A review of an emerging enteric pathogen: enteroaggregative Escherichia coli

Detection of diarrhoeagenic Escherichia coli in the abattoir wastewater-impacted Iyi-Etu River and other water types at the Amansea livestock market settlement, Anambra State, Nigeria: a matter of public health concern

BACKGROUND

Globally, diarrhoeagenic Escherichia coli (DEC) has been implicated in the spread of waterborne diseases and abattoir wastewater has played a role in its dissemination into watersheds. This study isolated and characterised DEC from the abattoir wastewater-impacted Iyi-Etu River and other water sources at the Amansea livestock market settlement.

METHODS

A total of 96 water samples comprising river water (upstream, downstream 1, downstream 2), borehole, well, sachet and abattoir wastewater samples were tested for DEC. In the inoculation process, membrane filtration was used, and selective media such as Eosin Methylene Blue, Chromoselect agar and Sorbitol Maconkey agar were used to screen for E. coli and Shiga toxin-producing E. coli (STEC) O157. Escherichia coli pathotypes were characterised using molecular techniques.

RESULTS

Overall, E. coli was presumptively detected in 28.1% (27/96) of all samples. Of the 27 isolates, three (11.1%) were non-sorbitol fermenters (typical of E. coli O157), while 20 (74.1%) were confirmed as E. coli based on uidA housekeeping gene positivity. The detected circulating pathotypes were enteropathogenic E. coli (EPEC) (35.0%; 7/20), enteroinvasive E. coli (EIEC) (40.0%; 8/20), enterotoxigenic E. coli (15.0%; 3/20), STEC (40.0%; 10/20) and enteroaggregative E. coli (5.0%; 1/20). Escherichia coli as well as EPEC, EIEC and STEC pathotypes were most prevalent at the downstream 1 sampling point compared with the upstream. EPEC, EIEC and STEC were also detected in borehole samples (5.0%, 1/20).

CONCLUSIONS

The Iyi-Etu River and borehole water sources used for domestic and drinking purposes, respectively, at Amansea livestock market settlement are contaminated with some pathotypes of E. coli and the level of pollution may pose a public health risk to humans and animals during contact. Thus, public health measures including proper treatment of wastewater before disposal and continuous monitoring may help to learn the associated effect of DEC pollution in the area.

Detection and characterization of potentially hybrid enteroaggregative Escherichia coli (EAEC) strains isolated from urinary tract infection

Uropathogenic Escherichia coli (UPEC) have the potential to receive the virulence markers of intestinal pathotypes and transform into various important hybrid pathotypes. This study aimed to investigate the frequency and characteristics of hybrid enteroaggregative E. coli (EAEC)/UPEC strains. Out of 202 UPEC strains, nine (4.5%) were detected as hybrid EAEC/UPEC. These strains carried one to four iron uptake systems. Among nine investigated pathogenicity islands (PAIs), PAI IV536, PAI II536, and PAI ICFT073 were found in 9 (100%), 3 (33.3%), and 1 (11.1%) strains, respectively. The chuA and sitA genes were detected in 5 (55.5%) and 3 (33.3%) hybrid strains, respectively. Six hybrid strains were found to be typical extraintestinal pathogenic E. coli (ExPEC) according to their virulence traits. Most of the hybrid strains belonged to the phylogenetic group E (6/9). Among the hybrid strains, seven (7/9) were able to form biofilm and adhere to cells; however, only two strains penetrated into the HeLa cells. Our findings reveal some of the virulence characteristics of hybrid strains that lead to fitness and infection in the urinary tract. These strains, with virulence factors of intestinal and non-intestinal pathotypes, may become emerging pathogens in clinical settings; therefore, further studies are needed to reveal their pathogenicity mechanisms and so that preventive measures can be taken.

A pilot study using hospital surveillance and a birth cohort to investigate enteric pathogens and malnutrition in children, Dili, Timor-Leste

In low-to-middle-income countries (LMICs), enteric pathogens contribute to child malnutrition, affecting nutrient absorption, inducing inflammation, and causing diarrhoea. This is a substantial problem in LMICs due to high disease burden, poor sanitation and nutritional status, and the cyclical nature of pathogen infection and malnutrition. This relationship remains understudied in Timor-Leste. In our pilot study of enteric pathogens and malnutrition in Dili, Timor-Leste (July 2019-October 2020), we recruited 60 infants in a birth cohort from Hospital Nacional Guido Valadares (HNGV) with up to four home visits. We collected faecal samples and details of demographics, anthropometrics, diet and food practices, and animal husbandry. Additionally, we collected faecal samples, diagnostics, and anthropometrics from 160 children admitted to HNGV with a clinical diagnosis of severe diarrhoea or severe acute malnutrition (SAM). We tested faeces using the BioFire® FilmArray® Gastrointestinal Panel. We detected high prevalence of enteric pathogens in 68.8% (95%CI 60.4-76.2%) of infants at home, 88.6% of SAM cases (95%CI 81.7-93.3%) and 93.8% of severe diarrhoea cases (95%CI 67.7-99.7%). Diarrhoeagenic Escherichia coli and Campylobacter spp. were most frequently detected. Pathogen presence did not significantly differ in birth cohort diarrhoeal stool, but hospital data indicated associations between Salmonella and Shigella and diarrhoea. We observed wasting in 18.4% (95%CI 9.2-32.5%) to 30.8% (95%CI 17.5-47.7%) of infants across home visits, 57.9% (95%CI 34.0-78.9%) of severe diarrhoea cases, and 92.5% (95%CI 86.4-96.2%) of SAM cases. We associated bottle feeding with increased odds of pathogen detection when compared with exclusive breastfeeding at home (OR 8.3, 95%CI 1.1-62.7). We detected high prevalence of enteric pathogens and signs of malnutrition in children in Dili. Our pilot is proof of concept for a study to fully explore the risk factors and associations between enteric pathogens and malnutrition in Timor-Leste.

Evaluation of chronic diarrhea in patients newly diagnosed with HIV infection through the FilmArray® gastrointestinal panel

INTRODUCTION

The treatment and diagnosis of chronic diarrhea in the immunocompromised patient depends on the ability to rapidly detect the etiologic agents.

AIMS

Our aim was to evaluate the results of the FilmArray® gastrointestinal panel in patients newly diagnosed with HIV infection that presented with chronic diarrhea.

MATERIAL AND METHODS

Utilizing nonprobability consecutive convenience sampling, 24 patients were included that underwent molecular testing for the simultaneous detection of 22 pathogens.

RESULTS

In 24 HIV-infected patients with chronic diarrhea, enteropathogen bacteria were detected in 69% of the cases, parasites in 18%, and viruses in 13%. Enteropathogenic Escherichia coli and enteroaggregative Escherichia coli were the main bacteria identified, Giardia lamblia was found in 25%, and norovirus was the most frequent viral agent. The median number of infectious agents per patient was three (range of 0 to 7). The biologic agents not identified through the FilmArray® method were tuberculosis and fungi.

CONCLUSIONS

Several infectious agents were simultaneously detected through the FilmArray® gastrointestinal panel in patients with HIV infection and chronic diarrhea.

Enteroaggregative Escherichia coli induced activation of epidermal growth factor receptor contributes to IL-8 secretion by cultured human intestinal epithelial cells

Enteroaggregative Escherichia coli (EAEC) has been identified as a new enteropathogen that causes acute and chronic diarrhea in children and travelers. One defining aspect of EAEC-pathogenesis is the induction of an inflammatory response in intestinal epithelium. In this study, we have found that EAEC-induced EGFR activation in human small intestinal and colonic epithelial was attenuated in the presence of a specific inhibitor of EGFR (Tyrphostin AG1478). Further, the aggregative stacked-brick type of adherence of this organism to both the cell lines and this pathogen-induced cytoskeletal rearrangement of these cells was also reduced in the presence of Tyrphostin AG1478. Moreover, EAEC-induced activation of downstream effectors (ERK-1/2, PI3K and Akt) of EGFR mediated cell signaling pathways were found to be suppressed in the presence of EGFR inhibitor. A decrease in IL-8 response in EAEC infected both the cell types were also noted in the presence of specific inhibitors of these downstream effectors, transcription factors and Tyrphostin AG1478. We propose that EAEC-induced activation of EGFR is quintessential for stacked-brick adherence of EAEC to human intestinal epithelial cells, their cytoskeletal rearrangements and stimulation of ERK-1/2 and PI3K/Akt mediated signal transduction pathways, resulting in the activation of NF-κB, AP-1, STAT-3 and finally IL-8 secretion by these cells.

