Pulmonary Infections PDF

• mutations in MYD88: severe necrotizing pneumococcal infections • congenital defects in IgA production: increased risk for pneumonias caused by encapsulated organisms such as pneumococcus and H.influenzae • defects in TH1 cell–mediated immunity:increased infections with intracellular microbes such...

• mutations in MYD88: severe necrotizing pneumococcal infections • congenital defects in IgA production: increased risk for pneumonias caused by encapsulated organisms such as pneumococcus and H.influenzae • defects in TH1 cell–mediated immunity:increased infections with intracellular microbes such as atypical mycobacteria. • cigarette smoke compromises mucociliary clearance and pulmonary macrophage activity, • alcohol impairs neutrophile function as well as cough and epiglottic reflexes(thereby increasing the risk for aspiration). Streptococcus pneumoniae • increased frequency in two clinical settings: • (1) chronic diseases such as CHF, COPD, or diabetes; • (2) congenital or acquired defectsin immunoglobulin production • decreased or absent splenic function • numerous neutrophils in sputum containing the typical gram-positive, lancet-shaped diplococci supports the diagnosis • S. pneumoniae is a part of the endogenous flora in 20 % of adults • Isolation of pneumococci from blood cultures is more specific but less sensitive • Pneumococcal vaccines containing capsular polysaccharides from the common serotypes are used in individuals at high risk for pneumococcal sepsis Haemophilus influenzae • Encapsulated forms can cause a particularly lifethreatening form of pneumonia in children, often after a respiratory viral infection. • Encapsulated H. İnfluenzae type b was formerly an important cause of epiglottitis and suppurative meningitis in children • vaccination in infancy has significantly reduced the risk. • Adults at risk for developing infections include those with chronic pulmonary diseases such as chronic bronchitis, cystic fibrosis, and bronchiectasis. • H. influenzae is the most common bacterial cause of acute exacerbations of COPD Moraxella catarrhalis • second most common bacterial cause of acute exacerbation of COPD in adults • Along with S. pneumoniae and H. influenzae, M. catarrhalis is one of the three most frequent causes of otitis media (infection of the middle ear) in children Staphylococcus aureus • an important cause of secondary bacterial pneumonia in children and healthy adults after viral respiratory illnesses • Staphylococcal pneumonia is associated with a high incidence of complications: lung abscess and empyema. • in association with right-sided staphylococcal endocarditis is a serious complication of intravenous drug abuse. • an important cause of nosocomial pneumonia Klebsiella pneumoniae • most frequent cause of gram-negative bacterial pneumonia. • debilitated and malnourished individuals, particularly chronic alcoholics • Thick and gelatinous sputum is characteristic Pseudomonas aeruginosa • association with infections in cystic fibrosis, • most commonly is seen in nosocomial settings • neutropenic, usually secondary to chemotherapy; • in victims of extensive burns; • in patients requiring mechanical ventilation • propensity to invade blood vessels at the site of infection • organisms invading the walls of necrotic blood vessels (Pseudomonas vasculitis), leading to secondary coagulative necrosis of the pulmonary parenchyma • Pseudomonas bacteremia is a fulminant disease, with death often occurring within a matter of days Legionella pneumophila • Pontiac fever is a related self-limited upper-respiratory tract infection caused by L. pneumophila, without pneumonic symptoms • artificial aquatic environments, such as watercooling towers and within the tubing system of domestic water supplies • transmission : inhalation of aerosolized organisms or aspiration of contaminated drinking water • Predisposing condition : • cardiac, renal, immunologic, or hematologic disease. • Organ transplant recipients • fatality rate of 30% to 50% in immunosuppressed individuals