Discovery and Phylogenetic Analysis of Novel Members of Class b Enterotoxigenic Escherichia coli Adhesive Fimbriae

摘要: Enterotoxigenic Escherichia coli (ETEC) is recognized to be a common cause of acute watery diarrhea in children from developing countries. Colonization factors (CFAs) have been identified predominantly ETEC isolates secreting heat-stable enterotoxin (ST) or cosecreting ST with heat-labile toxin (LT). We hypothesized that LT-only-secreting produces unique colonization not previously described and LTST-secreting ETEC. A set degenerate primers based on nucleotide sequence similarities between the major structural genes CS20 (csnA), CS18 (fotA), CS12 (cswA), porcine antigen 987 (fasA) was developed used screen collection 266 LT-secreting which no known CFA detected. PCR-amplified products different molecular masses were obtained 49 (18.4%) isolates. Nucleotide analysis PCR amplicons followed by GenBank BLASTn revealed five novel DNA sequences; translated amino acid BLASTx confirmed similarity class 1b proteins encoded csnA, fotA, fasA. Strains expressing CFAs phylotyped analyzed using multilocus typing (MLST; Achtman scheme), types detected compared those archived global E. strains. In conclusion, application primer sets surveillance studies increased total number detectable almost 20%. Additionally, MLST suggests for many CFAs, there may requirement certain genetic backgrounds acquire maintain plasmids carrying encoding CFAs.