Dog Pyoderma Severity and Treatment Calculator

Pyoderma Classification

Canine pyoderma is one of the most common dermatological conditions. Classification by DEPTH determines treatment duration and intensity:

Depth	Description	Examples
Surface	Colonization of INTACT epidermis	Skin fold pyoderma, hot spot, bacterial overgrowth
Superficial	Infection of HAIR FOLLICLE	Bacterial folliculitis (most common form)
Deep	Extension BELOW follicle into dermis/subcutis	Furunculosis, draining tracts, cellulitis

Causative Organisms

Staphylococcus pseudintermedius causes ~90% of canine pyoderma.

Other organisms:

• Staph aureus less common
• Staph schleiferi
• Pseudomonas aeruginosa (often deep pyoderma)
• E. coli, Proteus, Klebsiella less common

MRSP – The Growing Problem

Methicillin-Resistant Staphylococcus Pseudintermedius (MRSP) now affects 5-30% of canine pyoderma cases in many countries.

Critical features:

• Resistant to ALL beta-lactam antibiotics — cephalexin, amoxicillin-clavulanate, cefpodoxime DON’T WORK
• Standard empirical treatment fails
• Recognition: persistent or worsening pyoderma despite appropriate empirical antibiotic for 14-21 days
• Culture shows oxacillin resistance = MRSP confirmed
• Limited treatment options — based on full susceptibility panel

Zoonotic potential: rare human transmission but immunocompromised household contacts more at risk. Basic hygiene (handwashing after handling, avoid face contact during active infection).

Treatment By Depth

Surface Pyoderma (2-3 Weeks)

Topical alone often sufficient:

• Chlorhexidine 2-4% shampoo daily for 2-3 weeks
• Chlorhexidine wipes 1-2× daily
• Address underlying cause — fold management, trauma cessation, allergy management

Superficial Pyoderma (3-4 Weeks Minimum)

Combination topical + systemic typically:

Topical:

• Chlorhexidine 2-4% shampoo 2-3× weekly with 10-minute contact time
• Chlorhexidine wipes daily on affected areas

Systemic antibiotic (first-line empirical):

• Cephalexin 22-30 mg/kg q12h — see PuppaDogs Cephalexin Calculator
• Amoxicillin-clavulanate 12.5-25 mg/kg q12h — see PuppaDogs Clavamox Calculator
• Clindamycin 5.5-11 mg/kg q12h — see PuppaDogs Clindamycin Calculator

Duration: 3-4 weeks; minimum 1 week beyond clinical resolution.

Deep Pyoderma (6-8 Weeks Minimum)

Aggressive multimodal:

Topical every 2-3 days with 10-minute contact time.

Systemic antibiotic ESSENTIAL:

• Based on CULTURE & SUSCEPTIBILITY ideally
• Empirical: cephalexin or amoxicillin-clavulanate pending culture
• Treat 2 weeks beyond clinical resolution

Sometimes:

• Surgical debridement for cellulitis/furunculosis
• Warm compresses to draining lesions

Duration: 6-8 weeks minimum; some cases 3-6 months.

Treatment Duration Is Critical

Undertreatment is a major cause of:

• Treatment failure
• Resistance development
• Chronic recurrent disease

Minimum durations:

Depth	Duration
Surface	2-3 weeks
Superficial	3-4 weeks (1 week beyond resolution)
Deep	6-8 weeks (2 weeks beyond resolution)

Common error: stopping at clinical resolution — skin looks better but bacteria still present subclinically → relapse + resistance.

Cytology at end-of-treatment confirms microbiological resolution.

Cytology – The Workhorse

Tape strip or impression smear of pustule/pyoderma lesion → Diff-Quik stain → microscopy shows:

• Bacteria — cocci in “bunches of grapes” pattern (Staph pseudintermedius classic)
• Neutrophils — often degenerate with intracellular bacteria (confirms active infection vs colonization)
• Sometimes Malassezia yeasts (mixed infection common)

Culture & Susceptibility – When

Indicated for:

• Recurrent infection (≥3 episodes/year)
• Treatment failure after 14-21 days appropriate empirical
• Deep pyoderma
• Immunocompromised dog
• MRSP history in household
• Worsening despite treatment

How: aspirate intact pustule with sterile needle; or biopsy nodular lesion.

