MICROBIOLOGY

PRINCIPLES OF DIAGNOSTIC MEDICAL MICROBIOLOGY CONTD... LABORATORY AIDS IN THE SELECTION OF ANTIMICROBIAL THERAPY The antimicrobial drug used initially in the treatment of an infection is chosen on the basis of clinical impression  after the physician is convinced that an infection exists and has made a tentative etiologic diagnosis on clinical  grounds.  On the basis of this "best guess," a probable drug of choice can be selected .  Before  this drug is administered,  specimens are obtained for laboratory isolation of the causative agent.  The results of  these examinations may necessitate selection of a different drug.  The identification of certain microorganisms  that are uniformly drug-susceptible eliminates the necessity for further testing and permits the selection of  optimally effective drugs solely on the basis of experience. The commonly performed disk diffusion susceptibility test must be used judiciously and interpreted with restraint.  In general,  only one