Analysis of the Virulence and Inflammatory Markers Elicited by Enteroaggregative Escherichia coli Isolated from Clinical and Non-Clinical Sources in an Experimental Infection Model, India

Enteroaggregative Escherichia coli (EAEC) is highly heterogeneous in virulence; we wanted to understand the pathogenic potential of EAEC isolated from various clinical and non-clinical sources in an animal model. We infected male BALB/c mice in six mice/groups with 50 EAEC isolates isolated from clinical and non-clinical sources. We studied colonization, weight loss, stool shedding, and inflammatory markers and their relationship with 21 virulence genes and phylogroups, EAEC organ burden, and histopathological changes. We detected significantly more inflammatory changes and fecal lactoferrin and calprotectin levels in mice infected with EAEC isolated from symptomatic cases. In clinical EAEC isolates, the presence of chromosomal genes (aap (46%), aaiC (23.3%), SPATEs (pet (13.3%), sat (20%), sigA, and pic (6.6%)), the adhesive variantsof EAEC (agg4A (53.3%), aggA (53.3%), aafA (36.6%), andagg3A (40%)), and the master regulator gene aggR (66.6%) were associated with higher levels of lactoferrin and calprotectin. Additionally, 70% (9/13) of EAEC isolated from acute diarrheal cases bearing chuA (70%) in our study were assigned to groups B2 (4 isolates) and D (5 isolates). Real-time PCR analysis revealed that colonization by EAEC strains from different clinical and non-clinical sources occurs up to 10–15 days of life. Even from non-diarrheal stools and non-clinical sources, EAEC strainshad the potential to cause prolonged colonization, weight loss, and inflammation in the intestine, though the degree varied. Moreover, a better understanding of EAEC pathogenic pathways is desperately needed in different clinical scenarios.

The impact of human vaccines on bacterial antimicrobial resistance. A review

At present, the dramatic rise in antimicrobial resistance (AMR) among important human bacterial pathogens is reaching a state of global crisis threatening a return to the pre-antibiotic era. AMR, already a significant burden on public health and economies, is anticipated to grow even more severe in the coming decades. Several licensed vaccines, targeting both bacterial (Haemophilus influenzae type b, Streptococcus pneumoniae, Salmonella enterica serovar Typhi) and viral (influenza virus, rotavirus) human pathogens, have already proven their anti-AMR benefits by reducing unwarranted antibiotic consumption and antibiotic-resistant bacterial strains and by promoting herd immunity. A number of new investigational vaccines, with a potential to reduce the spread of multidrug-resistant bacterial pathogens, are also in various stages of clinical development. Nevertheless, vaccines as a tool to combat AMR remain underappreciated and unfortunately underutilized. Global mobilization of public health and industry resources is key to maximizing the use of licensed vaccines, and the development of new prophylactic vaccines could have a profound impact on reducing AMR.

Distribution and association of antimicrobial resistance and virulence traits in Escherichia coli isolates from healthy waterfowls in Hainan, China

There are rising concerns about microbes harboring antibiotic resistance genes (ARGs) and virulence-associated genes (VAGs) in humans and food-producing animals. Moreover, ARGs are considered as emerging environmental pollutants, posing probable life-threatening complications in humans and animals. Commensal Escherichia coli (E. coli) strain can carry a large number of VAGs, which may become opportunistic pathogen. The objective of this study was to determine the prevalence and possible association of ARGs and VAGs in E. coli isolates from clinically healthy waterfowls in China's tropical island, Hainan. For this purpose, 311 non-repeating E. coli isolates were evaluated for phenotypic drug resistance linked with ARGs. Additionally, strains were examined for subsequent resistance and virulence genes by uniplex or multiplex PCR and sequencing. Overall, 89 types of antibiotic resistance patterns were analysed, while 25 ARGs and 23 VAGs were observed, of which qnrS (99.4%) and iucD (99.7%) were the most commonly found genes, respectively. Significant positive associations were observed among ARGs and VAGs (p<0.05, OR>1). The strongest association between resistance and virulence gene was observed for qnrS and iss (OR, 76.25; 95% CI, 4.02-1445.42). Our results propose that waterfowls serve as a reservoir of E. coli carrying multi ARGs and various ExPEC associated VAGs. Therefore, this study provides necessary information on the occurrence and possible associations of ARGs and VAGs in healthy waterfowls, which may act as a reference for the regulatory use of antibiotics to stop the direct or indirect spread of these resistant and potential virulent microbes to natural environment.

Effect of Escherichia Coli Infection on Metabolism of Dietary Protein in Intestine

Dietary proteins are linked to the pathogenic Escherichia coli (E. coli) through the intestinal tract, which is the site where both dietary proteins are metabolized and pathogenic E. coli strains play a pathogenic role. Dietary proteins are degraded by enzymes in the intestine lumen and their metabolites are transferred into enterocytes to be further metabolized. Seven diarrheagenic E. coli pathotypes have been identified, and they damage the intestinal epithelium through physical injury and effector proteins, which lead to inhibit the digestibility and absorption of dietary proteins in the intestine tract. But the increased tryptophan (Trp) content in the feed, low-protein diet or milk fractions supplementation is effective in preventing and controlling infections by pathogenic E. coli in the intestine.

Global distribution of epidemic-related Shiga toxin 2 encoding phages among enteroaggregative Escherichia coli

Since the Shiga toxin-producing enteroaggregative Escherichia coli (Stx-EAEC) O104:H4 strain caused a massive outbreak across Europe in 2011, the importance of Stx-EAEC has attracted attention from a public health perspective. Two Stx-EAEC O86 isolates were obtained from patients with severe symptoms in Japan in 1999 and 2015. To characterize the phylogeny and pathogenic potential of these Stx-EAEC O86 isolates, whole-genome sequence analyses were performed by short-and long-read sequencing. Among genetically diverse E. coli O86, the Stx-EAEC O86 isolates were clustered with the EAEC O86:H27 ST3570 subgroup. Strikingly, there were only two loci with single nucleotide polymorphisms (SNPs) between the Stx2a phage of a Japanese O86:H27 isolate and that of the European epidemic-related Stx-EAEC O104:H4 isolate. These results provide evidence of global distribution of epidemic-related Stx2a phages among various lineages of E. coli with few mutations.

Mucus layer modeling of human colonoids during infection with enteroaggragative E. coli

EAEC is a common cause of diarrheal illness worldwide. Pathogenesis is believed to occur in the ileum and colon, where the bacteria adhere and form a robust aggregating biofilm. Among the multiple virulence factors produced by EAEC, the Pic serine protease has been implicated in bacterial colonization by virtue of its mucinolytic activity. Hence, a potential role of Pic in mucus barrier disruption during EAEC infection has been long postulated. In this study, we used human colonoids comprising goblet cells and a thick mucin barrier as an intestinal model to investigate Pic's roles during infection with EAEC. We demonstrated the ability of purified Pic, but not a protease defective Pic mutant to degrade MUC2. Western blot and confocal microscopy analysis revealed degradation of the MUC2 layer in colonoids infected with EAEC, but not with its isogenic EAECpic mutant. Wild-type and MUC2-knockdown colonoids infected with EAEC strains exposed a differential biofilm distribution, greater penetration of the mucus layer and increased colonization of the colonic epithelium by Wild-type EAEC than its isogenic Pic mutant. Higher secretion of pro-inflammatory cytokines was seen in colonoids infected with EAEC than EAECpic. Although commensal E. coli expressing Pic degraded MUC2, it did not show improved mucus layer penetration or colonization of the colonic epithelium. Our study demonstrates a role of Pic in MUC2 barrier disruption in the human intestine and shows that colonoids are a reliable system to study the interaction of pathogens with the mucus layer.