Underlying Disease – Critical For Recurrent

Pyoderma is RARELY a primary disease — usually secondary to:

Atopic Dermatitis

Most common underlying — see PuppaDogs Itch Severity Calculator and Allergy Diary Calculator.

Food Allergy

8-12 week elimination diet with novel protein or hydrolysed diet.

Endocrine Disease

• Cushing’s disease — see PuppaDogs Cushing’s Pre-Test Calculator
• Hypothyroidism — see PuppaDogs Hypothyroidism Pre-Test Calculator

Ectoparasites

• Demodicosis — see PuppaDogs Mites Calculator
• Severe flea allergy

Skin Fold Anatomy

Brachycephalic and wrinkled breeds:

• English/French Bulldog
• Pug
• Boston Terrier
• Shar Pei
• Pekingese

Primary Seborrhoea

Genetic predisposition particularly Cocker, Westie, Basset.

Hot Spot (Pyotraumatic Dermatitis)

Acute moist surface infection, usually triggered by:

• Allergic itching
• Ectoparasites
• Self-trauma
• Ear infection (causes scratching)

Treatment:

1. Clip hair around lesion (often shocking how much larger lesion is)
2. Clean with chlorhexidine 2% solution
3. Topical antibiotic + steroid combination (Hydro-B 1020, fusidic acid + steroid) 2-3× daily
4. Elizabethan collar to prevent further trauma
5. Address underlying trigger — flea control, allergy management, ear infection
6. Systemic antibiotic for 7-14 days if extensive or appears deep

Resolution: typically 1-2 weeks with appropriate treatment.

Skin Fold Pyoderma

Particularly Bulldog, French Bulldog, Pug, Boston, Shar Pei:

Lip folds, facial folds, tail-base folds, vulvar folds, axillary folds.

Management:

• Daily chlorhexidine wipes
• Topical antifungal-antibacterial wipes if mixed Malassezia
• Weight management to reduce fold depth
• Trim hair to ventilate folds
• Surgical fold revision for severe chronic cases (caudectomy for tail-base, fold resection for facial/vulvar)

Antibiotic Stewardship

Best practice:

1. Use topical therapy first/concurrent when feasible
2. Culture for recurrent or treatment-resistant cases — don’t keep switching empirical antibiotics blindly
3. Adequate duration — under-treatment drives resistance
4. Address underlying disease so antibiotic isn’t needed long-term
5. Reserve fluoroquinolones and rifampin for confirmed-resistant infections (not first-line)
6. Document treatment response with cytology
7. Specialist referral for refractory cases rather than escalating to last-resort antibiotics

MRSP Treatment Options

Based on FULL susceptibility panel:

• Doxycycline 5-10 mg/kg q12h — see PuppaDogs Doxycycline Calculator
• Clindamycin 11 mg/kg q12h (if susceptible)
• Chloramphenicol 50 mg/kg q8-12h
• Rifampin — combination only with another agent (monotherapy = rapid resistance)
• Sometimes amikacin/gentamicin (renal monitoring)
• Sometimes specialty drugs (linezolid, vancomycin — limited in vet med)

Dermatology referral appropriate.

Breed-Specific Notes

German Shepherd

Classic deep pyoderma / pyotraumatic folliculitis and furunculosis particularly lateral thigh and dorsal trunk; often atopic underlying. May need 3-6 month antibiotic course + multimodal atopic management. Some lines have focal metatarsal fistulation as distinct entity.

West Highland White Terrier

Chronic recurrent pyoderma classic alongside Malassezia overgrowth; almost always severe atopic underlying. Lifelong proactive management.

Brachycephalic / Wrinkled

Skin fold pyoderma lifelong management.

