LM2 – LC3

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

Presenter

Presentation Notes

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.

Presenter

Presentation Notes

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

Presenter

Presentation Notes

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).

Presenter

Presentation Notes

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

Presenter

Presentation Notes

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

Presenter

Presentation Notes

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