Virulence of enteropathogenic Escherichia coli, a global pathogen

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.

Design of ELISA-based diagnostic system for detection of enterohaemorrhagic Escherichia coli

Background and Objectives

Escherichia coli (E. coli) O157:H7 is an intestinal pathogen of humans and animals, which causes serious gastrointestinal, urinary tract infection and hemolytic uremic syndrome. Connecting to the host cell is important in pathogenesis. EspA, Intimin and Tir proteins (EIT) are the most important bacterial features in the process of binding. These antigens can be very useful in detecting these bacteria. The aim of this study was to produce recombinant EspA, Intimin and Tir proteins (rEIT) to detect pathogenic E. coli O157:H7 by means of ELISA method.

Materials and Methods

The eit recombinant gene was expressed using IPTG in E. coli BL21 (DE3) and evaluated by western blotting. The purified rEIT protein was injected to rabbits and mice subcutaneously. Purified antibody was evaluated using indirect, competitive and sandwich ELISA confirming the precise detection of E. coli O157: H7.

Results

Indirect, competitive and sandwich ELISA specifically detected E. coli O157:H7 and each methods had the ability to identify more than 104, 104, 103 bacteria. The specificity of this method was evaluated by Entroheamoragic E. coli, enterotoxygenic E. coli, Klebsiella pneumoniae, Vibrio cholera and Acinetobacter.

Conclusion

These methods are the fastest, most accurate and cost effective methods for diagnosis of E. coli O157: H7, comparing to the conventional methods.

Clinical presentation and antibiotic resistance trends of Escherichia coli isolated from clinical samples in South India: A two-year study (2022-2023)

BACKGROUND

Escherichia coli (E. coli) is a common pathogen responsible for various infections, particularly in healthcare settings. Its antibiotic resistance and susceptibility patterns are crucial for effective treatment. This study aims to assess the prevalence of E. coli in clinical samples and evaluate its antibiotic resistance patterns at SRM Medical Hospital and Research Center from 2022 to 2023.

METHODS

A retrospective study was conducted using microbiological records from 30,838 clinical samples collected over two years. Positive E. coli isolates were identified and subjected to antimicrobial susceptibility testing. Demographic data, including age and sex, were analysed. Resistance patterns were assessed using the Vitek 2 system and disc diffusion methods as per CLSI guidelines.

RESULTS

Out of 30,838 samples, 8694 yielded positive cultures, with 2597 E. coli isolates. Most isolates (69.6 %) were from urine, followed by exudate (20.4 %) and blood (6.8 %). E. coli infection was more prevalent in females (60.92 %) and individuals aged 41-70 years (48.97 %) (p < 0.001). High resistance was observed for amoxicillin-clavulanate (32 %) and ciprofloxacin (17.98 %), with high susceptibility to colistin (90.98 %) and piperacillin-tazobactam (90 %).

CONCLUSION

This study highlights the prevalence of E. coli, especially in urine samples and among females and older adults. High resistance to commonly used antibiotics emphasizes the need for regular susceptibility testing and antimicrobial stewardship.

CLINICAL IMPLICATION

This study emphasizes the need for ongoing antibiotic resistance monitoring and customized treatment strategies to combat E. coli infections. Future efforts should focus on enhancing antimicrobial stewardship programs to reduce the spread of resistant strains.

SLC26A3 (DRA, the Congenital Chloride Diarrhea Gene): A Novel Therapeutic Target for Diarrheal Diseases

Diarrhea associated with enteric infections, gut inflammation, and genetic defects poses a major health burden and results in significant morbidity and mortality. Impaired fluid and electrolyte absorption or secretion in the intestine are the hallmark of diarrhea. Electroneutral NaCl absorption in the mammalian GI tract involves the coupling of Na+/H+ and Cl-/HCO3- exchangers. SLC26A3 (Down Regulated in Adenoma, DRA) is the major anion exchanger involved in luminal Cl- absorption and HCO3- secretion. Mutations in the SLC26A3 gene cause a severe disease called congenital chloride diarrhea (CLD). Multiple studies have shown that DRA function or expression is downregulated in infectious diarrheal disorders caused by EPEC, C rodentium, Salmonella, Clostridioides difficile and Cryptosporidium parvum infection. In addition, DRA levels are severely depleted in colonic mucosa of IBD patients and in mouse models of IBD (eg, DSS, TNBS, adoptive T-cell transfer, anti-CD-40, and IL-10 KO colitis). In addition, genetic defects exhibiting diarrhea including microvillus inclusion disease (MVID), keratin-8 depletion, knock-out mouse models of transcriptional factors (eg, CDX-2 and HNF1α/1β) also exhibit severe down regulation of DRA. Also, recent studies have shown that DRA is not only critical for chloride absorption but also plays a key role in maintaining gut epithelial barrier integrity, microbiome composition, and has now emerged as an IBD susceptibility gene. In this review, we provide strong evidence that DRA may serve as a novel therapeutic target with dual benefits in not only correcting diarrheal phenotype but also improving gut barrier integrity and inflammation in pathogen infection or IBD.

Enteropathogenic Escherichia coli modulates the virulence and pathogenicity of Entamoeba dispar

Amoebiasis is a disease caused by Entamoeba histolytica, affecting the large intestine of humans and occasionally leading to extra-intestinal lesions. Entamoeba dispar is another amoeba species considered commensal, although it has been identified in patients presenting with dysenteric and nondysenteric colitis, as well as amoebic liver abscess. Amoebic virulence factors are essential for the invasion and development of lesions. There is evidence showing that the association of enterobacteria with trophozoites contributes to increased gene expression of amoebic virulence factors. Enteropathogenic Escherichia coli is an important bacterium causing diarrhea, with high incidence rates in the world population, allowing it to interact with Entamoeba sp. in the same host. In this context, this study aims to evaluate the influence of enteropathogenic Escherichia coli on ACFN and ADO Entamoeba dispar strains by quantifying the gene expression of virulence factors, including galactose/N-acetyl-D-galactosamine-binding lectin, cysteine proteinase 2, and amoebapores A and C. Additionally, the study assesses the progression and morphological aspect of amoebic liver abscess and the profile of inflammatory cells. Our results demonstrated that the interaction between EPEC and ACFN Entamoeba dispar strains was able to increase the gene expression of virulence factors, as well as the lesion area and the activity of the inflammatory infiltrate. However, the association with the ADO strain did not influence the gene expression of virulence factors. Together, our findings indicate that the interaction between EPEC, ACFN, and ADO Entamoeba dispar strains resulted in differences in vitro and in vivo gene expression of Gal/GalNAc-binding lectin and CP2, in enzymatic activities of MPO, NAG, and EPO, and consequently, in the ability to cause lesions.