QseC Signaling in the Outbreak O104:H4 Escherichia coli Strain Combines Multiple Factors during Infection

Enteroaggregative Escherichia coli (EAEC) from the O104:H4 specific serotype caused a large outbreak of bloody diarrhea with some complicated cases of hemolytic-uremic syndrome (HUS) in Europe in 2011. The outbreak strain consisted in an EAEC capable to produce the Shiga toxin (Stx) subtype 2a, a characteristic from enterohemorrhagic E. coli QseBC two-component system detects AI-3/Epi/NE and mediates the chemical signaling between pathogen and mammalian host. This system coordinates a cascade of virulence genes expression in important human enteropathogens. The blocking of QseC of EAEC C227-11 (Stx⁺) strain by N-phenyl-4-{[(phenylamino) thioxomethyl]amino}-benzenesulfonamide (also known as LED209) in vivo demonstrated a lower efficiency of colonization. The periplasmic protein VisP, which is related to survival mechanisms in a colitis model of infection, bacterial membrane maintenance, and stress resistance, here presented high levels of expression during the initial infection within the host. Under acid stress conditions, visP expression levels were differentiated in an Stx-dependent way. Together, these results emphasize the important role of VisP and the histidine kinase sensor QseC in the C227-11 (Stx⁺) outbreak strain for the establishment of the infectious niche process in the C57BL/6 mouse model and of LED209 as a promising antivirulence drug strategy against these enteric pathogens.IMPORTANCE EAEC is a remarkable etiologic agent of acute and persistent diarrhea worldwide. The isolates harbor specific subsets of virulence genes and their pathogenesis needs to be better understood. Chemical signaling via histidine kinase sensor QseC has been shown as a potential target to elucidate the orchestration of the regulatory cascade of virulence factors.

Large outbreak of multiple gastrointestinal pathogens associated with fresh curry leaves in North East England, 2013

A total of 592 people reported gastrointestinal illness following attendance at Street Spice, a food festival held in Newcastle-upon-Tyne, North East England in February/March 2013. Epidemiological, microbiological and environmental investigations were undertaken to identify the source and prevent further cases. Several epidemiological analyses were conducted; a cohort study; a follow-up survey of cases and capture re-capture to estimate the true burden of cases. Indistinguishable isolates of Salmonella Agona phage type 40 were identified in cases and on fresh curry leaves used in one of the accompaniments served at the event. Molecular testing indicated entero-aggregative Escherichia coli and Shigella also contributed to the burden of illness. Analytical studies found strong associations between illness and eating food from a particular stall and with food items including coconut chutney which contained fresh curry leaves. Further investigation of the food supply chain and food preparation techniques identified a lack of clear instruction on the use of fresh uncooked curry leaves in finished dishes and uncertainty about their status as a ready-to-eat product. We describe the investigation of one of the largest outbreaks of food poisoning in England, involving several gastrointestinal pathogens including a strain of Salmonella Agona not previously seen in the UK.

Impact of Childhood Nutritional Status on Pathogen Prevalence and Severity of Acute Diarrhea

Children with acute and chronic malnutrition are at increased risk of morbidity and mortality following a diarrheal episode. To compare diarrheal disease severity and pathogen prevalence among children with and without acute and chronic malnutrition, we conducted a cross-sectional study of human immunodeficiency virus-uninfected Kenyan children aged 6–59 months, who presented with acute diarrhea. Children underwent clinical and anthropometric assessments and provided stool for bacterial and protozoal pathogen detection. Clinical and microbiological features were compared using log binomial regression among children with and without wasting (mid-upper arm circumference ≤ 125 mm) or stunting (height-for-age z score ≤ −2). Among 1,363 children, 7.0% were wasted and 16.9% were stunted. After adjustment for potential confounders, children with wasting were more likely than nonwasted children to present with at least one Integrated Management of Childhood Illness danger sign (adjusted prevalence ratio [aPR]: 1.3, 95% confidence interval [CI]: 1.0 to 1.5, P = 0.05), severe dehydration (aPR: 2.4, 95% CI: 1.5 to 3.8, P < 0.01), and enteroaggregative Escherichia coli recovered from their stool (aPR: 1.8, 1.1–2.8, P = 0.02). There were no differences in the prevalence of other pathogens by wasting status after confounder adjustment. Stunting was not associated with clinical severity or the presence of specific pathogens. Wasted children with diarrhea presented with more severe disease than children without malnutrition which may be explained by a delay in care-seeking or diminished immune response to infection. Combating social determinants and host risk factors associated with severe disease, rather than specific pathogens, may reduce the disparities in poor diarrhea-associated outcomes experienced by malnourished children.

Persistent diarrhea: a persistent infection with enteropathogens or a gut commensal dysbiosis?

In children from developing countries 5-10% of acute diarrhea (AD) episodes develop into persistent diarrhea (PD) defined by > 14 days of diarrhea duration. PD represents a major health burden leading to growth faltering. It is also associated with half of all diarrhea mortality. A rational intervention is thus crucial, but depends on an understanding of the pathogenesis of PD, which is still lacking. Many surveys were conducted in Latin America and in South Asia; they differ, however, with respect to enteropathogens associated with PD. Enteroaggregative strains of Escherichia coli (EAEC) were identified by several studies, but they may reflect selection by the frequent antibiotic use during the preceding AD episode. Epidemiologists have in fact identified antibiotic misuse as a major risk factor for PD. Together with the effectiveness of empirical treatment based on nutritional interventions with lactose-reduced and lactose-free diets and particularly complex plant polysaccharides from green banana, one might suspect a role of commensal gut microbiota dysbiosis instead of a persistent infection with enteropathogens in many PD cases. An analysis of the commensal gut microbiota development in persistent diarrhea during nutritional interventions is likely to increase our understanding of PD pathogenesis.

Antibiotic resistance, serogroups, virulence genes, and phylogenetic groups of Escherichia coli isolated from yaks with diarrhea in Qinghai Plateau, China

Background

Ruminants serve as one of the most important reservoirs for pathogenic Escherichia coli. Infection with E. coli, a foodborne enteropathogen, can lead to asymptomatic infections that can cause life-threatening complications in humans. Therefore, from a clinical and human health perspective, it is important to know which virulence genes, phylogenetic groups, serogroups, and antibiotic resistance patterns are present in E. coli strains in yaks with diarrheic infections.

Methods

Two-hundred and ninety-two rectal swabs were collected from diarrheic yaks in Qinghai Plateau, China. The antimicrobial sensitivity of each resulting isolate was evaluated according to the disk diffusion method, and different PCR assays were performed for the detection of virulence genes and different phylogroups. Additionally, strains were allocated to different serogroups based on the presence of O antigen via the slide agglutination method.

Results

Among the E. coli isolates tested, most of the isolates were multidrug resistant (97%) and harbored at least one virulence gene (100%). We observed ten virulence genes (sfa, eaeA, cnf1, etrA, papC, hlyA, aer, faeG, rfc, and sepA), of which sfa was the most commonly found (96.9%). Significant positive associations between some resistance phenotypes and virulence genes were observed (P < 0.05, OR > 1). The majority of the E. coli isolates belonged to phylogroup A (79.5%), and the others belonged to phylogroups B1 (7.5%), D (4.1%), B2 (5.8%), and F (0.7%). Among all the E. coli strains tested, serogroups O₉₁ and O₁₄₅ were the most prevalent, accounting for 15.4 and 14.4%, respectively.

