examination, including:

    What are the Treatment Options for Staphylococcal Pyoderma?

    Initially, all patients with recurrent pyoderma related to staphylococcal hypersensitivity should be treated with an appropriate oral antibiotic for an appropriate length of time to clear the active episode.

    Ideally, the antibiotic should be chosen based on a culture and sensitivity test.

    Other factors to consider in selection of an antibiotic for initial treatment include cost and the possibility of adverse drug effects.

    Initial treatment of superficial pyoderma should last for 1 to 2 weeks past complete clinical resolution. Typically, this will entail 3 to 6 weeks of antibiotic treatment.

    Recurrent pyoderma is frequently a lifelong disease that can be satisfactorily controlled, but not often cured, and some trial and error will be necessary to find the best long-term control regimen for each patient.

    Because relapse after initial treatment is the expected result, additional treatment aimed at preventing such relapse should be initiated at the same time as antibiotics. Such treatment may be in the form of:

    1. Adjunct topical treatment; and/or,
    2. Immunomodulatory drugs.

    Adjunct topical treatment with antibacterial shampoos is aimed at long-term reduction in the bacterial antigen load present on the skin surface, which will in theory reduce the degree of hypersensitivity reaction. In order to be effective for long-term control of recurrent superficial pyoderma, shampooing must be done frequently -- twice weekly at first, then usually at least once weekly long-term after resolution of the active episode.

    Useful products include shampoos containing 0.5% chlorhexidine, or 2% benzoyl peroxide with a moisturizing additive (various manufacturers).

    Immunomodulatory bacterins are an aid in long-term management of recurrent pyoderma, including "staphylococcal hypersensitivity."

    Bacterins are not used to cure an active infection -- their major use lies in prevention of recurrence once the initial infection is cleared by antibiotics. It is clear that staphylococcal bacterins are effective for some dogs with recurrent pyoderma, perhaps 50% or more of carefully-selected cases (i.e., those cases where there is not a definable underlying cause for recurrence).

    Commercial products that are licensed for dogs and which have been subjected to study include SPL (Staphylococcus Phage Lysate, Delmont Laboratories), and ImmunoRegulin (Propionibacterium acnes bacterin, ImmunoVet).

    Bacterin treatment, if effective, is usually less expensive than chronic antibiotic use and will lessen the chance of developing antibiotic-resistant bacterial strains. This treatment generally should be considered a lifetime therapy, though some animals are apparently cured after 18-24 months of treatment and the injections can be stopped. Treatment is undertaken by giving injections twice weekly for two weeks, then once weekly until improved then start giving them at greater intervals (every three weeks, then once monthly, etc.).

    We hope that you will find this information helpful in your quest for better pet care. If you have any questions or comments, please call your veterinarian's office, or feel free to e-mail us.

    David E. Hammett, DVM
    and the Staff of All Creatures Veterinary Clinic, PC


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