Open AccessSerum resistance of Acinetobacter baumannii through the binding of factor H to outer membrane proteins
Author(s) -
Kim Sang Woo,
Choi Chul Hee,
Moon Dong Chan,
Jin Jong Sook,
Lee Jung Hwa,
Shin JiHyun,
Kim Jung Min,
Lee Yoo Chul,
Seol Sung Yong,
Cho Dong Taek,
Lee Je Chul
Publication year - 2009
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2009.01820.x
Subject(s) - acinetobacter baumannii , complement system , microbiology and biotechnology , factor h , innate immune system , bacterial outer membrane , alternative complement pathway , bacteremia , complement membrane attack complex , biology , bacteria , pathogen , immune system , immunology , gene , escherichia coli , pseudomonas aeruginosa , genetics , antibiotics
Bacteremia is a common systemic disease caused by Acinetobacter baumannii , an important hospital‐acquired pathogen among critically ill patients. The complement system is central to innate immune defense against invading bacteria in the blood. The present study investigated the susceptibility of clinical A. baumannii isolates to normal human sera (NHS), and determined the resistance mechanism of A. baumannii against complement‐mediated lysis. The survival of A. baumannii isolates from bacteremic patients was significantly decreased in undiluted NHS, but they were resistant to 40% NHS. The alternative complement pathway was responsible for the direct killing of bacteria. The main regulator of the alternative complement pathway, factor H, bound to the surface of live A. baumannii treated with NHS. Factor H interacted with the outer membrane proteins with molecular sizes of 38 (AbOmpA), 32, and 24 kDa. The isogenic AbOmpA − mutant was highly susceptible to NHS in comparison with the wild‐type A. baumannii strain, suggesting that AbOmpA was an important complement regulator‐acquiring surface protein. These results indicate that A. baumannii evades complement attack through the acquisition of factor H to their surface.