OmpR coordinates the expression of virulence factors of Enterohemorrhagic Escherichia coli in the alimentary tract of Caenorhabditis elegans.

Enterohemorrhagic Escherichia coli (EHEC), an enteropathogen that colonizes in the intestine, causes severe diarrhea and hemorrhagic colitis in humans by the expression of the type III secretion system (T3SS) and Shiga-like toxins (Stxs). However, how EHEC can sense and respond to the changes in the alimentary tract and coordinate the expression of these virulence genes remains elusive. The T3SS-related genes are known to be regulated by the locus of enterocyte effacement (LEE)-encoded regulators, such as Ler, as well as non-LEE-encoded regulators in response to different environmental cues. Herein, we report that OmpR, which participates in the adaptation of E. coli to osmolarity and pH alterations, is required for EHEC infection in Caenorhabditis elegans. OmpR protein was able to directly bind to the promoters of ler and stx1 (Shiga-like toxin 1) and regulate the expression of T3SS and Stx1, respectively, at the transcriptional level. Moreover, we demonstrated that the expression of ler in EHEC is in response to the intestinal environment and is regulated by OmpR in C. elegans. Taken together, we reveal that OmpR is an important regulator of EHEC which coordinates the expression of virulence factors during gastrointestinal infection in vivo.

Shiga Toxin Therapeutics: Beyond Neutralization.

Ribotoxic Shiga toxins are the primary cause of hemolytic uremic syndrome (HUS) in patients infected with Shiga toxin-producing enterohemorrhagic Escherichia coli (STEC), a pathogen class responsible for epidemic outbreaks of gastrointestinal disease around the globe. HUS is a leading cause of pediatric renal failure in otherwise healthy children, resulting in a mortality rate of 10% and a chronic morbidity rate near 25%. There are currently no available therapeutics to prevent or treat HUS in STEC patients despite decades of work elucidating the mechanisms of Shiga toxicity in sensitive cells. The preclinical development of toxin-targeted HUS therapies has been hindered by the sporadic, geographically dispersed nature of STEC outbreaks with HUS cases and the limited financial incentive for the commercial development of therapies for an acute disease with an inconsistent patient population. The following review considers potential therapeutic targeting of the downstream cellular impacts of Shiga toxicity, which include the unfolded protein response (UPR) and the ribotoxic stress response (RSR). Outcomes of the UPR and RSR are relevant to other diseases with large global incidence and prevalence rates, thus reducing barriers to the development of commercial drugs that could improve STEC and HUS patient outcomes.

Inhibitors of retrograde trafficking active against ricin and Shiga toxins also protect cells from several viruses, Leishmania and Chlamydiales.

Medical countermeasures to treat biothreat agent infections require broad-spectrum therapeutics that do not induce agent resistance. A cell-based high-throughput screen (HTS) against ricin toxin combined with hit optimization allowed selection of a family of compounds that meet these requirements. The hit compound Retro-2 and its derivatives have been demonstrated to be safe in vivo in mice even at high doses. Moreover, Retro-2 is an inhibitor of retrograde transport that affects syntaxin-5-dependent toxins and pathogens. As a consequence, it has a broad-spectrum activity that has been demonstrated both in vitro and in vivo against ricin, Shiga toxin-producing O104:H4 entero-hemorrhagic E. coli and Leishmania sp. and in vitro against Ebola, Marburg and poxviruses and Chlamydiales. An effect is anticipated on other toxins or pathogens that use retrograde trafficking and syntaxin-5. Since Retro-2 targets cell components of the host and not directly the pathogen, no selection of resistant pathogens is expected. These lead compounds need now to be developed as drugs for human use.

Perspectives on Shiga-like Toxin Infections in Argentina †.

