CURRENT CONCEPTS IN THE ANTIMICROBIAL THERAPY OF COMMUNITY-ACQUIRED PNEUMONIA

The majority of community-acquired pneumonias (CAPs) are caused by typ ical bacterial pathogens, i.e., S. pneumoniae, H. influenzae or M. cat arrhalis. Atypical pneumonias, i.e., legionnaires' disease, C. pneumon iae pneumonia and M. pneumoniae pneumonia are less common in frequency than typical bacterial pathogens, but are of considerable public heal th and therapeutic importance. The newest therapeutic considerations i n CAP are related to monotherapy versus combination therapy, parentera l versus oral therapy, minimizing the emergence of penicillin-resistan t pneumococci and an appreciation that comorbid factors in antibiotic selection are unimportant. Monotherapy using a respiratory quinolone o r doxycycline covers both typical and atypical causes of CAPs and is e qually efficacious and less expensive than double drug therapy. Except in patients unable to take oral medications/those in CCUs, patients w ith CAP may be started on i.v. antibiotic therapy, but should be switc hed to oral therapy after 48 hours/clinical defervescence. The combina tion of 2 days of i.v. therapy plus 12 days of oral therapy has been s hown to be as effective as 14 days of i.v. therapy. The use of doxycyc line or respiratory quinolones may forestall or eliminate the emergenc e of highly penicillin-resistant pneumococci, and, for this reason, th ese agents probably should be used preferentially over beta-lactam ant ibiotics to treat CAPs. The status of the host's immune system, partic ularly intact splenic function, and the underlying condition of the ca rdiorespiratory system are the critical factors in predicting mortalit y, morbidity, complications and hospital stay. However, antibiotic sel ection is not affected by comorbidities, and antibiotics should not be changed or added to the usual therapy of GAP because of comorbid fact ors. Multiple drug therapy does not improve the outcome, which is a fu nction of underlying host factors.