VTEC in Argentina: First screening of the circulating clones using multilocus sequence typing (MLST)

CADONA JS, GONZÁLEZ J, BUSTAMANTE AV, SANSO AM.

Boston

Simposio; 9th International Symposium on Shiga Toxin (Verocytotoxin) producing Escherichia coli infections (VTEC2015).; 2015

Although O157:H7 is the most notorious agent of VTEC, there is growing concern over the emergence or the increased frequency of non-O157 serotypes associated with human disease. VTEC serogroups have been classified into five seropathotypes (A?E) according to incidence and association with HUS and outbreaks. Argentina has the highest incidence of HUS in the world. Classification of VTEC serotypes by phylogenetic methods has also demonstrated clustering of some serotypes according to their public health impact. In this study, we aimed to characterize some selected VTEC strains corresponding to A, B and C seropathotypes isolated from Argentina by assigning genotypes ST using MLST.Seven housekeeping genes (aspC, clpX, fadD, icdA, lysP, mdh and uidA) were amplified in 11 VTEC strains, from 8 serotypes and isolated from foods, cattle and human, to characterize the multi-locus genotype. The combination of alleles from the 7 genes was used to determine the sequence type (ST) of each strain and STs were grouped in a clonal complex (CC) by STEC website (http://www.shigatox.net/new/tools/ecmlst.html). A phylogeny was constructed from the ST identified and ST from closely related E. coli strains downloaded from the EcMLST database.The O157:H7 isolate belonged to ST 66 of the previously described CC11. The 026:H11 isolates belonged to two STs, 943 and a novel one (ST1158). The remaining isolates belonging to serotypes into seropathotype B were defined for three STs 106 (O111:NM), 78 (O145:NM) and 119 (O103:H2), which were grouped into CCs 14, 12 and 17 respectively. Concerning the strains of serotypes belonging to seropathotype C, were defined three STs 89 (two O91:H21 isolates) of CC34, 223 (two O113:H21 isolates) of CC30 and 175 (O5:NM) of CC42.Results revealed that a number of cattle VTEC isolates were found to belong to the same STs that are commonly associated with strains from humans and, one novel ST for O26:H11: This is the first study that analyzes VTEC strains isolated in Argentina by MLST, therefore, it provides the first data about which clones are circulating in our country.