L-glutamine protects against enterohemorrhagic Escherichia coli infection by inhibiting bacterial virulence and enhancing host defense concurrently

IMPORTANCE

The type 3 secretion system (T3SS) was obtained in many Gram-negative bacterial pathogens, and it is crucial for their pathogenesis. Environmental signals were found to be involved in the expression regulation of T3SS, which was vital for successful bacterial infection in the host. Here, we discovered that L-glutamine (Gln), the most abundant amino acid in the human body, could repress enterohemorrhagic Escherichia coli (EHEC) T3SS expression via nitrogen metabolism and therefore had potential as an antivirulence agent. Our in vitro and in vivo evidence demonstrated that Gln could decline EHEC infection by attenuating bacterial virulence and enhancing host defense simultaneously. We repurpose Gln as a potential treatment for EHEC infection accordingly.

Characterizing the Crosstalk Between Programmed Cell Death Pathways in Cytokine Storm With an Agent-Based Model

Background: There is increasing recognition of extensive crosstalk between programmed cell death pathways (PCDPs), such as apoptosis, pyroptosis, and necroptosis, resulting in a highly redundant system responsive to a breadth of potential pathogens. However, because pyroptosis and necroptosis propagate inflammation, these redundancies also present challenges for therapeutic control of dysregulated hyperinflammation seen in cytokine storm (CS) generated organ dysfunction. Hypothesis: We hypothesize that the conversion of existing knowledge regarding apoptosis, pyroptosis, and necroptosis into a computational model can enhance our understanding of the crosstalk between PCDPs via simulation experiments of microbe interactions and experimental interventions. Materials and Methods: Literature regarding apoptosis, pyroptosis, and necroptosis was reviewed and transposed into an agent-based model, the programmed cell death agent-based model (PCDABM). Computational experiments were performed to simulate the activation of various PCDPs as seen by differing microbes, specifically: influenza A virus (IAV), enteropathic Escherichia coli (EPEC), and Salmonella enterica (SE). The potential protective value of PCDP crosstalk was evaluated by silencing either pyroptosis, necroptosis, or both. Computational experiments were also performed simulating the effect of potential therapies blocking tumor necrosis factor (TNF) and interleukin (IL)-1. Results: The PCDABM was implemented in the agent-based modeling toolkit NetLogo. Computational experiments of infection with IAV, EPEC, and SE reproduced cross-activation of PCDPs with effective microbial clearance. Simulations of anti-TNF and anti-IL-1 did not reduce the aggregated amount of inflammation-generated system damage, the surrogate for CS-generated tissue damage. Conclusions: Redundancies have evolved in host PCDPs to maintain protection against a wide range of pathogens. However, these redundancies also challenge attempts at dampening the pathogenic hyperinflammatory state of CS using therapeutic immunomodulation. Integrative simulation models such as the PCDABM can aid in identifying potentially targetable inflection points to mitigate CS while maintaining effective host defense.

Topology and function of translocated EspZ

EspZ and Tir are essential virulence effectors of enteropathogenic Escherichia coli (EPEC). EspZ, the second translocated effector, has been suggested to antagonize host cell death induced by the first translocated effector, Tir (translocated intimin receptor). Another characteristic of EspZ is its localization to host mitochondria. However, studies that explored the mitochondrial localization of EspZ have examined the ectopically expressed effector and not the more physiologically relevant translocated effector. Here, we confirmed the membrane topology of translocated EspZ at infection sites and the involvement of Tir in confining its localization to these sites. Unlike the ectopically expressed EspZ, the translocated EspZ did not colocalize with mitochondrial markers. Moreover, no correlation has been found between the capacity of ectopically expressed EspZ to target mitochondria and the ability of translocated EspZ to protect against cell death. Translocated EspZ may have to some extent diminished F-actin pedestal formation induced by Tir but has a marked effect on protecting against host cell death and on promoting host colonization by the bacteria. Taken together, our results suggest that EspZ plays an essential role in facilitating bacterial colonization, likely by antagonizing cell death mediated by Tir at the onset of bacterial infection. This activity of EspZ, which occurs by targeting host membrane components at infection sites, and not mitochondria, may contribute to successful bacterial colonization of the infected intestine. IMPORTANCE EPEC is an important human pathogen that causes acute infantile diarrhea. EspZ is an essential virulence effector protein translocated from the bacterium into the host cells. Detailed knowledge of its mechanisms of action is, therefore, critical for better understanding the EPEC disease. We show that Tir, the first translocated effector, confines the localization of EspZ, the second translocated effector, to infection sites. This activity is important for antagonizing the pro-cell death activity conferred by Tir. Moreover, we show that translocated EspZ leads to effective bacterial colonization of the host. Hence, our data suggest that translocated EspZ is essential because it confers host cell survival to allow bacterial colonization at an early stage of bacterial infection. It performs these activities by targeting host membrane components at infection sites. Identifying these targets is critical for elucidating the molecular mechanism underlying the EspZ activity and the EPEC disease.

Pathophysiology of Enteropathogenic Escherichia coli-induced Diarrhea

Enteropathogenic Escherichia coli (EPEC) are important diarrheal pathogens of infants and young children. Since the availability of molecular diagnosis methods, we now have new insights into the incidence and prevalence of these infections. Recent epidemiological studies indicate that atypical EPEC (aEPEC) are seen more frequently than typical EPEC (tEPEC) worldwide, including in both endemic diarrhea and diarrhea outbreaks. Therefore, it is important to further characterize the pathogenicity of these emerging strains. The virulence mechanisms and pathophysiology of the attaching and effacing lesion (A/E) and the type-three-secretion-system (T3SS) are complex but well-studied. A/E strains use their pool of locus of enterocyte effacement (LEE)-encoded and non-LEE-encoded effector proteins to subvert and modulate cellular and barrier properties of the host. However, the exact mechanisms of diarrhea in EPEC infection are not completely understood. From the clinical perspective, there is a need for fast, easy, and inexpensive diagnostic methods to define optimal treatment and prevention for children in endemic areas. In this article, we present a review of the classification of EPEC, epidemiology, pathogenesis of the disease caused by these bacteria, determinants of virulence, alterations in signaling, determinants of colonization vs. those of disease, and the limited information we have on the pathophysiology of EPEC-induced diarrhea. This article combines peer-reviewed evidence from our own studies and the results of an extensive literature search in the databases PubMed, EMBASE, and Scopus.

