Shiga (Vero)-toxigenic Escherichia coli: epidemiology, virulence and disease.
Shiga-toxigenic Escherichia coli (STEC), also known as Verotoxigenic E. coli (VTEC), are a toxin-producing subset of a normally commensal enteric bacterium. This subset is recognised to be a significant contributor to diarrhoeal disease worldwide. Much of the epidemiological and diagnostic effort regarding STEC is directed towards serogroup O157, because of its common association with severe forms of gastrointestinal disease, including haemorrhagic colitis (HC), and extra-intestinal disease, such as haemolytic uraemic syndrome (1, 2).
In recent years, international researchers and surveillance networks have noted increases in the number of cases of diarrhoea and more severe symptoms caused by STEC belonging to serogroups other than O157 (collectively referred to as 'non-O157') (3). Non-O157 STEC contribute to a significant proportion of STEC-related illness in developed countries (4), with some strains considered to have a pathogenic potential comparable to that of the most virulent O157 serotype, O157:H7 (4, 5). Much of the disease burden presented by non-O157 E. coli remains under-reported in many countries (2, 3), mainly due to limitations in popular diagnostic techniques to detect these serotypes (4, 5). However, this is changing with the introduction of molecular assays targeting Stx genes (4). E. coli O157:H7 related disease is notifiable in New Zealand, and national data accumulated since the first case in 1993 indicates that the incidence of all reported STEC has been steadily increasing, as shown in Figure 1 (6).
The purpose of this review is to trace the history of STEC, describe the relationship between major virulence factors and pathology, comment on disease course and current therapy, and discuss the epidemiology of these pathogens in New Zealand and elsewhere, highlighting distinctive differences.
Many major E. coli pathotypes have emerged overtime through the transfer of virulence factors from other bacterial species by way of mobile genetic elements such as pathogenicity islands, transposons, and plasmids (7). The different pathotypes associated with human diarrhoea have been extensively reviewed by Croxen et al (8) and are summarised in Table 1. There is uneven geographical distribution of some of these pathotypes; for example, enterotoxigenic E. coli (ETEC) are particularly problematic in developing countries (8). On the other hand, STEC have been reported to occur world-wide (9).
The role of STEC in human health emerged in 1983, when Karmali et al (10), discovered a substance acutely lethal to African green monkey kidney (Vero) cells in the filtered stools of children suffering from haemolytic uraemic syndrome. Vero cytotoxic E. coli recovered from patient stool samples belonged to semigroups O26, O111, O113 and O157 (10). This study was published in the same year as another investigation by Riley et al, where an unusual serotype of E. coli, expressing the somatic (O) antigen 157 and the flagellar (H) antigen 7, was reckoned to be the cause of bloody diarrhoea (11). Subsequent investigations confirmed the link between STEC infection and cases of diarrhoea, haemorrhagic colitis, haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura (12), and also revealed there are two main types of Shiga toxin, Stx1 and Stx2. Stx1 is antigenically similar to Shiga toxin produced by Shigella dysenteriae while Stx 2 is less closely related and antigenically distinct (12). The genes encoding these toxins (stx1 and stx2) appearto be highly mobile.
According to Law (13), STEC O157:H7 arose from the enteropathogenic serotype E. coli (EPEC) O55:H7. The chromosomes of enteropathogenic E. coli encode the cell adhesin intimin, a virulence factor also important in STEC. Originally, an E. coli O55:H7 is believed to have been infected with a stx2 carrying bacteriophage (a virus which can infect bacteria) then later acquired the large virulence plasmid pO157 and a gene encoding the O157 antigen. This progenitor is thought to have divided into two lineages: 1. non-motile, sorbitol fermenting Stx 2 producing strains seen in Germany and parts of Eastern Europe; 2. sorbitol non-fermenting strains producing both Stx1 and Stx2, the former toxin having crossed over from Shigella dysenteriae. The next step along the evolutionary pathway was the loss of the enzyme beta-glucuronidase to give the common beta-glucuronidase/MUG negative, sorbitol non-fermenting O157:H7 clone. Non-O157 STEC have not been so extensively studied, but from the wide diversity of E. coli semigroups found to harbour Stx, it can be surmised that transfer of stx by bacteriophages is a common event and occurred quite recently in an O104:H4 strain (13,14). Although the timescale for these events is not known, a large, post-war outbreak of diarrhoea with symptoms of haemolytic uraemic syndrome in the USA suggests they occurred prior to the 1950s (15).
