The advent of antibiotic therapy had a profound effect on the diagnostic microbiological laboratory. Technical procedures, such as pneumococcus typing, became useless as therapeutic tools, and for routine purposes it was no longer necessary to identify micro-organisms beyond the point of determining that they did or did not belong to a pathogenic species. On the other hand, a new technique of prime importance has been developed—i. e., the antibiotic susceptibility test. With it the laboratory can give valuable aid to the clinician in the selection of the most effective chemotherapeutic drug for his infectious patients. The present discussion deals with the use and value of this procedure.
The foregoing statements are not intended to imply that bacteriologic specimens need to be collected in all cases. As any clinician knows, most mild and uncomplicated acute infections respond promptly to empirical administration of any one of several antibiotics in general use. On