Professor, Department of Clinical Veterinary Science, Royal Veterinary College, Hawkshead Campus, North Mymms, Hertfordshire, UK
Canine pyoderma is a complex of diseases involving bacterial infection at different levels of the skin (Table 1) and requiring different approaches to therapy. These diseases are nearly always secondary and so it is important to identify underlying factors. Commonly these are allergies but endocrinopathy, immunodeficiency, ectoparasitic infestation, follicular dysplasia and breed predisposition may be involved. Diagnosis of underlying conditions may not be easy. Treatment during the diagnostic phase should be designed to advance diagnosis and avoid camouflaging diagnostic clinical signs. Antibiotic therapy is a good diagnostic strategy as it eliminates pyoderma and helps expose underlying conditions.
This presentation assumes that a diagnosis has been made and deals with current approaches to the treatment of the different forms of infection. Treatment of underlying causes is not covered.
Table 1. Classification of canine pyoderma.
Acute moist dermatitis
Skin fold pyoderma
Impetigo ("puppy pyoderma")
Superficial spreading pyoderma
Muzzle folliculitis & furunculosis
Localised deep pyodermas (nasal, pedal & pressure point pyodermas, pyotraumatic folliculitis & furunculosis)
Generalised deep pyoderma
*Not strictly pyoderma. Commonly both pathogenic staphylococci and Malassezia are present.
Acute Moist Dermatitis. Prevention of further trauma is essential and will sometimes allow healing without further therapy. Ensure that there is no underlying folliculitis or furunculosis. Because the epidermal damage is a consequence of trauma, healing is rapid. However, lesions are often painful and topical therapy, requiring direct contact with skin, can be hazardous. Topical antibiotic and steroid gels or creams are effective but spraying with a soothing, antimicrobial, astringent preparation has been shown to be as effective1 and is likely to be less hazardous. Lesions should be substantially healed in 7-10 days. Where there is marked pruritus, systemic glucocorticoids may be required.
Skin Fold Pyoderma. Ideally, folds are removed surgically. If surgery is not feasible, measures to render the microenvironment within the fold inhospitable to bacteria and yeasts are required. Cleansing every 2-3 days with an antimicrobial shampoo is effective. Benzoyl peroxide, chlorhexidine, and chlorhexidine and miconazole are effective. Chlorhexidine is quite unstable and so it is advisable to select well-formulated preparations with published efficacy against both bacteria and Malassezia.2 (Lloyd 1999) Benzoyl peroxide must used with care as animals may develop sensitivity and it can be irritant. Ethyl lactate may be effective in milder cases and has low irritancy. Intervals between shampooing may be extended by the use of antimicrobial creams and gels. Spraying with a soothing, antimicrobial, astringent preparation may also be effective.
Impetigo normally responds to antimicrobial shampoos. Use on two or three occasions over a period of 7-10 days should be effective in uncomplicated cases. Spontaneous resolution commonly occurs.
Mucocutaneous Pyoderma may respond to treatment with antibacterial shampoos, as described above, followed by the use of antibacterial ointment, such as mupirocin. Daily treatment for two weeks and then once or twice a week may be effective. Following resolution, the disease may remain in abeyance but commonly repeated treatment is required. With deeper or more extensive infection, or if topical treatment is difficult, systemic antibiotic is required. Treatment for 4 weeks or more may be necessary. If not successful, further diagnostic procedures, including biopsy, are required.
Superficial Folliculitis and Superficial Spreading Pyoderma. Normally systemic antibiotic therapy is used. Bacteriostatic antibiotics are effective but bactericides are preferable. Treatment for at least one week beyond clinical cure is advisable. Recovery may be promoted by use of antibacterial shampoos containing chlorhexidine or benzoyl peroxide, or in milder cases ethyl lactate, which aid removal of crusts and reduce surface bacterial populations.2,3 Mild superficial pyoderma can be treated with such shampoos without systemic antibiotic but this is labour-intensive; shampooing every 2-3 days is required. Once lesion resolution occurs, shampooing can be reduced to once or twice a week; in winter weekly to monthly shampooing may be sufficient to maintain remission.
Where there is recurrent infection and underlying causes cannot be identified or controlled, long-term treatment options need to be considered. Regular shampooing with antibacterial shampoo may give control. Otherwise, the main options are pulse therapy with antibiotics and staphylococcal vaccination. Vaccination is a better choice. Well-prepared autogenous vaccines (bacterins) are effective in about 50% of cases; responding dogs do not need other therapy.4 An American bacterial lysate prepared from S. aureus, has also been shown to reduce the frequency of folliculitis and decrease the need for repeated antibiotic therapy.5 Pulse or continual low dose therapy6 should be a last resort as it may promote development of antibiotic resistance, although recent evidence indicates that this risk may be low.
In view of the fact that the causative pathogen may be harboured on the mucosae, particularly of the upper respiratory tract and anus, some clinicians have used topical antibiotic to treat the nasal and or anal mucosae. Experimental studies have shown that S. intermedius populations can be eliminated by this method using fusidic acid.7 Anecdotally, this has helped in some cases of recurrent pyoderma.