Conclusions

Our results suggest that yaks with diarrhea serve as a reservoir of pathogenic E. coli carrying various virulence genes and resistance phenotypes. Therefore, clinicians and relevant authorities must ensure the regulatory use of antimicrobial agents and prevent the spread of these organisms through manure to farm workers and food-processing plants.

Phenotypic and Molecular Characterization of Enteroaggregative Escherichia coli Isolated in Kawasaki, Japan

Enteroaggregative Escherichia coli (EAEC), an enteric pathogen, causes persistent diarrhea in children, HIV-infected individuals, and travelers in economically developing countries. However, the pathogenesis of EAEC infection is not well understood. This study aimed to characterize EAEC in Japan. Between 2012 and 2014, we identified 40 EAEC strains carrying the aggR gene at the Kawasaki City Institute for Public Health, Japan. We characterized these strains using O:H-antigen typing, polymerase chain reaction (for pCVD432, astA, extended-spectrum beta-lactamase, and 4 aggregative adherence fimbriae genes), HEp-2 cell adherence, clump formation, and antimicrobial susceptibility testing. We were able to classify the 40 EAEC strains into 20 O:H types. Although specific O:H types were not correlated with HEp-2 cell aggregative adherence, all the O99:H10, O131:H27, and O176:H34 EAEC strains that were the most frequent O:H types detected in this study showed co-resistance to ampicillin, sulfamethoxazole-trimethoprim, and tetracycline. Based on results of the adhesion assay and detection of virulence-related genes, no significant difference was found between asymptomatic and symptomatic cases. Irrespective of the origin, their potential for virulence was retained. Further characterization is vital to determine whether EAEC is virulent in Japan.

Case-control study of diarrheal disease etiology in individuals over 5 years in southwest China

Background

Acute diarrhea is one of the major public health problems worldwide. Most of studies on acute diarrhea have been made on infants aged below 5 years and few efforts have been made to identify the etiological agents of acute diarrhea in people over five, especially in China.

Methods

271 diarrhea cases and 149 healthy controls over 5 years were recruited from four participating hospitals between June 2014 and July 2015. Each stool specimen was collected to detect a series of enteric pathogens, involving five viruses (Rotavirus group A, RVA; Norovirus, NoV; Sapovirus, SaV; Astrovirus, As; and Adenovirus, Ad), seven bacteria (diarrheagenic Escherichia coli, DEC; non-typhoidal Salmonella, NTS; Shigella spp.; Vibrio cholera; Vibrio parahaemolyticus; Aeromonas spp.; and Plesiomonas spp.) and three protozoa (Cryptosporidium spp., Giardia lamblia, G. lamblia, and Blastocystis hominis, B. hominis). Standard microbiological and molecular methods were applied to detect these pathogens. Data was analyzed using Chi square, Fisher-exact tests and logistic regressions.

Results

The prevalence of at least one enteric pathogen was detected in 29.2% (79/271) acute diarrhea cases and in 12.1% (18/149) in healthy controls (p < 0.0001). Enteric viral infections (14.4%) were the most common in patients suffering from acute diarrhea, followed by bacteria (13.7%) and intestinal protozoa (4.8%). DEC (12.5%) was the most common causative agent in diarrhea cases, followed by NoV GII (10.0%), RVA (7.4%) and B. hominis (4.8%). The prevalence of co-infection was statistically higher (p = 0.0059) in the case group (7.7%) than in the healthy control (1.3%). RVA–NoV GII (3.0%) was the most common co-infection in symptomatic cases.

Conclusions

DEC was the most predominant pathogen in diarrhea cases, but it was largely overlooked because the lack of laboratory capacities. Because of the high prevalence of co-infections, it is recommended the urgent development of alternative laboratory methods to assess polymicrobial infections. Such methodological improvements will result in a better prevention and treatment strategies to control diarrhea illness in China.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0141-1) contains supplementary material, which is available to authorized users.

Occurrence of diarrhoeagenic Escherichia coli virulence genes in water and bed sediments of a river used by communities in Gauteng, South Africa

In most developing countries, especially in Southern Africa, little is known about the presence of diarrhoeagenic Escherichia coli (DEC) pathotypes in riverbed sediments. The present study sought to investigate the presence of DEC virulence genes in riverbed sediments of the Apies River, a river used by many communities in Gauteng, South Africa. Water and sediment samples were collected from the river between July and August 2013 (dry season) and also between January and February 2014 (wet season) following standard procedures. Isolation of E. coli was done using the Colilert®-18 Quanti-Tray® 2000 system. DNA was extracted from E. coli isolates using the InstaGene™ matrix from Bio-Rad and used as template DNA for real-time PCR. Water pH, temperature, dissolved oxygen, electrical conductivity and turbidity were measured in situ. Over 59 % of 180 samples analysed were positive for at least one of the seven DEC virulence genes investigated. The eaeA gene was the most isolated gene (29.44 %) while the ipaH gene the least isolated (8.33 %). The ipaH gene (p = 0.012) and the ST gene (stIa, p = 0.0001, and stIb, p = 0.019) were positively correlated with temperature. The detection of diarrhoeagenic E. coli virulence genes in the sediments of the Apies River shows that the sediments of this river might not only be a reservoir of faecal indicator bacteria like E. coli but also pathogenic strains of this bacterium. These organisms could represent a public health risk for poor communities relying on this water source for various purposes such as drinking and recreational use. There is therefore an urgent need to monitor these DEC pathotypes especially in areas without adequate water supplies.

Pet serine protease from enteroaggregative Escherichia coli stimulates the inflammatory response activating human macrophages

Background

Pet is a toxin from the family of Serine Protease Autotransporters of Enterobacteriaceae which was initially identified in Enteroaggregative Escherichia coli strains. This protease exhibits enterotoxin properties, damages the cell cytoskeleton and induces intestinal epithelium alterations, which are associated with a severe inflammatory process. An in-vitro study was conducted to evaluate the effect of Pet on the migration of human peripheral blood monocytes-derived macrophages and its participation in the activation of the early inflammatory response and cytokine expression.

Results

In the macrophage migration activation assay, Pet produced a similar effect to that induced by opsonized zymosan (ZAS). Regarding the cytokine expression, an increase of IL-8, TNF-α (pro-inflammatory) and IL-10 (anti-inflammatory) was identified. In addition to the above results, the nuclear translocation of NF-kB pp65 was also identified. These events are probably related to the inflammatory response identified in the histological examination of intestine rat samples inoculated with Pet during a ligated loop assay.

Conclusion

The results showed that Pet participates as an immunostimulant molecule for macrophages, which activates both their mobility and cytokine expression. These observations suggest that the toxin participates in the inflammatory process that is observed during the host infection by EAEC Pet producing.

pic gene of enteroaggregative Escherichia coli and its association with diarrhea in Peruvian children

Enteroaggregative Escherichia coli (EAEC) causes acute and persistent diarrhea among children, HIV-infected patients, and travelers to developing countries. We have searched for 18 genes-encoding virulence factors associated with aggregative adherence, dispersion, biofilm, toxins, serine protease autotransporters of Enterobacteriaceae (SPATEs) and siderophores, analyzed in 172 well-characterized EAEC strains (aggR(+)) isolated from stool samples of 97 children with diarrhea and 75 healthy controls from a passive surveillance diarrhea cohort study in Peru. Eighty-one different genetic profiles were identified, 37 were found only associated with diarrhea and 25 with control samples. The most frequent genetic profile was aggC(+)aatA(+)aap(+)shf(+)fyuA(+), present in 19 strains, including diarrhea and controls. The profile set1A(+)set1B(+)pic(+) was associated with diarrhea (P < 0.05). Of all genes evaluated, the most frequent were aatA (CVD 342) present in 159 strains (92.4%) and fyuA in 157 (91.3%). When EAEC strains were analyzed as a single pathogen (excluding co-infections), only pic was associated with diarrhea (P < 0.05) and with prolonged diarrhea (diarrhea ≥ 7 days) (P < 0.05). In summary, this is the first report on the prevalence of a large set of EAEC virulence genes and its association with diarrhea in Peruvian children. More studies are needed to elucidate the exact role of each virulence factor.

