Résumé
Gram-negative bacteria are ubiquitous microorganisms of particular concern, especially the gram-negative bacilli (GNB), because of the fast spread of multidrug resistance (MDR). Mutations lead to new phenotypes with modified antibiotic targets, whereas genes encoding drug efflux permeases and genes encoding antibiotic-modifying enzymes are most often acquired via horizontal transfer. Specifically, the development of extended-spectrum beta-lactamases that confer resistance to penicillins and cephalosporins and of carbapenemases that confer resistance to carbapenems is considered of critical importance. It is noteworthy that in the World Health Organization priority list, all the critical priority (Priority 1) microorganisms are GNBs. In the intensive care setting, GNBs are responsible for multiple infections, such as bloodstream infections, ventilator-associated pneumonia, device-associated infections, intraabdominal infections, urinary tract infections, and soft tissue infections. MDR GNBs represent a healthcare burden and are associated with poor outcome. It should be highlighted that several reports have demonstrated suboptimal concentrations of antimicrobial agents in critically ill patients when conventional dosing schemes were used. Therefore during the last decade, apart from the efforts to develop new antimicrobial agents, research has focused on optimization of the use of the currently available antimicrobial agents in the critical care setting, aiming for both improvement of clinical outcomes and limiting resistance emergence. In this chapter we summarize the characteristics of the classes of antimicrobial agents used in the critical care setting for GNBs, including “older” antimicrobial agents that have been “reintroduced” as salvage treatments and present the newly approved anti-GNB agents.