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Background: Shiga toxin-producing Escherichia coli (STEC) infection is the most common cause of hemolytic uremic syndrome (HUS). Only few studies correlated serotypes and stx genotypes with disease severity. This study aimed to update STEC serotypes, stx genotypes, and virulence factors (eae and ehxA) in a cohort of patients with STEC-HUS and investigate whether they influence the severity of disease., Methods: In this multicentric study, children hospitalized between 2005 and 2016 with STEC-HUS confirmed by the National Reference Laboratory were included. Serotypes (O157, O145, O121, and others), stx genotypes (stx 1a , stx 2a , stx 2c, stx 2d , and others), and virulence factors were analyzed, and their association with dialysis requirement (>10 days); severe neurological, cardiovascular, and/or bowel involvement; and death was assessed., Results: The records of 280 patients were reviewed; 160 females, median age 21 months (IQR18m). STEC O157 was isolated in 206 (73.6%) patients, O145 in 47 (16.8%), O121 in 15 (5.4%), and other serotypes in 12 (4.2%). The stx 2a / 2c genotype was carried by 179 (63.9%) strains, stx 2a by 94 (33.6%), stx 1a /stx 2a by five (1.8%), and stx 1a only by two (0.7%). All strains except six harbored eae and ehxA genes. Fifty-nine (21.1%) patients had severe neurological involvement, 29 (10.4%) severe bowel injury, 14 (5%) cardiovascular involvement, 53 (18.9%) required > 10 days of dialysis, and 12 (4.3%) died. Neither serotypes nor stx genotypes detected were significantly linked to severity., Conclusions: Serotype O157 and virulence stx 2a/2c , eae, ehxA genotype are prevalent in Argentina, and no relationship was found between severity and serotypes and genotypes of STEC detected., (© 2021. IPNA.)

A quantitative risk assessment was developed for verocytotoxigenic Escherichia coli (E. coli VTEC) following hamburger consumption. The assessment considers initial contamination levels, cross-contamination and decontamination events during the cattle slaughter process and the distribution, storage and consumption patterns in Argentina and in similar countries in Latin-American. The model predicted an infection risk of 8.12x10(-7), a probability of Hemolytic Uremic Syndrome (HUS) of 4.6x10(-8) and a probability of mortality of 5.9x10(-9) per meal for adults. For children, the estimates per meal were 3.23x10(-7), 1.8x10(-8) and 6.31x10(-10) for infection, HUS and mortality, respectively. The risk of infection and HUS, were sensitive to the type of storage at home (r=-0.416), slaughterhouse storage temperature (r=0.240) and bacterial concentration in the cattle hide (r=0.239). There was an association between home preparation of hamburgers (r=-0.116) and the risk of illness, although this was a result of the type of storage at retail (r=-0.110) and at home and not their intrinsic characteristics. The most sensitive stages of the process were identified through the risk assessment and these can be used as a basis for measures of risk management.

One of the most frequent etiologic agents of Hemolytic Uremic Syndrome (HUS) is Escherichia coli O157H7, a microorganism that possesses virulence factors (Shiga-like Toxins I and II and adhesion fimbriae). The present study was set up to determine the relationship between HUS and the presence of Verotoxin in patients of "Niño Jesús" Children's Hospital. Tucumán, Argentina. 19 Children between 0 and 4 years old suffering from HUS (typical and atypical symptoms) and 15 control children of similar sex and age were selected. Presence of enterohemorrhagic E. coli was studied in both groups using molecular hybridization techniques. Free Verotoxin and Verotoxin-producing E. coli were analyzed in Vero cells. The following results were obtained: 1) The cytotoxic effect on Vero cells from fecal filtrates was observed in all children suffering from HUS 2) Verotoxin-producing E. coli was detected in only 12 of them 3) None of the filtrates of feces from control children presented a cytotoxic effect on Vero cells 4) In 8 of the patients suffering from HUS serotype O157H7 was isolated, in one O55K59 and in 3 typification of E. coli was not possible with the serums assayed 5) 77.5% of the strains isolated from HUS patients gave a positive molecular hybridization reaction, showing the following: Adhesion Fimbriae (AF) (25%); AF + Shiga-like Toxin I (13.75%); AF + Shiga-like Toxin II (20%); AF + Shiga-like Toxins I and II (41.25%). In patients suffering from atypical HUS a combination of AF + Shiga-like Toxins I and II was found. The 15 control children did not hybridize to the probes assayed. From the results obtained we may conclude that there exists a relationship between HUS and the presence of Verotoxin in the children suffering from HUS studied. The predominant serotype in our cases was O157H7 and Shiga-like Toxin II was found with highest frequency.

Argentina has an exceptionally high frequency of hemolytic-uremic syndrome (HUS). We sought to define prospectively the role of verocytotoxins (Shiga-like toxins [SLTs]) in 254 Argentinean children with grossly bloody diarrhea during spring and summer. Free fecal SLTs (I/II) and/or DNA probe-positive isolates were found in 99 (39%) of the children. During the follow-up period, HUS developed in 6 patients (4 with evidence of recent SLT infection based on stool studies); another 14 patients had some, but not all, of the abnormalities seen in typical HUS. The development of HUS or incomplete HUS in these children was significantly associated with recent SLT-Escherichia coli infection (p = 0.024). The high incidence of SLT-associated bloody diarrhea in Argentina explains, at least partially, the unusually high frequency of HUS. Our data indicate that incomplete forms of HUS may be common in patients with SLT-associated bloody diarrhea.

We conducted a prospective study in 87 household contacts of 51 children with hemolytic uremic syndrome to determine the frequency of infection with Shiga-like toxin-producing bacteria. Gastrointestinal tract symptoms occurred in only 1 of 87 contacts. Free fecal toxin was detected in 25 of 64 (39%) of the household members. Neutralization with specific antisera to Shiga-like toxins I and II (SLT-I, SLT-II) revealed that in 6 of these household contacts only SLT-I was present in stool, in 10 only SLT-II was present and in 9 both toxins were found. Thirty-three percent of the hemolytic uremic syndrome families in which 2 or more members were studied had more than 1 household member with free fecal toxin in stool. None of the household contacts was found to have E. coli O157:H7 in feces. Serum samples were available in 77 household contacts; 75% (58 of 77) had serum neutralizing titers of greater than or equal to 1:4 to 1 or both toxins. In those contacts for whom paired sera were available, seroconversion was found in 10 of 24 (42%). These data show that household contacts of children with hemolytic uremic syndrome are commonly colonized with Shiga-like toxin-producing E. coli and seroconversion to Shiga-like toxins occurs frequently in family members of children with hemolytic uremic syndrome.