Canine Pyodermas: Bacterial Skin Diseases PDF

Canine Pyodermas General Considerations Bacterial skin diseases Clarissa Souza  Bacterial skin diseases should be considered secondary until proven otherwise  Rarely a predisposing condition will not be identified Assistant Professor Dermatology and Otology Service Canine Pyodermas General Co...

Canine Pyodermas General Considerations Bacterial skin diseases Clarissa Souza  Bacterial skin diseases should be considered secondary until proven otherwise  Rarely a predisposing condition will not be identified Assistant Professor Dermatology and Otology Service Canine Pyodermas General Considerations  Common predisposing diseases/conditions: Allergies  Environmentally-induced atopic dermatitis  Food-induced atopic dermatitis  Flea allergy  Contact allergy Canine Pyodermas General Considerations  Common predisposing diseases/conditions: Parasitic diseases:  Demodicosis  Sarcoptic mange  Cheyletiellosis Endocrinopathies  Hyperadrenocorticism  Hypothyroidism  Sex hormone imbalances Canine Pyodermas Canine Pyodermas Etiology General Considerations  Common predisposing diseases/conditions: Cornification disorders:  Seborrhea  Ichthyosis Anatomic defects:  Staphylococcus pseudintermedius - most cases  S. schleiferi  Staph coagulase negative  S. aureus: less common  Skin folds  Proteus sp, Pseudomonas sp and E. coli: uncommon This is what you should expect on cytology of pyodermas Degenerate neutrophils Cocci Canine Pyodermas Surface Pyoderma Classification: Depth of Infection Pyotraumatic dermatitis Surface pyoderma Superficial pyoderma Deep pyoderma Synonyms: Acute moist dermatitis “Hot spot” Skin fold pyodermas or intertrigo Surface Pyoderma Pyotraumatic dermatitis General considerations: Self-inflicted Rapid onset (within hours) Moist and painful Surface Pyoderma Pyotraumatic dermatitis Predisposing Factors: Pruritic dermatoses (Fleas!) Dogs with thick, long coats (fur mats) Hot and humid weather Skin moisture: e.g. swimming Irritants Surface Pyoderma Surface Pyoderma Skin fold pyodermas or intertrigo Pyotraumatic dermatitis Skin fold pyodermas or intertrigo Pathogenesis:  Anatomic defect or breed conformation  Constant skin friction  Poor air circulation  Moisture accumulation  Moisture + skin friction → maceration + removal of stratum corneum + bacterial overgrowth → poor air circulation → > bacterial overgrowth Skin fold pyodermas or intertrigo History: Malodor Pruritus, pain → variable Clinical signs: Erythematous exudative lesions Surface Pyoderma Skin fold pyodermas or intertrigo Clinical Forms: Lip fold Facial Fold Perivulvar fold Tail fold Surface Pyoderma Skin fold pyodermas or intertrigo Diagnosis: History Clinical signs Cytology ± culture Surface Pyoderma Skin fold pyodermas or intertrigo Treatment:  Surgical → lip, tail, vulvar fold  Clip and clean with antiseptic solutions  Antimicrobial/steroid cream, ointment or solution Avoid systemic antibiotic therapy! Surface Pyoderma Skin fold pyodermas or intertrigo Treatment: Oral glucocorticoids → if severe inflammation → pain Weight reduction (perivulvar dermatitis) Long term maintenance therapy These lesions are localized and superficial! Superficial Pyoderma  General considerations:  Bacteria infect the superficial layers of the epidermis and/or the hair follicle  It frequently recurs History: Pruritus: ± present Try to determine the sequence of events to find the underlying cause Pruritus before lesions = allergies or pruritic parasitic diseases Lesions before pruritus = endocrinopathies, Demodex canis Superficial Pyoderma Clinical signs:  Papules, pustules, epidermal collarettes  Circumscribed areas of alopecia (“moth-eaten” alopecia – short coated breeds)  ± Pruritus Moth-eaten alopecia Pustule Epidermal collarettes Superficial Pyoderma Superficial Pyoderma  Other differential diagnoses for motheaten pattern:  Demodicosis caused by D. canis  Dermatophytosis If lesions are present on: Abdomen, groin and axillae and dog is < 1 year old → IMPETIGO  Other differential diagnosis for pustules, papules, crusts:  Pemphigus foliaceus Superficial Pyoderma Papules  Diagnosis:  History & clinical signs  Skin scrapings to rule in/out parasitic diseases as the underlying cause  Cytology  ± Bacterial culture & susceptibility Remember to look for the underlying disease to prevent or reduce the frequency of recurrences Pyoderma Bacterial culture & susceptibility