Abstract
Escherichia albertii is a newly described and emerging diarrheagenic pathogen responsible for outbreaks of gastroenteritis. Serotyping plays an important role in diagnosis and epidemiological studies for pathogens of public health importance. The diversity of O-antigen biosynthesis gene clusters (O-AGCs) provides the primary basis for serotyping. However, little is known about the distribution and diversity of O-AGCs of E. albertii strains. Here, we presented a complete sequence set for the O-AGCs from 52 E. albertii strains and identified seven distinct O-AGCs. Six of these were also found in 15 genomes of E. albertii strains deposited in the public database. Possession of wzy/wzx genes in each O-AGC strongly suggest that O-antigens of E. albertii were synthesized by the Wzx/Wzy-dependent pathway. Furthermore, we performed an O-antigen serotyping scheme for E. albertii based on specific antisera against seven O-antigens and a high throughput xTAG Luminex assay to simultaneously detect seven O-AGCs. Both methods accurately identified serotypes of 64 tested E. albertii strains. Our data revealed the high-level diversity of O-AGCs in E. albertii. We also provide valuable methods to reliably identify and serotype this bacterium.
Highlights
Lipopolysaccharide (LPS) molecules form the outer leaflet of the outer membrane of many Gramnegative bacteria and are essential components of the bacterial cell envelope
On the basis of sequences and genetic structures of the entire O-antigen biosynthesis gene clusters (O-AGCs) regions, the O-AGCs from 52 strains were placed into seven groups where O1 (n = 17) was the most prevalent, followed by O4 (n = 9), O2 (n = 8), O3 (n = 6), O5 (n = 5), O6 (n = 4), and O7 (n = 3)
The data indicated that O-AGCs extracted are responsible for the O-antigen synthesis of E. albertii
Summary
Lipopolysaccharide (LPS) molecules form the outer leaflet of the outer membrane of many Gramnegative bacteria and are essential components of the bacterial cell envelope. The O-antigen polysaccharide constitutes the exterior part of the LPS and consists of oligosaccharide repeats (O-units) containing three to six sugar residues. The O-antigen is a major surface antigen and is responsible for serological diversity of Gram-negative bacteria which are clinically and. The genes in O-AGC are clustered into three major classes: sugar synthesis genes, glycosyltransferase genes, and O-unit processing genes. Polymerization of the O-units into an Oantigen is mostly mediated though two of three pathways in Gram-negative species: Wzx/Wzy-dependent pathway and ABC transporter-dependent pathway (Valvano, 2003). Two genes, encoding the O antigen flippase (wzx) and O antigen polymerase (wzy), are unique in most of the O-AGCs, and have been used as targets for molecular O serogrouping (DebRoy et al, 2016)
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