VIRULENCE AND PATHOLOGY
In STEC, Stx1 and Stx2 are encoded on two mobile genetic elements (H19B and 933W, respectively) derived from bacteriophages (16). These prophages have the ability to insert themselves into the chromosomal DNA of E. coli through the action of recombinase enzymes (17). The prophages permit the host E. coli to express Stx and can also multiply and excise themselves from E. coli genomes (18-20). The toxins expressed form a protein complex composed of two subunits; a single A subunit attached to five identical B subunits (21). The B subunit pentamer component of the toxin binds to glycosphingolipid globotriosylceramide (Gb3) receptors of absorptive villi and Paneth cells in the mammalian intestine, and globotetraosylceramide (Gb4) surface receptors in renal glomerular cells and brain endothelia (18, 21-23). Binding by B subunits promotes the internalisation of the toxin complex in an early endosome. A proposed alternative route for Stx entry is through bacterial invasion of the host cell (24). From the endosome, the toxin is transported to the trans-Golgi network, then through the Golgi apparatus to the endoplasmic reticulum, where the released A subunit induces a number of host cell responses including inhibition of protein synthesis, apoptosis (programmed cell death), autophagy (degradation of cellular components) and increases in chemokine and cytokine production (21, 23, 24) (Figure 2). The toxins cause bloody and non-bloody diarrhoea through the killing of intestinal endothelial cells either directly, or indirectly through inducing mesenteric ischaemia in the regional vasculature (2). The toxins are also able to translocate across the gastrointestinal endothelia and enter the systemic circulation, causing a host of pathological thrombotic and immunomodulatory effects on both the renal glomerulus and systemic microvasculature (21, 23). The mechanism by which the toxins traverse to the circulation is unknown (25), and the systemic effects are not usually accompanied by bacteraemia (26).
Stx2 has at least a 100-fold higher toxicity against renal endothelial cells than Stx1 (1,21) due to differences in the DNA sequences encoding the toxin components (27). As a result, Stx2 is the variant most often associated with clinical cases of STEC and the progression of such cases to haemorrhagic colitis and haemolytic uraemic syndrome (21,27). Stx2 is also noted to have a number of subvariants (Stx2, stx2c2, stx2d, stx2e, and stx2f) each with varying toxicity (28, 29). Perhaps unsurprisingly, O157 serotypes associated with clinical symptoms are generally found to produce Stx2, usually in preference to Stx1. Stx2 may occur in other semigroups but the frequency is lower than Stx1 (27, 30, 31).
A virulence factor that STEC and EPEC can have in common is the adherence factor intimin, which has the encoding sequence eaeA. Intimin is a bacterial outer membrane protein encoded within a chromosomal pathogenicity island referred to as the Locus of Enterocyte Effacement (LEE) (1). The LEE encodes a syringe-like type III secretion system, capable of injecting over 50 bacterial effector proteins directly into the cytosol of the human host cell (21, 32). In strains possessing LEE, intimin anchors bacteria to host cells (33, 34) facilitating injection of the effector proteins. These reshape the actin cytoskeleton of intestinal epithelial cells to form characteristic 10 pm pedestal formations on the cell surface, as shown in Figure 3 (33, 35). The close bacterium/host cell association formed by the components of the LEE mechanism are recognised to greatly aid in the delivery of Stx to enterocytes and the underlying mesenteric vasculature (33). Most of the strains isolated from outbreaks of haemorrhagic colitis and haemolytic uraemic syndrome, and those infections with more severe symptoms, typically express both Stx and intimin along with carriage of pO157 (30, 31, 36), and are usually designated as the pathotype enterohaemorrhagic E. coli (EHEC) (37). The tendency for haemolytic uraemic patients to form strong antibody responses to intimin and other LEE components underscores the importance of the adhesion determinant in advanced STEC infections (32).
The high virulence of serotype O157:H7 is attributed to Stx2 production, LEE and accessory virulence factors carried on a plasmid, pO157 (21,38). pO157 encodes putative virulence factors such as proteases, enterohaemolysin (ehx) and cell adhesins on a heterogeneous mix of prophages, transposons and genetic elements thought to have evolved to aid intestinal colonisation in cattle (21, 32, 39). However, haemolytic uraemic syndrome-causing strains do not consistently have the full complement of known virulence factors (37). A second large plasmid, pO113, is believed to encode other virulence factors which may allow LEE negative STEC to cause haemolytic uraemic syndrome (40).
DISEASE COURSE AND THERAPY
Due to the confluence of host and virulence factors, the clinical spectrum of STEC is appreciably broad and patient outcomes may be difficult to predict. Symptoms can range from asymptomatic or subclinical (and hence unreported) diarrhoea to severe haemorrhagic and neurological complications and death. Clinical cases of STEC infection typically present as self-limiting, with painful abdominal cramps and non-bloody diarrhoea that occur 1-8 days post ingestion (35, 41), but may progress to bloody diarrhoea without fever or raised leucocyte count after a further 2-7 days (21, 35). The progression to haemorrhagic colitis and haemolytic uraemic syndrome is difficult to predict (19), but is especially frequent in children <10 years of age (35, 42), the immunocompromised and the elderly, with the highest rates associated with EHEC ([stx.sup.+], [eaeA.sup.+]) and particularly O157 serotypes (21, 35). The rate of progression to haemorrhagic colitis and haemolytic uraemic syndrome is generally 10-15%, although this is subject to patient factors, the accessory virulence factors present, and the Stx variant expressed (18, 42, 43). Haemolytic uraemic syndrome is characterised by the onset of microangiopathic anaemia (damaged erythrocytes), thrombocytopenia and may be accompanied in adults by thrombotic thrombocytopenic purpura (a diffuse formation of microangiopathic thrombi, often with concurrent neurological abnormalities) (12, 44). Haemolytic uraemic syndrome is the clinical manifestation of Stx-induced damage of the kidney glomerular vasculature, and may even result in long term sequelae such as renal insufficiency and neurological aberrations (35). Overall, 3-5% of cases are fatal (21).
