Difference between revisions of "Bacterial skin infections - Pathology"

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#REDIRECT[[:Category:Integumentary System - Bacterial Infections]]
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{{review}}
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{{toplink
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|backcolour = FFCCCC
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|linkpage =Integumentary System - Pathology
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|linktext =Integumentary System
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|maplink = Integumentary System (Content Map) - Pathology
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|pagetype =Pathology
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|sublink1 = Skin Infectious - Pathology
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|subtext1 = SKIN INFECTIOUS
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<br>
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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.
 +
===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===
 +
* = '''Superficial pustular dermatitis'''
 +
*Caused by coagulase-positive [[Staphylococcus spp.|''Staphylococcus'' spp.]]
 +
*Associated with:
 +
**Abrasions
 +
**Poor nutrition
 +
**Viral infections
 +
**Immunosuppression (often due to [[Adrenal Glands - Pathology#Adrenal Hyperfunction|hyperadrenocorticism]])
 +
*Grossly:
 +
**[[Skin Glossary - Pathology|Pustules -> crusts]], mostly in hairless skin
 +
*Microscopically:
 +
**Interfollicular neutrophilic subcorneal pustule
 +
 
 +
====Dermatophilosis====
 +
[[Image: Dermatophilosis in cow.jpg|100px|thumb|right|<small><center>Dermatophilosis in a cow (Courtesy of Bristol BioMed Image Archive)</center></small>]]
 +
 
 +
*Caused by [[Dermatophilus congolensis|''Dermatophilus congolensis'']]
 +
*Affects cattle, horses, sheep mainly
 +
*More common in wet and warm weather
 +
*Transmotted from animal to animal
 +
*Lesions tend to form on dorsal back and extremities
 +
*Associated with skin trauma, prolonged wetting or [[Parasitic skin infections - Pathology#Parasitic| parasites]]
 +
** -> penetration of zoospores
 +
*Bacteria proliferate in outer sheath of hair follicles and superficial epidermis
 +
*Gram-positive, filamentous branching organisms, subdivided longitudinally and transversly
 +
*Causing:
 +
**Acute inflammatory response -> neutrophil migration through dermis and epidermis -> formation of microabscesses
 +
**Further penetration of bacteria is thus prevented
 +
**Regenerated epidermis is invaded again by remaining organisms
 +
**Repeated reinfection -> multilaminated pustular crusts
 +
*Grossly:
 +
**[[Skin Glossary - Pathology|Papules, pustules, crusts]] may coalesce and mat the coat
 +
*Microscopically:
 +
**Hyperplastic superficial perivascular dermatitis
 +
**Multilaminated crusts, alternating keratin and inflammatory cell layers
 +
 
 +
====Greasy pig disease====
 +
 
 +
* = '''Exudative epidermitis of pigs'''
 +
*Caused by [[Staphylococcus spp.#Staphylococcus hyicus|''Staphylococcus hyicus'']]
 +
*Affects neonatal piglets - often fatal, older piglets - milder disease
 +
*Focal erosion of stratum corneum
 +
*Brown exudate
 +
*Dermatitis around eyes, ears, snout, chin and medial legs, may spread to ventral abdomen and thorax
 +
*Rapidly becomes generalised -> greasy exudate over red skin -> hardened, cracked exudate
 +
*In older piglets, milder localised disease develops around eyes, ears and face
 +
*Grossly:
 +
**Thickened epidermis, scaling
 +
*Microscopically:
 +
**Early - subcorneal pustular dermatitis extending to hair follicles -> superficial suppurative folliculitis
 +
**Late - hyperplastic epidermis, thick keratin crusts with cocci, microabscesses
 +
 
 +
====Ovine fleece rot====
 +
 
 +
*Caused by [[Pseudomonas aeruginosa and Burkholderia species|''Pseudomonas'']] and excessive moisture
 +
*Prediscposes to [[Parasitic skin infections - Pathology#Myiasis|myiasis]]
 +
 
 +
====Equine pastern folliculitis====
 +
 
 +
* = '''Greasy heel'''
 +
*Secondary pyoderma
 +
*Affects caudal pastern and fetlock
 +
 