When deep infection occurs, there are local factors causing skin damage and more serious deficiencies in the immune system of the affected animal. If these can be resolved, recovery should be complete. Determined efforts to identify the underlying factors should be made. Demodicosis is a common cause.
With discharging lesions, antimicrobial washes and soaks are useful to remove pus and debris, and may accelerate recovery. Clipping is helpful, enables the extent of lesions to be demonstrated and can be useful in persuading clients to comply with treatment. Prolonged systemic antibiotic treatment with bactericidal antibiotic is necessary and must continue for at least two weeks beyond clinical cure. Where lesions are in areas with poor blood supply or large granulomatous lesions, fluoroquinolones, which penetrate well, are particularly useful. On rare occasions it may be necessary to use unusual antibiotics to achieve penetration, such as rifampicin.
In some cases, unusual organisms such as actinomycetes or mycobacteria are involved, and there may be concurrent infection with fungi. Careful diagnostic procedures, including discussion with the laboratory concerned, may be required as routine methods may not be effective.
Choice of Antibiotics and Dosage
Although antibiotics can be selected empirically, where recurrent infection occurs or there is a lack of response, microbiological culture and sensitivity should be carried out.8,9 Ensure that you use a reliable laboratory and question unusual results e.g., very broad resistance in an organism identified as S. intermedius; this could turn out to be a methicillin-resistant S. aureus or S. schleiferi.10,11 Remember that several different strains of pathogenic staphylococci may be present on a single animal. Thus a single sensitivity test may not give the full picture. Failure of a particular antibiotic may mean you have only eliminated part of the causative bacterial population. If in doubt, always retest. Ensure your sample contains material from deep within the lesions; biopsy may be necessary for this.
Generally, manufacturer's recommended dose rates will be effective. Occasionally you will need to use higher doses to achieve effective levels of antibiotic within lesions or to overcome low level resistance. The range of antibiotics commonly used in veterinary dermatology and their properties and use are reviewed in a special issue of Veterinary Dermatology published in 1999, which is still relevant and provides excellent summaries.12
1. Ascher F, Madin F, Guaguere E et al. Intérêt d'une solution topique non antibiocorticoide dans le traitement de la dermatite pyotraumatique du chien. Pratique Médicale et Chirurgicale de L'Animal de Compagnie. 1995; 30:345-354.
2. Lloyd DH, Lamport AI. Activity of chlorhexidine shampoos in vitro against Staphylococcus intermedius, Pseudomonas aeruginosa and Malassezia pachydermatis. Veterinary Record 1999; 144: 536-537.
3. De Jaham c. Effects of an ethyl lactate shampoo in conjunction with a systemic antibiotic in the treatment of canine superficial bacterial pyoderma in an open-label, non placebo-controlled study. Veterinary Therapeutics 2003; 4: 94-100.
4. Curtis CF, Lamport AI, Lloyd DH. Blinded, controlled study to investigate the efficacy of a staphylococcal autogenous bacterin for the control of canine idiopathic recurrent pyoderma. Proceedings of the 16th Annual Congress of the ESVD-ECVD, Helsinki, Finland, August 1999. p. 148.
5. Deboer DJ, Moriello KA, Thomas CB, et al. Evaluation of a commercial staphylococcal bacterin for management of idiopathic recurrent pyoderma in dogs. American Journal of Veterinary Research 1990; 51: 636-639.
6. Carlotti DN, Jasmin P, L. Gardey L, Sanquer A. (2004): Evaluation of cephalexin intermittent therapy (weekend therapy) in the control of recurrent idiopathic pyoderma in dogs: a randomized, double-blinded, placebo-controlled study. Veterinary Dermatology 2004; 15 ( s1): 7-8.
7. Saijonmaa-Koulumies L., Parsons E., Lloyd, DH. Elimination of Staphylococcus intermedius in healthy dogs by topical treatment with fusidic acid. Journal of Small Animal Practice 1998; 39: 341-7.
8. Holm BR, Petersson U, Morner A, et al. Antimicrobial resistance in staphylococci from canine pyoderma: a prospective study of first-time and recurrent cases in Sweden. Veterinary Record 2002; 151: 600-5.
9. Kruse H, Hofshagen M, Thoresen SI, et al. The antimicrobial susceptibility of Staphylococcus species isolated from canine dermatitis. Veterinary Research Communication 1996; 20: 205-14.
10. Loeffler A, Boag AK, Sung J, et al. Prevalence of methicillin-resistant Staphylococcus aureus among staff and pets in a small Animal referral hospital in the UK. Journal of Antimicrobial Chemotherapy 2005; 56: 692-7.
11. Frank, LA, Kania, SA, Hnilica, KA, et al. Isolation of Staphylococcus schleiferi from dogs with pyoderma. Journal of the American Veterinary Medical Association 2003; 222 (4); 451-4.
12. Special Issue on Antibiotics in Veterinary Dermatology. Veterinary Dermatology 1999; 10: 161-262.