Generally, non-O157 infections have a milder course than that of O157:H7. In the latter, diarrhoea has a greater likelihood of being bloody (>90% chance with O157 vs 60%), abdominal cramping is usually more severe, and the need for hospitalisation (43% vs 18%) and progression to haemolytic uraemic syndrome (10-15% vs <10%) is more pronounced (3). Combined eae and stx2 carriage is regarded as a stronger predictor for bloody diarrhoea and haemolytic uraemic syndrome than the presence of serogroup O157 (45). The haemolytic uraemic syndrome that accompanies severe STEC infection can mimic other intestinal diseases such as Crohn's disease and induce elevated faecal calprotectin levels, while chronic STEC infections may result in irritable bowel syndrome (IBS) (21). Many physicians have an incomplete understanding of STEC infection and do not consider non-O157:H7 infection as part of a differential diagnosis (46). The clinical presentation of STEC infection may also potentially lead to confusion with other gastrointestinal disorders such as intussusception, appendicitis, inflammatory bowel disease (IBD), or infection with Clostridium, Shigella, Yersinia, Salmonella, or Campylobacter species (12, 19, 47, 48).
Treatments options for STEC infections are largely supportive, as antibiotics that induce DNA damage in E. coli have a tendency to activate a lysogenic SOS response in the Shiga prophage and cause upregulation of the expression of Stx (29). As a result, treatments involving quinolones, ciprofloxacin, in addition to anti-motility agents, are contraindicated in STEC infection, having been associated with increased incidences of progression to haemolytic uraemic syndrome (21, 26, 49). Parenteral volume expansion with liberal amounts of intravenous fluids (21, 50), particularly in conjunction with peritoneal dialysis is the recommended course for advanced cases of STEC infection (19, 25). Early administration of the monoclonal anti-Shiga toxin antibody Eculizumab is also recognised to increase platelet counts and limit toxin-mediated neurological effects (25, 50). The development of vaccines capable of stimulating a strong antibody response against pathogenic E. coli antigens such as intimin (29, 51), is currently ongoing, albeit hampered by the difficulty in finding an appropriate animal model (35).
The global impact of STEC infection is difficult to estimate because of inconsistencies in reporting methods between countries and the varying prevalence of detected and undetected serotypes within such countries. A recent estimate, a meta-analysis of papers and databases of 21 countries, places the global number of acute STEC infections at approximately 2.8 million per year, with an estimated 3890 cases of haemolytic uraemic syndrome, 270 cases of end-stage renal disease, and 230 mortalities (52). STEC infections are usually sporadic and generally affect children and the elderly, with the typical source of infection being the ingestion of contaminated foodstuffs (35). The natural reservoir of STEC is the intestine and rectum of cattle, and the contamination of processed beef carcasses combined with modern mass distribution is recognised as the classic cause of larger outbreaks (1, 53, 54). STEC may also be carried by a variety of farmyard animals including sheep, goats, chickens, pigs and deer, with outbreaks traced to contact with these animals or consumption of improperly prepared foodstuffs (42, 55, 56).
World-wide, STEC outbreaks have also been associated with person-to-person spread, as well as contaminated or unpasteurised milk, juice, sprouts and other vegetables (43). The durability of STEC in bovine faecal matter and groundwater is thought to permit the spread of STEC to mass-produced crops via effluent run-off and exposures through environmental water sources (29, 51, 57, 58). Perhaps the most notable case of an outbreak of STEC infection was the 2011 O104:H4 outbreak in Germany, involving an especially virulent strain of non-O157 E. coli that caused over 4000 STEC illnesses, 908 cases of haemolytic uraemic syndrome and 90 deaths (49). The source of infection was ultimately traced to a batch of contaminated fenugreek sprouts (49), and although the strain did not employ intimin as its primary attachment factor (59), the outbreak served to highlight the contribution of non-O157 STEC to human disease in developed countries. Non-O157 STEC infection is usually dominated by the semigroups 026, 045, O103, O111, O121 and O145, which together typically comprise -70% of the non-O157 STEC infections in many countries and are well represented amongst isolates retrieved from sufferers of haemolytic uraemic syndrome, thrombotic thrombocytopenic purpura and bloody diarrhoea (27, 31). These semigroups, known as the 'Big 6' possess many of the virulence factors and associations to complicated enteric disease seen in O157:H7 strains (5), although the dominant strain may vary from country to country (Table 2).The contribution of the 'Big 6' to STEC disease is noted to be underreported (3), and international data suggests that the proportion of STEC disease caused by non-O157 semigroups is increasing (3, 4, 60, 61). It's important to note that semigroup alone is not a determinant of virulence as carriage of virulence genes varies between strains ofthe same semigroup.
