Studies of cytolethal distending toxin Escherichia coli strains isolated from humans, animals and food / Estudo de cepas de Escherichia coli portadoras dos genes da toxina citoletal distensora isoladas de humanos, animais e alimentos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Cytolethal distending toxin, CDT, is a termolabile cytotoxin found in a great number of enteropathogens, including Escherichia coli. The CDT genes are called cdtA, cdtB and cdtC and they are placed in an operon and five alleles (I, II, III, IV and V) were described until the moment. E. coli strains may be classified in four ECOR phylogenetic groups: A, B1, B2 and D; strains belonging to A and B1 groups are called commensal or opportunist pathogens and strains grouped as B2 and D, as pathogenic strains. The goals of this work were to relate the CDT alleles and some virulence factors associated to four ECOR phylogenetic groups and analyze three strain sets by pulsed field gel electrophoresis (PFGE). This study used 80 cdt-positive E. colistrains isolated from swines, bovines, ovines, humans, water and meat. CDT alleles and phylogenetic groups were identified using polymerase chain reaction (PCR). Twenty-five strains belonging to O91:H21, O113:H21 and O116:H21 serotypes were studied by PFGE for evaluation of genetic diversity. The results show that CDT-V was the most frequent allele, present in 45,0% of strains, and showing strong association with VT2 (97%); CDT-III was observed in 36,2% of strains, showing association with VT1 in 79,0% of strains. CDT-I was detected in 8,7% of strains and CDT-IV, in 5,0%. In the phylogenetic studies, 45 strains (56,0 %) was grouped in group B1, 15 strains (18,7%) was grouped in B2, D grouped 13 strains (16,2%) and the group A congregate 7 strains (8,7%). In PFGE studies it was possible to identify, in the same serotype, since clones until non-related strains. For the studied strains, data allows to conclude that CDT-V is associated to phylogenetic group B1 and CDT-III is associated to B2 and D groups

ASSUNTO(S)

toxins pulsed-field gel eletrophoresis phylogeny filogenia escherichia coli toxinas eletroforese em gel de campo pulsado escherichia coli toxina citoletal distensora cytolethal distending toxin

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