Genetic diversity and antibiogram profile of diarrhoeagenic Escherichia coli pathotypes isolated from human, animal, foods and associated environmental sources

INTRODUCTION

Infectious diarrhoea particularly due to pathogenic bacteria is a major health problem in developing countries, including India. Despite significant reports of diarrhoeagenic Escherichia coli (DEC) pathotypes around the globe, studies which address genetic relatedness, antibiogram profile and their correlation with respect to their isolation from different sources are sparse. The present study determines isolation and identification of DEC pathotypes from different sources, their genetic characterisation, antibiogram profile and their correlation if any.

MATERIALS AND METHODS

A total of 336 samples comprising diarrhoeic stool samples from infants (n=103), young animal (n=106), foods (n=68) and associated environmental sources (n=59) were collected from Bareilly region of India. All the samples were screened by using standard microbiological methods for the detection of E. coli. The identified E. coli were then confirmed as DEC pathotypes using polymerase chain reaction-based assays. Those DEC pathotypes identified as Enteroaggregative E. coli (EAEC) were further confirmed using HEp-2 adherence assay. All the isolated DEC pathotypes were studied for their genetic diversity using pulsed-field gel electrophoresis (PFGE), and antimicrobial susceptibility testing was performed by using disc diffusion method as per Clinical Laboratory Standards Institute guidelines.

RESULTS AND DISCUSSION

Of the four DEC pathotypes investigated, EAEC was found to be the predominant pathogen with an isolation rate of 16.5% from infants, 17.9% from young animals, 16.2% from foods and 3.4% from the associated environmental sources. These EAEC isolates, on further characterisation, revealed predominance of 'atypical' EAEC, with an isolation rate of 10.7% from infants, 15.1% from young animals, 16.2% from foods, and 3.4% from the associated environmental sources. On PFGE analysis, discrimination was evident within DEC pathotypes as 52 unique pulsotypes were observed for 59 recovered DEC pathotypes. However, a few EAEC isolates were found to be clonal (clusters A, B, C, D, F, G, and H) irrespective of their source of isolation, suggests sharing and/or circulation among different sources. Further, a high antibiotic resistance pattern was observed among isolated DEC pathotypes as almost 86.4% of isolates were found to be resistant against ≥3 tested drugs.

Comparative genetic characterization of Enteroaggregative Escherichia coli strains recovered from clinical and non-clinical settings

The origin of pathogenic Enteroaggregative Escherichia coli (EAEC), a major causative agent of childhood diarrhea worldwide, remains ill-defined. The objective of this study was to determine the relative prevalence of EAEC in clinical and non-clinical sources and compare their genetic characteristics in order to identify strains that rarely and commonly cause human diarrhea. The virulence gene astA was commonly detectable in both clinical and non-clinical EAEC, while clinical isolates, but not the non-clinical strains, were consistently found to harbor other virulence factors such as aap (32%), aatA (18%) and aggR (11%). MLST analysis revealed the extremely high diversity of EAEC ST types, which can be grouped into three categories including: (i) non-clinical EAEC that rarely cause human infections; (ii) virulent strains recoverable in diarrhea patients that are also commonly found in the non-clinical sources; (iii) organisms causing human infections but rarely recoverable in the non-clinical setting. In addition, the high resistance in these EAEC isolates in particular resistance to fluoroquinolones and cephalosporins raised a huge concern for clinical EAEC infection control. The data from this study suggests that EAEC strains were diversely distributed in non-clinical and clinical setting and some of the clinical isolates may originate from the non-clinical setting.

Escherichia coli O104:H4 Pathogenesis: an Enteroaggregative E. coli/Shiga Toxin-Producing E. coli Explosive Cocktail of High Virulence

A major outbreak caused by Escherichia coli of serotype O104:H4 spread throughout Europe in 2011. This large outbreak was caused by an unusual strain that is most similar to enteroaggregative E. coli (EAEC) of serotype O104:H4. A significant difference, however, is the presence of a prophage encoding the Shiga toxin, which is characteristic of enterohemorrhagic E. coli (EHEC) strains. This combination of genomic features, associating characteristics from both EAEC and EHEC, represents a new pathotype. The 2011 E. coli O104:H4 outbreak of hemorrhagic diarrhea in Germany is an example of the explosive cocktail of high virulence and resistance that can emerge in this species. A total of 46 deaths, 782 cases of hemolytic-uremic syndrome, and 3,128 cases of acute gastroenteritis were attributed to this new clone of EAEC/EHEC. In addition, recent identification in France of similar O104:H4 clones exhibiting the same virulence factors suggests that the EHEC O104:H4 pathogen has become endemically established in Europe after the end of the outbreak. EAEC strains of serotype O104:H4 contain a large set of virulence-associated genes regulated by the AggR transcription factor. They include, among other factors, the pAA plasmid genes encoding the aggregative adherence fimbriae, which anchor the bacterium to the intestinal mucosa (stacked-brick adherence pattern on epithelial cells). Furthermore, sequencing studies showed that horizontal genetic exchange allowed for the emergence of the highly virulent Shiga toxin-producing EAEC O104:H4 strain that caused the German outbreak. This article discusses the role these virulence factors could have in EAEC/EHEC O104:H4 pathogenesis.

The Role of Long Polar Fimbriae in Escherichia coli O104:H4 Adhesion and Colonization

A renewed interest in Shiga toxin-producing Escherichia coli (STEC) strains was sparked due to the appearance of an outbreak in 2011, causing 3,816 diarrheal cases and some deaths in Europe. The causative strain was classified as enteroaggregative E. coli of serotype O104:H4 that had acquired Shiga toxin genes. The ability of STEC O104:H4 to cause disease relies greatly on the bacteria’s capacity to colonize, persist, and produce Shiga toxin. However, not much is known about the colonization factors of this strain. Because long polar fimbriae (lpf) lpf1 and lpf2 operons encode important colonization factors in other STEC isolates and E. coli O104:H4 possesses both loci, we hypothesized that Lpf is required for adhesion and colonization. In this study, isogenic lpfA1 and lpfA2 major fimbrial subunit mutants were constructed. To determine their role in O104:H4’s virulence, we assessed their ability to adhere to non-polarized and polarized intestinal epithelial cells. The ΔlpfA1 showed decreased adherence in both cell systems, while the ΔlpfA2 only showed a decrease in adherence to polarized Caco-2 cells. We also tested the O104:H4 mutants’ ability to form biofilm and found that the ΔlpfA1 was unable to form a stable biofilm. In an in vivo murine model of intestinal colonization, the ΔlpfA1 had a reduced ability to colonize the cecum and large intestine, consistent with the in vitro data. Further, we tested the lpfA1 mutants’ ability to compete against the wild type. We found that in the in vitro and in vivo models, the presence of the wild type O104:H4 facilitates increased adherence of the ΔlpfA1 to levels exceeding that of the wild type. Overall, our data demonstrated that Lpf1 is one of the factors responsible for O104:H4 intestinal adhesion and colonization.

Occurrence of virulence gene signatures associated with diarrhoeagenic and non-diarrhoeagenic pathovars of Escherichia coli isolates from some selected rivers in South-Western Nigeria

BACKGROUND

Diarrhoeal diseases are attributable to unsafe water stemming from improper sanitation and hygiene and are reportedly responsible for extensive morbidity and mortality particularly among children in developed and developing countries.

METHODS

Water samples from selected rivers in Osun State, South-Western Nigeria were collected and analyzed using standard procedures. Escherichia coli isolates (n=300) were screened for 10 virulence genes using polymerase chain reaction for pathotyping.

