Immunomodulation by Acinetobacter baumannii of endotracheal tube biofilm in ventilator-associated pneumonia

Abstract Acinetobacter baumannii is an opportunistic bacterial pathogen associated with hospital-acquired infections especially in intensive care units (ICU). Main reasons for A. baumannii acquired infections are high ability to acquire antibiotic resistant and biofilm formation. The formation of biofilm that confers persistent to A.baumannii infections and its immunological response are not studied. A.baumannii isolate originated from endotracheal tube of patients admitted to ICU was recovered and selected for further study based on its biofilm forming ability and adherent property. Immune modulations by A. baumannii biofilms were studied by infected PBTE cell-line with biofilm coated ETT and uncoated ETT, at different time points (6, 12 h). Various cytokines were estimated by ELISA and the mRNA levels were used to evaluate the gene expression using real time PCR. Immune-modulations by AB78 biofilms on ETT was infected the Primary Bronchial/Tracheal Epithelial Cells (PBTE) and it showed that all the cytokines were significantly elevated compared to negative control. IL-1β production was more against biofilm grown for 48 h. Increasing of biofilm formation time showed to have significant effect for IL-6 levels, otherwise other cytokines level were comparable at different time hours. The fold change in expression were highly significant for IL-6 and significant for IL-10 and TNF-α. Biofilm formed in medical device are capable of up regulating inflammatory cytokines promoting macrophage phagocytosis leading to the assumption that biofilm is not only mechanism at work in the persistence of Bactria on endotracheal tube that leads to development of ventilator associated pneumonia.