title: Evolutionary genetics of a new pathogenic Escherichia species: Escherichia albertii and related Shigella boydii strains.
abstract: A bacterium originally described as Hafnia alvei induces diarrhea in rabbits and causes epithelial damage similar to the attachment and effacement associated with enteropathogenic Escherichia coli. Subsequent studies identified similar H. alvei-like strains that are positive for an intimin gene (eae) probe and, based on DNA relatedness, are classified as a distinct Escherichia species, Escherichia albertii. We determined sequences for multiple housekeeping genes in five E. albertii strains and compared these sequences to those of strains representing the major groups of pathogenic E. coli and Shigella. A comparison of 2,484 codon positions in 14 genes revealed that E. albertii strains differ, on average, at approximately 7.4% of the nucleotide sites from pathogenic E. coli strains and at 15.7% from Salmonella enterica serotype Typhimurium. Interestingly, E. albertii strains were found to be closely related to strains of Shigella boydii serotype 13 (Shigella B13), a distant relative of E. coli representing a divergent lineage in the genus Escherichia. Analysis of homologues of intimin (eae) revealed that the central conserved domains are similar in E. albertii and Shigella B13 and distinct from those of eae variants found in pathogenic E. coli. Sequence analysis of the cytolethal distending toxin gene cluster (cdt) also disclosed three allelic groups corresponding to E. albertii, Shigella B13, and a nontypeable isolate serologically related to S. boydii serotype 7. Based on the synonymous substitution rate, the E. albertii-Shigella B13 lineage is estimated to have split from an E. coli-like ancestor approximately 28 million years ago and formed a distinct evolutionary branch of enteric pathogens that has radiated into groups with distinct virulence properties.
authors.affiliation: Microbial Evolution Laboratory, 165 Food Safety & Toxicology Building, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Hyma
authors.forename: David W
authors.initials: DW
authors.lastname: Lacher
authors.forename: Adam M
authors.initials: AM
authors.lastname: Nelson
authors.forename: Alyssa C
authors.initials: AC
authors.lastname: Bumbaugh
authors.forename: J Michael
authors.initials: JM
authors.lastname: Janda
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Strockbine
authors.forename: Vincent B
authors.initials: VB
authors.lastname: Young
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Whittam
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000633:toxicity; D002460:Cell Line; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D003967:Diarrhea / Q000382:microbiology; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D004925:Escherichia / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D019143:Evolution, Molecular; D020611:Hafnia alvei / Q000145:classification / Q000235:genetics / Q000472:pathogenicity; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011817:Rabbits; D012486:Salmonella typhimurium / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D012761:Shigella boydii / Q000235:genetics*; D014774:Virulence
chemical_list: D018829:Adhesins, Bacterial; D001427:Bacterial Toxins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C067044:cytolethal distending toxin; C073819:eaeA protein, E coli