RESULTS

While the virulence gene (VG) lt for enterotoxigenic E. coli had the highest prevalence of 45%, the enteropathogenic E. coli genes eae and bfp were detected in 6 and 4% of the isolates respectively. The VGs stx1 and stx2 specific for the enterohemorrhagic E. coli pathotypes were detected in 7 and 1% of the isolates respectively. Also, the VG eagg harboured by enteroaggregative pathotype and diffusely-adherent E. coli VG daaE were detected in 2 and 4% of the isolates respectively and enteroinvasive E. coli VG ipaH was not detected. In addition, the VGs papC for uropathogenic and ibeA for neonatal meningitis were frequently detected in 19 and 3% of isolates respectively.

CONCLUSIONS

These findings reveal the presence of diarrhoeagenic and non-diarrhoeagenic E. coli in the selected rivers and a potential public health risk as the rivers are important resources for domestic, recreational and livelihood usage by their host communities.

Phenotypic and Genotypic Characterization of Enteroaggregative Escherichia coli Strains Isolated From Diarrheic Children in Iran

Background:

Several studies performed in developed and developing countries have identified enteroaggregative Escherichia coli (EAEC) as the emerging cause of pediatric diarrhea.

Objectives:

This study investigated the phenotypic and genetic characteristics of EAEC strains isolated from children with diarrhea between 2007 - 2008 in Tehran, Iran.

Materials and Methods:

EAEC strains were examined for virulence plasmid genes (aap, aggR, and aatA), biofilm formation, and drug resistance. In addition, pulsed-field gel electrophoresis (PFGE) profiles of these strains were determined.

Results:

Significant percentage of local EAEC strains carried the virulence plasmid genes and formed biofilms. In addition, these strains showed high resistance to ampicillin (100%), tetracycline (65.7%), streptomycin (58.7%), chloramphenicol (52.6%), and trimethoprim/sulfamethoxazole (51.7%) and had different PFGE patterns.

Conclusions:

These results indicated that EAEC strains isolated from Iranian children with diarrhea were heterogeneous and showed high resistance rates against commonly used antibiotics, which was similar to that reported in studies performed in other countries.

[Detection of virulence genes of the enteroaggregative pathotype in Escherichia coli strains isolated from groundwater sources in the province of Chaco, Argentina]

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.

Biofilm formation and fibrinogen and fibronectin binding activities by Corynebacterium pseudodiphtheriticum invasive strains

Biofilm-related infections are considered a major cause of morbidity and mortality in hospital environments. Biofilms allow microorganisms to exchange genetic material and to become persistent colonizers and/or multiresistant to antibiotics. Corynebacterium pseudodiphtheriticum (CPS), a commensal bacterium that colonizes skin and mucosal sites has become progressively multiresistant and responsible for severe nosocomial infections. However, virulence factors of this emergent pathogen remain unclear. Herein, we report the adhesive properties and biofilm formation on hydrophilic (glass) and hydrophobic (plastic) abiotic surfaces by CPS strains isolated from patients with localized (ATCC10700/Pharyngitis) and systemic (HHC1507/Bacteremia) infections. Adherence to polystyrene attributed to hydrophobic interactions between bacterial cells and this negatively charged surface indicated the involvement of cell surface hydrophobicity in the initial stage of biofilm formation. Attached microorganisms multiplied and formed microcolonies that accumulated as multilayered cell clusters, a step that involved intercellular adhesion and synthesis of extracellular matrix molecules. Further growth led to the formation of dense bacterial aggregates embedded in the exopolymeric matrix surrounded by voids, typical of mature biofilms. Data also showed CPS recognizing human fibrinogen (Fbg) and fibronectin (Fn) and involvement of these sera components in formation of "conditioning films". These findings suggested that biofilm formation may be associated with the expression of different adhesins. CPS may form biofilms in vivo possibly by an adherent biofilm mode of growth in vitro currently demonstrated on hydrophilic and hydrophobic abiotic surfaces. The affinity to Fbg and Fn and the biofilm-forming ability may contribute to the establishment and dissemination of infection caused by CPS.

Adherence and virulence genes of Escherichia coli from children diarrhoea in the Brazilian Amazon

The bacterial pathogen most commonly associated with endemic forms of childhood diarrhoea is Escherichia coli . Studies of epidemiological characteristics of HEp-2 cell-adherent E. coli in diarrhoeal disease are required, particularly in developing countries. The aim of this study was evaluate the presence and significance of adherent Escherichia coli from diarrhoeal disease in children. The prevalence of LA, AA, and DA adherence patterns were determined in HEp-2 cells, the presence of virulence genes and the presence of the O serogroups in samples obtained from 470 children with acute diarrhoea and 407 controls in Porto Velho, Rondônia, Brazil. E. coli isolates were identified by PCR specific for groups of adherent E. coli . Out of 1,156 isolates obtained, 128 (11.0%) were positive for eae genes corresponding to EPEC, however only 38 (29.6%) of these amplified bfpA gene . EAEC were isolated from 164 (14.1%) samples; of those 41(25%), 32 (19%) and 16 (9.7%) amplified eagg , aggA or aafA genes, respectively and aggA was significantly associated with diarrhoea ( P = 0.00006). DAEC identified by their adhesion pattern and there were few isolates. In conclusion, EAEC was the main cause of diarrhoea in children, especially when the aggA gene was present, followed by EPEC and with a negligible presence of DAEC.

Involvement of main diarrheagenic Escherichia coli, with emphasis on enteroaggregative E. coli, in severe non-epidemic pediatric diarrhea in a high-income country

Background

Bacterial and viral enteric pathogens are the leading cause of diarrhea in infants and children. We aimed to identify and characterize the main human diarrheagenic E. coli (DEC) in stool samples obtained from children less than 5 years of age, hospitalized for acute gastroenteritis in Israel, and to examine the hypothesis that co-infection with DEC and other enteropathogens is associated with the severity of symptoms.

Methods

Stool specimens obtained from 307 patients were tested by multiplex PCR (mPCR) to identify enteroaggregative E. coli (EAEC), enterohemorrhagic (EHEC), enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC). Specimens were also examined for the presence of rotavirus by immunochromatography, and of Shigella, Salmonella and Campylobacter by stool culture; clinical information was also obtained.

Results

Fifty nine (19%) children tested positive for DEC; EAEC and atypical EPEC were most common, each detected in 27 (46%), followed by ETEC (n = 3; 5%), EHEC and typical EPEC (each in 1 child; 1.5%). Most EAEC isolates were resistant to cephalexin, cefixime, cephalothin and ampicillin, and genotypic characterization of EAEC isolates by O-typing and pulsed-field gel electrophoresis showed possible clonal relatedness among some. The likelihood of having > 10 loose/watery stools on the most severe day of illness was significantly increased among patients with EAEC and rotavirus co-infection compared to children who tested negative for both pathogens: adjusted odds ratio 7.0 (95% CI 1.45-33.71, P = 0.015).

Conclusion

DEC was common in this pediatric population, in a high-income country, and mixed EAEC and rotavirus infection was characterized by especially severe diarrhea.

Characterization and biofilm forming ability of diarrhoeagenic enteroaggregative Escherichia coli isolates recovered from human infants and young animals

Enteroaggregative Escherichia coli (EAEC) is an important pathotype that causes infection in humans and animals. EAEC isolates (n=86) recovered from diarrhoeal cases in human infants (37) and young animals (49) were characterized as 'typical' and/or 'atypical' EAEC strains employing PCR for virulence associated genes (cvd432, aaiA, astA, pilS, irp2, ecp, pic, aggR, aafA, aggA, and agg3A). Besides, biofilm formation ability of human and animal EAEC isolates was assessed using microtiter plate assay. In addition, the transcriptional profile of biofilm associated genes (fis and ecp) was also evaluated and correlated with biofilm formation assay for few selected EAEC isolates of human and animal origins. Overall, a diverse virulence gene profile was observed for the EAEC isolates of human and animal origins as none of the EAEC isolates revealed the presence of all the genes that were targeted. Nine 'typical' EAEC isolates were identified (6 from humans and 3 from animals) while, the majority of the isolates were 'atypical' EAEC strains. Isolation and identification of three 'typical' EAEC isolates from animals (canines) appears to be the first report globally. Further, based on the observations of the biofilm formation assay, the study suggested that human EAEC isolates in particular were comparatively more biofilm producers than that of the animal EAEC isolates. The fis gene was highly expressed in majority of 'typical' EAEC isolates and the ecp gene in 'atypical' EAEC isolates.

