Recurrent Pyoderma is a chronic relapsing bacterial infection of the skin usually associated with an underlying predisposing disease. The bacterial infection can be cleared with a proper antibiotic and topical antibacterial therapy but reoccurs, after discontinuation of treatment.

Recurrent Pyoderma is associated with such a long list of underlying disease that the diagnostic approach is complex. Adding to this complexity is the fact to be determined whether the prutitus is due to the pyoderma itself or associated with the underlying predisposing disease. Any plan for controlling the pyoderma without serious consideration of the predisposing diseases will fail. However, there are cases in which a diligent search does not reveal a cause for the recurrent pyoderma. The practioner at this point still has treatment opitions for long term successful management of the patient.

Classification	Common Causative Agents
Superficial Pyoderma	Staphylocossus aureus
Deep Pyoderma	S. intermedius
Recurrent Pyoderma	Proteus spp
	E.Coli

Successful management of recurrent pyoderma requires,

1. Recognition of various clinical manifestations
2. Formulation of a logical differential diagnoses and diagnostic plan for potential predisposing diseases.
3. Development of a rational therapeutic plan that will control the pyoderma and the predisposing disease.
   
   

CLINICAL SIGNS

Recurrent superficial pyoderma

Folliculitis is the most common clinical type of recurrent pyoderma. In its active erupting stage the lesions consist of papules and pustules associated with hair follicles. Papules are more common, since the pustules are fragile and transient and quickly become crusted when traumatized.

In many cases, especially if anti-inflammatory medication has been used, it is more common to see advanced resolving lesions or what have been referred to as " foot print" lesions of folliculitis. these include multifocal areas of postinfalmmatory (postinfection), pyperpigmentation, a "moth-eaten" alopecia and bull's-eye-type lesions (characterized by focal alopecia, central hyperpigmentation, epidermal collarettes and erythema). Very chronic lesions with associated, hyperpigmented, lichenified plaques that may involve large areas of the skin surface.

Recurrent deep pyoderma

Chronic recurrent deep pyoderma is less commonly encountered in practice than is recurrent sup[erficial pyoderma. However, the disease is more debilitating and harder to control, and it can be life-threatening if septicemia develops, especially if secondarily complicated by gram-negative bacteria.

Deep pyoderma lesions are characterized by red or purple, raised, nodules from which blood and purulent exudates can be expressed. Fistulous tracts may form and the tissue may become necrotic at extremely friable. Older "footprint" lesions consist of multifocal, tightly adherent crusts that when removed reveal ulcerated, necrotic skin. Such lesions are usually prutitic but are painful for the dog.

Diagnosis

Diagnosis is done on the basis of the following parameters : History/Clinical lesions/Cytolog/Culture and susceptibility test/Response to antibiotics/Skin biopsy.

Diagnostic Techniques

It is usually easy to make a diagnosis of superficial or deep pyoderma when pustules are present or when there is a productive purulent lesion. However, classical lesions are not always present and all pustules are not always due to pyoderma.

Cytology

If classical type lesions are present, then smears should be made of purulent exudates and stained with a modified
Wright's stain (Diff-Quik) or Gram stain.

Culture Susceptibility

Culture and susceptibility testing is useful in suspected pyodermas that fail to respond to empirical antibiotics, when there is a question about the presence of pyoderma because of a typical or unusual clinical lesions, when chronic antibiotic therapy is being used and there is concern about development of resistance. Cytology performed alongwith the culture and susceptibility is valuable to document and the organisms grown are actually causing the pyoderma.

Skin Biopsy

A skin biopsy submitted for routine histopathologic examination may be helpful in cases of chronic recurrent pyoderma. Not only will a biopsy confirm the presence of folliculitis or deep pyoderma, other pathogenic changes may help in diagnostics of the precipitating disease.

Plan to Investigate the Precipitating Dermatoses

To determine that the pyoderma has been treated correctly, there are several important considerations,

1. Has the correct antibiotic been selected?
2. Has the right dose been used for the proper duration?
3. Has clinical re-evaluation been performed prior to discontinuation of therapy?
4. Has the antibiotics been used without steroids or other immunosuppressive drugs?

