Host range and zoonotic potential linked to P-like fimbrial adhesin specificity in avian pathogenic Escherichia coli

Abstract

Fimbrial adhesins are surface-associated bacterial proteins that contribute to colonization, tissue tropism, and biofilm formation. Genomic analysis of the avian pathogenic Escherichia coli (APEC) strain QT598 identified a plasmid-localized fimbrial operon, termed plf which encodes P-like (PL) fimbriae. Herein, we investigated the role of P-like (PL) fimbriae, encoded on the ColV plasmid of APEC strain QT598, in a natural host turkey respiratory infection model. We determined that deletion of the plf genes reduced colonization in the lungs of turkeys. The PlfG class II fimbrial adhesin from APEC strain QT598 demonstrated species- and tissue-specific adherence, as adherence to turkey lung sections in vitro was more pronounced than adherence to chicken lung sections. In vivo, expression of plf was also found to be upregulated in the lungs of turkeys during infection, as determined by qRT-PCR. Glycan array analysis showed that the PlfG class II adhesin recognizes Lewis b, Lewis y, and H antigens as potential receptors that are present on human red blood cells and on the surface of turkey respiratory tissues, implicating specific -1,2-linked glycans as receptors. Structural modelling of Plf adhesin revealed conserved {beta}-sandwich folds with distinct binding pockets that predict receptor specificity differences between Plf adhesin variants and other fimbrial adhesins such as PapG II and the PlfG class I adhesin from UMEA 3703-1. These findings highlight the role of PL fimbriae in APEC virulence and suggest a potential zoonotic and foodborne risk from poultry to humans, demonstrating the common recognition of glycans present on both turkey and mammalian host cells and tissues. Author summaryFimbrial adhesins may play a role in bacterial attachment and colonization of host cells. We examined the role of new pap-like (PL) fimbriae in an Avian Pathogenic E. coli (APEC) strain originally isolated from a systemic infection in a young turkey poult using genetic, molecular, and cell culture methods, as well as a turkey infection model. Deletion of plf genes also decreased colonization in the turkeys lungs, and comparison between the wild-type APEC isolate and the plf-mutant showed that these fimbriae strongly promote adherence to turkey lung sections compared to chicken lung sections. The PL fimbrial adhesin of strain QT598 demonstrated receptor-specificity to fucose [a]-1,2-galactose containing glycans, including Lewis b, Lewis y, and H antigens or similar glycans as determined by carbohydrate inhibition and glycan array experiments. These findings highlight the role of PL fimbriae in APEC virulence and suggest a potential zoonotic and foodborne risk from poultry to humans, demonstrating the common recognition of glycans present on both turkey and mammalian host cells and tissues.