The crisis of resistant pathogens in respiratory tract infections - Use ofpharmacodynamic principles

Infectious disease experts and public health officials continue to warn the medical community and the public that more strains of respiratory tract pa thogens are becoming resistant to the antibiotics commonly used to eradicat e them. The inappropriate use of antibiotics to treat viral infections has contributed to the development of multidrug resistance in the 3 key bacteri al pathogens that cause respiratory tract infections: Streptococcus pneumon iae, Haemophilus influenzae, and Moraxella catarrhalis. Tradition ally susc eptibility of pathogens to antibiotics has been evaluated with in vitro tes ting by minimum inhibitory concentration (MIC) determination, which has als o been used to establish breakpoints between susceptible and resistant orga nisms based on MIC distributions. However, a more clinical approach has bee n developed based on the correlation of pharmacokinetics (PK) and pharmacod ynamics (PD) oi antimicrobials with MICs and clinical studies, thereby esta blishing the new concept of PK/PD breakpoints. New guidelines for outpatien t management oi respiratory tract infections have been based on PD paramete rs.