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Groundwater is an important source of drinking water for many communities in Northern Argentina; particularly, in the province of Chaco, where about 14% of households use this natural resource. Enteroaggregative Escherichia coli is an emerging pathogen whose global importance in public health has increased in recent years. Despite the significant risk of disease linked to contaminated water exposure, the prevalence of E. coli pathotypes in aquatic environments is still not so well defined. The aim of the present study was to detect the presence of typical enteroaggregative E. coli through the recognition of its virulence factors aap, AA probe and aggR by molecular techniques. A total of 93 water samples from different small communities of Chaco were analyzed. E. coli was identified in 36 (38.7%) of the tested samples. Six strains isolated from different samples harbored the studied genes. Of these 6 isolates, 3 carried the aap gene, 2 the AA probe and the last one the combination of aap/aggR genes. The prevalence of E. coli isolates harboring enteroaggregative virulence genes in groundwater sources was 6.4%. This work represents the first contribution to the study of the presence and distribution of virulence genes of EAEC in groundwater sources in this region of Argentina., (Copyright © 2014 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.)

We describe the first isolation of an enteroaggregative Escherichia coli (EAEC) O104:H4 strain associated with an acute diarrhea case in Argentina. Two multiplex PCRs (mPCR) were performed as screening of genes mPCR1 (eae, lt, and st) and mPCR2 (IpaH, aggR, stx1 and stx2). A mPCR to detect the rfbO104, fliCH4 and terD genes, and PCR assays for the detection of pCVD432 plasmid, aaiC and lpfO113 genes were included. Biochemical and antimicrobial susceptibility assays as well as serotyping were performed. The identified E. coli strain was susceptible to all antimicrobials tested and harbored the aggR, aaiC, pCVD432 plasmid, lpfO113, rfbO104, fliCH4 and terD genes. Although serotype EAEC O104:H4 rarely spreads and sporadic cases have been reported, global concern increased after the large-scale outbreak in Europe in 2011. The finding of EAEC O104:H4 reinforces the need for improved methodologies for the detection of all E. coli pathotypes., (Copyright © 2014 Asociación Argentina de Microbiología. Publicado por Elsevier España. All rights reserved.)

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 and enteropathogenic E. coli (EPEC) trigger actin polymerization at the site of bacterial adhesion by inducing different signaling pathways. Actin assembly by EPEC requires tyrosine phosphorylation of Tir, which subsequently binds the host adaptor protein Nck. In contrast, Tir(EHEC O157) is not tyrosine phosphorylated and instead of Nck utilizes the bacterially encoded Tir-cytoskeleton coupling protein (TccP)/EspF(U), which mimics the function of Nck. tccP is carried on prophage CP-933U/Sp14 (TccP). Typical isolates of EHEC O157:H7 harbor a pseudo-tccP gene that is carried on prophage CP-933 M/Sp4 (tccP2). Here we report that atypical, beta-glucuronidase-positive and sorbitol-fermenting, strains of EHEC O157 harbor intact tccP and tccP2 genes, both of which are secreted by the LEE-encoded type III secretion system. Non-O157 EHEC strains, including O26, O103, O111, and O145, are typically tccP negative and translocate a Tir protein that encompasses an Nck binding site. Unexpectedly, we found that most clinical non-O157 EHEC isolates carry a functional tccP2 gene that encodes a secreted protein that can complement an EHEC O157:H7 DeltatccP mutant. Using discriminatory, allele-specific PCR, we have demonstrated that over 90% of tccP2-positive non-O157 EHEC strains contain a Tir protein that can be tyrosine phosphorylated. These results suggest that the TccP pathway can be used by both O157 and non-O157 EHEC and that non-O157 EHEC can also trigger actin polymerization via the Nck pathway.