 +
===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 [[Staphylococcus spp.|''Staphylococcus'' spp.]], especially ''S. intermedius'' in dogs, [[Streptococci|''Streptococcus'' spp.]], ''[[Corynebacterium pseudotuberculosis]]'', [[Pseudomonas aeruginosa and Burkholderia species|''Pseudomonas'']], [[Pasteurella and Mannheimia species|''Pasteurella'']], [[Proteus|''Proteus'']], [[Escherichia coli|''E.coli'']]
 +
 
 +
====Staphylococcal folliculitis and furunculosis====
 +
 
 +
*Occurs in dogs, horses, sheep and goats
 +
*Dogs:
 +
**Localised or generalised lesions
 +
**Affected areas include: muzzle, chin, bridge of nose, pressure points and interdigital areas
 +
**'''German Shepherd deep pyoderma'''
 +
***Genetically predisposed
 +
***Dorsal lumosacral, ventral adbomen  and thigh areas
 +
*Horses:
 +
**Areas under tack ususlly involved
 +
*Goats:
 +
**Extremities, ventral abdomen, udder, medial thigh, perineum tend to be affected
 +
*Sheep:
 +
**Adults: face, limbs and teats
 +
**Lambs: [[Lips - Anatomy & Physiology|lips]] and perineum
 +
 
 +
====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|''Fusobacterium'' spp.]], [[Streptococci|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 - WikiBlood|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'''
 +
**Granulomatous dermatitis caused by nonfilamentous bacteria
 +
**Usually [[staphylococcus spp.|''Staphylococcus aureus'']]
 +
**Small, yellow granules are formed - sulfur granules
 +
***Central bacteria surrounded by homogeneous eosinophilic material
 +
*Filamentous bacteria can also cause granulomas
 +
**''E.g.'' [[:Category:Actinomycetes|''Actinomyces'' and ''Nocardia'']], [[:Category:Actinobacillus species|''Actinobacillus'']]
 +
 
 +
===Bacterial pododermatitis===
 +
 
 +
*Digital infections in ruminants
 +
*'''Contagious footrot'''
 +
**Usually caused by [[Bacteroides|''Bacteroides nodosus'']] together with [[Fusobacterium|''Fusobacterium necrophorum'']]
 +
**Moisture and trauma allow ''B. nodosus'' to enter -> aids bacterial penetration of epidermis -> ''F. necrophorum'' invades -> necrosis and inflammation
 +
**Grossly:
 +
***Early lesions - red, moist, swollen, eroded interdigital skin
 +
***Spreads to epidermal matrix of hoof -> separation of horn + malodorous exudate
 +
***Regeneration attempted as germinal epithelium is not destroyed
 +
***Chronic infections -> long , misshapen hoof
 +
**Benign footrot (scald)- only interdigital ski affected, slight separation of heel horn
 +
***Mostly the type occuring in cattle
 +
*'''Necrobacillosis''' of the foot
 +
**Usually caused by [[Fusobacterium|''Fusobacterium necrophorum'']] with other bacteria
 +
**In sheep:
 +
***'''Ovine interdigital dermatitis'''
 +
****Acute necrotising dermatitis similar to benign footrot
 +
***'''Foot abscesses'''
 +
****Bulbular or lamellar
 +
****Mostly in wet conditions and in heavy sheep
 +
**In cattle:
 +
***'''Interdigital dermatitis and cellulitis'''
 +
***Caused by ''F. necrophorum'' and [[Bacteroides|''Bacteroides melaninogenicus'']]
 +
***Predisposed by trauma
 +
***Grossly:
 +
****Fissures, necrotic swollen edges in interdigital spaces
 +
****Inflammation may spread to joint spaces
 +
===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'
 +
*[[Streptococci|''Streptococcus equi'']]
 +
**In horses
 +
**Immune complex vasculitis -> [[Haemorrhage - Pathology#Purpura haemorrhagica|purpura]]

Revision as of 12:34, 14 May 2010

 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.


