Acinetobacter baumannii

Acinetobacter baumannii is a ubiquitous, Gram-negative, nonflagellated coccobacillus bacterium commonly isolated from the environment. In human medicine, this opportunistic pathogen is responsible for hospital- and community-acquired infections. Resistance to last-resort antibiotics, such as colistin, tigecycline, and carbapenems, earns this bacterium a place among the most problematic nosocomial ESKAPE pathogens, being classified as a bacterium for which research and development of new antibiotics is critically needed by the World Health Organization (WHO) and as an urgent threat to public health by the Centers for Disease Control and Prevention (CDC). Its ability to form biofilms and resist desiccation and disinfectants is additionally alarming as these characteristics allow A. baumannii to thrive within hospital settings. The antibiotic resistance, the environmental persistence, along with the absence of identified host-damaging toxins in its genome, suggest that the virulence potential of A. baumannii is based on a 'persist and resist' strategy wherein these bacteria also resist complement-mediated killing and oxidative stress. At the genetic level, due to a plastic genome, we observe a high heterogeneity amongst isolates, adding complexity to the study of A. baumannii as an entity. Therefore, A. baumannii represents a modern and worldwide challenge which requires constant surveillance by the public health community.