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Pyoderma

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Pyoderma

Post  northernwitch on 5/23/2011, 8:21 pm

Causes
- Staphylococci (‘Staph bacteria’) are the most common organisms found in bacterial skin diseases (pyoderma's) in dogs. Fortunately, these bacteria (S. intermedius) are not contagious to humans or other pets.

Signs
- Commonly itchy, yellow pustules are often observed early in the disease, and the dog’s skin can be reddened and ulcerated. Dry, crusted areas appear as the condition advances, along with loss of hair in the affected areas (lesions) and an odour.

All areas of a dog’s body may be involved, but most cases are confined to the trunk. The chin is one area commonly affected. Called chin acne, this condition is actually a deep bacterial infection. Obese dogs and dogs of the pug-nosed breeds are frequently affected by pyoderma in the skin folds on their face, lips and vulva.

Other areas where pyoderma may occur include between the toes and on the calluses of the elbows that mostly affects the abdominal area in young puppies.

Diagnosis
- This is usually made from the case history and appearance and location of the lesions. In some cases, it may be necessary to culture the skin (grow the bacteria) and conduct sensitivity tests to determine which antibiotic will be effective in treatment. Most bacterial skin infections in dogs are secondary to another disease such as parasitism, allergies, endocrine (hormonal) disorders or abnormalities in the immune system. Therefore, in recurrent cases, it is important to search for underlying causes. It may be necessary to do blood tests, allergy tests or skin biopsies to achieve a complete diagnosis.

Treatment
- Initial treatments may entail removal of the hair in and around the lesions, washing of the whole dog with antibiotic shampoos such as benzoyl peroxide, careful drying and the application of an antibiotic ointment to local lesions, in most cases, antibiotics will also be administered orally for 3-4 weeks. Bandages or a protective collar which prevents the dog from mutilating the lesions may be applied.
Some pyoderma involving skin folds can require corrective surgery. In recurrent cases where testing reveals no definable underlying cause, special staphylococcal vaccines as an alternative to long-term antibiotic treatment can be tried.

It may be necessary to continue treatments such as antiseptic shampooing, antibiotic ointment applications and giving antibiotics orally at home. While most cases respond to treatment, recurrences of pyoderma are common, particularly if treatment recommendations and follow-up visits to your veterinarian are neglected. Glucocorticoid steroids cannot be administered.


From Columbia Animal Hospital
Web Site


Clinical Aspects, Diagnosis and Therapy of
CANINE PYODERMA

INTRODUCTION

There are a large number of bacterial diseases of the skin in dogs, with different histopathological and clinical aspects. Some are superficial and benign (the basement membrane is not destroyed by the infectious process) and some are deep and severe (the basement membrane is destroyed). Pseudopyodermas are not real pyodermas since infection plays only a secondary role and anti-infectious therapy is not effective. Staphylococcus intermedius is the most common infectious agent cultured in canine pyoderma. It can multiply easily in the dog's skin, due to the thinness of the stratum corneum and the lack of sebum plug in the hair follicles. Inflammation of the skin, particularly due to allergy, is the most common cause of pyoderma, more than real immunodeficiency.

SUPERFICIAL PYODERMA

1. Skin fold pyoderma (intertrigo)

These lesions are seen in anatomical defects where there is an important bacterial colonization: lip, facial, vulvar, caudal, obese and mammary folds. The dermatosis is localized with erythema, exudation, suppuration and bad odour.

2. Impetigo

In juvenile impetigo, subcorneal pustules are present on the ventral side of the body, with crusting. The disease is self-limited. In adult impetigo, large pustules ("bullae") are seen all over the body. In general, adult impetigo is severe and secondary to an underlying disease (hyperadrenocorticism, glucocorticoid therapy...) or multiple traumas (e.g., during hunting).

3. Folliculitis

Juvenile folliculitis: numerous follicular pustules are present on the ventral side of the body. The condition often heals at puberty.