Honest Caveats

• Pyoderma is treatable but requires correct depth diagnosis and adequate duration
• Under-treatment is the #1 reason for treatment failure and resistance
• MRSP is increasing — culture for recurrent cases is increasingly important
• Underlying disease must be addressed or pyoderma will recur
• Cost of treatment can be substantial (medications + repeat exams + culture)
• Owner compliance with topical therapy + adequate antibiotic duration is critical

Conclusion

Canine pyoderma classification by DEPTH (surface / superficial / deep) determines treatment duration and intensity. Staphylococcus pseudintermedius causes ~90% of cases; MRSP affects 5-30% and is rising — resistant to all beta-lactams so standard empirical treatment fails. Topical chlorhexidine is the foundation; systemic antibiotics (cephalexin/amoxicillin-clavulanate first-line empirical) added for superficial and deep. Adequate duration is critical — under-treatment drives resistance. Underlying disease workup is MANDATORY for recurrent cases — atopic dermatitis, food allergy, endocrine disease, ectoparasites, skin folds, primary seborrhoea. Culture & susceptibility for treatment-resistant cases. Antibiotic stewardship — topical first, culture-guided systemic, address underlying disease.

Frequently Asked Questions

What is the difference between surface, superficial and deep pyoderma?

DEPTH classification determines treatment. SURFACE pyoderma = colonization of INTACT epidermis – skin fold pyoderma (intertrigo, in folds of Bulldog/Pug/Shar Pei face/lip/tail-base/vulva), pyotraumatic dermatitis (HOT SPOT – localised moist surface infection), bacterial overgrowth syndrome. Treatment – topical only, 2-3 weeks chlorhexidine shampoo/wipes. SUPERFICIAL pyoderma = infection of HAIR FOLLICLE = bacterial folliculitis – papules, pustules, epidermal collarettes (peeling rings), focal alopecia. Most common form. Treatment – topical + systemic antibiotic 3-4 weeks (cephalexin or amoxicillin-clavulanate). DEEP pyoderma = infection extends BELOW follicle into dermis/subcutis – furunculosis, draining tracts, nodules, fistulae. Treatment – aggressive topical + systemic 6-8 weeks MINIMUM.

What antibiotic treats dog pyoderma?

FIRST-LINE EMPIRICAL: CEPHALEXIN 22-30 mg/kg q12h (PuppaDogs Cephalexin Calculator); AMOXICILLIN-CLAVULANATE (Clavamox) 12.5-25 mg/kg q12h (PuppaDogs Clavamox Calculator); CLINDAMYCIN 5.5-11 mg/kg q12h (PuppaDogs Clindamycin Calculator). DURATION CRITICAL – superficial 3-4 weeks (1 week beyond clinical resolution); deep 6-8 weeks (2 weeks beyond resolution). MRSP-RESISTANT cases need culture-guided therapy – options include doxycycline (PuppaDogs Doxycycline Calculator), clindamycin if susceptible, chloramphenicol, rifampin (combination only – monotherapy = rapid resistance). TOPICAL chlorhexidine 2-4% shampoo with 10-minute contact time is FOUNDATION of treatment alongside systemic – reduces antibiotic dependence and resistance development.

Why does my dog keep getting skin infections?

RECURRENT pyoderma (more than 3 episodes in 12 months) = UNDERLYING DISEASE issue. Workup ESSENTIAL: (1) ATOPIC DERMATITIS – most common; itchy + AD-distribution + breed predisposition; PuppaDogs Itch Severity and Allergy Diary calculators. (2) FOOD ALLERGY – 8-12 week strict elimination diet trial. (3) ENDOCRINE DISEASE – CUSHING’S DISEASE (PuppaDogs calculator); HYPOTHYROIDISM (PuppaDogs calculator); bloods + ACTH stim or LDDS test as appropriate. (4) IMMUNE COMPROMISE – chronic steroids, chemotherapy, severe systemic disease. (5) ECTOPARASITES – demodicosis (PuppaDogs Mites Calculator), severe flea allergy. (6) SKIN FOLD ANATOMY – brachycephalic + wrinkled breeds. (7) PRIMARY SEBORRHOEA – genetic. Treating infection without addressing underlying = relentless recurrence.

What is MRSP in dogs?

