Pulmonary infectionsPredisposing factors1- Impairment of defense mechanisms* Loss of cough reflex (coma,anaesthesia,drugs---etc)* Injury to mucociliary action (smoking,viral,genetic— etc)* interference with the phagocytic or bactericidal action of alveolarmacrophages.* pulmonary congestion & edema.* Accumulation of secretions (bronchial obstruction)2- lower host resistance (chronic diseases, immunologic deficiency,chemotherapy.3- Virulent infection.
Acute Inflammation &consolidation of lung parenchymadue to infectious agent.By clinical setting ( Communityacquired vs. hospital acquired(nosocomial) infection.By etiology & organism(pneumococcal, viral, etc )By morphology (lobar pneumonia,bronchopneumonia, interstitial)
Lobar pneumonia:(inflammatory exudates inalveoli lead to lobarconsolidation)
Pathology of lobar pneumonia:4 phases:CongestionLasts < 24 hours: Alveoli filled with fluid andbacteria.Red hepatization• Firm red, liver-like and airless appearance oflung.• massive exudation with neutrophils, red cells,and fibrin filling the alveoli.• Pleura: Fibrinous exudateGrey hepatizationLess hyperaemia.Macrophages, neutrophils + fibrinResolution-Lysis and removal of fibrin via sputum,lymphatics, ingested by macrophages ororganized by fibrosis.
Bronchopneumonia:• Infants + young children and theelderly.• Usually secondary to other conditionsassociated with decrease local andgeneral defense as- viral infections- aspiration of food or vomits-obstruction of a bronchus (foreign body orneoplasm)-chronic debilitating diseases, malnutritionGross:- Patchy suppurative consolidationLM:- suppurative neutrophil - richexudate that fills bronchi, bronchioles &adjacent alveoli.
Complications of lobar pneumonia1. Abscess formation2. Empyema (pus in the pleuralcavity3. Failure of resolution ⇒ intra-alveolar scarring (fibrosis ororganization⇒ permanent loss of ventilatoryfunction of affected parts of lung.4. Bacteraemia:- Infective endocarditis- Cerebral abscess / meningitis- Septic arthritis
Atypical pneumonia :-Acute febrile respiratory disease characterized by:-Patchy inflammation confined to alveolar septa.The term atypical indicate:--No consolidation & alveolar exudate.- Inflammation confined to alveolar surface.-Moderate amount of sputum.Causes:-Viral, Mycoplasma pneumonia, Chlamydia pneumonia.
interstitial lymphocyticinfiltrates. Note thatthere is no alveolarexudates.Thus, the patient withthis type of pneumoniawill probably not have aproductive cough.