Difference between revisions of "Bacterial skin infections - Pathology"

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#REDIRECT[[:Category:Integumentary System - Bacterial Infections]]
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Cutaneous bacterial infections tend to be called '''pyodermas'''. They are superficial, deep and are common in dogs, but less common in other species.
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===Superficial pyoderma===
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[[Image: Superficial pyoderma dog.jpg|100px|thumb|right|<small><center>Superficial pyoderma in a dog (Courtesy of Bristol BioMed Image Archive)</center></small>]]
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*Affects epidermis and upper infundibulum of hair follicles
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*No scarring when healed
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*Grossly:
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**Erythema
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**Alopecia
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**[[Skin Glossary - Pathology|Papules and pustules]]
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**[[Skin Glossary - Pathology|Crusts]]
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**[[Skin Glossary - Pathology|Epidermal collarettes]]
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*Microscopically:
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**Intraepidermal pustular dermatitis
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**Superficial suppurative folliculitis
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**Bacteria commonly not seen
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===[[Impetigo]]===
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====[[Dermatophilosis]]====
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====[[Greasy pig disease]]====
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====[[Ovine Fleece Rot]]====
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====[[Equine Pastern Folliculitis]]====
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===Deep pyoderma===
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*Less common than superficial pyoderma
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*Occurs mainly in dogs
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*Affects infundibulum, isthmic portion of hair follicles and surrounding dermis and subcutis
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*Heals with scarring
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*Local lymph nodes are often affected
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*Often secondary to immunosuppression, follicular hyperkeratosis or [[Parasitic skin infections - Pathology#Demodicosis|demodicosis]]
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*May also be a sequele to [[Bacterial skin infections - Pathology#Superficial pyoderma|superficial pyoderma]]
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*Grossly:
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**[[Skin Glossary - Pathology|Crusted papules, pustules, alopecia, abscesses, nodules, fistulas, ulcers, haemorrhagic bullae]]
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**In dogs may look similar to [[Skin Environmental - Pathology#Pyotraumatic dermatitis|pyotraumatic dermatitis]]
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*Microscopically:
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**Pyogranulomatous folliculitis and furunculosis
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**Nodular or diffuse dermatitis
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**Panniculitis
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*May involve a foreign bodey reaction to follicular contents and draining sinuses develop
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*If chronic, scarring and loss of adnexa
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*Bacteria often isolated include [[:Category:Staphylococcus species|''Staphylococcus'' spp.]], especially ''S. intermedius'' in dogs, [[:Category:Streptococcus species|''Streptococcus'' spp.]], ''[[Corynebacterium pseudotuberculosis]]'', [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']], [[:Category:Pasteurella and Mannheimia species|''Pasteurella'']], [[Proteus|''Proteus'']], [[Escherichia coli|''E.coli'']]
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====[[Staphylococcal Folliculitis and Furunculosis]]====
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====Subcutaneous abscesses====
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*Purulent exudate within dermis and subcutis
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*Commonly occurs in cats due to contamination of penetrating wounds
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*Surrounding wall of collagen and fibroblasts may develop
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*Common bacteria (often normal mouth flora)
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**[[Pasteurella multocida|''Pasteurella multocida'']], [[Fusobacterium necrophorum|''Fusobacterium'' spp.]], [[:Category:Streptococcus species|beta - haemolytic streptococci]], [[Bacteroides|''Bacteroides'']]
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====Bacterial granulomatous dermatitis====
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*Usually due to saprophytes
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*Grossly:
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**Diffuse or nodular lesions
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**May ulcerate and form drainage fistulas
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*Microscopically:
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**Macrophages +/- multinucleated giant cells
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**[[Necrosis - Pathology#Caseation Necrosis|Caseous necrosis]] and [[Neutrophils|neutrophils]]
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*'''Mycobacterial granulomatous or pyogranulomatous lesions'''
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**Usually caused by ''[[Mycobacterium lepraemurium]]'' (feline leprosy) or other ''Mycobacteria''
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**Most commonly lesions appear on head, neck and legs
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*'''[[Botryomycosis]]'''
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===Bacterial pododermatitis===
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*Digital infections in ruminants
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*'''[[Contagious Footrot]]'''
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*'''[[Necrobacillosis]]''' of the foot
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===Systemic bacterial infections===
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*[[Salmonella|'''Salmonellosis''']]
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**Capillary dilatation and congestion -> cyanosis of external ears and abdoman
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**Thrombosis -> necrosis of extremities
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*'''Erysipelas''' in pigs
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**Caused by [[Erysipelothrix rhusiopathiae|''Erysipelothrix rhusiopathiae'']]
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**Vasculitis, thrombosis, ischaemia -> cutaneous lesions - firm, raises, rhomboidal pink to dark purple areas
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*[[Clostridium novyi|''Clostridium novyi'']]
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**Severe cellulitis, toxaemia and death of young rams during breeding season (due to traumatised heads) - 'big head'
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*[[Streptococcus equi subsp. equi|''Streptococcus equi'']]
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**In horses
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**Immune complex vasculitis -> [[Haemorrhage#Purpura haemorrhagica|purpura]]
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[[Category:Integumentary System - Pathology]]

Revision as of 14:54, 14 February 2011


Cutaneous bacterial infections tend to be called pyodermas. They are superficial, deep and are common in dogs, but less common in other species.

Superficial pyoderma

Superficial pyoderma in a dog (Courtesy of Bristol BioMed Image Archive)
  • Affects epidermis and upper infundibulum of hair follicles
  • No scarring when healed
  • Grossly:
  • Microscopically:
    • Intraepidermal pustular dermatitis
    • Superficial suppurative folliculitis
    • Bacteria commonly not seen

Impetigo

Dermatophilosis

Greasy pig disease

Ovine Fleece Rot

Equine Pastern Folliculitis

Deep pyoderma

Staphylococcal Folliculitis and Furunculosis

Subcutaneous abscesses

Bacterial granulomatous dermatitis

  • Usually due to saprophytes
  • Grossly:
    • Diffuse or nodular lesions
    • May ulcerate and form drainage fistulas
  • Microscopically:
  • Mycobacterial granulomatous or pyogranulomatous lesions
    • Usually caused by Mycobacterium lepraemurium (feline leprosy) or other Mycobacteria
    • Most commonly lesions appear on head, neck and legs
  • Botryomycosis

Bacterial pododermatitis

Systemic bacterial infections

  • Salmonellosis
    • Capillary dilatation and congestion -> cyanosis of external ears and abdoman
    • Thrombosis -> necrosis of extremities
  • Erysipelas in pigs
    • Caused by Erysipelothrix rhusiopathiae
    • Vasculitis, thrombosis, ischaemia -> cutaneous lesions - firm, raises, rhomboidal pink to dark purple areas
  • Clostridium novyi
    • Severe cellulitis, toxaemia and death of young rams during breeding season (due to traumatised heads) - 'big head'
  • Streptococcus equi
    • In horses
    • Immune complex vasculitis -> purpura
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