Elizabethkingia anophelis, an emerging pathogen, inhibits RAW 264.7 macrophage function

Abstract

Elizabethkingia anophelis is a pathogen that can cause a life‐threatening infection in immunocompromised patients. The first case of E. anophelis infection was reported in 2013; subsequently, an increase in its incidence has been reported globally. Additionally, a mortality rate of more than 30% was observed in the US outbreak of 2015. To date, the pathogenic mechanisms underlying E. anophelis infection, such as toxin production, remain unclear. Since tissue macrophages act as the first line of defense against pathogens, in the present study the interactions between E. anophelis and a macrophage‐like cell line RAW 264.7 were examined. Although E. anophelis showed no cytotoxicity toward RAW 264.7 macrophages, the infection inhibited LPS‐induced morphological changes and activation of differentiation markers for the polarization of RAW 264.7 macrophages toward an M1‐like phenotype. However, when the cell contact was restricted using Transwell inserts or bacterial culture supernatants were used instead of live bacteria, no such inhibition was observed. Moreover, it was shown that E. anophelis evaded phagocytosis. Overall, the results suggest that E. anophelis infection inhibits the differentiation of RAW 264.7 macrophages to a pro‐inflammatory phenotype in a contact‐dependent manner.

The Evolutionary Trend and Genomic Features of an Emerging Lineage of Elizabethkingia anophelis Strains in Taiwan

“…The MFS, RND, and ABC-type transporters have been long regarded as members of the bacterial efflux pump systems that may play a role in facilitating the efflux transport of antimicrobials, ions, or bioactive molecules across the membrane ( 27 , 28 ). In a recent review, the bacterial efflux pump is not only associated with antibiotic resistance but also play roles in quorum sensing, biofilm formation, pathogenicity and virulence ( 29 , 30 ). It is plausible that these extra transporter genes in the GRs may be a benefit to the dominant of the specific lineage of E. anophelis strains.…”

Inhibition of capD gene confers disrupted capsule development and decreased pathogenicity in Elizabethkingia miricola

“…The interaction between bacteria and macrophages is also crucial in the host defense against bacterial infections, with macrophages typically responsible for pathogen phagocytosis [38]. Mouse macrophage RAW264.7 is a very important cell, and multiple studies have examined the interaction of this cell with bacteria [39,40]. In this study, compared with the WT group, intracellular mutant bacteria increased signi cantly, indicating that E. miricola is more easily phagocytosed by macrophages after deletion of the capD gene.…”