Short-haired dog pyoderma: there are generalized follicular pustules, epidermal collarettes and crusts, with a "moth-eaten" hair. Pruritus disappears when the lesion heal.

Secondary folliculitis: this common disease is characterized by follicular pustules, epidermal collarettes and crusts which are often generalized. Pruritus is still present after lesions healing in case of underlying pruritic dermatosis. The disease may also generate pruritus in a usually nonpruritic dermatosis (in such cases pruritus disappears when lesions heal).

"Bacterial hypersensitivity" and/or superficial spreading pyoderma: bacterial hypersensitivity is an uncommon disease based on a clinical triad: erythematous follicular pustules, target lesions/seborrhoeic plaques, haemorrhagic bullae. There is sometimes a severe pruritus. The existence of a real bacterial allergy is presumed and debatable. In superficial spreading pyoderma, nummular areas of alopecia and erythema are centrifugally expanding, with epidermal collarettes and crusts. These lesions are often associated to intact but transient follicular pustules.

Deep folliculitis: it is the so-called acral lick dermatitis, most often a deep follicular bacterial infection with retrograde hidrosadenitis secondary to a psychogenic and/or an allergic cause.

Pyotraumatic folliculitis: some cases of folliculitis (e.g., in Labradors, Retrievers) appear as oozing suppurative plaque with pain. They are surrounded by satellite pustules of folliculitis or even furunculosis, which help to differentiate them from the "classical" pyotraumatic dermatitis.

DEEP PYODERMA

1 Furunculosis

Acne: papulo-pustules and pustules are seen on the face, particularly the chin, in young dogs.

Secondary furunculosis: localized or generalized pustules are associated or secondary to a folliculitis and the disease is triggered or aggravated by an excessive therapy (e.g., glucocorticosteroids).

Nasal pyoderma: pustules and crusts are present on the bridge of the nose and eyelids. There may be an unpleasant scaring. This true bacterial nasal pyoderma of unknown cause should be differentiated from the sterile eosinophilic furunculosis possibly due to arthropod bites.

2. Cellulitis

A. Localized cellulitis

Pressure points pyoderma: there are necrotizing lesions of the elbows, the rump, the stifles, the hocks and the lateral digits. They are due to permanent trauma in heavy dogs.

Various localized cellulites: These are other localized necrotizing lesions (e.g., perianal). Their cause is often unknown; they are sometimes secondary to a furunculosis.

B. Generalized cellulitis

Pyodemodicosis: There is an extensive necrotizing skin disease, which is secondary to a generalized demodicosis (an immunodeficiency status).

Various generalized cellulites: necrotizing lesions are extensive and often secondary to other immunodeficiencies.

3. The interdigital pyoderma complex

There are very numerous causes of non infectious pododermatitis with erythema, oedema, oozing and alopecia. The same lesions are present in interdigital pyoderma along with furunculosis, ulcerations, fistulae and necrosis (cellulitis). Interdigital pyoderma is often secondary.

PSEUDO-PYODERMA

1. Pyotraumatic dermatitis

The typical lesions have an acute onset and are characterized by alopecia, erythema, oozing, suppuration, pruritus and/or pain. These lesions are common, and most often associated to pruritic skin disease. They are poorly understood (sometimes due to vasculitis?). There is a spontaneous healing in a few days, but a short treatment is useful.

2. Juvenile pyodermas

Juvenile pyoderma of new-born puppies: crusty lesions are present on the face, thorax and dorso-lumbar area. They might be due to trauma. No treatment is required since there is a spontaneous healing.

Juvenile cellulitis: The aetiology of this disease is unknown. The typical clinical aspect is a facial oedema and furunculosis, with fistulae, crusting and a suppurative otitis externa. Adenopathy and sterile abscesses (cellulitis) are present. The onset of this uncommon disease occurs before 4 months of age in one or several puppies of a litter. There is a spontaneous healing in a few weeks with scaring but treatment is required.


