Pneumonia in the community affects between 1 and 5 per 1000 per year. The microbial aetiology is diverse and influenced by preexisting disease, seasonality, as well as animate and inanimate environmental sources; pneumococci, Legionella spp., Mycoplasma pneumoniae, and more recently Chlamydia pneumoniae are the predominant bacterial pathogens. Gram-negative enteric bacteria although less common are particularly virulent. Antibiotic resistance is well established for Haemophilus influenzae and Gram-negative bacillary infections, but has been a recent phenomenon in the case of Streptococcus pneumoniae, which is numerically the leading pathogen. Despite the concerns raised by this reduced susceptibility to penicillin, evidence that this has been translated into increased clinical failures is currently difficult to establish. Macrolide and tetracycline resistance among pneumococci is more common. beta-Lactamase production by H. influenzae has now reached levels where, in those with severe pneumonia, beta-lactamase stable agents are preferred. Concensus Guidelines on the treatment of community acquired pneumonia have been published by the British Thoracic Society, the American Thoracic Society, and from Expert Panels in Canada and France. These emphasize severity assessment and differentiate management in the community or hospital setting. The recommended regimens are compared and contrasted. In conclusion, mild/moderate pneumonia, when pneumococcal in nature, is likely to still respond to amoxycillin or penicillin G, but in higher dosages where pneumococcal resistance is documented. However, in severe infection where pneumococcal resistance, other beta-lactamase-producing pathogens, or an atypical infection could be operating, it is important that initial empirical therapy be broad spectrum and promptly administered. Treating multiresistant pneumococcal disease in those allergic to beta-lactams presents a particular dilemma. Glycopeptides are currently preferred.