In New Zealand, the annual notification rate for all STEC infection has been increasing since 1997, with the highest number notified in the most recent Annual Surveillance Report produced by Environmental and Science Research (330 cases; 7.2/100,000 population) (6). However, this significant increase is most probably due to the introduction of PCR screening of all faecal samples in an Auckland laboratory (Figure 1) (6). Most STEC cases are unrelated or occur in small outbreaks confined to a family or geographic region with exposure to contaminated farmland or private water supplies as primary risk factors (62). Infection peaks in the summer months when outdoor activities increase (63). ESR identified common risk factors in 2015 as contact with pets, farm animals and manure (6).
The Enteric Reference Laboratory at ESR identified 53% of received STEC isolates as serotype O157:H7 in 2015, with the remainder confirmed as non-O157 E. coli (29.3%) or of undetermined serotype (17.7%) (6). In a recent qPCR study of over 500 diarrhoeic stool samples received by Southern Community Laboratories, Dunedin, the only STEC semigroups detected using molecular techniques were O103 and O157 (both in two patients). A further six stool samples from six patients were positive for stx but non-typable, indicating they did not belong to semigroup O157 or any of the 'Big 6' (63). This lack of dominance of the 'Big 6' semigroups among non-O157 STEC is compatible with previous studies of human cases, STEC types found in in retail meat and animal carriage and is likely related to agricultural practices in New Zealand (64-67).
E. coli O157:H7 was the first STEC to be discovered but it is now clear that non-O157 STEC are capable of causing disease, which can be severe if they produce Stx2 and encode intimin or other cell adherence factors. The roles of Stx, intimin and accessory gene products have been well described and a clear link to the pathology and clinical manifestations established. However, the virulence genotype(s) of the enterohaemorrhagic subset, EHEC, has not been fully defined and STEC strains are designated as EHEC mainly based on clinical associations. Some of the prophages encoding stx are able to infect other E. coli. This, and the potential mobility of other virulence factors, points to future evolutionary changes in the STEC pathotype (68). An example of this type of horizontal gene transfer is provided by the O104:H4 enteroaggregative E. coli strain, which acquired stx and caused a massive outbreak of illness in Europe, including haemolytic uraemic syndrome (69).
Compared to most other countries, there are distinctive differences in NZ with regard to the dominant risk factors and semigroups of non-O157 STEC. Elsewhere in the world food is the most significant transmission vehicle for O157 and the 'Big 6' semigroups, but in New Zealand STEC infection occurs with a greater diversity of semigroups mainly through contact with contaminated agricultural environments or animals. So far, New Zealand has not experienced the large STEC outbreaks seen in other countries, probably because of differences in food production and/or regulation of the industry. With few treatment options available, STEC represent an important and previously underestimated pathogen group. Due to the varying clinical picture, diagnosis can be difficult but it is anticipated that the adoption of molecular diagnostic techniques for STEC detection will lead to correct diagnosis and better reflect the true incidence of STEC infection.
Rowan Thomas thanks the University of Otago and Dunedin Basic Medical Sciences for Masters and Sandy Smith scholarships respectively. The authors thank Douglas McComish for construction of Figure 2 and the Otago Centre for Electron Microscopy for electron micrograph images (Figure 3).
Rowan R Thomas, BMLSc MMLSc 
Mabel LH Gaastra, BSc PGDipSci, Medical Student 
Heather JL Brooks, BSc(Hons) PhD, Senior Lecturer and Course Director for Medical Laboratory Science 
 Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago
 Dunedin School of Medicine, University of Otago
 Department of Pathology, Dunedin School of Medicine, University of Otago
Correspondence: Dr Heather Brooks, Department of Pathology, University of Otago, PO Box 913, Dunedin 9054, New Zealand.
(1.) Mainil JG, Daube G. Verotoxigenic Escherichia coli from animals, humans and foods: who's who? J Appl Microbiol 2005; 98: 1332-1344.
(2.) Tarr PI, Gordon CA, Chandler WL. Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome. Lancet 2005; 365: 1073-1086.
(3.) Gould LH, Mody RK, Ong KL, Clogher P, Cronquist AB, Garman KN, et al. Increased recognition of non-O157 Shiga toxin-producing Escherichia coli infections in the United States during 2000-2010: epidemiologic features and comparison with E. coli O157 infections. Foodborne Pathog Dis 2013; 10: 453-460.
(4.) Johnson KE, Thorpe CM, Sears CL. The emerging clinical importance of non-O157 Shiga toxin-producing Escherichia coli. Clin Infect Dis 2006; 43: 1587-1595.