Molecular mechanisms of multidrug resistance in clinically relevant enteropathogenic bacteria (Review)

Multidrug resistant (MDR) enteropathogenic bacteria are a growing problem within the clinical environment due to their acquired tolerance to a wide range of antibiotics, thus causing severe illnesses and a tremendous economic impact in the healthcare sector. Due to its difficult treatment, knowledge and understanding of the molecular mechanisms that confer this resistance are needed. The aim of the present review is to describe the mechanisms of antibiotic resistance from a genomic perspective observed in bacteria, including naturally acquired resistance. The present review also discusses common pharmacological and alternative treatments used in cases of infection caused by MDR bacteria, thus covering necessary information for the development of novel antimicrobials and adjuvant molecules inhibiting bacterial proliferation.

B4galnt2-mediated host glycosylation influences the susceptibility to Citrobacter rodentium infection

Histo-blood group antigens in the intestinal mucosa play important roles in host–microbe interactions and modulate the susceptibility to enteric pathogens. The B4galnt2 gene, expressed in the GI tract of most mammals, including humans, encodes a beta-1,4-N-acetylgalactosaminyltransferase enzyme which catalyzes the last step in the biosynthesis of the Sd(a) and Cad blood group antigens by adding an N-acetylgalactosamine (GalNAc) residue to the precursor molecules. In our study, we found that loss of B4galnt2 expression is associated with increased susceptibility to Citrobacter rodentium infection, a murine model pathogen for human enteropathogenic Escherichia coli. We observed increased histopathological changes upon C. rodentium infection in mice lacking B4galnt2 compared to B4galnt2-expressing wild-type mice. In addition, wild-type mice cleared the C. rodentium infection faster than B4galnt2^−/− knockout mice. It is known that C. rodentium uses its type 1 fimbriae adhesive subunit to bind specifically to D-mannose residues on mucosal cells. Flow cytometry analysis of intestinal epithelial cells showed the absence of GalNAc-modified glycans but an increase in mannosylated glycans in B4galnt2-deficient mice compared to B4galnt2-sufficient mice. Adhesion assays using intestinal epithelial organoid-derived monolayers revealed higher C. rodentium adherence to cells lacking B4galnt2 expression compared to wild-type cells which in turn was reduced in the absence of type I fimbriae. In summary, we show that B4galnt2 expression modulates the susceptibility to C. rodentium infection, which is partly mediated by fimbriae-mannose interaction.

Presence of Escherichia coli O157:H7 in Dairy Farms located in Najaf, Baghdad, Kirkuk, and Erbil, Iraq

It has been approved that one of the most dangerous foodborne pathogenic bacteria is E. coli O157:H7, which is responsible for several infection and death cases worldwide. It is well documented that in the developing countries E. coli O157:H7 is considered the main causative pathogen of human gastrointestinal infections. Therefore, the current research was aimed to evaluate the prevalence of E. coli O157:H7 in dairy cattle's milk using a rapid method, in Iraq (Najaf, Baghdad, Kirkuk, and Erbil). Over a period of 6 months (During hot months) samples were obtained and investigated by culturing on selective media (CT-SMAC). The multiplex PCR (m-PCR) also used for milk sample direct investigation. Using biochemical tests the recorded data showed that, 2 recognized isolates were E. coli, while the recorded data obtained from m-PCR assay revealed that none of the isolated E. coli was toxigenic E.coli O157:H7. The results of m-PCR on the milk samples revealed that 45 milk samples contained at least one of the following genes: O157, H7, stx1, stx2 genes. Also the results of the m-PCR revealed that 2 samples (raw milk) were toxigenic O157:H7 positive. In conclusion, to the best of authors' knowledge, this investigation was the first report on the prevalence of E. coli O157:H7 in the raw milk samples in Iraq. The results showed that the proportion of contaminated milk samples contaminated with E. coli O157:H7 identified in the current survey were similar to that the results of the previously published research from different dairy products across different countries in the Middle East region.

Salmonella enterica subsp. II serovar 4,5,12:a:- may cause gastroenteritis infections in humans

Some serovars of Salmonella are not or rare found to cause salmonellosis in human. In our clinic-based surveillance, three rare Salmonella 4,5,12:a:- strains were recovered from three patients with diarrhea. To explore their genetic and epidemiological characteristics and pathogenesis, we conducted whole-genome sequencing, in vitro invasion assays in mammalian cells, and in vivo virulence assays in an animal model. The three isolates had indistinguishable molecular patterns and similar genome sequences, and clustered together with an isolate from edible fish traded among countries. The isolates had biochemical reactions identical with those of Salmonella subspecies enterica but belonged to subspecies salamae according to genome phylogeny, revealing a new serovar, S. enterica subsp. II serovar 4,5,12:a:-. The strains contained multiple virulence genes, elicited temporary bacteremia and enteritidis and caused cell damage in the mouse liver and cecum. This study provides evidence that this new Salmonella salamae serovar can infect humans and cause clusters of cases, and whole-genome sequencing detection and surveillance of Salmonella can help to accurately define Salmonella classification and clonality, improve diagnosis, facilitate outbreak detection and aid in the source tracing of salmonellosis epidemics.

Characterization of a Treponema denticola ATCC 35405 mutant strain with mutation accumulation, including a lack of phage-derived genes

Trepoenema denticola, a spirochetal bacterium, is associated with periodontal diseases. The type strain of the bacterium, ATCC 35405, is commonly used in a basic research. Here, we report that our stock strain derived from ATCC 35405 had a mutation on the chromosome and expressed differential characteristics from the original strain. Genome sequencing analysis revealed the lack of a phage-derived region, and over 200 mutations in the mutant strain. The mutant grew to a higher density in broth culture as compared with the origin. In addition, the mutant formed a colony on the surface of the agar medium, whereas the origin could not. On contrary, the mutant showed decreased motility and adhesion to gingival epithelial cells. There were no differences in the bacterial cell length and a chymotrypsin-like protease activity between the two strains. RNA and genome sequencing analysis could not identify the genes that introduced the phenotypic differences between the strains. This mutant is potentially useful for examining the genetic background responsible for the physiological and pathogenic characteristics of T. denticola.