Overview and Historical Perspectives

In this overview, we describe the history of Shiga toxin (Stx)-producing Escherichia coli (STEC) in two phases. In phase one, between 1977 and 2011, we learned that E. coli could produce Shiga toxin and cause both hemorrhagic colitis and the hemolytic-uremic syndrome in humans and that the prototype STEC-E. coli O157:H7-adheres to and effaces intestinal epithelial cells by a mechanism similar to that of enteropathogenic E. coli. We also recognized that the genes for Stx are typically encoded on a lysogenic phage; that STEC O157:H7 harbors a large pathogenicity island that encodes the elements needed for the characteristic attaching and effacing lesion; and that the most severe cases of human disease are linked to production of Stx type 2a, not Stx type 1a. Phase two began with a large food-borne outbreak of hemorrhagic colitis and hemolytic-uremic syndrome in Germany in 2011. That outbreak was caused by a novel strain consisting of enteroaggregative E. coli O104:H4 transduced by a Stx2a-converting phage. From this outbreak we learned that any E. coli strain that can adhere tightly to the human bowel (either by a biofilm-like mechanism as in E. coli O104:H4 or by an attaching and effacing mechanism as in E. coli O157:H7) can cause severe diarrheal and systemic illness when it acquires the capacity to produce Stx2a. This overview provides the basis for the review of current information regarding these fascinating and complex pathogens.

Occurrence of virulence genes associated with diarrheagenic Escherichia coli isolated from raw cow's milk from two commercial dairy farms in the Eastern Cape Province, South Africa

Escherichia coli remains a public health concern worldwide as an organism that causes diarrhea and its reservoir in raw milk may play an important role in the survival and transport of pathogenic strains. Diarrheagenic E. coli strains are diverse food-borne pathogens and causes diarrhea with varying virulence in humans. We investigated the prevalence of pathogenic E. coli in raw milk from two commercial dairy farms. Four hundred raw milk samples, 200 from each dairy farm, were screened for the presence of fliCH7, eagR, ial, eagg, lt, and papC genes. In dairy farm A, 100 E. coli were identified based on culture, oxidase and Gram staining, while 88 isolates from dairy farm B were identified in the same manner. Gene detection showed fliCH7 27 (54%) to be the highest gene detected from farm A and lt 2 (4%) to be the lowest. The highest gene detected in dairy farm B was fliCH7 16 (43.2%) and papC 1 (2.7%) was the least. The amplification of pathogenic genes associated with diarrheagenic E. coli from cows' raw milk demonstrates that potentially virulent E. coli strains are widely distributed in raw milk and may be a cause of concern for human health.

Zinc deficiency alters host response and pathogen virulence in a mouse model of enteroaggregative Escherichia coli-induced diarrhea

Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a major cause of diarrheal disease globally. In the current study, we investigated the impact of zinc deficiency on the host and pathogenesis of EAEC. Several outcomes of EAEC infection were investigated including weight loss, EAEC shedding and tissue burden, leukocyte recruitment, intestinal cytokine expression, and virulence expression of the pathogen in vivo. Mice fed a protein source defined zinc deficient diet (dZD) had an 80% reduction of serum zinc and a 50% reduction of zinc in luminal contents of the bowel compared to mice fed a protein source defined control diet (dC). When challenged with EAEC, dZD mice had significantly greater weight loss, stool shedding, mucus production, and, most notably, diarrhea compared to dC mice. Zinc deficient mice had reduced infiltration of leukocytes into the ileum in response to infection suggesting an impaired immune response. Interestingly, expression of several EAEC virulence factors were increased in luminal contents of dZD mice. These data show a dual effect of dietary zinc in benefitting the host while impairing virulence of the pathogen. The study demonstrates the critical importance of zinc and may help elucidate the benefits of zinc supplementation in cases of childhood diarrhea and malnutrition.

Enteroaggregative coli: A Pathogen Bridging the North and South

Enteroaggregative Escherichia coli (EAEC) is a heterogeneous emerging enteric pathogen. Identified during the 1980's when EAEC strains where isolated from cases of acute and persistent diarrhea among infants from developing countries and of traveler's diarrhea. Subsequently, EAEC strains were linked with foodborne outbreaks and diarrhea illness in adults and children from industrialized countries, HIV-infected subjects and stunting of malnourished poor children. Nowadays, EAEC is increasingly recognized as a major cause of acute diarrhea in children recurring hospitalization and of traveler's diarrhea worldwide. EAEC strains defining phenotype is the aggregative adherence (AA) pattern on epithelial cells. AggR a transcriptional regulator of several EAEC virulence genes has been a key factor in both understanding EAEC pathogenesis and defining typical EAEC (tEAEC) strains. EAEC virulence genes distribution among these strains is highly variable. Present challenges are the identification of key virulence genes and how they coordinately function in the setting of enteric disease.

Identification of cell surface-exposed proteins involved in the fimbria-mediated adherence of enteroaggregative Escherichia coli to intestinal cells

Fimbria-mediated adherence to the intestinal epithelia is a key step in enteroaggregative Escherichia coli (EAEC) pathogenesis. To date, four fimbriae have been described for EAEC; aggregative adherence fimbria II (AAF/II) is the most important adherence factor for EAEC prototype strain 042. Previously, we described results showing that extracellular matrix (ECM) components might be involved in the recognition of AAF/II fimbriae by intestinal cells. In this study, we sought to identify novel potential receptors on intestinal epithelial cells recognized by the AAF/II fimbriae. Purified AafA-dsc protein, the major subunit of AAF/II fimbriae, was incubated with a monolayer of T84 cells, cross-linked to the surface-exposed T84 cell proteins, and immunoprecipitated by using anti-AafA antibodies. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of cellular proteins bound to AafA-dsc protein identified laminin (previously recognized as a potential receptor for AAF/II) and cytokeratin 8 (CK8). Involvement of the major subunit of AAF/II fimbriae (AafA protein) in the binding to recombinant CK8 was confirmed by adherence assays with purified AAF/II fimbriae, AafA-dsc protein, and strain 042. Moreover, HEp-2 cells transfected with CK8 small interfering RNA (siRNA) showed reduced 042 adherence compared with cells transfected with scrambled siRNA as a control. Adherence of 042 to HEp-2 cells preincubated with antibodies against ECM proteins or CK8 was substantially reduced. Altogether, our results supported the idea of a role of CK8 as a potential receptor for EAEC.

Genotypic and phenotypic characterisation of enteroaggregative Escherichia coli from children in Rio de Janeiro, Brazil

Enteroaggregative Escherichia coli (EAEC) is a significant cause of diarrhoeal illness in both children and adults. Genetic heterogeneity and recovery of EAEC strains from both healthy and diseased individuals complicates our understanding of EAEC pathogenesis. We wished to establish if genetic or phenotypic attributes could be used to distinguish between strains asymptomatically colonising healthy individuals and those which cause disease. Genotypic screening of a collection of twenty four EAEC isolates from children with and without diarrhoea revealed no significant differences in the repertoire of putative virulence factors present in either group of strains. In contrast, EAEC strains from phylogroup A were more strongly associated with asymptomatic groups whereas strains from phylogroup D were more associated with cases of diarrhoea. Phenotypic screening revealed no differences in the ability of strains from either cohort of children to form biofilms, to adhere to and invade cells in tissue culture or to cause disease in the Caenorhabditis elegans model of infection. However, the latter assay did reveal significant reduction in nematode killing rates when specific virulence factors were deleted from human pathogenic strains. Our results suggest that current models of infection are not useful for distinguishing avirulent from pathogenic strains of EAEC but can be useful in studying the effect of specific virulence factors.

