Difference between revisions of "Bacterial skin infections - Pathology"

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#REDIRECT[[:Category:Integumentary System - Bacterial Infections]]
 
 
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|backcolour = FFCCCC
 
|linkpage =Integumentary System - Pathology
 
|linktext =Integumentary System
 
|maplink = Integumentary System (Content Map) - Pathology
 
|pagetype =Pathology
 
|sublink1 = Skin Infectious - Pathology
 
|subtext1 = SKIN INFECTIOUS
 
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<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 [[:Category:Staphylococcus species|''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]]====
 
 
 
====Ovine fleece rot====
 
 
 
*Caused by [[:Category:Pseudomonas 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 [[: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====
 
 
 
*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.]], [[: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'''
 
**Granulomatous dermatitis caused by nonfilamentous bacteria
 
**Usually [[:Category:Staphylococcus species|''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'
 
*[[Streptococcus equi subsp. equi|''Streptococcus equi'']]
 
**In horses
 
**Immune complex vasculitis -> [[Haemorrhage - Pathology#Purpura haemorrhagica|purpura]]
 

Latest revision as of 19:12, 21 February 2011