Characterization and Epidemiologic Subtyping of Shiga Toxin–ProducingEscherichia coliStrains Isolated from Hemolytic Uremic Syndrome and Diarrhea Cases in Argentina

Abstract

Argentina has a high incidence of hemolytic uremic syndrome (HUS); 12.2 cases per 100,000 children younger than 5 years old were reported in 2002. Shiga toxin (Stx)-producing Escherichia coli (STEC) is the primary etiologic agent of HUS, and STEC O157 is the predominant serogroup isolated. The main objective of the present work was to establish the phenotypic and genotypic characteristics of the STEC strains in general isolated from Argentine children during a prospective study and the clonal relatedness of STEC O157:H7 strains using subtyping techniques. One hundred and three STEC strains isolated from 99 children were included. The phenotypic and genotypic features were established, and a polymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) was performed to determine stx2 variants. The clonal relatedness of E. coli O157 isolates was established by phage typing and pulsed-field gel electrophoresis (PFGE). The 103 STEC strains belonged to 18 different serotypes, and 59% were of serotype O157:H7. Stx2 was identified in 90.3%, and stx1 in 9.7%. Among the 61 STEC O157 strains, 93.4% harbored the stx2/stx2vh-a genes; PT4 (39.3%) and PT2 (29.5%) were the predominant phage types. Using PFGE with the enzyme XbaI, a total of 41 patterns with at least 80% similarity were identified, and seven clusters with identical profiles were established. Some of the clusters were further split by PFGE using BlnI as the second enzyme. Isolates with indistinguishable PFGE patterns were with one exception also indistinguishable by phage typing and stx genotyping. These findings confirmed that some isolates were genetically related. However, no epidemiological linkages were identified. STEC strains with different genotypes and belonging to diverse serotypes were isolated in Argentina. Some STEC O157 strains could not be distinguished by applying subtyping techniques such as PFGE and phage typing.

Detection of phenotypes, virulence genes and phylotypes of avian pathogenic and human diarrheagenic Escherichia coli in Egypt

“…Different serotypes determined from the diarrheic isolates were mostly the classical non-O157 enterohemorrhagic E. coli (EHEC) serotypes such as O26:H11, O111:H2, O113:H7, O103:H2, and O145:H28 [19]. From healthy persons, only two serotypes were identified (O26:H11 and O111:H2); this finding is in agreement with many previous studies which verified that O26 is considered one of the most clinically serotypes that could be isolated from both diarrheic and healthy persons [20,21].…”

Enterotoxigenic Escherichia coli associated with childhood diarrhoea in Colombia, South America

“…A more recent Mexican case-control study reported that in more than 50% of cases of diarrhoea there was more than one pathogen implicated, including any combination of E. histolytica, Salmonella, or E. coli pathogens [33]. Case-control studies reported from Argentina have concentrated more on STEC, as this country has a high incidence of hemolytic uremic syndrome associated with O157:H7 and non-O157:H7 STEC strains [34].…”

Shiga Toxin/Verocytotoxin-Producing Escherichia coli Infections: Practical Clinical Perspectives

“…Most compellingly, E. coli O157:H7 is the STEC/VTEC that remains to this day the near-exclusive cause of postdiarrheal HUS (8,12,16,21,(43)(44)(45)(46)(47)(48)(49). This serotype is also the one most strongly associated with outbreaks (though most infections are sporadic).…”