(5.) Kobayashi N, Lee K, Yamazaki A, Saito S, Furukawa I, Kono T, et al. Virulence gene profiles and population genetic analysis for exploration of pathogenic semigroups of Shiga toxin-producing Escherichia coli. J Clin Microbiol 2013; 51: 4022-4028.
(6.) Annual Surveillance Report. The Institute of Environmental Science and Research Ltd. Notifiable Diseases in New Zealand: Annual Report 2015, Porirua, New Zealand.
(7.) Buvens G, Pierard D. Virulence profiling and disease association of verocytotoxin-producing Escherichia coli O157 and non-O157 isolates in Belgium. Foodborne Pathog Dis 2012; 9: 530-535.
(8.) Croxen MA, Law RJ, Scholz R, Keeney KM, Wlodarska M, Finlay BB. Recent Advances in understanding enteric pathogenic Escherichia coli. Clin Microbiol Rev 2013; 26: 822-880.
(9.) Majowicz SE, Scallan E, Jones-Bitton A, Sargeant JM, Stapleton J, Angulo FJ et al. Global incidence of human shiga toxin-producing Escherichia coli Infections and Deaths: A systematic review and knowledge synthesis Foodborne Pathog Dis 2014; 11: 447-455.
(10.) Karmali MA, Petrie M, Lim C, Fleming PC, Steele BT. Escherichia coli cytotoxin, haemolytic-uraemic syndrome, and haemorrhagic colitis. Lancet 1983; 2: 1299-1300.
(11.) Riley LW, Remis RS, Helgerson SD, McGee HB, Wells JG, Davis BR, et al. Hemorrhagic colitis associated with rare Escherichia coli serotype. N Engl J Med 1983; 308: 681-685.
(12.) Tarr PI. Escherichia coli O157:H7: Clinical, diagnostic and epidemiological aspects of human infection. Clin Infect Dis 1995; 20: 1-8.
(13.) Law D. The history and evolution of Escherichia coli O157 and other Shiga toxin-producing E. coli. World J Microbiol Biotechnol 2000; 16: 701-709.
(14.) Kaper JB, O'Brien AD. Overview and historical perspectives. Microbiol Spectr 2014; 2: doi:10.1128/microbiolspec.EHEC-0028-2014.
(15.) Johnson RP, Clarke RC, Wilson JB, Read SC, Rahn K, Renwick SA, et al. Growing concerns and recent outbreaks involving non-O157:H7 serotypes of vero-toxigenic Escherichia coli. J Food Prot 1996; 59: 1112-1122.
(16.) Strockbine N, Marques LRM, Newland JW, Smith HW, Holmes RK, O'Brien A. Two toxin-converting phages from Escherichia coli O157:H7 strain 933 encode antigenically distinct toxins with similar biologic activites. Infect Immun 1986; 53: 135-140.
(17.) Herold S, Karch H, Schmidt H. Shiga toxin-encoding bacteriophages-genomes in motion. Int J Med Microbiol 2004; 294: 115-121.
(18.) Melton-Celsa A, Mohawk K, Teel L, O'Brien A. Pathogenesis of Shiga-toxin producing Escherichia coli. Curr Top Microbiol Immunol 2012; 357: 67-103.
(19.) Thorpe CM. Shiga toxin-producing Escherichia coli infection. Clin Infect Dis 2004; 38: 1298-1303.
(20.) Wagner PL, Livny J, Neely MN, Acheson DWK, Friedman Dl, Waldor MK. Bacteriophage control of Shiga toxin 1 production and release by Escherichia coli. Mol Microbiol 2002; 44: 957-970.
(21.) Ho NK, Henry AC, Johnson-Henry K, Sherman PM. Pathogenicity host responses and implications for management of enterohemorrhagic Escherichia coli O157:H7 infection. J Gastroenterol 2013; 27: 281-285.
(22.) Croxen MA, Finlay BB. Molecular mechanisms of Escherichia coli pathogenicity. Nat Rev Microbiol 2010; 8: 26-38.
(23.) Sears CL, Kaper JB. Enteric bacterial toxins: Mechanisms of action and linkage to intestinal secretion. Microbiol Rev 1996; 60: 167-215.
(24.) Lee M-S, Koo S, Jeong DG, Tesh VL. Shiga toxins as multifunctional proteins: induction of host cellular stress responses, role in pathogenesis and therapeutic applications Toxins (Basel) 2016; 8: 77; doi:10.3390/ toxins8030077.
(25.) Trachtman H, Austin C, Lewinski M, Stahl RA. Renal and neurological involvement in typical Shiga toxin-associated HUS. Nat Rev Nephrol 2012; 8: 658-669.
(26.) Ibarra C, Amaral MM, Palermo MS. Advances in pathogenesis and therapy of hemolytic uremic syndrome caused by Shiga toxin-2. IUBMB Life 2013; 65: 827-835.
(27.) Eklund M, Leino K, Siitonen A. Clinical Escherichia coli strains carrying stx genes: Stx variants and stx-positive virulence profiles. J Clin Microbiol 2002; 40: 4585-4593.