Pathophysiology of enteropathogenic Escherichia coli during a host infection

Enteropathogenic Escherichia coli (EPEC) is a major cause of infantile diarrhea in developing countries. However, sporadic outbreaks caused by this microorganism in developed countries are frequently reported recently. As an important zoonotic pathogen, EPEC is being monitored annually in several countries. Hallmark of EPEC infection is formation of attaching and effacing (A/E) lesions on the small intestine. To establish A/E lesions during a gastrointestinal tract (GIT) infeciton, EPEC must thrive in diverse GIT environments. A variety of stress responses by EPEC have been reported. These responses play significant roles in helping E. coli pass through GIT environments and establishing E. coli infection. Stringent response is one of those responses. It is mediated by guanosine tetraphosphate. Interestingly, previous studies have demonstrated that stringent response is a universal virulence regulatory mechanism present in many bacterial pathogens including EPEC. However, biological signficance of a bacterial stringent response in both EPEC and its interaction with the host during a GIT infection is unclear. It needs to be elucidated to broaden our insight to EPEC pathogenesis. In this review, diverse responses, including stringent response, of EPEC during a GIT infection are discussed to provide a new insight into EPEC pathophysiology in the GIT.

Recovery Rate of Cells of the Seven Regulated Serogroups of Shiga Toxin-Producing Escherichia coli from Raw Veal Cutlets, Ground Veal, and Ground Beef from Retail Stores in the Mid-Atlantic Region of the United States

ABSTRACT

A total of 482 veal cutlet, 555 ground veal, and 540 ground beef samples were purchased from retail establishments in the mid-Atlantic region of the United States over a noncontiguous 2-year period between 2014 and 2017. Samples (325 g each) were individually enriched and screened via real-time PCR for all seven regulated serogroups of Shiga toxin-producing Escherichia coli (STEC). Presumptive STEC-positive samples were subjected to serogroup-specific immunomagnetic separation and plated onto selective media. Up to five isolates typical for STEC from each sample were analyzed via multiplex PCR for both the virulence genes (i.e., eae, stx1 and/or stx2, and ehxA) and serogroup-specific gene(s) for the seven regulated STEC serogroups. The recovery rates of non-O157 STEC from veal cutlets (3.94%, 19 of 482 samples) and ground veal (7.03%, 39 of 555 samples) were significantly higher (P < 0.05) than that from ground beef (0.93%, 5 of 540 samples). In contrast, only a single isolate of STEC O157:H7 was recovered; this isolate originated from 1 (0.18%) of 555 samples of ground veal. Recovery rates for STEC were not associated with state, season, packaging type, or store type (P > 0.05) but were associated with brand and fat content (P < 0.05). Pulsed-field subtyping of the 270 viable and confirmed STEC isolates from the 64 total samples testing positive revealed 78 pulsotypes (50 to 80% similarity) belonging to 39 pulsogroups, with ≥90% similarity among pulsotypes within pulsogroups. Multiple isolates from 43 (67.7%) of 64 samples testing positive had an indistinguishable pulsotype. STEC serotypes O26 and O103 were the most prevalent serogroups in beef and veal, respectively. These findings support related findings from regulatory sampling studies over the past decade and confirm that recovery rates for the regulated STEC serogroups are higher for raw veal than for raw beef samples, as was observed in the present study of meat purchased at food retailers in the mid-Atlantic region of the United States.

HIGHLIGHTS

Enteropathogenic Escherichia coli—A Summary of the Literature

Diarrheal disease is still a major public health concern, as it is still considered an important cause of death in children under five years of age. A few decades ago, the detection of enteropathogenic E. coli was made by detecting the O, H, and K antigens, mostly by agglutination. The recent protocols recommend the molecular methods for diagnosing EPEC, as they can distinguish between typical and atypical EPEC by identifying the presence/absence of specific virulence factors. EPEC are defined as diarrheagenic strains of E. coli that can produce attaching and effacing lesions on the intestinal epithelium while being incapable of producing Shiga toxins and heat-labile or heat-stable enterotoxins. The ability of these strains to produce attaching and effacing lesions enable them to cause localized lesions by attaching tightly to the surface of the intestinal epithelial cells, disrupting the surfaces of the cells, thus leading to the effacement of the microvilli. EPEC are classified on typical and atypical isolates, based on the presence or absence of E. coli adherence factor plasmids. All the EPEC strains are eae positive; typical EPEC strains are eae+, bfpA+, while atypical strains are eae+, bfpA−. No vaccines are currently available to prevent EPEC infections.

Virulence-determinants and antibiotic-resistance genes of MDR-E. coli isolated from secondary infections following FMD-outbreak in cattle

This study aimed to evaluate the prevalence, multidrug-resistance traits, PCR-detection of virulence, and antibiotic-resistance genes of E. coli isolated from secondary infections following FMD-outbreak in cattle. A total of 160 random samples were gathered from private dairy farms in Damietta Province, Egypt. The specimens were subjected to bacteriological examination, serotyping, congo-red binding assay, antibiogram-testing, and PCR-monitoring of virulence-determinant genes (tsh, phoA, hly, eaeA, sta, and lt) as well as the antibiotic-resistance genes (bla_TEM, bla_KPC, and bla_CTX). The prevalence of E. coli was 30% (n = 48) distributed in 8 serogroups (40/48, 83.3%), while 8 isolates (8/48, 16.6%) were untypable. Besides, 83.3% of the examined isolates were positive for CR-binding. The tested strains harbored the virulence genes phoA, hly, tsh, eaeA, sta, and lt with a prevalence of 100% and 50%, 45.8%, 25%, 8.4%, and 6.2%, respectively. Furthermore, 50% of the recovered strains were multidrug-resistant (MDR) to penicillins, cephalosporins, and carbapenems, and are harboring the bla_TEM, bla_CTX, and bla_KPC genes. Moreover, 25% of the examined strains are resistant to penicillins, and cephalosporins, and are harboring the bla_TEM and bla_CTX genes. To the best of our knowledge, this is the first report concerning the E. coli secondary bacterial infections following the FMD-outbreak. The emergence of MDR strains is considered a public health threat and indicates complicated treatment and bad prognosis of infections caused by such strains. Colistin sulfate and levofloxacin have a promising in vitro activity against MDR-E. coli.

Typical and atypical enteropathogenic Escherichia coli in children with acute diarrhoea: Changing trend in East Delhi

Background

Worldwide around 2 million deaths occur every year due to diarrhoeal illnesses among children less than 5 years of age. Among diarrhoeagenic Escherichia coli, Enteropathogenic E. coli (EPEC) is highly prevalent in both community and hospital settings and is one of the main causes of persistent diarrhea in children in developing countries. EPEC remains underdiagnosed in India due to lack of conventional tools for identification.