Argentina has the highest frequency of hemolytic uremic syndrome (HUS) in the world (300 cases/year). The risk of HUS in children from 6 to 48 months old is approximately 22/100,000 in Buenos Aires. In Argentina, HUS is the most frequent cause of acute renal damage and the second cause of chronic renal injury in children. We have shown that during the spring/summer season, the incidence of Shiga-like toxin (SLT)-associated bloody diarrhea in children less than 5 years old is 30 to 39%. The risk of HUS in SLT-associated bloody diarrhea is about 4 to 5%; 14% of children with SLT diarrhea developed incomplete HUS. Household contacts of children with HUS are commonly colonized with SLT-producing Escherichia coli (39%), and seroconversion occurs in 42% of these. No evidence of free fecal SLTs was observed in healthy children. In Argentina E. coli serotype O157:H7 has been associated with only 2 to 18% of HUS patients and in 4.5 to 7% of children with bloody diarrhea. Other serotypes were also recognized. About 20% of Argentine children start to eat meat at 5 months old, and 80% of them have meat in their diets at least three times a week. Eighty percent of the meat consumed is undercooked. Few data about the incidence of SLT-producing E. coli in cows in our country are available. E. coli O157:H7 was isolated in only 7.7% of calves aged 1 to 3 weeks with E. coli bacillosis from different farms in Argentina. Preliminary data show that SLT-producing E. coli were also present in stools from healthy animals and in fresh retail ground beef, determined by polymerase chain reaction.

Detection of Shiga-Like Toxin-Producing Escherichia coli in Ground Beef and Milk by Commercial Enzyme Immunoassay.

Shiga-like toxin (SLT)-producing Escherichia coli (SLTEC) is the leading cause of acute renal failure among children. SLTEC are most commonly ingested from contaminated food, and because cattle are a major reservoir, ground beef and milk have been a significant source of contamination associated with multiperson outbreaks. While serotype O157:H7 has been principally identified in the United States there are many other SLTEC serotypes associated with human disease. We have therefore examined the utility of an enzyme immunoassay (EIA) for Shiga-like toxins as a means of detecting the presence of low levels of multiple SLTEC serotypes in ground beef and milk. In the present study we demonstrated that it is possible to detect low levels (approximately 1 SLTEC per g of ground beef) in both small-scale (2 g of beef per 5 ml) and standard large-scale (25 g of beef per 225 ml) food microbial cultures. The EIA was also capable of allowing detection of SLTEC in nonspiked retail ground beef samples: we were able to recover SLTEC isolates (O113:Hu; O22:H-; O82:H8) from 3 of 12 ground beef samples. The EIA detected SLTs produced in spiked milk samples when as few as 1 SLTEC per ml was added. Overall the EIA proved to be a highly sensitive way to detect the presence of SLTEC in either ground beef or milk samples after overnight enrichment culturing in an appropriate broth and should provide a rapid and convenient method for the detection of multiple pathogenic SLTEC serotypes.

Growing Concerns and Recent Outbreaks Involving Non-O157:H7 Serotypes of Verotoxigenic Escherichia coli.

Verocytotoxin-producing E. coli (VTEC) of serotype O157:H7 have been shown to be important agents of foodborne disease in humans worldwide. While the majority of research effort has been targeted on this serotype it is becoming more evident that other serotypes of VTEC can also be associated with human disease. An increasing number of these non-O157:H7 VTEC have been isolated from humans suffering from HUS and diarrhea. Recently a number of foodborne outbreaks in the USA, Australia, and other countries have been attributed to non-O157:H7 VTEC serotypes. Surveys of animal populations in a variety of countries have shown that the cattle reservoir contains more than 100 serotypes of VTEC, many of which are similar to those isolated from humans. The diversity and complexity of the VTEC family requires that laboratories and public health surveillance systems have the ability to detect and monitor all serotypes of VTEC.

Escherichia coli O157: H7: Overview of Clinical and Epidemiological Issues.

Escherichia coli O157:H7 is an important and common human pathogen which causes diarrhea, bloody diarrhea (hemorrhagic colitis) and the life threatening post-diarrheal disorder, hemolytic uremic syndrome (HUS). Escherichia coli O157:H7 produces one or two potent cytotoxins, designated Shiga-like toxins (or verocytotoxins) I and II. While additional serotypes of cytotoxin-producing E. coli may cause human disease, E. coli O157:H7 is the most important such enteric pathogen in the United States. Epidemiologic data suggest that the incidence of hemolytic uremic syndrome is probably increasing. Until data emerge from controlled studies, conservative management of infected patients remains the mainstay of therapy, rather than specific antibacterial or antitoxin therapy. The serious nature of illness caused by E. coli O157:H7 should make prevention of human infection with this pathogen a high priority for the food industry.