TISSUE RESPONSES TO INFECTIOUS AGENTS
Infectious diseases are very prevalent worldwide and are a major cause of morbidity and mortality. Infectious agents tend to have tropism for specific tissues and organs.
There are 6 major histologic patterns:
· Exudative inflammation is acute inflammatory response with neutrophils.Examples include bacterial meningitis, bronchopneumonia, and abscess.
· Necrotizing inflammation occurs when a virulent organism produces severetissue damage and extensive cell death. Examples include necrotizing fasciitis and necrotizing pharyngitis.
· Granulomatous inflammation.Granulomatous response predominates withslow-growing organisms such as mycobacteria, fungi, and parasites.
· Interstitial inflammation is a diffuse mononuclear interstitial infiltrate thatis a common response to viral infectious agents. Examples include myocarditis (Coxsackie virus) and viral hepatitis.
· Cytopathic/cytoproliferative inflammation refers to inflammation in whichthe infected/injured cell is altered. The changes may include intranuclear/ cytoplasmic inclusions (cytomegalic inclusion disease, rabies [Negri body]); syncytia formation (respiratory syncytial virus and herpes virus); and apop-tosis (Councilman body in viral hepatitis).
· No inflammation. An inflammatory response to microbes cannot occur inseverely immunosuppressed individuals due to primary immunodeficiencies or acquired immunodeficient states (e.g., AIDS).