Shiga toxin producing-Escherichia coli (STEC) is an important emerging pathogen, and ruminants are recognized as their main natural reservoir. The aim of this work was to establish the frequency of STEC in non-domestic mammals of the Zoo and Botanical Garden of La Plata City, Argentina, and to pheno-genotypically characterize STEC isolates. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 50.8% of 65 fecal samples. Twenty-five STEC strains were isolated from 38.5% of the Zoo's animals. Ten species of order Cetartiodactyla and one species of order Rodentia were recognized as new STEC carriers. STEC strains belonged to 7 different serotypes including new serotypes O12:H25 and O13:H6. Serotype O146:H28, previously associated with human infections, represented 24% of STEC isolates. The most frequent Shiga toxin identified were type 1c and type 2c. Nineteen strains were positive for iha gene, 8 strains were positive for ehxA gene. Moreover, all strains were positive for lpfAO113 and negative for rfbO157, eae, saa, lpfAO157/OI-141, lpfAO157/OI-154, efa1, and toxB genes. Results obtained by XbaI-pulsed-field gel electrophoresis (XbaI-PFGE) confirmed the transmission of STEC strains among different animal species and suborders. In addition, we observed a potential association between STEC-harboring animal and factors such as belonging to order Cetartiodactyla, living in a pit, and belonging to a non-autochthonous species. This is the first work developed with zoological mammals and STEC in Argentina.

The aim of the study was to establish the microbiological quality of morcillas, typical Argentine sausages, and to investigate the presence of Shiga toxin-producing Escherichia coli (STEC). Between October 2001 and October 2002, a total of 100 morcilla samples were analysed. Several samples showed high levels of total aerobic mesophilic bacteria counts, molds and yeasts. The samples analysed contained Enterobacteriaceae (100%) and fecal coliforms (81%), indicating inadequate application of the thermal treatment and deficient hygiene conditions during the elaboration of the product. STEC strains were isolated from three out of 100 (3%) morcilla samples. Two strains (2%) were characterized as E. coli O157:H7 stx2+stx2vh-a/eae/EHEC-hlyA and one strain (1%), as E. coli O26:H11 stx1/eae/EHEC-hlyA. Considering both the high microbial count in all tested samples and the presence of STEC strains in three of them, morcillas should be considered a food unsafe to consume when inadequately cooked.

Long polar fimbriae (LPF) are related to type I fimbriae in genetic organization and were first identified in Salmonella enterica serovar Typhimurium. Four lpfA genetic variants designated lpfA(O157/OI-141), lpfA(O157/OI-154), lpfA(O26) and lpfA(O113) have been identified in Shiga toxin-producing Escherichia coli (STEC). In this study, PCR was employed to determine the distribution of STEC-lpfAs in enteropathogenic, enteroaggregative, enterotoxigenic and enteroinvasive E. coli (EPEC, EAEC, ETEC and EIEC) and in the standard E. coli collection of reference (ECOR). Among the 97 diarrheagenic strains from our collection, only 2 EPEC strains of serotypes O55:H7 and O119:NM were positive for both lpfA(O157/OI-141) and lpfA(O157/OI-154). lpfA(O157/OI-141) was also positive in 1 of 25 ETEC strains. lpfA(O113) was present in 51 of 97 strains and lpfA(O26) in 13 of 97 strains of diverse diarrheagenic categories. STEC-lpfAs were also present in non-pathogenic ECOR strains of all phylogenetic groups. This study showed that the lpfA genes identified in the genome of STEC strains are not specific to this category. Our results suggest that there is a relationship between the lpfA variant and the phylogenetic group.

Between July 1999 and December 2000, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was established in 200 Argentine healthy young beef steers (14-16 months old) grown under local production systems with a feed grain period of 3-4 months, and the STEC strains isolated were examined in regard to their phenotypic and genotypic characteristics. Stool samples (n = 70) and rectal swabs (n = 130) were taken at the slaughterhouse level. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 69% of the samples. Eighty-six STEC strains were isolated from 39% of the animals. Serogroups identified, in order of frequency, were: O8 (16 strains), O113 (14), O103 (5), O91 (4), O171 (3), O174 (3), O25 (2), O112 (2), O145 (2), O2, O11, O104, O121, O128, O143, O146, O157. The most frequent serotype isolated was O8:H19 (12.9%). A total of 17 serotypes, including E. coli O157:H7 found in one animal (0.5%), have been previously associated with hemolytic uremic syndrome (HUS), bloody and non-bloody diarrhea in different countries, including Argentina. The prevalent genotype isolated was stx2 (51 of 86, 59.3%). Subtyping of stx2 variants showed the prevalence of stx2vh-b (25.6%) and stx2vh-a types (24.4%), and revealed the presence of an atypical stx2-v. Only 7.0% of STEC strains carried eae, and 33.7% harbored EHEC-hlyA gene. The full virulent genotype (stx/eae/EHEC-hlyA) was found to be present in 4 of the 86 (4.7%) STEC strains isolated. This research indicates that young steers from the main beef-producing area of Argentina are an important reservoir of STEC strains; however, its importance as agents of human diseases in our country has still to be established.