Methods

We in this study investigated the prevalence and regional variation of EPEC in paediatric population suffering from diarrhoea in East Delhi, India. Two hundred stool samples were collected from children, aged between 0.5 and 5 years, with acute diarrhoea. E. coli were identified by conventional tests and PCR.

Results

We observed 7% atypical EPEC (aEPEC) and 2.5% typical EPEC (tEPEC), with an overall 9.5% EPEC prevalence amongst total samples. E. coli phylogenetic group A was the predominant. The most common age group affected was 6–23 months with common symptoms being vomiting, watery diarrhoea and severe dehydration. High drug resistance pattern was observed in EPEC isolates.

Conclusion

The study depicts a changing trend of aEPEC over tEPEC in children less than 5 years with diarrhoea, an emerging drug resistant enteropathogen and a public health concern demanding monitoring and surveillance.

Transcriptional Activator OvrA Encoded in O Island 19 Modulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli O157:H7

The human intestinal pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes bloody diarrhea, hemorrhagic colitis, and fatal hemolytic uremic syndrome. Its genome contains 177 unique O islands (OIs), which contribute largely to the high virulence and pathogenicity although most OI genes remain uncharacterized. In the current study, we demonstrated that OI-19 is required for EHEC O157:H7 adherence to host cells. Z0442 (OI-encoded virulence regulator A [OvrA]) encoded in OI-19 positively regulated bacterial adherence by activating locus of enterocyte effacement (LEE) gene expression through direct OvrA binding to the gene promoter region of the LEE gene master regulator Ler. Mouse colonization experiments revealed that OvrA promotes EHEC O157:H7 adherence in mouse intestine, preferentially the colon. Finally, OvrA also regulated virulence in other non-O157 pathogenic E. coli, including EHEC strains O145:H28 and O157:H16 and enteropathogenic E. coli strain O55:H7. Our work markedly enriches the understanding of bacterial adherence control and provides another example of laterally acquired regulators that mediate LEE gene expression.

Cortex Phellodendri extract's anti-diarrhea effect in mice related to its modification of gut microbiota

Cortex Phellodendri extract (CPE) has been used in China to treat diarrhea whereas the underlying mechanisms remain poorly understood. Given that dysbiosis of gut microbiota is a potential reason for diarrhea, and that oral CPE has a low absorption rate in intestine, we hypothesized that modification of gut microbiota is an important factor in CPE's anti-diarrhea effect. To test this hypothesis, we established a diarrhea model by challenging post-weaning mice with oral Enterotoxigenic-Escherichia coli (ETEC), and then the mice were treated with two doses of CPE (80 mg/kg bodyweight and 160 mg/kg bodyweight) or the vehicle control (phosphate buffered saline). Diarrhea indices, inflammatory factors, morphology of jejunum, short-chain fatty acids (SCFAs), and serum endocrine were determined. Modification of gut microbiota was analyzed using 16S rDNA high-throughput sequencing. The changes in functional profiles of gut microbiota were predicted using software PICRUSt. We then explored the association between CPE-responding bacteria and the symptoms indices with the spearman's rank correlation coefficient and significance test. Compared with diarrheal mice, CPE decreased Gut/Carcass ratio and water content of stool, increased goblet cell density and villus height/crypt depth of jejunum, as well as decreased inflammatory indices (Tumour Necrosis Factor-α, Myeloperoxidase and Interleukin-1α). CPE shifted the gut microbiota significantly by increasing alpha diversity (observed species, ace, Shannon, and Simpson) and restoring the gut microbiota. CPE increased Firmicutes and decreased Bacteroidetes. The reduced genus Prevotella, Acinetobacter, and Morganella were positively associated with the diarrhea indices, whereas increased genus Odoribacter, Rikenella, and Roseburia were negatively associated with the diarrhea indices. The abundance of carbohydrate metabolism-related gene and SCFAs-producing bacteria were increased, which was evidenced by increased butyric acid and total SCFAs concentration in the caecum. Consequently, endocrine peptides glucagon-like peptide-1, epidermal growth factor, and peptide tyrosine tyrosine in serum were elevated. CONCLUSIONS: CPE shows a shift function on the gut microbiota in alleviating the diarrhea of mice in a dose-dependent manner. In addition, the microbial metabolites SCFAs may mediate CPE's anti-diarrhea effect by enhancing endocrine secretion in mice.

Bicarbonate Resensitization of Methicillin-Resistant Staphylococcus aureus to β-Lactam Antibiotics

Endovascular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major health care concern, especially infective endocarditis (IE). Standard antimicrobial susceptibility testing (AST) defines most MRSA strains as “resistant” to β-lactams, often leading to the use of costly and/or toxic treatment regimens. In this investigation, five prototype MRSA strains, representing the range of genotypes in current clinical circulation, were studied.

Endovascular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major health care concern, especially infective endocarditis (IE). Standard antimicrobial susceptibility testing (AST) defines most MRSA strains as “resistant” to β-lactams, often leading to the use of costly and/or toxic treatment regimens. In this investigation, five prototype MRSA strains, representing the range of genotypes in current clinical circulation, were studied. We identified two distinct MRSA phenotypes upon AST using standard media, with or without sodium bicarbonate (NaHCO₃) supplementation: one highly susceptible to the antistaphylococcal β-lactams oxacillin and cefazolin (NaHCO₃ responsive) and one resistant to such agents (NaHCO₃ nonresponsive). These phenotypes accurately predicted clearance profiles of MRSA from target tissues in experimental MRSA IE treated with each β-lactam. Mechanistically, NaHCO₃ reduced the expression of two key genes involved in the MRSA phenotype, mecA and sarA, leading to decreased production of penicillin-binding protein 2a (that mediates methicillin resistance), in NaHCO₃-responsive (but not in NaHCO₃-nonresponsive) strains. Moreover, both cefazolin and oxacillin synergistically killed NaHCO₃-responsive strains in the presence of the host defense antimicrobial peptide (LL-37) in NaHCO₃-supplemented media. These findings suggest that AST of MRSA strains in NaHCO₃-containing media may potentially identify infections caused by NaHCO₃-responsive strains that are appropriate for β-lactam therapy.

