Difference between revisions of "Bacterial skin infections - Pathology"

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

Latest revision as of 19:12, 21 February 2011