The distribution of eight putative adhesins that are not encoded in the locus for enterocyte effacement (LEE) in 139 Shiga toxin-producing Escherichia coli (STEC) of different serotypes was investigated by PCR. Five of the adhesins (Iha, Efa1, LPF(O157/OI-141), LPF(O157/OI-154), and LPF(O113)) are encoded in regions corresponding to genomic O islands of E. coli EDL933, while the other three adhesins have been reported to be encoded in the STEC megaplasmid of various serotypes (ToxB [O157:H7], Saa [O113:H21], and Sfp [O157:NM]). STEC strains were isolated from humans (n = 54), animals (n = 52), and food (n = 33). They were classified into five seropathotypes (A through E) based on the reported occurrence of STEC serotypes in human disease, in outbreaks, and in the hemolytic-uremic syndrome (M. A. Karmali, M. Mascarenhas, S. Shen, K. Ziebell, S. Johnson, R. Reid-Smith, J. Isaac-Renton, C. Clark, K. Rahn, and J. B. Kaper, J. Clin. Microbiol. 41:4930-4940, 2003). The most prevalent adhesin was that encoded by the iha gene (91%; 127 of 139 strains), which was distributed in all seropathotypes. toxB and efa1 were present mainly in strains of seropathotypes A and B, which were LEE positive. saa was present only in strains of seropathotypes C, D, and E, which were LEE negative. Two fimbrial genes, lpfA(O157/OI-141) and lpfA(O157/OI-154), were strongly associated with seropathotype A. The fimbrial gene lpfA(O113) was present in all seropathotypes except for seropathotype A, while sfpA was not present in any of the strains studied. The distribution of STEC adhesins depends mainly on serotypes and not on the source of isolation. Seropathotype A, which is associated with severe disease and frequently is involved in outbreaks, possesses a unique adhesin profile which is not present in the other seropathotypes. The wide distribution of iha in STEC strains suggested that it could be a candidate for vaccine development.

A multiplex PCR assay for the identification of human diarrheagenic Escherichia coli was developed. The targets selected for each category were eae for enteropathogenic E. coli, stx for Shiga toxin-producing E. coli, elt and est for enterotoxigenic E. coli, ipaH for enteroinvasive E. coli, and aggR for enteroaggregative E. coli. This assay allowed the categorization of a diarrheagenic E. coli strain in a single reaction tube.

Between 9 October and 12 November 1996, an outbreak of bloody diarrhea occurred in the neonatal nursery ward of the Policlínico Neuquén, in Neuquén, a city in the southwestern region of Argentina. Seven patients of the intermediate care unit were affected. Isolates of Escherichia coli O18ac:H31 that were non-lactose and -sorbitol fermenting were recovered from outbreak cases. Although the strains were negative for a number of virulence factors typically found in diarrheagenic groups of E. coli, all isolates from the present neonatal outbreak possessed the enterohemolysin gene, ehl1. All isolates showed resistance to the antibiotics ampicillin and chloramphenicol. These isolates showed a low adherence property in HeLa cells without any recognizable pattern. In order to evaluate the outbreak dissemination in the neonatology ward, a prevalence study was conducted on 13 November. Stool specimens were obtained from 16 neonates hospitalized in the sector and from 33 medical staff members. E. coli isolates with identical biochemical characteristics of the outbreak strain were recovered from 11 of 16 inpatients and from 4 of 33 staff members during the prevalence study. A total of 15 E. coli strains recovered both from the outbreak and the prevalence study were processed by random amplified polymorphic DNA (RAPD)-PCR and pulsed-field gel electrophoresis (PFGE). By RAPD-PCR 14 of 15 strains showed patterns with 85 to 100% similarity, and by PFGE these strains were identical, each showing a unique pattern with 15 bands between 40 and 400 kb. One strain isolated from a nurse during the prevalence study presented a pattern not related to the others, and this was characterized as E. coli O81:HNM resistant to ampicillin only and negative for all the virulence factors studied. This outbreak occurred despite strict regulations in place to prevent cross-infection in the hospital. Postoutbreak prevalence studies were performed weekly thereafter without detecting new cases.

