Empiric therapy in lower respiratory tract infection--an ongoing challenge.

Lower respiratory tract infections are a common cause of morbidity and mortality. The pattern of pneumonia is altering, owing to changes in a number of influencing factors. These include patient characteristics, such as an aging population, increased immunosuppression and chronic disease, and changes in medical practice. There is also an increasing level of resistance to antimicrobial agents by organisms such as Streptococcus pneumoniae and Haemophilus influenzae, the pathogens most commonly associated with community-acquired pneumonia. In the management of pneumonia, it is important to be able to differentiate between atypical and typical pneumonia in the clinical setting and to grade the severity of the infection. Currently, there are no internationally agreed treatment recommendations for pneumonia. The role of antimicrobial agents in acute exacerbations of chronic bronchitis is still a controversial issue.