부산대학교 도서관

Adherent Invasive Escherichia coli (AIEC) strains recovered from Crohn's disease lesions survive and multiply within macrophages. A reference strain for this pathovar, AIEC LF82, forms microcolonies within phagolysosomes, an environment that prevents commensal E. coli multiplication. Little is known about the LF82 intracellular growth status, and signals leading to macrophage intra-vacuolar multiplication. We used single-cell analysis, genetic dissection and mathematical models to monitor the growth status and cell cycle regulation of intracellular LF82. We found that within macrophages, bacteria may replicate or undergo non-growing phenotypic switches. This switch results from stringent response firing immediately after uptake by macrophages or at later stages, following genotoxic damage and SOS induction during intracellular replication. Importantly, non-growers resist treatment with various antibiotics. Thus, intracellular challenges induce AIEC LF82 phenotypic heterogeneity and non-growing bacteria that could provide a reservoir for antibiotic-tolerant bacteria responsible for relapsing infections. Author summary: Intestinal microbiome dysbiosis has been consistently described in patients with Crohn's disease. The adherent-invasive E. coli (AIEC) pathotype in particular, has been implicated in the pathogenesis. AIEC colonize intestinal epithelial cells and survive and replicate within macrophages. Here we demonstrated that growth of AIEC LF82 inside the toxic mature phagolysosomes of macrophages requires sequential adaptations and phenotype switches. First, the stringent response halts the replicative cell cycle of AIEC LF82 for few hours. During this period a large number of AIEC LF82 acquires the ability to tolerate antibiotic treatments. Later when, AIEC multiplication restarts it requires DNA repair suggesting that AIEC have accumulated lesions during the first hours post infection. We observed that non growing bacteria appear frequently from the population of growing AIEC LF82 in this second phase. This raises the proportion of antibiotic tolerant AIEC LF82 up to 10% of the population. Thus, intracellular challenges induce AIEC LF82 phenotypic heterogeneity and non-growing bacteria that could provide a reservoir for antibiotic-tolerant bacteria responsible for relapsing infections. [ABSTRACT FROM AUTHOR]