DIAGNOSIS OF CANINE PYODERMA

Diagnosis of canine pyoderma is based on history, physical examination and complementary examinations: cytology, histopathology and bacteriology.

1. Cytology

In intertrigo (skin fold pyoderma), images of "bacterial colonization" are observed, i.e., healthy neutrophils, Cocci and Bacilli in an extracellular position and degenerated neutrophils in a state of phagocytosis. In impetigo and folliculitis, impaired (degenerated) neutrophils are only found. The pictures of Cocci phagocytosis are not particularly numerous. This is an image of "bacterial invasion", i.e., the penetration of pathogenic germs into the skin. The significance of the pictures of phagocytosis differs considerably depending on whether they are observed on the surface or in a cutaneous lesion. In effect, when they are observed inside the skin (epidermis, hair follicles, dermis) one might consider that the phagocytosed germs are pathogenic and that there is a real bacterial pustulosis. In contrast, phagocytosis observed on the surface indicates multiplication of germs which are not necessarily and probably rarely pathogenic. In deep pyoderma cytology is less likely to reveal the germs and pictures of phagocytosis, although they must be looked for. Frequently there are a granulomatous reaction, eosinophils and red blood cells. Bacterial colonization is observed in pyotraumatic dermatitis as in intertrigo but it is not significant and treatment with antibiotic does not result in remission. In juvenile cellulitis, the degenerated neutrophils are very numerous, with a granulomatous reaction. No germs are seen.

2. Histopathology

This will show typical lesions, but is relatively rarely performed for the diagnosis of canine pyoderma, except in case of difficult differential diagnosis.

3. Bacteriology

This can confirm the bacterial infection and allows sensitivity testing.

TREATMENT OF CANINE PYODERMA

Systemic (antibiotic) and topical therapy can be used in canine pyoderma.

1. Selection of antibiotics

The criteria for the choice of an antibiotic are as follows: appropriate kinetics and good cutaneous penetration, activity against Staphylococci, activity in pus and reactive tissues, bactericidal activity rather than bacteriostatic activity particularly in severe cases, easy administration (oral, q12h or q24h), absence of secondary effects, reasonable cost. The choice can be empirical, particularly in superficial pyoderma, after cytological examination of pus from an intact pustule which shows bacterial invasion. Bacteriology and sensitivity testing must be used in case of deep pyoderma, recurrent pyoderma, when cytology shows a complex flora with rods, and in case of empirical antibiotic therapy failure. They can be repeated during therapy.

2. Dosage and duration of treatment

Ideal doses must be used and duration of treatment must be long enough (a few weeks to several months depending of extension and depth of lesions, and always beyond clinical cure). Maintenance pulse treatment (e.g., 2 to 3 days a week) can be used in chronically relapsing pyoderma but it could theoretically select resistant strains as well as the use of subminimal doses. They are both used for economical reasons but the former is preferable.

3. Antibiotics useable in canine pyoderma

Antibiotics useful in canine pyoderma are included in the following table. They all have a good cutaneous diffusion (because of their liposolubility) and can be given orally, which is useful because of long therapeutic courses (ease of administration). They are all bactericidal except macrolides which are bacteriostatic.

Class


Characteristics


Examples

Macrolides


narrow spectrum/Gram+


erythromycin : 30 to 50 mg/kg div. bid or tid
lincomycin : 40 to 50 mg/kg div. bid or tid
clindamycin : 5,5 to 11 mg/kg sid or div. Bid
tylosin : 40 mg/kg div. bid

