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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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 [[Actinomycetes#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 species|''Corynebacterium pseudotuberculosis'']], [[Pseudomonas aeruginosa and Burkholderia species|''Pseudomonas'']], [[Pasteurella species and Mannheimia haemolytica|''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 species and Mannheimia haemolytica#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
 +
*'''Mycobacterial granulomatous or pyogranulomatous lesions'''
 +
**Usually caused by [[Mycobacteria spp.|''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.'' [[Actinomycetes|''Actinomyces'' and ''Nocardia'']], [[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 species#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 20:30, 13 August 2009

 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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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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