Shiga toxin-producing Escherichia coli (STEC) is known as a pathogen associated with food-borne diseases. The STEC O145 serogroup has been related with acute watery diarrhea, bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Argentina has the highest rate of HUS worldwide with 70% of the cases associated with STEC infections. We aimed to describe the epidemiology and genetic diversity of STEC O145 strains isolated across Argentina between 1998–2020. The strains isolated from 543 cases of human disease and four cattle, were pheno-genotipically characterized. Sequencing of five strains was performed. The strains were serotyped as O145:NM[H28]/H28, O145:H25, and O145:HNT, and mainly characterized as O145:NM[H28]/stx2a/eae/ehxA (98.1%). The results obtained by sequencing were consistent with those obtained by traditional methods and additional genes involved in different mechanisms of the pathogen were observed. In this study, we confirmed that STEC O145 strains are the second serogroup after O157 and represent 20.3% of HUS cases in Argentina. The frequency of STEC O145 and other significant serogroups is of utmost importance for public health in the country. This study encourages the improvement of the surveillance system to prevent severe cases of human disease. [ABSTRACT FROM AUTHOR]

The objective is to establish the frequency of STEC infections in household contacts of HUS patients. We studied 292 household contacts of 82 HUS patients attended from 2010 to 2018. In HUS cases, diagnostic criteria were (1) isolation and characterization of STEC strains, (2) detection of free fecal Shiga toxin (FFStx), and (3) detection of anti-O serogroup-specific antibodies. Contacts were studied by screening of stx genes by polymerase chain reaction and/or STEC isolation from stool samples. Clonal relation of STEC strains was established by pulsed-field gel electrophoresis (PFGE). Frequencies of HUS patients without STEC isolation with STEC-positive contacts were determined. Serotypes and stx-genotypes in patients and contacts were analyzed. Thirty (36.6%) HUS patients had 36 STEC-positive contacts. Fourteen (38.8%) were children, 20 adults, and 2 dogs. One sibling developed HUS, 6 contacts had gastrointestinal symptoms, and the rest were asymptomatic. In 5 of 30 HUS patients, STEC infection could not be confirmed, and 2 cases were diagnosed only by FFStx detection. Of the remaining 23 HUS patients, 16 had E. coli O157 and 7 E. coli O145 infection. Serotype and/or stx-genotype concordance was established in 19 (83%) of 23 HUS patients and their contacts. Five HUS cases and their contacts studied by PFGE showed macrorestriction patterns with more than 90% similarity. Nearly one third of HUS patients had STEC-positive family contacts, and one third of them were children. Early identification is important to prevent ongoing contamination among family and institutional contacts and to facilitate prompt detection of HUS in STEC-positive contacts. [ABSTRACT FROM AUTHOR]

Long polar fimbriae ( Lpf) are intestinal adhesins and important virulence factors of pathogenic Escherichia coli strains. We cloned and sequenced the lpf2-1 operon ( lpf2ABCD ) and its flanking regions of an intimin- and Shiga toxin-negative atypical E. coli O157: H43 strain of bovine origin and also sequenced the lpf2-1 operon of six additional atypical O157 bovine E. coli strains of various serotypes. Nucleotide sequence comparison of these lpf operons showed sequence conservation as they contained only four polymorphic nucleotide positions. Investigation of these O157 strains as well as 13 E. coli Reference Collection ( ECOR) strains carrying the lpf2-1 allele revealed high degree of sequence conservation in the lpf2 flanking regions. The lpf2-1 allele is also present in a bovine Shiga toxin-producing E. coli STEC O136: H12 strain, and in vitro adherence assays revealed that the absence of lpf2-1 in this strain did not affect its host cell-binding properties. Our data indicate that lpf2 loci are highly conserved in E. coli isolates; however, its role in adherence might be masked by other uncharacterized adhesins. [ABSTRACT FROM AUTHOR]

