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

Abstract

Although O157:H7 is the most notorious agent of VTEC, there is growing concern over 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 and phylogenetic methods have also demonstrated clustering of some serotypes according to their public health impact. Argentina has the highest incidence of HUS in the world. Our aim was to characterize a selection of VTEC strains corresponding to A, B and C seropathotypes isolated in Argentina using multilocus sequence typing (MLST). Seven housekeeping genes (aspC, clpX, fadD, icdA, lysP, mdh and uidA) were amplified in 11 VTEC strains belonged to 8 serotypes, isolated from foods, cattle and human. All alleles, sequence types (ST) and clonal groups (CG) were assigned in accordance with the STEC Center. A phylogenetic network was constructed from the STs identified and STs from closely related VTEC strains downloaded from the EcMLST database. Seropathotype A isolate (O157:H7) was identified as ST 66 into CG11. Isolates belonging to seropathotype B were defined for five STs: 026:H11 isolates belonged to two STs, 943 and a novel one (ST 1158), both not determined CG; and the remaining isolates belonged to ST 106 (O111:NM), 78 (O145:NM) and 119 (O103:H2), which were clustered into CGs 14, 12 and 17 respectively. Concerning the strains belonging to seropathotype C, were defined by three STs, 89 (two O91:H21 isolates) into CG34, 223 (two O113:H21 isolates) into CG30 and 175 (O5:NM) into CG42.