The Immune Response against Acinetobacter baumannii, an Emerging Pathogen in Nosocomial Infections

Abstract

Acinetobacter baumannii is the etiologic agent of a wide range of nosocomial infections, including pneumonia, bacteremia, and skin infections. Over the last 45 years, an alarming increase in the antibiotic resistance of this opportunistic microorganism has been reported, a situation that hinders effective treatments. In order to develop effective therapies against A. baumannii it is crucial to understand the basis of host–bacterium interactions, especially those concerning the immune response of the host. Different innate immune cells such as monocytes, macrophages, dendritic cells, and natural killer cells have been identified as important effectors in the defense against A. baumannii; among them, neutrophils represent a key immune cell indispensable for the control of the infection. Several immune strategies to combat A. baumannii have been identified such as recognition of the bacteria by immune cells through pattern recognition receptors, specifically toll-like receptors, which trigger bactericidal mechanisms including oxidative burst and cytokine and chemokine production to amplify the immune response against the pathogen. However, a complete picture of the protective immune strategies activated by this bacteria and its potential therapeutic use remains to be determined and explored.

Biological sex influences susceptibility to Acinetobacter baumannii pneumonia in mice

“…Its extreme genome plasticity and ability to quickly develop resistance to a plethora of antibiotics makes it an important pathogen and one of the reasons it has been designated as a serious threat and critical target by the CDC and World Health Organization (3)(4)(5)(6)(7). This has driven significant research in recent years to understand how the host senses and responds to A. baumannii infection (8,9). However, given that the emergence of A. baumannii is relatively recent, there are still several aspects of the immune response that have not been fully investigated.…”

MF59 adjuvant enhances the immunogenicity and protective immunity of the OmpK/Omp22 fusion protein from Acineterbacter baumannii through intratracheal inoculation in mice

“…Bacterial infections inevitably accompany with the activating of inflammatory cells, such as macrophages and neutrophils, which produce various inflammatory factors. Some of these factors, especially the proinflammatory cytokines can lead to cell damage and promote the spread of infections . In this study, very high bacteria loads were detected in mice blood and lung tissue from the two control groups, and very high level of blood inflammatory cytokines and severe lung tissue pathological changes were also observed in the mice from this two group.…”

Vesicle-Mediated Dendritic Cell Activation in Acinetobacter baumannii Clinical Isolate, which Contributes to Th2 Response

“…A. baumannii is increasingly becoming an opportunistic pathogen threatening public health. As a common bacterium causing nosocomial infections, especially pneumonia and bloodstream infection, A. baumannii has been listed as one of the major clinical challenges because of its high morbidity and mortality in hospitals [13]. Recently, many reports show that A. baumannii have a high rate of antibiotic resistance, which may aggravate the already harsh situations against A. baumannii infection [14,15].…”