If the answers to all these questions are "yes" but the pyoderma recurs whenever therapy is discontinued, a complete diagnostic evaluation is warranted.

Differential Diagnosis

Pyoderma should be differentiated from the following diseases.

Demodicosis, Dermatophytosis, Drug eruption, Atopy Scabies, Flea bite dermatitis, Food allergy

Treatment

Antibiotics and topical therapy may be needed on the continual or intermittent basis for long periods until the primary disease is controlled.

Choice of Antibiotic

Erythromycin : (10 to 15 mg / kg q8h PO) is a bacteriostatic macrolide antibiotic that inhibits ribosomal protein synthesis. It is inexpensive and of low toxicity but must be given three times per day, which may limit usage.

Linomycin hydrochloride : ( 22 mg / kg q12h PO) is a macrolide-like antibiotic with a mode of action similar to that of erythromycin.

Clindamycin hydrocholoride : is closely related to lincomycin and shows cross-resistance. It is better-absorbed and more potent, attaches to white blood cells and attains good levels in bone. It therefore, has demonstrated activity in superficial and deep infections, including osteomyeltis and is used in dermatology for deep pyoderma, especially fibrosed lesions, caused by susceptible staphylococci. Unfortunately resistance develops rapidly and it is very expensive used at higher dosage. Clindamycin is available in capsules and oral liquid. Two dosages are suggested, one for superficial (5.5 mg / kg q12h PO) and one for deep (11 mg / kg q12h PO) infections.

Chloramphenicol : (50 mg / kg q8h PO) is a broad-spectrum, bacteriostatic antibiotic that inhibits bacterial ribosomal protein synthesis. It is relatively inexpensive and in dogs has few side effects.

Fluroquinolones : are derivatives of nalidixic acid. They are broad-spectrum bactericidal antibiotics that work by inhibiting DNA replication. They are especially effective against E.Coli and Salmonella and moderately effective against staphylococci and Pseudomonas. Resistance is rare but may develop by mutation over many generations. The recomended dosage fo enrofloxacin is 2.5 to 5 mg / kg q12 h PO on an empty stomach.

Aminoglycosides : are not commonly utilized in pyodermas because of parenteral administration, nephrotocicity, ototoxicity.

Gentamicin : (2 mg / kg q8h SQ or IM) is most commonly utitized, but amikacin, (10 mg / kg q12h SQ or IM) is also effective and has less potential for nephrotoxicity than gentamicin.

Topical Therapy:

Rarely a dog with chronic recurrent pyoderma may be completely controlled with topical therapy alone, without systemic antibiotics. Antibacterial shampoos are usually needed two to three times a week to have any chance of achieving this goal. However, topical therapy is an important ajunct in the management of recurrent superficial and deep pyodermas.

In deep pyodermas clipping the hair coat followed by warm water soaks, whirlpool baths, and shampoos are very helpful. Povidone-iodine solutions and chlorhexidine solution are excellent antimicrobial agents when added to the soaking or whirlpool solutions.

Antibacterial shampoos are the most commonly employed method of topical therapy for superficial and deep pyodermas. In most cases of chronic recurrent pyoderma they must be used at least weekly to have efficacy. Benzoyl peroxide products are especially effective, not only because of their excellent antimicrobial activity but because they possess a follicular flushing activity. Benzoyl peroxide was shown in a controlled quantitative study (Kwachka and Kowalski, 1991) to have superior prophylactic activity against S.intermedius when compared to chlorhexidine, complexed iodine and triclosan.

Chlorhexidine is another excellent antimicrobial agent found in shampoo, formulations. Although it does not have the follicular flushing activity of benzoyl peroxide, it has the advantage of being in an emollient formulation for long-term use on dry skin and coat.

Mupirocin is a topical antibiotic in a polyethylene glycol base for localized pyoderma. It has excellent activity against gram-positive cocci, is bactericidal, works well at an acid pH, is not systemicaly absorbed, and is not chemically related to other antibiotics.

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