Prevalence of pathogenic Escherichia coli from salad vegetable and fruits sold in Jakarta

OBJECTIVE

Escherichia coli is a normal inhabitant of mammalian's gut, but some strains acquired virulence factor and became pathogenic. Enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), and enteroaggregative E. coli (EAEC) are among pathogenic strains of E. coli. Vegetables and fruits could be sources of transmission. Samples were collected and subjected to three-tubes Most Probable Number (MPN) analysis followed by Multiplex PCR. Six sets of primer encoding virulence genes were used: stx, ipah, aggr, eae, elt and est.

RESULTS

From this study we found, the highest maximum number for the MPN result reached > 1100 MPN/mL and the lowest is 3 MPN/mL. From first multiplex PCR showed 65 salad vegetable samples, 7.69% were positive and from the 63 fruit samples, 11.11% were positive. From second multiplex PCR for 76 isolates, 55 (72.37%) isolates were aggR positive (EAEC), 12 (15.79%) isolates were eae positive (EPEC), and 9 (11.84%) were elt positive (ETEC). Antimicrobial resistance assay showed that 83.33% of the isolates were multi resistant. Resistances are observed to 10 μg Ampicillin (22.22%), 5 μg Ciprofloxacin (11.11%), 10 μg Gentamycin (33.33%), 30 μg Kanamycin (38.89%), 10 μg Streptomycin (55.56%), 5 μg Trimethoprim (16.67%), and 300 U Polymyxin B (61.11%).

DIARRHEAGENIC Escherichia coli IN RAW MILK, WATER, AND CATTLE FECES IN NON-TECHNIFIED DAIRY FARMS

Abstract This study focused on detecting diarrheagenic Escherichia coli, enteropathogenic E. coli (EPEC), Shiga-toxin-producing E. coli (STEC), enterohemorrhagic E. coli (EHEC or STEC:EPEC), enterotoxigenic E. coli (ETEC), and enteroaggregative E. coli (EAEC) in raw milk, water, and cattle feces sampled from non-technified dairy farms located in the northeastern São Paulo State, Brazil. Thirty-six water samples were collected at different points, namely, water wells (8 samples), water intended for human consumption (8 samples), water from milking parlor (8 samples), and water intended for animal consumption (7 samples), headwaters (1 sample), rivers (3 samples), and reservoirs (1 sample). Three raw milk samples were taken directly from bulk tanks in each farm, totalizing 24 samples. Feces samples were collected using rectal swabs from 160 bovines (20 animals per farm). E. coli was detected in 128 feces samples (80%), 16 raw milk samples (66.67%), and 20 water samples (55.56%). STEC (26 samples, 16.25%), EPEC (10 samples, 6.25%), STEC: EPEC (5 samples, 3.13%), and STEC: ETEC (1 sample, 0.63%) were the most prevalent strains detected in samples from cattle feces. EPEC, STEC, and STEC: EPEC strains were detected in 4.17% (1 sample), 16.67% (4 samples), and 4.17% (1 sample) of raw milk samples, respectively. STEC strains were detected in water used in the milking parlor, while no EAEC strain was detected. As a conclusion, cattle feces are important contamination sources of pathogenic E. coli in non-technified dairy farms and, consequently, cross-contamination among feces, water, and/or raw milk can occur. The use of quality water and hygienic practices during milking are recommended to avoid contamination since pathogens can be transmitted to humans via raw milk or raw milk cheese ingestion.

Novel type of pilus associated with a Shiga-toxigenic E. coli hybrid pathovar conveys aggregative adherence and bacterial virulence

A large German outbreak in 2011 was caused by a locus of enterocyte effacement (LEE)-negative enterohemorrhagic E. coli (EHEC) strain of the serotype O104:H4. This strain harbors markers that are characteristic of both EHEC and enteroaggregative E. coli (EAEC), including aggregative adhesion fimbriae (AAF) genes. Such rare EHEC/EAEC hybrids are highly pathogenic due to their possession of a combination of genes promoting severe toxicity and aggregative adhesion. We previously identified novel EHEC/EAEC hybrids and observed that one strain exhibited aggregative adherence but had no AAF genes. In this study, a genome sequence analysis showed that this strain belongs to the genoserotype O23:H8, MLST ST26, and harbors a 5.2 Mb chromosome and three plasmids. One plasmid carries some EAEC marker genes, such as aatA and genes with limited protein homology (11–61%) to those encoding the bundle-forming pilus (BFP) of enteropathogenic E. coli. Due to significant protein homology distance to known pili, we designated these as aggregate-forming pili (AFP)-encoding genes and the respective plasmid as pAFP. The afp operon was arranged similarly to the operon of BFP genes but contained an additional gene, afpA2, which is homologous to afpA. The deletion of the afp operon, afpA, or a nearby gene (afpR) encoding an AraC-like regulator, but not afpA2, led to a loss of pilin production, piliation, bacterial autoaggregation, and importantly, a >80% reduction in adhesion and cytotoxicity toward epithelial cells. Gene sets similar to the afp operon were identified in a variety of aatA-positive but AAF-negative intestinal pathogenic E. coli. In summary, we characterized widely distributed and novel fimbriae that are essential for aggregative adherence and cytotoxicity in a LEE-negative Shiga-toxigenic hybrid.

Occurrence of multidrug-resistant and ESBL-producing atypical enteropathogenic Escherichia coli in China

Background

Atypical enteropathogenic Escherichia coli (aEPEC) is regarded as a globally emerging enteropathogen. aEPECs exhibit various level of resistance to a range of antibiotics, which is increasing alarmingly. The present study investigated the antimicrobial resistance of aEPEC isolates recovered from diarrheal patients, healthy carriers, animals, and raw meats.

Results

Among 267 aEPEC isolates, 146 (54.7%) were resistant to tetracycline, followed by ampicillin (49.4%), streptomycin (46.1%), and piperacillin (41.2%). Multidrug resistance (MDR) was detected in 128 (47.9%) isolates, and 40 MDR isolates were resistant to ≥ 10 antimicrobial agents. A total of 47 (17.6%) aEPEC isolates were identified as extended-spectrum β-lactamase (ESBL)-producers. The bla_CTX-M-14 and bla_CTX-M-15 genes were predominant among ESBL-producing isolates.

Conclusions

This investigation depicted the occurrence of multidrug-resistant and ESBL-producing aEPEC isolates in China. The results suggested that it is necessary to continuously monitor the emergence and spread of MDR aEPEC.

Electronic supplementary material

The online version of this article (10.1186/s13099-018-0234-0) contains supplementary material, which is available to authorized users.