Penicillins M


resistant to penicillinases
narrow spectrum/Gram+


oxacillin : 30 to 50 mg/kg div. bid

Penicillins A
potentiated by
clavulanic acid


resistant to penicillinases larger spectrum


amoxicillin-clavulanic acid : 25 mg/kg/div. bid

Cephalosporins


resistant to penicillinases
broad spectrum


cephalexin : 30 to 60 mg/kg div. Bid
cefadroxil : 44 to 70 mg/kg div. bid

Cephalosporin P


resistant to penicillinases narrow spectrum/Gram+ synergy with penicillins and erythromycin


fusidic acid (the only one of this group) :
60 mg/kg div. tid

Sulfonamides-
Diaminopyrimidines


broad spectrum


trimethoprim-sulfa : 30 mg (i.e., 5 mg
trimethoprim)/kg sid or div. Bid
baquiloprim-sulfadimethoxine : 30 mg (i.e., 5mg
baquiloprim)/kg q.48h
ormetoprim-sulfadimethoxine : 30 mg (i.e., 5mg
ormetoprim)/kg sid after a single double dose
the first day

Fluoroquinolones


broad spectrum excellent tissue
penetration (not to be used in puppies of giant breeds)


enrofloxacin : 5mg/kg sid of div. Bid
marbofloxacin : 2 mg/kg sid
difloxacin : 5 mg/kg sid
orbifloxacin : 2.5 mg/kg sid

Penicillin G (which is injectable) and A are sensitive to penicillinases. Aminoglycosides have a low cutaneous diffusion (they are hydrosoluble), are injectable and toxic. Chloramphenicol has a bad reputation in humans and the cat (haematologic toxicity). Tetracyclines have a very low activity against Staphylococci. These antibiotics are never or rarely used in canine pyoderma. Rifampicin is effective against Staphylococci but, as it is still used to treat human tuberculosis, it should be used when there is no other possibility (5 to 10 mg/kg SID). In addition, it should be then associated to a betalactamine to prevent the selection of resistant strains of Staphylococci. Mupirocine, a topically active bactericidal antibiotic, in a polyethylene glycol base is effective against Gram+ Cocci, is not systematically absorbed and is not chemically related to other antibiotics. It can be used in localized pyodermas (acne, pressure point pyoderma, interdigital pyoderma).

4. Associated treatments

Topical therapy is always beneficial in canine pyoderma, particularly in superficial staphylococcal disease. Clipping can be useful and is necessary in deep pyoderma such as cellulitis. The main useful topical products are chlorhexidine (lotion and/or shampoo), povidone-iodine (lotion and/or shampoo), benzoyl-peroxide (shampoo and eventually gel), ethyl-lactate (shampoo). They should be used frequently, e.g., once a day, at the beginning of therapy. Later, frequency of application may decrease. Each shampoo should be followed by the application of an appropriate humectant. Topical or systemic glucocorticoids should never be used in true canine pyoderma, even in case of pruritus, because they cause severe relapses ("rebound effect"). In contrast they can be used and are effective in pseudo-pyoderma (e.g., oral prednisolone: 1 mg/kg/day for pyotraumatic dermatitis and 2 mg/kg/day for juvenile cellulitis).

CONCLUSION

Canine pyoderma is a group of various skin diseases and an accurate diagnosis is mandatory. An appropriate antibacterial therapy is required in most cases of canine pyoderma, in association with topical therapy. Antibiotics must be selected carefully and used with appropriate dosage and duration of treatment.


D.N. Carlotti, DECVD
Cabinet de Dermatologie Vétérinaire
Bordeaux-Mérignac, France
Web Site


THE APPROACH TO CANINE RECURRENT PYODERMA

THE DEVELOPMENT OF PYODERMA

It is believed that staphylococcal pyoderma develops following surface spread from the carrier sites. Factors that ordinarily prevent the development of pyoderma are:

The physical barrier of the intact skin. Normal desquamation is extremely important in preventing niches in which pathogenic bacteria could become established.

Antibacterial substances present in normal sebum, and secreted onto the skin surface from apocrine secretions. This would include immunoglobulin, and other non-specifically acting substances such as those produced by resident bacteria.

The bacterial barrier. If non-pathogenic bacteria occupy all available colonization sites, pathogens will not become established.

There is thus a dynamic balance between the host defenses, the virulence of any potential pathogens and their ability to gain access, and the host defenses that are brought into play in a damage limitation exercise.