The long polar fimbriae (Lpf) is one of few adhesive factors of Shiga toxin-producing Escherichia coli (STEC) and it is associated with colonization of the intestine. Studies have demonstrated the presence of lpf genes in several pathogenic E. coli strains, and classification of variants based on polymorphisms in the lpfA1 and lpfA2 genes has been adopted. Using a collection of Argentinean locus of enterocyte effacement (LEE)-negative STEC strains, we determined that the different lpfA types were present in a wide variety of serotypes with no apparent association between the types of lpfA1 or lpfA2 genes and the severity of human disease. The lpfA2-1 was the most prevalent variant identified, which was present in 95.8% of the isolates, and lpfA1-3 and lpfA2-2, proposed as specific biomarkers of E. coli O157:H7, were not found in any of the serotypes studied. The prevalence of lpf genes in a large number of strains is useful to understand the genetic diversity of LEE-negative STEC and to define the association of some of these isolates carrying specific lpf-variants with disease. [ABSTRACT FROM AUTHOR]

We examined O157:non-H7 strains isolated from various sources and geographical locations and found 15/57 strains to carry eae alleles, including α, β, ℇ and κ/δ, suggesting that these strains may be prevalent. All strains were serologically and genetically confirmed to be O157, but none were the H7 serotype or carried any trait virulence factors of the Escherichia coli O157:H7 serotype. Genetic H typing of the eae-positive strains showed that the α- eae-bearing strain was H45, while the β- and ℇ- eae strains were H16 and the κ/δ- eae strains were H39. The β- and ℇ- eae-bearing O157:H16 strains shared ∼90% pulsed-field gel electrophoresis (PFGE) similarity and were distinct from the other strains that had other eae alleles. Interestingly, an ℇ- eae O157:H16 strain isolated from meat in France shared PFGE similarity to the O157:H16 strains from water in the United States. Multilocus sequence typing showed that there is clonal diversity within the O157 serogroup, as some O157:non-H7 strains clustered with EPEC clonal groups, while others clustered within the ST-171 group of diverse strains and serotypes that had not previously included any strains from the O157 serogroup. Clonal analysis also showed that none of the eae-positive O157:non-H7 strains we examined were closely related to the pathogenic O157:H7 serotype. [ABSTRACT FROM AUTHOR]

Abstract: The majority of Shiga toxigenic Escherichia coli (STEC) strains isolated from severe STEC disease are those harboring the locus of enterocyte effacement (LEE), which encodes factors involved in adherence to epithelial cells. However, LEE-negative STEC are increasingly isolated from clinical cases. STEC autoagglutinating adhesin (Saa) is widely used as a marker of adhesin in the absence of LEE. In the present study, we compared the adherence of 32 saa-harboring STEC strains to cultured epithelial cells in the absence or presence of d-mannose. In the absence of d-mannose, 19 strains were adherent to HEp-2 and Caco-2 cells, while 12 were non-adherent. One strain showed detachment of epithelial cells. The adherence of 13 strains was sensitive to the presence of d-mannose. The saa mutant of strain T141, in which adherence was mannose resistant, did not show a significant decrease in adherence compared to the wild type, suggesting a Saa-independent mechanism of adherence. saa-harboring STEC exhibited differential binding properties to epithelial cells, which could not be attributed to the number of C-terminal repeats of Saa, or to the expression of Saa as detected by Western blotting. Our results suggest that multiple adherence mechanisms are present in saa-harboring STEC, implying a high degree of diversity in this group of STEC. [Copyright &y& Elsevier]

We evaluated risk factors for sporadic Shiga toxin-producing Escherichia coli (STEC) infection among children in Argentina. We conducted a prospective case-control study in 2 sites and enrolled 150 case-patients and 299 controls. The median age of case-patients was 1.8 years; 58% were girls. Serotype O157:H7 was the most commonly isolated STEC. Exposures associated with infection included eating undercooked beef, living in or visiting a place with farm animals, and contact with a child <5 years of age with diarrhea. Protective factors included the respondent reporting that he or she always washed hands after handling raw beef and the child eating more than the median number of fruits and vegetables. Many STEC infections in children could be prevented by avoiding consumption of undercooked beef, limiting exposure to farm animals and their environment, not being exposed to children with diarrhea, and washing hands after handling raw beef. [ABSTRACT FROM AUTHOR]