(28.) de Sablet T, Bertin Y, Vareille M, Girardeau JP, Garrivier A, Gobert AP, et al. Differential expression of stx2 variants in Shiga toxin-producing Escherichia coli belonging to seropathotypesAand C. Microbiology 2008; 154: 176-186.
(29.) Serna IV A, Boedeker EC. Pathogenesis and treatment of Shiga toxin-producing Escherichia coli infections. Curr Opin Gastroenterol 2008; 24: 38-47.
(30.) Anjum MF, Jones E, Morrison V, Tozzoli R, Morabito S, Toth I, et al. Use of virulence determinants and seropathotypes to distinguish high- and low-risk Escherichia coli O157 and non-O157 isolates from Europe. Epidemiol Infect 2014; 142: 1019-1029.
(31.) Brooks JT, Sowers EG, Wells JG, Greene KD, Griffin PM, Hoekstra RM, et al. Non-O157 Shiga toxin-producing Escherichia coli infections in the United States, 1983-2002. J Infect Dis 2005; 192: 1422-1429.
(32.) Kaper JB, Nataro JP, Mobley HL. Pathogenic Escherichia coli. Nat Rev Microbiol 2004; 2: 123-140.
(33.) Farfan MJ, Torres AG. Molecular mechanisms that mediate colonization of Shiga toxin-producing Escherichia coli strains. Infect Immun 2012; 80: 903-913.
(34.) Finlay BB, Ruschkowski S, Kenny B, Stein M, Reinscheid DJ, Stein MA, et al. Enteropathogenic E. coli exploitation of host epithelial cells. Ann N Y Acad Sci 1996: 797: 26-31.
(35.) Nataro JP, Kaper JB. Diarrheagenic Escherichia Coli. Clin Microbiol Rev 1998;11:142-200.
(36.) 36. Boerlin P, McEwen SA, Boerlin-Petzold F, Wilson JB, Johnson RP, Gyles CL. Associations between virulence factors of Shiga toxin-producing Escherichia coli and disease in humans. J Clin Microbiol 1999; 37: 497-503.
(37.) Karmali MA, Mascarenhas M, Shen S, Ziebell K, Johnson S, Reid-Smith R, et al. Association of genomic O island 122 of Escherichia coli EDL 933 with verocytotoxin-producing Escherichia coli seropathotypes that are linked to epidemic and/or serious disease. J Clin Microbiol 2003; 41: 4930-4940.
(38.) Cookson AL, Bennett J, Thomson-Carter F, Attwood GT. Molecular subtyping and genetic analysis of the enterohemolysin gene (ehxA) from Shiga toxin-producing Escherichia coli and atypical enteropathogenic E. coli. Appl Environ Microbiol 2007; 73: 6360-6369.
(39.) Lim JY, Yoon JW, Hovde CJ. A brief overview of Escherichia coli O157:H7 and its plasmid O157. J Microbiol Biotechnol 2010; 20: 5-14.
(40.) Newton HJ, Sloan J, Bulach DM, Seemann T, Allison CC, Tauschek M, Robins-Browne RM, et al. Shiga toxin-producing Escherichia coli strains negative for locus of enterocyte effacement. Emerg Infect Dis 2009; 15: 372-380.
(41.) Vanaja SK, Jandhyala DM, Mallick EM, Leong JM, Balasubramanian S. Enterohemorrhagic and other Shiga toxin-producing Escherichia coli. In: Donnenberg M, ed. Escherichia coli: Pathotypes and principles of pathogenesis. Academic Press, Cambridge, MA, USA, 2013: 121-182.
(42.) Mathusa EC, Chen Y, Enache E, Hontz L. Non-O157 shiga toxin-producing Escherichia coli in foods. J Food Prot 2010; 73: 1721-1736.
(43.) Gould LH, Bopp C, Strockbine N, Atkinson R, Baselski V, Body B, et al. Recommendations for diagnosis of Shiga toxin-producing Escherichia coli infections by clinical laboratories. MMWR Recomm Rep 2009; 58: 1-14.
(44.) Tarr PI, Neill MA. Perspective: The problem of non-O157:H7 Shiga toxin (Verocytotoxin)-producing Escherichia coli. J Infect Dis 1996; 174: 1136-1139.
(45.) Ethelberg S, Olsen KEP, Scheutz F, Jensen C, Schiellerup P, Engberg J, et al. Virulence factors for hemolytic uremic syndrome, Denmark. Emerg Infect Dis 2004; 10: 842-847.
(46.) Clogher P, Hurd S, Hoefer D, Hadler JL, Pasutti L, Cosgrove S, et al. Assessment of physician knowledge and practices concerning Shiga toxin-producing Escherichia coli infection and enteric illness, 2009, Foodborne Diseases Active Surveillance Network (FoodNet). Clin Infect Dis 2012; 54 Suppl 5: S446-452.