Animal models of enteroaggregative Escherichia coli infection

Enteroaggregative Escherichia coli (EAEC) has been acknowledged as an emerging cause of gastroenteritis worldwide for over two decades. Epidemiologists are revealing the role of EAEC in diarrheal outbreaks as a more common occurrence than ever suggested before. EAEC induced diarrhea is most commonly associated with travelers, children and immunocompromised individuals however its afflictions are not limited to any particular demographic. Many attributes have been discovered and characterized surrounding the capability of EAEC to provoke a potent pro-inflammatory immune response, however cellular and molecular mechanisms underlying initiation, progression and outcomes are largely unknown. This limited understanding can be attributed to heterogeneity in strains and the lack of adequate animal models. This review aims to summarize current knowledge about EAEC etiology, pathogenesis and clinical manifestation. Additionally, current animal models and their limitations will be discussed along with the value of applying systems-wide approaches such as computational modeling to study host-EAEC interactions.

Prevalence and antibiotic resistance profiles of diarrheagenic Escherichia coli strains isolated from food items in northwestern Mexico

Diarrheogenic Escherichia coli (DEC) strains are an important cause of intestinal syndromes in the developing world mainly affecting children. DEC strains often infect tourists from developed countries traveling to Mexico, causing so-called "traveler diarrhea". DEC strains are typically transmitted by contaminated food and water; however, the prevalence of these strains in food items that are produced, consumed and sometimes exported in northwestern Mexico has not been evaluated. In this study, we conducted a large microbiological survey of DEC strains in 5162 food items and beverages consumed throughout Sinaloa state during 2008 and 2009. We developed a panel of eight sequential PCR reactions that detected the presence of all DEC categories, including typical or atypical variants. Thermotolerant coliforms (also known as fecal coliforms) and E. coli were detected by conventional bacteriology in 13.4% (692/5162) and 7.92% (409/5162) of food items, respectively. Among 409 E. coli isolates, 13.6% (56/409) belonged to DEC strains. Dairy products (2.8%) were the most contaminated with DEC, while DEC strains were not detected in beverages and ice samples. The pathogenic type that was most commonly isolated was EPEC (78.5%), followed by EAEC (10.7%), STEC (8.9%) and ETEC (1.7%). EHEC, DAEC and EIEC strains were not detected. Approximately 80% of EPEC and EAEC strains were classified as atypical variants; they did not adhere to a culture of HEp-2 cell. Of the isolated DEC strains, 66% showed resistance to at least one commonly prescribed antibiotic. In conclusion, the presence of DEC strains in food items and beverages available in northwestern Mexico is low and may not represent a threat for the general population or those traveling to tourist areas.

Enteroaggregative Escherichia coli strain in a novel weaned mouse model: exacerbation by malnutrition, biofilm as a virulence factor and treatment by nitazoxanide

Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a common cause of diarrhoea in healthy, malnourished and immune-deficient adults and children. There is no reproducible non-neonatal animal model for longitudinal studies of disease mechanism or therapy. Using two strains of human-derived EAEC to challenge weaned C57BL/6 mice, we explored an in vivo model of EAEC infection in mice, in which disease was monitored quantitatively as the growth rate, stool shedding and tissue burden of organisms; nutritional status was varied, and a new class of therapeutics was assessed. A single oral challenge of EAEC strain 042 resulted in significant growth shortfalls (5-8 % of body weight in 12 days), persistent shedding of micro-organisms in stools [>10(3.2) c.f.u. (10 mg stool)(-1) for at least 14 days] and intestinal tissue burden [~10(3) c.f.u. (10 mg tissue)(-1) detectable up to 14 days post-challenge]. Moderate malnourishment of mice using a 'regional basic diet' containing 7 % protein and reduced fat and micronutrients heightened all parameters of infection. Nitazoxanide in subMIC doses, administered for 3 days at the time of EAEC challenge, lessened growth shortfalls (by >10 % of body weight), stool shedding [by 2-3 logs (10 mg stool)(-1)] and tissue burden of organisms (by >75 % in the jejunum and colon). Thus, weaned C57BL/6 mice challenged with EAEC is a convenient, readily inducible model of EAEC infection with three highly quantifiable outcomes in which disease severity is dependent on the nutritional status of the host, and which is modifiable in the presence of inhibitors of pyruvate ferredoxin oxidoreductase such as nitazoxanide.

Occurrence of virulence genes associated with Diarrheagenic pathotypes in Escherichia coli isolates from surface water

Escherichia coli isolates (n = 300) collected from six sites in subtropical Brisbane, Australia, prior to and after storm events were tested for the presence of 11 virulence genes (VGs) specific to diarrheagenic pathotypes. The presence of eaeA, stx(1), stx(2), and ehxA genes specific for the enterohemorrhagic E. coli (EHEC) pathotype was detected in 56%, 6%, 10%, and 13% of isolates, respectively. The VGs astA (69%) and aggR (29%), carried by enteroaggregative (EAEC) pathotypes, were frequently detected in E. coli isolates. The enteropathogenic E. coli (EPEC) gene bfp was detected in 24% of isolates. In addition, enteroinvasive E. coli (EIEC) VG ipaH was also detected in 14% of isolates. During dry periods, isolates belonging to the EAEC pathotype were most commonly detected (23%), followed by EHEC (11%) and EPEC (11%). Conversely, a more uniform prevalence of pathotypes, EPEC (14%), EAEC (12%), EIEC (10%), EHEC (7%), and ETEC (7%), was observed after the storm events. The results of this study highlight the widespread occurrence of potentially diarrheagenic pathotypes in the urban aquatic ecosystems. While the presence of VGs in E. coli isolates alone is insufficient to determine pathogenicity, the presence of diarrheagenic E. coli pathotypes in high frequency after the storm events could lead to increased health risks if untreated storm water were to be used for nonpotable purposes and recreational activities.

Escherichia coli virulence factors

Escherichia coli was described in 1885 by a German pediatrician, Theodor Escherich, in the faeces of a child suffering diarrhoea. In 1893, a Danish veterinarian postulated that the E. coli species comprises different strains, some being pathogens, others not. Today the E. coli species is subdivided into several pathogenic strains causing different intestinal, urinary tract or internal infections and pathologies, in animal species and in humans. Since this congress topic is the interaction between E. coli and the mucosal immune system, the purpose of this manuscript is to present different classes of adhesins (fimbrial adhesins, afimbrial adhesins and outer membrane proteins), the type 3 secretion system, and some toxins (oligopeptide, AB, and RTX pore-forming toxins) produced by E. coli, that can directly interact with the epithelial cells of the intestinal, respiratory and urinary tracts.

Escherichia coli O104:H4 outbreak from sprouted seeds

From May to July 2011, one of the largest reported outbreaks of haemolytic uraemic syndrome (HUS) and bloody diarrhoea caused by the Shiga toxin-producing Escherichia coli (STEC) O104:H4 occurred in Germany and France. The hypothetical origin of the outbreak strain was a combined enteroaggregative E. coli and an enterohaemorrhagic E. coli with the ability to resist multi-antibiotics and produce Shiga-toxin 2. The combination of aggregative ability, antibiotic resistance and the production of Shiga-toxin 2 significantly affected the severity of the symptoms presented. Since humans may be the primary reservoir, it is likely that contamination could have occurred through contact with infected individuals. Farm food safety management, and hand hygiene training programmes are crucial to primary production to prevent or reduce risks of contamination.