Pathology Chapter on Suppurative Inflammation

Acute Inflammation Types

• Acute inflammation is categorized by the presence or absence of pus
• Acute suppurative inflammation includes localized types (abscesses, boils, furuncles) and diffuse types (cellulitis)
• Acute non-suppurative inflammation includes various types based on exudate characteristics

Suppurative Inflammation (Purulent)

• This type involves pus formation
• Associated with septic or pyogenic bacteria
• Localized:
• Abscess: A localized collection of pus
• Furuncle (boil): A localized infection of a hair follicle or sebaceous gland
• Carbuncle: A cluster of interconnected furuncles
• Diffuse:
• Cellulitis: A widespread bacterial infection of connective tissue

Mechanism of Pus Formation

• Strong pyogenic bacteria (like Staphylococcus aureus and Streptococcus haemolyticus) cause necrosis
• Large numbers of neutrophils are attracted, but die due to bacterial virulence
• Presence of proteolytic enzymes produced by neutrophils and necrotic tissue liquefy the necrotic tissue and fibrin
• The liquefied material mixed with pus cells and fluid exudate forms pus

Abscess

• Definition: Localized suppurative inflammation forming a pus-filled cavity
• Site: Commonly subcutaneous, but can be in internal organs
• Pathogenesis: The abscess initially has a necrotic center surrounded by inflammatory cells. Later it develops a 3 zone structure consisting of:
• Central necrotic core
• Mid zone containing pus (formed in ~48 hours)
• Peripheral zone of inflamed tissue which is called pyogenic membrane.
• Course:
• Abscess enlarges by further necrosis and liquefaction of surrounding tissue.
• Staphylococci produce coagulase to help localize the inflammation.
• Subcutaneous abscess appears as a localized tender swelling covered by red, edematous skin with a yellow center
• The covering epidermis may undergo necrosis.
• An ulcer is formed as pus is evacuated.
• An internal abscess can open into a hollow organ.
• Complications of Acute Abscess
• Ulcers
• Sinuses
• Fistulas
• Hemorrhage
• Complications of Healing: Keloid (excessive scarring)
• If not evacuated (Chronic Abscesses): can develop fibrosis and may contain cholesterol crystals or dystrophic calcification (e.g., chronic breast abscess)
• Spread of infection: direct spread, lymphatic spread, blood spread (toxemia, septicemia, pyemia)

Types of Acute Non-suppurative Inflammation

• Serous inflammation: Thin, watery fluid exudate (e.g., blisters after burns)
• Serofibrinous inflammation: Fluid exudate rich in fibrin; occurs in serous membranes like the pleura, peritoneum, and pericardium
• Allergic/Hypersensitivity inflammation: Eosinophil-rich fluid exudate; occurs in hypersensitivity reactions (e.g., urticaria, asthma, allergic rhinitis, and contact dermatitis)
• Catarrhal inflammation: Mild inflammation of mucous membranes with excess mucous secretion; (e.g., rhinitis)
• Pseudomembranous inflammation: Acute inflammation characterized by pseudomembrane formation consisting of fibrin, desquamated epithelial cells, and inflammatory cells (e.g., diphtheria, bacillary dysentery)
• Hemorrhagic inflammation: Inflammation characterized by bleeding (e.g., meningococcal infection)
• Necrotizing inflammation: Acute inflammation with extensive tissue necrosis (e.g., oral mucosa in malnourished children)

Furuncle (Boil)

• Definition: Small abscess related to hair follicles, sebaceous glands, or sweat glands.
• Cause: Staphylococci
• Site: Primarily hairy areas (face, axilla); multiple boils are termed furunculosis

Carbuncle

• Definition: Multiple communicating suppurative foci in skin and subcutaneous tissue (fat)
• Cause: Staphylococci
• Site: Thick skin areas (back of neck, scalp, buttocks)
• Often associated with diabetes

Cellulitis

• Definition: Acute diffuse suppurative inflammation of connective tissue
• Cause: Streptococcus hemolyticus that produce hyaluronidase enzyme and fibrinolysin (streptokinase) enzyme.
• Sites: Loose connective tissue areas; orbit, scrotum, appendix
• Pus characters: Thin and bloody, many sloughs

Complications:

• Lymphatic dissemination of infection
• Blood spread with conditions like septicemia and pyemia

Summary & Wrap-up

• Acute inflammation is classified into two categories based on the presence and absence of pus
• Acute, non-suppurative, and exudate-based further classification further subcategories.

Test your knowledge on the characteristics and mechanisms of suppurative inflammation with this quiz. It covers important concepts such as the roles of enzymes, abscess formation, and the bacterial species involved. Perfect for students studying pathology or related fields.