(47.) Kallinowski F, Wassmer A, Hofmann MA, Harmsen D, Heesemann J, Karch H, et al. Prevalence of enteropathogenic bacteria in surgically treated chronic inflammatory bowel disease. Hepatogastroenterology 1998; 45: 1552-1558.
(48.) Paton JC, Paton AW. Pathogenesis and diagnosis of shiga toxin-producing Escherichia coli infections. Clin Microbiol Rev 1998; 11: 450-479.
(49.) Jandhyala DM, Vanguri V, Boll EJ, Lai Y, McCormick BA, Leong JM. Shiga toxin-producing Escherichia coli O104:H4: an emerging pathogen with enhanced virulence. Infect Dis Clin North Am 2013; 27: 631-649.
(50.) Gerritzen A, Wittke JW, Wolff D. Rapid and sensitive detection of Shiga toxin producing Escherichia coli directly from stool samples by real-time PCR in comparison to culture, enzyme immunoassay and Vero cell cytotoxicity assay. Clin Lab 2011; 57: 993-998.
(51.) Beutin L. Emerging enterohaemorrhagic Escherichia coli, causes and effects of the rise of a human pathogen. J Med Vet 2006; 53: 299-305.
(52.) Majowicz SE, Scallan E, Jones-Bitton A, Sargeant JM, Stapleton J, Angulo FJ, et al. Global incidence of human Shiga toxin-producing Escherichia coli infections and deaths: A systematic review and knowledge synthesis. Foodborne Pathog Dis 2014; 11: 447-455.
(53.) Acheson DW, Keusch GT. Which Shiga toxin-producing types of E. coli are important? ASM News 1996; 62: 302-306.
(54.) Ethelberg S, Smith B, Torpdahl M, Lisby M, Boel J, Jensen T, et al. Outbreak of non-O157 Shiga toxin-producing Escherichia coli infection from consumption of beef sausage. Clin Infect Dis 2009; 48: e78-81.
(55.) Cookson AL, Taylor SC, Bennett J, Thomson-Carter F, Attwood GT. Serotypes and analysis of distribution of Shiga toxin producing Escherichia coli from cattle and sheep in the lower North Island, New Zealand. N Z Vet J 2006; 54: 7884.
(56.) DebRoy C, Roberts E. Screening petting zoo animals for the presence of potentially pathogenic Escherichia coli. J Vet Diagn Invest 2006; 18: 597-600.
(57.) Fremaux B, Prigent-Combaret C, Beutin L, Gleizal A, Trevisan D, Quetin P, et al. Survival and spread of Shiga toxin-producing Escherichia coli in alpine pasture grasslands. J Appl Microbiol 2010; 108: 1332-1343.
(58.) Fukushima H, Hoshina K, Gomyoda M. Long-term survival of Shiga toxin-producing Escherichia coli O26, O111, and O157 in bovine feces. Appl Environ Microbiol 1999; 65: 5177-5181.
(59.) Guy L, Jernberg C, Arven Norling J, Ivarsson S, Hedenstrom I, Melefors O, et al. Adaptive mutations and replacements of virulence traits in the Escherichia coli O104:H4 outbreak population. PloS One 2013; 8: e63027.
(60.) Johnson RP, Clarke RC, Wilson JB, Read SC, Rahn K, Renwick SA, et al. Growing concerns and recent outbreaks involoving non-O157:H7 serotypes of verotoxigenic Escherichia coli. J Food Prot 1996; 59: 1112-1122.
(61.) Stigi KA, MacDonald K, Tellez-Marfin AA, H. LK. Laboratory practices and incidence of non-O157 Shiga toxin-producing Escherichia coli infections. Emerg Infect Dis 2012; 18: 477-479.
(62.) Baker M, Eyles R, Bennett J, Nicol C, Wong W, Garrett N. Emergence of verotoxigenic Escherichia coli (VTEC) in New Zealand. New Zealand Public Health Report 1999; 6: 9-12.
(63.) Thomas R, Brooks HJL, O'Brien R. Prevalence of Shiga toxin-producing and enteropathogenic Escherichia coli marker genes in diarrhoeic stools in a New Zealand catchment area. J Clin Path 2017; 70: 81-84.
(64.) Cookson AL, Cao M, Bennett J, Nicol C, Thomson-Carter F, Attwood GT. Relationship between virulence gene profiles of atypical enteropathogenic Escherichia coli and Shiga toxin-producing E. coli isolates from cattle and sheep in New Zealand. Appl Environ Microbiol 2010; 76: 3744-3747.
(65.) Cookson AL, Croucher D, Pope C, Bennett J, Thomson-Carter F, Attwood GT. Isolation, characterization, and epidemiological assessment of Shiga toxin-producing Escherichia coli 084 isolates from New Zealand. J Clin Microbiol 2006; 44: 1863-1866.
(66.) Jaros P, Cookson AL, Campbell DM, Besser TE, Shringi S, Mackereth GF, et al. A prospective case-control and molecular epidemiological study of human cases of Shiga toxin-producing Escherichia coli in New Zealand. BMC Inf Dis 2013; 13: 450-465.
