High mortality of Acinetobacter baumannii infection is attributed to macrophage_mediated induction of cytokine storm

Acinetobacter baumannii is one of the bacterial pathogens that commonly causes hospital-acquired infections, for which the mortality rate was estimated to be as high as 26.0% to 55.7% in different countries. The continuous emergence of multidrug-resistant (MDR) strains of this pathogen poses further challenges to clinical management of A. baumannii infections. It is necessary to explore unconventional strategies to control outbreaks of drug-resistant infections. In this work, we conducted a study of the host immune response elicited by A. baumannii. The results highlighted the critical role of alveolar and interstitial macrophages as targets of Ab during the infection process, as these cells were found to undergo polarization towards the M1 phenotype, triggering a cytokine storm that eventually caused the death of the host. The polarization and excessive inflammatory response mediated by macrophages were mainly regulated by the TLR2/Myd88/NfkB signaling pathway. Findings in this work depicted the major mechanisms underlying the high mortality rate of A. baumannii infections.