Role of immunodeficiency in Acinetobacter baumannii associated pneumonia in mice

Abstract

Background Acinetobacter baumannii ( A. baumannii ) has become one of the most important opportunistic pathogens inducing nosocomial pneumonia and increasing mortality in critically ill patients recently. The interaction between A. baumannii infection and immune response can influence the prognosis of A. baumannii related pneumonia. The target of the present study was to investigate the role of immunodeficiency in A. baumannii induced pneumonia. Methods Male BALB/c mice were randomly divided into the normal immunity control (NIC) group, normal immunity infection (NIA) group, immune compromised control (CIC) group, and immune compromised infection (CIA) group ( n = 15 for each group). Intraperitoneal injection of cyclophosphamide and intranasal instillation of A. baumannii solution were used to induce compromised immunity and murine pneumonia, respectively. The mice were sacrificed at 6 and 24 h later and the specimens were collected for further tests. Seven-day mortality of mice was also assessed. Results After A. baumannii stimulation, the recruitment of neutrophils in mice with normal immunity increased sharply ( P = 0.030 at 6 h), while there was no significant raise of neutrophil counts in mice with compromised immune condition ( P = 0.092 at 6 h, P = 0.772 at 24 h). The Th cell polarization presented with pulmonary interleukin (IL)-4 and interferon (IFN)-γ level in response to the A. baumannii in CIA group were significantly depressed in comparison with in NIA group (IFN-γ: P = 0.003 at 6 h; P = 0.001 at 24 h; IL-4: P < 0.001 at 6 h; P < 0.001 at 24 h). The pulmonary conventional dendritic cell accumulation was even found to be inhibited after A. baumannii infection in immunocompromised mice ( P = 0.033). Correspondingly, A. baumannii associated pneumonia in mice with compromised immunity caused more early stage death, more severe histopathological impairment in lung. Conclusion A. baumannii could frustrate the immune response in immunocompromised conditions, and this reduced immune response is related to more severe lung injury and worse outcome in A. baumannii induced pneumonia.

Acinetobacter baumannii Biofilm Formation and Its Role in Disease Pathogenesis: A Review

“…Cell surface, hydrophobicity, surface charge, adhesion proteins, and extracellular polymeric compounds all have an impact on the production of A. baumannii biofilms. 28,62,63 Furthermore, the formation of the biofilm process of A. baumannii on abiotic surfaces has a positive correlation with multidrug resistance and with virulence factors expression such as the OmpA, the extracellular polysaccharide poly-β- 1,6 -N-acetyl glucosamine (PNAG), type I pili, Rec A, Bap, and the Omp CarO. On an animate surface, it needs chaperone-usher pili to produce biofilm.…”

“… 5 As a result of colonization and living on much medical equipment, it causes severe infections in immune-compromised people. 6 According to evidence meningitis, wound, pneumonia (hospital and community-acquired), bacteremia, burn, endocarditis, urinary tract infections (UTI) as well as skin and soft tissue infections are the most prevalent Acinetobacter -associated nosocomial illnesses. 5 , 7 Community-acquired pneumonia is more severe than nosocomial pneumonia; it is usually fulminant, and fatality rates can reach 60%.…”

Neutrophil and Macrophage Response in Acinetobacter Baumannii Infection and Their Relationship to Lung Injury

“…There are few powerful and effective antibiotics for MDR strains under development, but progress in the development of new intervention measures is limited, which makes the treatment of MDR AB infection increasingly difficult. In addition to the use of antibiotics, appropriate immune participation in the human body also plays a vital role in bacterial clearance ( Liu et al., 2020 ). In recent years, there have been multiple studies on the relationship between immunity and AB infections.…”

Evaluating the Activity of Ultrasound on Biofilm Formation by Acinetobacter baumannii isolated from clinical Specimens

“…Nowadays, A. baumannii is largely coupled with a significant infection among patients 3 , as it exhibits a tremendous resistance against practically all known antibiotics as well as to a host immune response, which makes it a crucial concern in treatment and public health 4 The efficiency of A. baumannii to form biofilm and it's persistence in dry and desiccated surrounding conditions generated problems and outbreaks in health-care treatment options, particularly for ill patients in the intensive care units (ICUs) 5 . Biofilm is the aggregation of bacterial cells embedded in an extracellular polymeric substances (EPS), called matrix, which enable bacterial cells to attach to various abiotic and biotic surfaces and protect their growth from the immune system and antibiotics 6 .…”