In this context, this principle takes into account development of resistance or cross-resistance to important antimicrobials. Therapeutic antimicrobial use should be confined to appropriate clinical indications. An accurate diagnosis includes characterization of the etiology. Practitioners should strive to rule out parasitism, mycotoxicoses, nutritional imbalances, and viral infections. Secondary bacterial pathogens may require antimicrobial therapy.
Therapeutic exposure involves both dose and duration.
Continued use of antimicrobials in chronic, non-responsive clinical cases should be discouraged. Withdrawal times must always be considered during the selection of antimicrobials. Consider group morbidity and mortality rates when deciding whether or not to initiate herd, group, or individual therapy. Consider the herd health history for the therapeutic use of antimicrobials in the control and prevention of disease. When these factors are appropriately considered, preventative therapy is a judicious use of antimicrobials.