FACTORS THAT PREDISPOSE TO RECURRENT PYODERMAS

Pyoderma is likely to prove recurrent in a number of situations

Where there is a tendency to surface colonization:

a. Seborrhoea, of whatever cause, is likely to lead to colonization with Staph intermedius.

b. Atopic disease. In this condition it has been shown that Stratum corneum cells of atopics have a greater tendency to adhere to the organism than do cells from normals.

Where the integrity of the skin barrier is impaired: This may occur secondarily to any inflammatory skin disease, or one that leads to self-trauma from pruritus. Flea allergy is a rather special case. The secondary infection in such cases is often minor, and does not necessitate antibiotic therapy. However a minority of animals will break with a staphylococcal infection whenever they acquire an infestation. In demodicosis, a recurrence of the infection is often the first sign of recurrence of the mite population.

In the immuno-compromised animal: This is generally limited to deficiencies in non-specific defenses or in cell-mediated immunity, as antibody response is always evident.

a. Congenital non-specific immune defects. Delayed intracellular killing by neutrophils has been noted in Weimaraner's and Dobermans. Irish setters have been reported with a severe, intracellular killing defect, but this is exceedingly rare. However, absence of the neutrophil complement receptors CD11b and CD18, which aid attachment prior to engulfment, is quite common in Irish setters in the UK and Scandinavia. Such animals would be expected to have difficulties in handling infections of all types.

b. Impaired cell-mediated immunity. It has been documented that atopic dogs have impaired cell-mediated immunity. In animals with impaired cell-mediated immunity from other causes has also been documented. Some animals with recurrent pyoderma have impaired cell-mediated immunity- where their lymphocytes appear to have an inbuilt defect, or where there are serum immunosuppressive factors present. This seems to be an excellent way by which the infection can be potentiated.

Food allergy: Typically, affected animals are less pruritic when on antibiotics with their pyoderma controlled, but relapse occurs either immediately on cessation of therapy or within 2-3 weeks. In other cases the pruritus is fully controlled by antibiotic therapy, and the animal appears to be suffering from a food allergy which is sub clinical as far as the pruritus is concerned.

In cases of hypersensitivity to staphylococcal antigens: It is well documented in experimental animals that development of hypersensitivity renders the animal much easier to infect. This has been shown also to be true in dogs.

Hypothyroidism: This is well recognized as a cause of recurrent staphylococcal infection, but it is not clear whether it results from the accompanying seborrhea, or to impaired defenses that may accompany the condition.

Iatrogenic:

a. Improper use of antibiotics. These must be given in full doses for the full length of time.

b. Use of corticosteroids. Although these may appear to produce an improvement, merely from their anti-inflammatory action, in the long term they are working against our best interests as they (a), tend to dry the skin inducing scaling and thus favoring colonization, and (b), they may further impair cell-mediated immunity.

Antibiotic selection

Suitable antibiotics are directed at the Staph. intermedius. Where there is secondary infection with gram-negatives, these will disappear once the Staph. is controlled unless the animal is severely immuno-deficient, or there is an overwhelming infection.

Macrolides. Erythromycin and lincomycin are good, first choice bacteriostatic antibiotics. Clindamycin does not appear to offer any major advantages over the other, cheaper, products. The vomiting with erythromycin can be obviated by feeding an anti-emetic 30 minutes prior to each dose for the first two days. There is cross-resistance between the two drugs. The dose for erythromycin is 10-15mg/kg TID, and for lincomycin 20mg/kg BID.

Potentiated sulphonamides. Trimethoprim-sulphadiazine (or sulphamethoxazole), ormetoprim-sulphadimethoxine and bacquiloprim-sulphadimethoxine are very useful antibiotics for pyoderma's. The dose for the first is 30mg/kg given twice daily, although some clinicians are comfortable with SID dosage. The dose for ormetoprim is 55mg/kg for the first day, and then 27.5mg/kg once daily thereafter. Drug reactions are not uncommon with trimethoprim sulphur, and result from the sulphadiazine, which also has the propensity to induce a transient arthropathy, especially in Dobermans. The tendency to induce keratoconjunctivitis sicca must be watched.