Background: Shiga toxin-producing Escherichia coli (STEC) is an important cause of bloody diarrhoea (BD), non-bloody diarrhoea (NBD) and the haemolytic uraemic syndrome (HUS). In Argentina and New Zealand, the most prevalent STEC serotype is O157:H7, which is responsible for the majority of HUS cases. In Australia, on the other hand, STEC O157:H7 is associated with a minority of HUS cases. The main aims of this study were to compare the phenotypic and genotypic characteristics of STEC O157 strains isolated between 1993 and 1996 from humans in Argentina, Australia and New Zealand, and to establish their clonal relatedness. Results: Seventy-three O157 STEC strains, isolated from HUS (n = 36), BD (n = 20), NBD (n = 10), or unspecified conditions (n = 7) in Argentina, Australia and New Zealand, were analysed. The strains were confirmed to be E. coli O157 by biochemical tests and serotyping. A multiplex polymerase chain reaction (PCR) was used to amplify the stx1, stx2 and rfbO157 genes and a genotyping method based on PCR-RFLP was used to determine stx1 and stx2 variants. This analysis revealed that the most frequent stx genotypes were stx2/stx2c (vh-a) (91%) in Argentina, stx2 (89%) in New Zealand, and stx1/stx2 (30%) in Australia. No stx1-postive strains were identified in Argentina or New Zealand. All strains harboured the eae gene and 72 strains produced enterohaemolysin (EHEC-Hly). The clonal relatedness of strains was investigated by phage typing and pulsed-field gel electrophoresis (PFGE). The most frequent phage types (PT) identified in Argentinian, Australian, and New Zealand strains were PT49 (n = 12), PT14 (n = 9), and PT2 (n = 15), respectively. Forty-six different patterns were obtained by XbaI-PFGE; 37 strains were grouped in 10 clusters and 36 strains showed unique patterns. Most clusters could be further subdivided by BlnI-PFGE. Conclusion: STEC O157 strains isolated in Argentina, Australia, and New Zealand differed from each other in terms of stx-genotype and phage type. Additionally, no common PFGE patterns were found in strains isolated in the three countries. International collaborative studies of the type reported here are needed to detect and monitor potentially hypervirulent STEC clones. [ABSTRACT FROM AUTHOR]

There is great geographical variation in the frequency of Escherichia coli O157 infections that correlates with important differences in the bovine reservoir of each country. Our group carried out a broad molecular characterization of human and bovine E. coli O157 strains circulating in Argentina using different methodologies. Our data allows us to conclude that in Argentina, a high homogeneity is observed in both cattle and human strains, with almost exclusive circulation of strains belonging to the hypervirulent clade 8 described by Manning. The aim of this review was to compare the genetic background of E. coli O157 strains isolated in countries that have conducted similar studies, to try to correlate specific O157 genotypes with the incidence and severity of E. coli O157 associated diseases. The characteristics of the strains that cause disease in humans reflect the predominant genotypes in cattle in each of the countries analyzed. The main features clearly linked to high incidence or severity of E. coli O157 infections are lineage-specific polymorphism assay-6 lineage I/II, clade 8 strains and probably, clade 6 strains, the stx2a/stx2c genotype, the presence of q933 and q21 simultaneously, and putative virulence factor EC_3286. In countries with an absence of these features in O157 strains, the overall incidence of O157 disease is low. Argentina, where these characteristics are detected in most strains, shows the highest incidence of hemolytic uremic syndrome (HUS) worldwide. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli (STEC) is th etiological agent of gastrointestinal diseases as haemorrhagic colitis and haemolytic-uraemic syndrome (HUS). Shiga toxin (Stx) is the main virulence factor. There are two types, Stx1 and Stx2, and several subtypes. Other virulence factors are involved in pathogenesis. While O157:H7 is the predominant serotype, at present non-O157 STEC strains are increasingly recognized as foodborne pathogens worldwide. In Argentina, STEC O174 stands out as an emerging pathogen and is one of the four most prevalent non-O157 STEC serogroups. The aim of this study was to characterize 41 O174:[H21, H28] STEC strains isolated from animals, food, and humans. Isolates were characterized by stx genotyping, adhesion factors ( afa C, eae , iha , lpf O113 , saa , and tox B), additional toxins ( cdt V, ehx A, sub A) and clonal relationship by pulsed-field gel electrophoresis (PFGE). Among 30 O174:H21 strains, the most prevalent stx subtype was stx 2c (56.7%), and among 11 O174:H28 strains, the most prevalent was stx 2a (90.9%). Regarding virulence factors, all strains were positive for afa C gene and negative for eae and tox B genes. In O174:H21, the frequency of additional factors was lpf O113 (96.6%), iha (83.3%), ehx A and saa (10%), and sub A (3.3%), meanwhile in O174:H28 strains the frequency was iha and sub A (100%), lpf O113 (90.9%), ehx A and saa (90.9%), and cdt V (9.09%). By Xba l-PFGE, 29 patterns were established with 64.01% similarity and three clusters were detected. Given the fact that the O174 serogroup is a local emergent, it is important to study the virulence profiles to understand its potential pathogenicity. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli strains of serotype O113:H21 have caused severe human diseases, but they are unusual in that they do not produce adherence factors coded by the locus of enterocyte effacement. Here, a PCR microarray was used to characterize 65 O113:H21 strains isolated from the environment, food, and clinical infections from various countries. In comparison to the pathogenic strains that were implicated in hemolytic-uremic syndrome in Australia, there were no clear differences between the pathogens and the environmental strains with respect to the 41 genetic markers tested. Furthermore, all of the strains carried only Shiga toxin subtypes associated with human infections, suggesting that the environmental strains have the potential to cause disease. Most of the O113:H21 strains were closely related and belonged in the same clonal group (ST-223), but CRISPR analysis showed a great degree of genetic diversity among the O113:H21 strains. [ABSTRACT FROM AUTHOR]