MRSP = Methicillin-Resistant Staphylococcus pseudintermedius – resistant strain of the most common bacterial cause of canine pyoderma (Staph pseudintermedius causes 90%+ canine pyoderma). MRSP affects 5-30% of canine pyoderma cases in many countries and is RISING. CRITICAL FEATURES – RESISTANT TO ALL BETA-LACTAM ANTIBIOTICS including cephalexin, amoxicillin-clavulanate, cefpodoxime which are standard empirical treatments; standard treatment FAILS. RECOGNITION – persistent or worsening pyoderma despite appropriate empirical antibiotic for 14-21 days; CULTURE & SUSCEPTIBILITY shows oxacillin resistance. TREATMENT – based on full susceptibility panel – doxycycline, clindamycin if susceptible, chloramphenicol, rifampin (combination only). ZOONOTIC potential – rare human transmission but immunocompromised contacts at risk; basic hygiene (handwashing, avoid face contact during active infection).

How long should my dog be on antibiotics for pyoderma?

MINIMUM durations – SURFACE pyoderma 2-3 weeks (topical only often adequate); SUPERFICIAL pyoderma 3-4 WEEKS MINIMUM (1 week beyond clinical resolution); DEEP pyoderma 6-8 WEEKS MINIMUM (2 weeks beyond clinical resolution; some cases 3-6 months). UNDER-TREATMENT is the MAJOR CAUSE of treatment failure and resistance development. COMMON ERROR – stopping when skin LOOKS better; bacteria still present subclinically; infection rebounds + resistance develops. CYTOLOGY at end-of-treatment confirms microbiological resolution. After resolution, address UNDERLYING DISEASE to prevent recurrence (atopic, food allergy, endocrine, ectoparasites, skin folds, seborrhoea). Refractory cases warrant CULTURE & SUSCEPTIBILITY rather than blindly switching antibiotics.

What is a hot spot on a dog?

HOT SPOT (pyotraumatic dermatitis) = localised acute moist SURFACE PYODERMA infection, usually triggered by allergic itching, ectoparasites, ear infection, or other self-trauma cause. Dogs lick/chew an itchy area until it becomes secondarily infected. Often dramatic appearance – red, moist, painful, hairless patch. TREATMENT – (1) CLIP HAIR around lesion (lesion often much larger than apparent under hair); (2) CLEAN with chlorhexidine 2% solution; (3) TOPICAL antibiotic + steroid combination (Hydro-B 1020, fusidic acid + steroid) 2-3x daily; (4) ELIZABETHAN COLLAR to prevent further trauma; (5) ADDRESS UNDERLYING TRIGGER – flea control, allergy management, ear infection control (PuppaDogs Otitis Externa Calculator); (6) systemic antibiotic 7-14 days if extensive or appears deep. Resolution typically 1-2 weeks with appropriate treatment.

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References & Further Reading

The dosing ranges and safety information on this page are drawn from the following veterinary references. Always defer to your own veterinarian and the manufacturer’s label for your specific product.

1. Hillier A, Lloyd DH, Weese JS, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Veterinary Dermatology, 2014.
2. Loeffler A, Lloyd DH. What has changed in canine pyoderma? A narrative review. The Veterinary Journal.
3. Beco L, Guaguere E, Lorente Mendez C, et al. Suggested guidelines for using systemic antimicrobials in bacterial skin infections (1): diagnosis based on clinical presentation, cytology and culture. Veterinary Record.
4. Beco L, Guaguere E, Lorente Mendez C, et al. Suggested guidelines for using systemic antimicrobials in bacterial skin infections (2): antimicrobial choice, treatment regimens and compliance. Veterinary Record.
5. Bannoehr J, Guardabassi L. Staphylococcus pseudintermedius in the dog: taxonomy, diagnostics, ecology, epidemiology and pathogenicity. Veterinary Dermatology.
6. BSAVA Guide to Responsible Use of Antibacterials.
7. PuppaDogs. Cephalexin, Clavamox, Clindamycin, Doxycycline Calculators + Itch Severity + Allergy Diary + Mites Calculators. puppadogs.com.