Résumé
Antimicrobial agents kill microorganisms, principally bacteria and fungi, although viruses are often considered here as well. While treating infection is important, the emergence of resistant microorganisms and drug-related adverse events are potential collateral damage. Therefore, antimicrobial prescription requires clear justification and needs ongoing evaluation. In critically ill patients, delay in the initiation of appropriate antimicrobials in severe infections and septic shock is associated with higher mortality, and empirical antimicrobials with a spectrum that is sufficiently broad to cover the most likely etiological pathogens must be administered as soon as possible. At the same time, all efforts to diagnose infection must be taken, of which collection of appropriate cultures prior to initiation of the antimicrobial therapy is paramount. Critically ill patients may require different doses compared to patients in the wards, because of the pharmacodynamic particularities of nosocomial infections and the pharmacokinetic variations driven by the disease itself and clinical management; augmented renal clearance and increased volume of distribution predispose them to underdosing which may lead to therapy failure and potential emergence of antimicrobial resistance. In such scenarios, it is therefore prudent to use high-dose, short antimicrobial courses using antimicrobials with as narrow a spectrum as possible once the cultures are available and the source of infection is controlled. Therapeutic drug monitoring not only for toxicity but also for efficacy can help with optimisation. There are selected clinical situations where a conservative approach of watchful waiting, consisting of close monitorisation and antimicrobial initiation only after an infection is demonstrated, may be beneficial.