Like in any
infection, the choice of antibacterials in pulmonary
infections of known bacterial etiology is simple. When etiology is not known, the choice must rest upon knowledge of the epidemiology of lower
respiratory infections and the antibacterial spectrum of the
antibiotics in question. The epidemiology of community-acquired lower
respiratory infections is not too well studied. However, some studies indicate that approximately 50% of lower
respiratory infections are caused by bacteria among which Streptococcus pneumoniae prevails, followed by Haemophilus influenzae. Streptococci, Branhamella catarrhalis and other Neisseria species, staphylococci and Enterobacteriaceae account for less than 10% each. The prevalence of Legionella pneumophila is unknown, but it is of limited significance. Mycoplasma pneumoniae varies in prevalence according to time and geographic area. In acute exacerbations of
chronic bronchitis, the epidemiology is similar, except that H. influenzae is more commonly found than pneumococci. The traditional strong position of
penicillin in the blind, primary treatment of community-acquired lower
respiratory infections is challenged by the increasing frequency of
penicillin-resistant H. influenzae and the discovery of new agents not sensitive to
penicillins. The same can be said for the more recently introduced primary treatment with
erythromycin. However, most
community-acquired infections in the lower respiratory tract respond to
penicillin;
tetracycline or
erythromycin may be used for treatment when the clinical response is unsatisfactory. In patients who are known or suspected to have compromised host defense,
beta-lactams such as ureido-
penicillins and the new
cephalosporins should be used as primary
therapy. In hospital-acquired lower
respiratory tract infections, the etiological diagnosis is more likely to be made.(ABSTRACT TRUNCATED AT 250 WORDS)