EPITHELIAL-CELL ADHESION AND INVASION OF EXTENDED-SPECTRUM BETA LACTAMASE-PRODUCING EXTRA INTESTINAL ESCHERICHIA COLI ISOLATES REVEAL ST131 SUPERIORITY

Background: Multidrug-resistant ESBL-producing extraintestinal Escherichia coli (MDR ExPEC) is reaching endemic occurrence worldwide due to the clonal expansion of sequence type (ST) 131 lineage. This clone colonizes various hosts including humans. Adhesion and invasion capabilities of various ExPEC lineages to human epithelial cells were compared to explain the superiority of ST131 due to its higher gut-colonization potential.

Methods: A collection of 14 MLST-genotyped CTX-M-producing MDR community-onset bloodstream isolates were included, 7 belonged to ST131 lineage and 7- NonST131 isolates. Phylogrouping and nine adhesion genes (fimH, afa/draBC, papEF, hra, gafD, bmaE, sfaS, focG, iha) were determined by PCR. Adhesion and invasion were assessed with human Caco-2 cells at a multiplicity of infection of 10. Statistical comparison between groups of ST131 and NonST131 isolates was analyzed using Non-parametric Mann-Whitney test. Fluorescence microscopy visualization using anti-LPS E. coli antisera supported quantitative results.

Results: All ST131 isolates belonged to the virulent phylogenetic group B2 while NonST131 isolates belonged to phylogenetic groups D (5/7), A and B2 (both 1/7). All ST131 isolates were positive to fimH, gafD, iha, and NonST131 isolates showed different adhesins profiles. The average adhesion level of ExPEC to Caco-2 cells varied significantly (8.9±2.6% to 25.4±2.8%), with ST131 isolates showing a significantly higher adherence rate compared to NonST131 lineages (17.09±5% versus 13.06±4.41%, respectively, p<0.05). Moreover, ST131 isolates showed pronounced invasion rates (0.4±0.26% versus 0.16±0.15%, p=0.015).

Conclusions: ST131 ExPEC isolates showed a significant superiority in adhesion and invasion to human Caco-2 epithelial cells compared to other ExPEC genetic lineages suggesting a possible advantage to ST131 in gut-colonization together with an enhanced invasion capabilities.