In ammation of the bronchi in lower respiratory tract (rt) usually caused by infection. One of the most common conditions seen in primary care. Usually follows an upper respiratory tract infection (uri) A type of acute bronchitis is acute exacerbation of chronic bronchitis (aecb) Most cases of aecb are d/t viral (rhinovirus, in uenza) infection. Bacterial causes are also common in both smokers (strep puneumoniae, haemophilius in uenzae) and nonsmokers (mycoplasma pneumoniae, chlamydia pneumoniae). Production of clear, mucoid sputum, although some patients produce purulent sputum. Mildly elevated temp, pulse, and rr with either normal breath sounds or expiratory wheezing. Radiography can differentiate between acute bronchitis and pneumonia, as there is no radiographic evidence of consolidation or in ltrates with bronchitis. Acute in ammation of lung parenchyma caused by microbial agent. Discovery of sulpha drugs and penicillin was pivotal in treatment of pneumonia. Still common and associated with signi cant morbidity and mortality rates. Pneumococcal pneumonia = most common bacterial pneum.