Characterization of Urinary Tract Infection-Associated Shiga Toxin-Producing Escherichia coli (original) (raw)
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Clinical Infectious Diseases, 2008
Attaching and effacing Escherichia coli (AEEC) that lack Shiga toxin genes (stx) and the enteropathogenic E. coli adherence factor (EAF) plasmid (stx-/EAF-) are classified as atypical enteropathogenic E. coli and cause diarrhea worldwide. However, it is unknown whether there are bacterial lineage-specific human disease phenotypes. We compared stx-/EAF- AEEC recovered from patients (mostly children) with bloody and nonbloody diarrhea. stx-/EAF- AEEC were isolated using eae colony blot hybridization and were serotyped, tested (by polymerase chain reaction) for putative virulence genes, and analyzed for phylogenetic relationships by use of multilocus sequence typing. During the period 1995-2007, stx-/EAF- AEEC were isolated as the only bacterial pathogens from stool specimens obtained from 18 (15.3%) of 118 patients with bloody diarrhea and from 141 (1.3%) of 10,550 patients with nonbloody diarrhea (P<.001). All but 1 of 18 strains recovered from patients with bloody diarrhea resembled enterohemorrhagic E. coli (EHEC) on the basis of serotypes, non-stx virulence profiles, and multilocus sequence types. In contrast, most (75.9%) of 141 stx-/EAF- AEEC recovered from patients with nonbloody diarrhea belonged to other serotypes and differed from the former strains phylogenetically and with regard to virulence genes. Three of 18 patients with bloody diarrhea and none of 141 patients with nonbloody diarrhea who shedded stx-/EAF- AEEC developed hemolytic uremic syndrome. Most stx-/EAF- AEEC associated with bloody diarrhea are plausibly EHEC that lost Shiga toxin during infection (EHEC-LST). To prevent serious complications of such infections, Shiga toxin-independent diagnostic strategies to accurately and rapidly identify such patients should be developed and applied. Multilocus sequence typing has potential to distinguish EHEC-LST from less pathogenic stx-/EAF- AEEC.
Shiga Toxin–producing Escherichia coli Strains Negative for Locus of Enterocyte Effacement
Emerging Infectious Diseases, 2009
Most Shiga toxin-producing Escherichia coli (STEC) infections that are associated with severe sequelae such as hemolytic uremic syndrome (HUS) are caused by attaching and effacing pathogens that carry the locus of enterocyte effacement (LEE). However, a proportion of STEC isolates that do not carry LEE have been associated with HUS. To clarify the emergence of LEE-negative STEC, we compared the genetic composition of the virulence plasmids pO113 and pO157 from LEE-negative and LEE-positive STEC, respectively. The complete nucleotide sequence of pO113 showed that several plasmid genes were shared by STEC O157:H7. In addition, allelic profi ling of the ehxA gene demonstrated that pO113 belongs to a different evolutionary lineage than pO157 and that the virulence plasmids of LEEnegative STEC strains were highly related. In contrast, multilocus sequence typing of 17 LEE-negative STEC isolates showed several clonal groups, suggesting that pathogenic LEE-negative STEC has emerged several times throughout its evolution.
Revista Argentina de microbiología
STEC strains can infect extra-intestinal sites such as the human urinary tract and sometimes cause severe complications. We report two cases of urinary tract infection caused by STEC in two elderly women with comorbidities. Although both strains belonged to the O157:H7 serotype and carried genes associated with severe illness, none of the patients developed hemolytic uremic syndrome (HUS). These findings provide additional evidence for the presence of these agents in our country and in the region, and highlight the need to maintain an active surveillance system of HUS cases, placing special emphasis on the study of other sites of infection in patients with non-diarrheal HUS.
International Journal of Food Microbiology, 2010
A micro-array has been developed, based on the GeneDisc ® array, for the genetic identification of 12 O-types and 7 H-types of Shiga toxin-producing Escherichia coli (STEC) including the most clinically relevant enterohemorrhagic E. coli (EHEC) serotypes. The genes selected for determination of the O antigens (rfbE O157 , wzx O26 , wzx O103 , wbd1 O111 , ihp1 O145 , wzx O121 , wzy O113 , wzy O91 , wzx O104 , wzy O118 , wzx O45 , and wbgN O55) and H-types (fliC H2 , fliC H7 , fliC H8 , fliC H11 , fliC H19 , fliC H21 , and fliC H28) showed a high specificity and concordance with serology. The micro-array also had a high specificity for EHEC-associated virulence factors, including Shiga toxins 1 and 2 (stx1 and stx2), intimin (eae), enterohemolysin (ehxA), serine protease (espP), catalase peroxidase (katP), the type II secretion system (etpD), subtilase cytotoxin (subA), autoagglutinating adhesin (Saa) and type III secreted effectors encoded in the genomic islands OI-122 (ent/espL2, nleB, and nleE) and OI-71 (nleF, nleH1-2, and nleA). The eae gene was detected in all typical EHEC strains, and the pattern of nle genes encoded in OI-71 and OI-122 was found to be closely associated with certain serotypes of typical EHEC and emerging EHEC strains. Virulence plasmid associated genes such as katP, espP, and etpD were more common in EHEC than in STEC strains; this supports their association with virulence. This array constitutes a valuable approach for the identification of STEC strains with a high potential for human virulence.
Journal of clinical microbiology, 1999
Associations between known or putative virulence factors of Shiga toxin-producing Escherichia coli and disease in humans were investigated. Univariate analysis and multivariate logistic regression analysis of a set of 237 isolates from 118 serotypes showed significant associations between the presence of genes for intimin (eae) and Shiga toxin 2 (stx2) and isolates from serotypes reported in humans. Similar associations were found with isolates from serotypes reported in hemorrhagic colitis and hemolytic-uremic syndrome. The enterohemorrhagic E. coli (EHEC) hemolysin gene was significantly associated with isolates from serotypes found in severe diseases in univariate analysis but not in multivariate logistic regression models. A strong association between the intimin and EHEC-hemolysin genes may explain the lack of statistical significance of EHEC hemolysin in these multivariate models, but a true lack of biological significance of the hemolysin in humans or in disease cannot be exc...