Cephalosporins. Cephadroxyl and cephalexin are excellent for the treatment of pyoderma's. Although they are broader spectrum than is oxacillin, they do not classify as broad-spectrum drugs, and are perfectly acceptable for the routine treatment of canine pyoderma. Drug reactions are seen, but probably with less frequency than with the sulphonamides. They are bactericidal. Doses are 20-25mg/kg BID.

Oxacillin. This is an excellent, narrow spectrum bactericidal antibiotic to which resistance is extremely rare. Unfortunately there are no veterinary preparations. The dose is 20mg/kg TID.

Amoxacillin/clavulonic acid. This broad-spectrum bactericidal antibiotic is very useful. Doses used range from 15-20mg/kg BID.

Fluoroquinolones. These are very broad spectrum, bactericidal antibiotics. It would be indicated where there is a significant involvement of gram negatives. Recommended doses are 2.5mg/kg BID (or 5mg SID) for enrofloxacin, 2.0mg/kg SID for marbofloxacin. 2.5mg/kg SID for orbofloxacin and 5-10 mg/kg BID for difloxacin. They are, however, not indicated for routine use in dermatology, due to the possibility of inducing resistance in Pseudomonas.

Topical therapy

Antibacterial shampoos using products containing benzoyl peroxide (2-3%), clorhexidene (2-4%) or ethyl lactate (10%) form a most valuable supplementary treatment. Chitosanide, which is contained in the new spherulite-based shampoos of Virbac, also has antibacterial properties. Shampoos can be used 1-2 times weekly therapeutically, and are also useful as part of a preventative maintenance strategy.

In the case of deep pyoderma's, antibacterial soaks employing povidone iodine are a valuable aid, and can be done twice weekly in the initial stages of treatment. In the case of localised deep pyoderma's, benzoyl peroxide gels are of value. Also, where there is evidence of ingrown hairs forming foreign body reactions, these should be gently massaged out in warm water soaks.

THE APPROACH TO THE RECURRENT INFECTION

Search for a predisposing cause.

a. Evaluate for seborrhea. If this is evident, look for a cause of the seborrhea.

b. Evaluate for evidence of ectoparasitic disease. Be sure to search repeatedly for Demodex in any case of recurrent deep pyoderma, particularly pododermatitis. Biopsies are sometimes necessary to demonstrate mites in such cases.

c. Check for thyroid function, even in animals that are not overtly seborrheic.

d. Skin test, or undertake in vitro tests for atopy, even if animals are not pruritic when their pyoderma is controlled.

e. Do an elimination diet for food allergy, again, even if the animal is not pruritic when the pyoderma is controlled.

f. Unfortunately, work-up for immunological defects is not generally available, but should be pursued if possible if all of the above are negative.

Therapy for the recurrent case with no apparent cause.

a. Be sure to use the appropriate antibiotic therapy supported by results of in vitro sensitivity tests. Bactericidal therapy is preferred in recurrent cases.

b. Use good supporting antibacterial shampoos. These may be alternated with antiseborrhoeic shampoos if seborrhoea is evident.

c. Consider using immunotherapy with a staphylococcal product e.g., Staph Phage Lysate (Delmont Labs, Swarthmore, PA, USA).

d. As a last resort some clinicians advocate:

i. Continued antibiotic therapy in normal doses,

ii. Intermittent full courses at full dosage with one month on and one month off.

iii. Intermittent full dose therapy on, say, two consecutive days each week.

iv. Continual low dose therapy, which seems conceptually the least desirable approach.


Richard EW Halliwell, MA VetMB PhD MRCVS DECVD
Professor, University of Edinburgh, Royal (Dick) School of Veterinary Studies,
Summerhall, Edinburgh, UK
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