Abstract: For comparison purposes, the prevalence of 8 virulence markers was investigated, by PCR, in 153 cattle and 47 human Locus for Enterocyte Effacement (LEE)-negative Shiga toxin-producing Escherichia coli (STEC) strains isolated in Argentina. Also, their correlation with severe disease was established. The virulence markers studied comprises 5 fimbrial and nonfimbrial adhesin-encoding genes (fimA, iha, efa1, lpfA O113, and saa) and 3 toxin genes (cdt-V, subAB and astA) in addition to the Shiga toxins. The most prevalent virulence marker found was that encoded by the lpfA O113 gene (199/200, 99%). Comparatively, the lpfA O113, fimA, iha, saa, subAB, cdt-V and astA genes were detected in 100%, 92.8%, 85%, 52.9%, 36%, 11.8% and 9.8% of the cattle strains and in 97.9%, 95.7%, 89.4%, 40.4%, 32%, 17% and 10.6% of the human strains, respectively. All STEC strains were efa1 negative. The most prevalent profile observed among cattle and human STEC strains was lpfA O113 iha fimA. These results show that bovine LEE-negative STEC strains possessed genes encoding virulence factors present in human LEE-negative STEC strains that are associated with disease. Despite a great diversity of virulence profiles observed, further studies comparing wild type strains and their allelic mutants are needed to evaluate the role of each factor in the pathogenesis of LEE-negative STEC strains during human infections. [Copyright &y& Elsevier]

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from animals and food in Argentina (n=44) and Brazil (n=20) were examined and compared in regard to their phenotypic and genotypic characteristics to evaluate their pathogenic potential. The clonal relatedness of STEC O157 isolates (n=22) was established by phage typing (PT) and pulsed-field gel electrophoresis (PFGE). All O157 strains studied carried eae and enterohemorrhagic E. coli (EHEC)-hly sequences. In Argentina, these strains occurred both in cattle and meat, and 50% of them carried stx2/stx2vh-a genes, whereas in Brazil the O157 strains were isolated from animals, and most harbored the stx2vh-a sequence. At least 13 different O:H serotypes were identified among the non-O157 strains studied, with serotype O113:H21 being found in both countries. All but one non-O157 strains did not carry eae gene, but EHEC-hlyA gene was found in 85.7% of them, and the stx2 genotype was also more prevalent in Argentina than in Brazil (P<0.01), where stx1 alone or in association was most common (68.8%). One STEC strain isolated from a calf in Brazil harbored the new variant referred to as stx2-NV206. PFGE analysis showed that STEC O157 strains were grouped in four clusters. One Brazilian strain was considered possibly related (≥80%) to Argentinean strains of cluster I. Differences in the pathogenic potential, especially in regard to serotypes and stx genotypes, were observed among the STEC strains recovered from animals and food in both countries. [Copyright &y& Elsevier]