Bacterial infection confirmed on cytology Poor response to empirical therapy (possible resistant infection) Recurrent pyoderma = many previous courses of antibiotic therapy (possible resistant infection) Deep pyoderma Rods on cytology Superficial Pyoderma  Treatment: Consider the following 1st tier choices in order of preference     1st generation cephalosporines (e.g cephalexin, cefadroxil) Amoxicillin + clavulanic acid Potentiated sulfas Clindamycin Antibacterial shampoos and other topicals are good adjunctive therapy Superficial Pyoderma Treatment: Identify and treat any underlying condition Do not use empirically penicillin, ampicillin, amoxicillin ((B-lactams) Most strains of S. pseudintermedius, S. aureus and S. schleiferi produce Beta lactamase Superficial Pyoderma Treatment: 2nd tier  3rd generation cephalosporines (e.g. cefpodoxime, cefovecin)  Fluoroquinolones Should only be used if the bacterial strain is resistant to all 1st tier antibiotics or patient do not tolerate them Only prescribe if the bacterial strain is susceptible to these antibiotics = You have to culture! Superficial Pyoderma Treatment: 2nd tier  Doxycycline  Chloramphenicol  Rifampin Should only be used if the bacterial strain is resistant to all 1st tier antibiotics or patient do not tolerate them Superficial Pyoderma Treatment: 3rd tier  Linezolid  Vancomycin AVOID!!!! Only prescribe if the bacterial strain is susceptible to these antibiotics = You have to culture! Canine Pyodermas Deep Pyoderma Canine Pyodermas Deep Pyoderma  It can be localized:  The bacterial infection is associated with rupture of the hair follicle (furunculosis)  Lesions affect different layers of the skin  Chin and lips  Feet: interdigital deep pyoderma  Callus pyoderma  Acral lick dermatitis  It can be generalized:  Generalized deep pyoderma Deep Pyoderma Localized Clinical signs: Nodules, ulceration and/or draining tracts ± Pruritus: Seen less often than with superficial pyoderma;  Lymphadenopathy or systemic signs may be present in the generalized form Nodule draining blood Nodules and draining tracts exuding blood Localized Nodules draining blood Nodules INTERDIGITAL PYODERMA Most common in shortcoated breeds One or more feet can be affected Abnormal body weight bearing on feet may predispose to interdigital deep pyoderma! Generalized deep pyoderma German Shepherds are predisposed! Eroded to ulcerated skin draining blood Deep Pyoderma  Differential diagnosis:  Demodicosis with furunculosis  Deep or subcutaneous fungal infection or atypical bacterial infections  Neoplasia  Localized lesions→ foreign body Deep Pyoderma Diagnosis: Cytology: always! Skin scrapings Bacterial culture The selection of antibiotic should be based on C&S: use the tier-based principles for antibiotic selection! ± Fungal culture If suspecting of deep systemic fungal infections ± Biopsy If not responding to therapy as expected If lesions appear unusual Cytology of pyodermas Deep Pyoderma  Treatment:  Identify and treat underlying disorder  Choose antibiotic based on C&S  Often requires a few weeks of antibiotic therapy, until resolution of clinical signs Other inflammatory cells are also present in deep pyoderma! Be aware that often it is difficult to find bacteria on samples from deep pyoderma = lower numbers + inflammatory cells hide them Deep Pyoderma Topical treatment: Associated with systemic antibacterial treatment Shampoos Chlorhexidine 2-4% Benzoyl peroxide 2.5% ± Topical mupirocin – for localized lesions  Only for methicillin-resistant S. pseudintermedius (MRSP) Clip long hair Atypical deep bacterial skin infections  Nocardiosis  Branching filamentous aerobic bacteria  Common soil saprophytes  Canine leproid granuloma  Slow growing Mycobaterium  Suspected insect to play a role as vectors Nocardiosis Nocardiosis  Diagnosis:  Cytology  Culture  Biopsy (histopathology)  Treatment:  Surgical removal of lesion  Varying antimicrobial susceptibility  Continuing treatment for 1 month past clinical cure Canine leproid granuloma  Localized nodular disease  Typically affecting head, especially pinnae  Common in short coated breeds Canine Leproid Granuloma  Diagnosis  Culture typically negative  Cytology  Identification of negatively stained bacilli (Diff-Quik) or Acid Fast Bacteria (Ziehl Neelsen)  PCR Canine Leproid Granuloma  Surgical excision is curative  Systemic antibiotic therapy:  Rifampin, clarithromycin or doxycycline