Clinical Uses of Antimicrobial Drugs

CLINICAL USE

The choice of antimicrobial chemotherapy is initially dependent on the clinical diagnosis. In some circumstances the clinical diagnosis implies a microbiological diagnosis which may dictate specific therapy. For example, typhoid fever is caused by Salmonella enterica serovar Typhi, which is generally sensitive to cotrimoxazole, ceftriaxone and ciprofloxacin. However, for many infections, establishing a clinical diagnosis implies a range of possible microbiological causes and requires laboratory confirmation from samples collected, preferably before antibiotic therapy is begun. Laboratory isolation and susceptibility testing of the causative agent establish the diagnosis with certainty and make drug selection more rational. However, in many circumstances, especially in general practice, microbiological documentation of an infection is not possible. Hence knowledge of the usual microbiological cause of a particular infection and its susceptibility to antimicrobial agents is essential for effective drug prescribing. The following section explores a selection of the problems associated with antimicrobial drug prescribing for a range of clinical conditions.