چكيده لاتين
Acinetobacter spp. have been recognized as an important nosocomial pathogen due to its ability to survive in the hospital environment and on a wide range of surfaces. Human infections caused by Acinetobacter spp. include pneumonia, endocarditis, meningitis, skin and wound infections, urinary tract infections, and bacteremia. One of the characteristics of Acinetobacter baumannii is the presence of virulence factors that, in addition to pathogenicity, play an effective role in escaping from the hostʹs immune system. Among these factors is outer membrane protein A (OmpA), which plays a key role in regulating adhesion, invasion, biofilm formation, and host immune response. Another protein is Bap, which plays a role in biofilm formation and resistance to the humoral part of the immune system. This study aims to investigate the expression of bap and ompA immune evasion genes before and after co-culture with human peripheral blood mononuclear cells (PBMC) to determine the expression behavior of these genes after exposure to immune cells.
For this purpose, Acinetobacter baumannii was isolated from respiratory samples of patients and co-cultured with PBMC and their supernatant. After 24 hours, the number and viability of PBMC, CFU, production of inflammatory and anti-inflammatory cytokines, gene expression, and biofilm formation were investigated.
The results of this research showed that the proliferation of PBMC in the co-culture with bacteria has a significant decrease compared to the control group. Cell viability in this group was also significantly reduced compared to the PBMC without bacteria. No significant change in CFU was observed in the group of co-culture of bacteria and PBMC and the group of co-culture of bacteria with cell supernatant. In the group of co-culture of bacteria and PBMC, compared to the PBMC alone, an increase in the production of cytokine TNF-α and a decrease in the production of IL-6 and IL-10 were observed. bap gene expression in the co-culture group of bacteria and PBMC and supernatant was associated with a significant decrease compared to before co-culture. while ompA gene expression did not significantly change in all the groups. The tested samples were strong producers of biofilm both before and after co-culture, and despite the increase in biofilm production after co-culture, this increase was not significant.
Total results of this research showed that A. baumannii in co-culture with PBMC induced an inflammatory response, which resulted in cell proliferation, but due to the inflammation, cell survival decreased. Also, this inflammatory response probably decreases bap gene expression, however, this downregulated of gene expression does not affect the number of bacteria and biofilm formation.
