Fructose transporter knockdown S. aureus reveals critical role of the airway epithelium in limiting ASL sugar accumulation and bacterial growth (897.4)

Abstract

Sugars promote the growth of S. aureus, a key bacterium in respiratory infections. We used an airway epithelial‐bacterial co‐culture model to examine the effect raising basolateral sugar concentration on the apical growth of S. aureus and the role of the epithelium in limiting this effect.S. aureus addition on the apical surface of H441 monolayers led to enhanced paracellular 14C‐L‐glucose flux across the epithelium. S. aureus growth was significantly increased by elevating basolateral glucose or fructose concentrations (p < 0.05, n = 5). A S. aureus strain in which the fructose specific permease (fruA) had been disrupted (NE768), exhibited significantly reduced growth in the presence of fructose compared to glucose, in both isolated culture (p < 0.001, n = 3) and in epithelial‐bacterial co‐culture (after 7h; p < 0.05, n = 5). S. aureus JE2 (parent strain) growth in co‐culture was greater in fructose than glucose, despite similar growth rates in isolated culture. This correlated with the reduced rate of epithelial fructose uptake compared to glucose (p < 0.05, n = 5) which we predict results in increased availability of fructose for apical bacterial growth. Pre‐treatment of H441 monolayers with metformin (1 mM, 18h), significantly inhibited both glucose‐ and fructose‐induced bacterial growth (p < 0.05, n = 4), which corresponded to reduced paracellular flux of sugar across metformin‐treated monolayers (p < 0.001, n = 8).These data provide new evidence that fructose and glucose diffuse across the airway epithelium and are utilised by S. aureus to support its growth and highlights the importance of the airway epithelium in restricting S. aureus growth by limiting airway surface liquid (ASL) sugar accumulation through paracellular permeability and uptake.Grant Funding Source: Supported by the Medical Research Council