Unlike viruses, airborne transmission of bacteria is uncommon, except for tuberculosis. Aspiration of potentially pathogenic bacteria from the oropharynx is the most frequently implicated mechanism of bacterial pneumonia. Several host defense mechanisms account for pulmonary protection from various infectious agents. Balance of defense mechanisms and bacterial factors. The upper airway passages are capable of filtering and trapping pathogens by means of the mucociliary system and the cough reflex.
Alveolar macrophages eliminate organisms that reach alveoli.
Elimination of infectious organisms is enhanced by immunoglobulins G and A and other factors, such as complement, antiproteases, lysozyme, and fibronectin. The introduction of antibacterial chemotherapy in the industrialized countries was associated with a dramatic reduction in the pneumonia death rate in children. Because there are no alternatives to antimicrobials for the treatment of bacterial pneumonia, and because rapid access to correct case management is essential to prevent mortality from pneumonia, antibiotic usage has been dramatically increased in the last decades for the treatment of pneumonia. Besides antibiotics, vitamin A supplementation should be considered in countries where vitamin A deficiency incidence is high, where patients six months to two years of age are hospitalized for measles and complicating pneumonia. The recommended dosage of vitamin A is 100,000 IU, orally, for children between 6 and 12 months of age, and 200,000 IU for children 12 months and older.