Characterization of complement activation on the surface of klebsiella pneumoniae

Abstract

Background: Life threatening infections caused by the opportunistic pathogen K. pneumoniae are one of the most serious infections that elevate mortality rate in hospitals, worldwide. K. pneumoniae develops several mechanisms for avoiding killing by the complement system for survival in the host. The complement system is the first line of immune defense against different bacteria including K. pneumoniae. Objective: In this study we assessed the role of complement system in killing of both serum resistant and serum sensitive strains of K. pneumoniae. Methodology: Six clinical isolates of K. pneumoniae were collected from urine, sputum and the blood samples from patients in Mansoura Hospitals University. Serum bactericidal effect was assessed and confirmed by Turbidimetric method, Complement mediated lysis, complements C3b deposition and fH binding were assessed by ELISA. Results: our results demonstrated that complement mediated killing of K. pneumoniae is driven via the Alternative pathways, it was found that a lower C3b deposition via AP and a higher fH binding to surface of serum resistant K. pneumoniae strains compared with serum sensitive K. pneumoniae Conclusions: This study explains the role of complement system in killing K. pneumoniae and how serum resistant strains escape the immune defense via sequestering complement factor H.