(67.) Brooks HJL, Mollison BD, Bettelheim KA, Matejka K, Paterson KA, Ward VK. Occurrence and virulence factors of non-O157 Shiga toxin-producing Escherichia coli in retail meat in Dunedin, New Zealand. Lett Appl Microbiol 2001; 32: 118-123.
(68.) Asadulghani M, Ogura Y, Ooka T, Itoh T, Sawaguchi A, Iguchi A, et al. The defective prophage pool of Escherichia coli O157: prophage-prophage interactions potentiate horizontal transfer of virulence determinants. PLoS Pathog 2009; 5: e1000408.
(69.) Grad YH, Lipsitch M, Feldgarden M, Arachchi HM, Cerqueira GC, Fitzgerald M, et al. Genomic epidemiology of the Escherichia coli O104:H4 outbreaks in Europe, 2011. Proc Natl Acad Sci USA 2012; 109: 3065-3070.
Rowan R Thomas, Mabel LH Gaastra and Heather JL Brooks
Department of Pathology, University of Otago, Dunedin
Caption: Figure 1. Number of all STEC infections reported to ESR by community and hospital based diagnostic laboratories 1997-2015. The number of notifications of STEC infections has been increasing since 1997 (6).
Caption: Figure 2. Proposed mode of action of Shiga toxin. Shiga toxin binds to the host cell receptor Gb3 (globotriaosylceramide, [P.sup.k] blood group antigen). Following internalisation in an early endosome, the toxin is transported to the Golgi apparatus then to the endoplasmic reticulum where the dissociated A subunit inhibits protein synthesis by destroying the function of ribosomal RNA (28S subunit). The toxin A subunit is subsequently released into the cytosol. Host cell responses include autophagy (degradation of cell constituents), apoptosis (programmed cell death), ribotoxic and endoplasmic reticulum stress, and release of pro-inflammatory cytokines and chemokines (reviewed by Lee et al (24)).
Caption: Figure 3. Formation of actin pedestals. Formation of actin pedestals (a) due to the interaction of intimin with translocated intimin receptor (22). This is preceded by an initial loose attachment (b), then firm attachment with underlying effacement of the microvilli (c). Figure shows serogroup O111 Escherichia coli attached to the surface of Hep-2 tissue culture cells (prepared for transmission electron microscopy using standard fixation and osmium tetroxide staining by M. Gaastra).
Table 1. Diarrhoeagenic Escherichi coli pathotypes E. coli pathotype Acronym Disease eaeA, stx genes * Shiga-toxigenic/ STEC/EHEC Watery diarrhoea, [eaeA.sup.+/-], Enterohaemorrhagic haemorrhagic [stx.sup.+] colitis, haemolytic uraemic syndrome Enteropathogenic EPEC Watery diarrhoea [eaeA.sup.+], (typical/atypical) [stx.sup.-] ([dagger]) Enteroinvasive EIEC Dysentery [eaeA.sup.-], ([double dagger]) [stx.sup.-] Enteroaggregative EAEC syn. Traveller's [eaeA.sup.-], EAggEC diarrhoea, [stx.sup.-] (haemolytic (serotype uraemic syndrome) O104:H4 [stx.sup.+]) Enterotoxigenic ETEC Persistent watery [eaeA.sup.-], diarrhoea [stx.sup.-] Diffusely adherent DAEC Persistent watery [eaeA.sup.-], diarrhoea in [stx.sup.-] children (Crohn's in adults?) * Important genetic markers of virulence for STEC and EPEC ([dagger]) Typical EPEC possess E. coli adherence factor plasmid pEAF, atypical EPEC do not ([double dagger]) Closely related to Shigella spp.; S. dysenteriae [stx.sup.+] Table 2. Prevalent and predominant Shiga-toxigenic Escherichia coli semigroups by country Country/Continent Prevalent Predominant serogroups serogroup United States O157, O26, O111, O157 of America O103, O121, O45, O145 Canada O157, O55, O125, O157 O26, O126, O128, O18 South America O1, O2, O15, O25, Non-O157 O26, O49, O92, O11 United Kingdom O157 0157 Continental O157, O26, O111, Both O157 and Europe O104, O103, O128, non-O157 O91, O113, O2, O9, O145 Australia O157, O111, O26 Both O157 and non-O157 Japan O157, O26, O111 0157 Table adapted from Vanaja et al (41)
|Printer friendly Cite/link Email Feedback|
|Author:||Thomas, Rowan R.; Gaastra, Mabel L.H.; Brooks, Heather J.L.|
|Publication:||New Zealand Journal of Medical Laboratory Science|
|Date:||Apr 1, 2018|
|Previous Article:||GREETINGS TO YOU ALL, FROM THE PPTC.|
|Next Article:||Prevalence of extended spectrum [beta]-lactamase, AmpC [beta]-lactamase and metallo-[beta]-lactamase enzymes among clinical isolates recovered from...|