LM2 – LC3 Integumentary System Bacterial Diseases
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LM2 – LC3
Integumentary System
Bacterial Diseases
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Learning Component 3 – Integumentary System Bacterial Diseases
Gangrenous Dermatitis
• Clostridium Infection
• Characterized By:– Diffuse Necrosis
• Including Necrosis/Lysis of Erythrocytes
– Large Numbers of Intralesional Bacteria
– Limited or No Inflammatory Response
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Gangrenous Dermatitis Clostridium infection Clostridium septicum or Staphylococcus aureus – alone or in combination Clostridium perfringens type A may be isolated.
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Gangrenous Dermatitis A. Necrosis is diffuse and involves all regions of skin as well as extends into muscle (M). Epidermis is E. B. Higher magnification of A shows epidermis (E) and diffuse necrosis entending to involve muscle (M). C. Higher magnification of B shows muscle (M) and adjacent necrotic tissue. Note lysis of erythrocytes and presence of bacteria (basophilic material) D. Higher magnification of C shows necrotic tissue adjacent to skeletal muscle (M). Arrow identifies bacteria. Note lysis of erythrocytes in blood vessels.
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Gangrenous Dermatitis A. Diffuse necrosis is shown. B. Higher magnification shows numerous bacteria within necrotic tissue. C. Giemsa stain shows large numbers of bacteria. D. Higher magnification of C shows many large rod-shaped bacteria typical of Clostridium.
Mycobacteriosis
• Mycobacterium Infection
• Dermis and Underlying Tissues Expanded by Histiocytic Cells
• Demonstration of Acid‐Fast Positive Bacteria in Cytoplasm of Histiocytes
• Other Body Systems are Often Involved– Skin May Not Be Involved
• Skin Involvement More Common in Pet Avian
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Mycobacteriosis Mycobacterium avium or Mycobacterium genavense are most common causes.
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Mycobacteriosis A. S/Q tissue is expanded by a population of histiocytic cells including some giant cells (arrow). E is epidermis and D is dermis B. Higher magnification of A shows epidermis (E), dermis (D), and histiocytes in S/Q tissue. A focal granuloma (*) contains a giant cell. C. Higher magnification shows the characteristic large, foamy histiocytes and giant cells (arrow). D. Higher magnification of C shows histiocytes and giant cells (arrow).
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Mycobacteriosis A. Shown are epidermis (E), dermis (D),a feather follicle (FF), and large numbers of histiocytes (H) in S/Q tissue. B. Higher magnification of A shows the feather follicle (FF) and histiocytes (H). C. Higher magnification of B shows the large cells with pale cytoplasm (H). D. Acid –fast stain shows numerous acid-fast positive bacteria within the cytoplasm of histiocytes.
Erysipelas
• Necrosis ‐May be Extensive
• Thrombi in Blood Vessels in Subcutaneous Tissues
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Erysipelas
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Erysipelas A. Low-power magnification shows a large region of necrotic skin. B. Higher magnification shows thick crust covering epidermis that has separated from dermis. Box contains several small arteries that are shown at higher magnification in C and D. C. Higher magnification of the arteries within the box in B shows thrombosis. D. Higher magnification of C shows thrombi.
Pasteurella
• Pasteurellosis– May be similar to Colibacillosis
– Caseous Necrosis in Wattles
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Pasteurellosis Pasteurella multocida
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Pasteurellosis A. Shown are the epidermis (E) of a wattle, dense collagenous tissue in the dermis (D), a wide zone of fibrin and inflammation (F), and a central zone of caseous necrosis (CN). B. Higher magnification of A shows epidermis (E), dermis (D), zone of fibrin and acute inflammation (F), and central caseous necrosis (CN). C. Higher magnification of B shows fibrin with few inflammatory cells and the zone of caseous necrosis (CN). D. Higher magnification shows numerous bacteria (arrow) within the necrotic material.
Other Bacterial Infections
• E. coli (Colibacillosis)– Fibrinoheterophilic Exudate Predominates
– May Have Lymphohistiocytic Cells – Perivascular Location
• Other Bacteria May Cause similar Lesions– Staphylococci
• Cellulitis Often Associated with Multiple Bacterial Infections – Staph and Pasteurella Frequent
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Other Bacterial Infections Colibacillosis is most common. Multiple infections are common.
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