S100A4 contributes to colitis development by increasing the adherence of Citrobacter rodentium in intestinal epithelial cells

S100A4 has been implicated in cancer and several inflammatory diseases, but its role in inflammatory bowel disease has not been well investigated. Here, upon infection with Citrobacter rodentium, a model for enteropathogenic Escherichia coli infection in humans, induced the infiltration of a large number of S100A4⁺ cells into the colon in wild type (WT) mice. Deficiency of S100A4 reduced weight loss, bacterial colonization and colonic pathology. Furthermore, the expression of inflammatory cytokines and the recruitment of macrophages and neutrophils also decreased significantly in S100A4 knock out (S100A4 ^-/-) mice. In vitro, soluble S100A4 directly up-regulated expression of integrin β-1 in intestinal epithelial cells and significantly increased the adherence of C. rodentium to intestinal epithelial cells. Additionally, the effects of S100A4 on the adherence of C. rodentium to epithelial cells could be abolished by a receptor for advanced glycation end products (RAGE)-specific inhibitor (FPS-ZM1). Therefore, these data indicate a novel mechanism for S100A4 that promotes colitis development by enhancing host adhesion and colonization of Citrobacter rodentium through the S100A4-mediated host inflammatory responses.

Prevalence of multi drug resistant enteropathogenic and enteroinvasive Escherichia coli isolated from children with and without diarrhea in Northeast Indian population

Background

Diarrheagenic Escherichia coli are associated with infantile diarrhea in the developing countries. The present study was conducted to determine the occurrence and antimicrobial resistance pattern of enteropathogenic and enteroinvasive E. coli associated with diarrhoea among the paediatric patients.

Methods

A total of 262 stool samples were collected from children with and without diarrhea from Mizoram, Northeast India. E. coli were isolated and subjected to multiplex PCR to detect virulent genes of EPEC (eaeA and bfpA) and EIEC (ial). Isolates were subjected to antimicrobial sensitivity assay using disc diffusion method. Selected eaeA genes were sequenced for identification and genetic relationship.

Results

A total of 334 E. coli was isolated, of which 17.37% were carrying at least one virulent gene. Altogether, 14.97 and 2.40% isolates were categorized as EPEC and EIEC, respectively. Among the DEC isolates, 4.79% were EPEC and 7.78% were EIEC. A total of 8 (2.40%) isolates were EIEC (ial+), of which 6 (1.80%) and 2 (0.60%) were from diarrhoeic and non-diarrhoeic patients, respectively. A total of 24 (41.40%) DEC isolates were MDR (resistance against ≥5 antimicrobials).

Conclusions

A high frequency of EPEC pathotypes associated with paediatric diarrhea was observed in Mizoram, Northeast India and majority of the isolates are resistant to antibiotics with a high frequency of MDR, which is a matter of concern to the public health. This also raises an alarm to the world communities to monitor the resistance pattern and analyse in a global scale to combat the problems of resistance development.

Prevalence of Virulence Genes Associated with Diarrheagenic Pathotypes of Escherichia coli Isolates from Water, Sediment, Fish, and Crab in Aby Lagoon, Côte d'Ivoire

This study was conducted to characterize virulence genes of Escherichia coli isolates from water, sediment, fish, and crab in Aby Lagoon. Serogrouping was performed by EPEC antisera in 113 E. coli strains. The presence of diarrhea-associated genes (eae, stx, AggR, elt, and est) was assessed by multiplex PCR using specific primers. Based on the multiplex PCR, sixty-two isolates (42 from water, 19 from sediment, and 1 from crab) were positive for virulence genes, including 34 positive for elt (ETEC), 46 positive for est (ETEC), 24 positive for both elt and est, 6 positive for stx (EHEC), 1 positive for both stx + est, and 1 positive for both stx + elt. Genes eae (EPEC) and AggR (EAEC) were not detected. Nine serogroups (O114, O127, O55, O111, O86, O119, O126, O128, and O142) were identified. This study revealed the presence of diarrheagenic and nondiarrheagenic E. coli and potential public health risks if fishery products are not appropriately cooked.

A long-term epigenetic memory switch controls bacterial virulence bimodality

When pathogens enter the host, sensing of environmental cues activates the expression of virulence genes. Opposite transition of pathogens from activating to non-activating conditions is poorly understood. Interestingly, variability in the expression of virulence genes upon infection enhances colonization. In order to systematically detect the role of phenotypic variability in enteropathogenic E. coli (EPEC), an important human pathogen, both in virulence activating and non-activating conditions, we employed the ScanLag methodology. The analysis revealed a bimodal growth rate. Mathematical modeling combined with experimental analysis showed that this bimodality is mediated by a hysteretic memory-switch that results in the stable co-existence of non-virulent and hyper-virulent subpopulations, even after many generations of growth in non-activating conditions. We identified the per operon as the key component of the hysteretic switch. This unique hysteretic memory switch may result in persistent infection and enhanced host-to-host spreading.

DOI:http://dx.doi.org/10.7554/eLife.19599.001

Bacteria typically cope with harsh and changing environments by activating specific genes or accumulating those mutations that change genes in a beneficial way. Recently, it was also shown that the levels of gene activity can vary between otherwise identical bacteria in a single population. This provides an alternative strategy to deal with stressful conditions because it generates sub-groups of bacteria that potentially already adapted to different environments. Bacteria that enter the human body face many challenges, and this kind of pre-adaptation could help them to invade humans and overcome the immune system. However, this hypothesis had not previously been tested in a bacterium called enteropathogenic E.coli, which infects the intestines and is responsible for the deaths of many infants worldwide.

Ronin et al. show that cells in enteropathogenic E.coli colonies spontaneously form into two groups when exposed to conditions that mimic the environment inside the human body. Once triggered, one of these groups is particularly dangerous and this “hypervirulent” state is remembered for an extremely long time meaning that the bacteria remain hypervirulent for many generations. In addition, Ronin et al. identified the specific genes that control the switch to the hypervirulent state.

These findings have uncovered the existence of groups of enteropathogenic E.coli that are pre-adapted to invading human hosts. Finding out more about how the switching mechanism works and its relevance in other bacteria may help researchers to develop new therapies that can help fight bacterial infections.