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()Map INTEGUMENTARY SYSTEM (Map)
SKIN INFECTIOUS



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

  • = Superficial pustular dermatitis
  • Caused by coagulase-positive Staphylococcus spp.
  • Associated with:
  • Grossly:
  • Microscopically:
    • Interfollicular neutrophilic subcorneal pustule

Dermatophilosis

Dermatophilosis in a cow (Courtesy of Bristol BioMed Image Archive)
  • Caused by Dermatophilus congolensis
  • Affects cattle, horses, sheep mainly
  • More common in wet and warm weather
  • Transmotted from animal to animal
  • Lesions tend to form on dorsal back and extremities
  • Associated with skin trauma, prolonged wetting or parasites
    • -> penetration of zoospores
  • Bacteria proliferate in outer sheath of hair follicles and superficial epidermis
  • Gram-positive, filamentous branching organisms, subdivided longitudinally and transversly
  • Causing:
    • Acute inflammatory response -> neutrophil migration through dermis and epidermis -> formation of microabscesses
    • Further penetration of bacteria is thus prevented
    • Regenerated epidermis is invaded again by remaining organisms
    • Repeated reinfection -> multilaminated pustular crusts
  • Grossly:
  • Microscopically:
    • Hyperplastic superficial perivascular dermatitis
    • Multilaminated crusts, alternating keratin and inflammatory cell layers

Greasy pig disease

  • = Exudative epidermitis of pigs
  • Caused by Staphylococcus hyicus
  • Affects neonatal piglets - often fatal, older piglets - milder disease
  • Focal erosion of stratum corneum
  • Brown exudate
  • Dermatitis around eyes, ears, snout, chin and medial legs, may spread to ventral abdomen and thorax
  • Rapidly becomes generalised -> greasy exudate over red skin -> hardened, cracked exudate
  • In older piglets, milder localised disease develops around eyes, ears and face
  • Grossly:
    • Thickened epidermis, scaling
  • Microscopically:
    • Early - subcorneal pustular dermatitis extending to hair follicles -> superficial suppurative folliculitis
    • Late - hyperplastic epidermis, thick keratin crusts with cocci, microabscesses

Ovine fleece rot

Equine pastern folliculitis

  • = Greasy heel
  • Secondary pyoderma
  • Affects caudal pastern and fetlock

Deep pyoderma

Staphylococcal folliculitis and furunculosis

  • Occurs in dogs, horses, sheep and goats
  • Dogs:
    • Localised or generalised lesions
    • Affected areas include: muzzle, chin, bridge of nose, pressure points and interdigital areas
    • German Shepherd deep pyoderma
      • Genetically predisposed
      • Dorsal lumosacral, ventral adbomen and thigh areas
  • Horses:
    • Areas under tack ususlly involved
  • Goats:
    • Extremities, ventral abdomen, udder, medial thigh, perineum tend to be affected
  • Sheep:
    • Adults: face, limbs and teats
    • Lambs: lips and perineum

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
    • Granulomatous dermatitis caused by nonfilamentous bacteria
    • Usually Staphylococcus aureus
    • Small, yellow granules are formed - sulfur granules
      • Central bacteria surrounded by homogeneous eosinophilic material
  • Filamentous bacteria can also cause granulomas

Bacterial pododermatitis

  • Digital infections in ruminants
  • Contagious footrot
    • Usually caused by Bacteroides nodosus together with Fusobacterium necrophorum
    • Moisture and trauma allow B. nodosus to enter -> aids bacterial penetration of epidermis -> F. necrophorum invades -> necrosis and inflammation
    • Grossly:
      • Early lesions - red, moist, swollen, eroded interdigital skin
      • Spreads to epidermal matrix of hoof -> separation of horn + malodorous exudate
      • Regeneration attempted as germinal epithelium is not destroyed
      • Chronic infections -> long , misshapen hoof
    • Benign footrot (scald)- only interdigital ski affected, slight separation of heel horn
      • Mostly the type occuring in cattle
  • Necrobacillosis of the foot
    • Usually caused by Fusobacterium necrophorum with other bacteria
    • In sheep:
      • Ovine interdigital dermatitis
        • Acute necrotising dermatitis similar to benign footrot
      • Foot abscesses
        • Bulbular or lamellar
        • Mostly in wet conditions and in heavy sheep
    • In cattle:
      • Interdigital dermatitis and cellulitis
      • Caused by F. necrophorum and Bacteroides melaninogenicus
      • Predisposed by trauma
      • Grossly:
        • Fissures, necrotic swollen edges in interdigital spaces
        • Inflammation may spread to joint spaces

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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