Clinical perspective of antibacterial usage.

Under clinical conditions there are two main aspects of antibacterial usage: community or hospital acquired infection. If there is not any severe underlying disease in general it is not difficult to treat a community acquired infection for example a pneumonia successfully with any of the available antiinfective drugs if the strain is sensitive. In case of nosocomial infections when ever possible the causative organism should be identified and antimicrobial testing must be performed. It must be considered that the host response is variable at the extremes of life for example infancy and old age but also in immunocompromised patients and patients under stress conditions like polytrauma and difficult and long time operations. Diffusion into the site of infection may be achieved more readily with one agent than with another. Resistance that emerges clinically usually does so through either selection of resistant strains in the environment or the genetic exchange of material between species. Most clinically important resistant species are selected, as clearly shown by the differences in antibiotic sensitivity patterns of hospital--versus community-acquired organisms.