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Bacterial skin infections - Pathology (view source)
Revision as of 12:15, 31 July 2008
, 12:15, 31 July 2008New page: {{toplink |backcolour = FFCCCC |linkpage =Integumentary System - Pathology |linktext =Integumentary System |maplink = Integumentary System (Content Map) - Pathology |pagetype =Pathology |...
{{toplink
|backcolour = FFCCCC
|linkpage =Integumentary System - Pathology
|linktext =Integumentary System
|maplink = Integumentary System (Content Map) - Pathology
|pagetype =Pathology
|sublink1 = Skin Infectious - Pathology
|subtext1 = SKIN INFECTIOUS
}}
<br>
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#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#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#Demodicosis|demodicosis]]
*May also be a sequele to [[Bacterial skin infections#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
**[[General Pathology - Necrosis#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 -> [[General Pathology - Haemorrhage#Purpura haemorrhagica|purpura]]
|backcolour = FFCCCC
|linkpage =Integumentary System - Pathology
|linktext =Integumentary System
|maplink = Integumentary System (Content Map) - Pathology
|pagetype =Pathology
|sublink1 = Skin Infectious - Pathology
|subtext1 = SKIN INFECTIOUS
}}
<br>
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#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#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#Demodicosis|demodicosis]]
*May also be a sequele to [[Bacterial skin infections#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
**[[General Pathology - Necrosis#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 -> [[General Pathology - Haemorrhage#Purpura haemorrhagica|purpura]]