DOI:http://dx.doi.org/10.7554/eLife.19599.002

PerC Manipulates Metabolism and Surface Antigens in Enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli is an important cause of profuse, watery diarrhea in infants living in developing regions of the world. Typical strains of EPEC (tEPEC) possess a virulence plasmid, while related clinical isolates that lack the pEAF plasmid are termed atypical EPEC (aEPEC). tEPEC and aEPEC tend to cause acute vs. more chronic type infections, respectively. The pEAF plasmid encodes an attachment factor as well as a regulatory operon, perABC. PerC, a poorly understood regulator, was previously shown to regulate expression of the type III secretion system through Ler. Here we elucidate the regulon of PerC using RNA sequencing analysis to better our understanding of the role of the pEAF in tEPEC infection. We demonstrate that PerC controls anaerobic metabolism by increasing expression of genes necessary for nitrate reduction. A tEPEC strain overexpressing PerC exhibited a growth advantage compared to a strain lacking this regulator, when grown anaerobically in the presence of nitrate, conditions mimicking the human intestine. We show that PerC strongly down-regulates type I fimbriae expression by manipulating fim phase variation. The quantities of a number of non-coding RNA molecules were altered by PerC. In sum, this protein controls niche adaptation, and could help to explain the function of the PerC homologs (Pch), many of which are encoded within prophages in related, Gram-negative pathogens.

Comparative genomic analysis of Shiga toxin-producing and non-Shiga toxin-producing Escherichia coli O157 isolated from outbreaks in Korea

Background

The Shiga toxin-producing Escherichia coli (STEC) O157 strain NCCP15739 and non-STEC O157 strain NCCP15738 were isolated from outbreaks in Korea. We characterized NCCP15739 and NCCP15738 by genome sequencing and a comparative genomic analysis using two additional strains, E. coli K-12 substr. MG1655 and O157:H7 EDL933.

Results

Using the Illumina HiSeq 2000 platform and the RAST server, the whole genomes of NCCP15739 and NCCP15738 were obtained and annotated. NCCP15739 and NCCP15738 clustered with different E. coli strains based on a whole-genome phylogeny and multi-locus sequence typing analysis. Functional annotation clustering indicated enrichment for virulence plasmid and hemolysis-related genes in NCCP15739 and conjugation- and flagellum-related genes in NCCP15738. Defense mechanism- and pathogenicity-related pathways were enriched in NCCP15739 and pathways related to the assimilation of energy sources were enriched in NCCP15738. We identified 66 and 18 virulence factors from the NCCP15739 and NCCP15738 genome, respectively. Five and eight antibiotic resistance genes were identified in the NCCP15739 and NCCP15738 genomes, respectively. Based on a comparative analysis of phage-associated regions, NCCP15739 and NCCP15738 had specific prophages. The prophages in NCCP15739 carried virulence factors, but those in NCCP15738 did not, and no antibiotic resistance genes were found in the phage-associated regions.

Conclusions

Our whole-genome sequencing and comparative genomic analysis revealed that NCCP15739 and NCCP15738 have specific genes and pathways. NCCP15739 had more genes (410), virulence factors (48), and phage-related regions (11) than NCCP15738. However, NCCP15738 had three more antibiotic resistance genes than NCCP15739. These differences may explain differences in pathogenicity and biological characteristics.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-017-0156-2) contains supplementary material, which is available to authorized users.

The mechanism underlying Ler-mediated alleviation of gene repression by H-NS

Secretion of effector proteins in Enteropathogeneic Escherichia coli (EPEC) and Enterohemorrhagic Escherichia coli (EHEC) is mediated by a specialized type III secretion system, components of which are encoded in the LEE operons 1 to 5. H-NS, a global repressor in E. coli, silences the expression of LEE operons. Ler, a master regulator in LEE operons, shares 24% amnio acid identity and 44% amino acid similarity to H-NS. Interestingly, rather than a gene silencer, its main role has been characterized as an antagonizing protein that relieves H-NS-mediated transcriptional silencing. In the previous study we reported molecular mechanism for the repression of LEE5 promoter in EPEC and EHEC by H-NS as a protein interaction between upstream DNA-bound H-NS and the αCTD of promoter-bound RNA polymerase. The mechanism underlying Ler-mediated alleviation of the genes repression by H-NS is largely unknown. We examined regulatory effect of these proteins on LEE5p activity using various in vitro tools. Our results revealed that binding affinity of Ler to the LEE5p DNA is about 40 folds greater than that of H-NS as determined by surface plasmon resonance. We verified that Ler binding removed H-NS bound to the same stretch of DNA on LEE5 promoter resulting in a derepression.

The 12 Gastrointestinal Pathogens Spectrum of Acute Infectious Diarrhea in a Sentinel Hospital, Shenzhen, China

Acute infectious gastroenteritis is one of the most common diseases among all ages, particularly in developing countries. The pathogen spectrum may differ among different regions and seasons. To investigate the etiology of acute diarrhea in Shenzhen, a prospective study was conducted from August 2014 to September 2015. Stools from 412 patients with diarrhea (286 of whom were adults) including the general epidemiological information of the patients were collected. The 19 pathogens were detected by conventional culture method or multiplex PCR assay, which included five viruses (rotavirus, adenovirus, sapovirus, norovirus, and astrovirus), 11 bacterial pathogens (Salmonella, Campylobacter jejuni, Shigella, Listeria monocytogenes, Vibrio parahaemolyticus, Vibrio cholera, Enterohemorrhagic (EHEC), enteropathogenic (EPEC), enteroinvasive (EIEC), enterotoxigenic (ETEC); and enteroaggregative Escherichia coli (EAEC)) and three parasites (Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum). A potential pathogen and coinfection was found in 41.5 and 7.0% of cases, respectively. The bacterial infection was the dominant cause of diarrhea (32.3%), and the three most frequently identified organisms were Salmonella (12.1%), ETEC (8.0%), and Campylobacter jejuni (4.9%). Salmonella enteritidis was the leading serotype of Salmonella sp. Norovirus (8.3%) and sapovirus (2.2%) were the most common viral pathogens, followed by adenovirus (1.5%) and rotavirus (1.2%). No EHEC, L. monocytogenes, V. cholera, Shigella, and parasites were found. The single most important causes of diarrhea were Salmonella spp. and Campylobacter jejuni, which points toward the need for testing and surveillance for these pathogens in this region.

Comparison of two methods for detection of E. coli O157H7 in unpasteurized milk

BACKGROUND AND OBJECTIVES

The most common serotype of enterohaemorrhagic Esherichia coli group or Shiga-toxin-producing E. coli is O157:H7. Domestic and wild ruminants are regarded as the main natural reservoirs. O157:H7 serotype is the major cause of gastrointestinal infections in developed countries. In this study was conducted to survey on the toxigenic E. coli O157: H7 strains in milk of industrial dairy farms.

MATERIALS AND METHODS

A total number of 150 milk samples were collected from dairy industry in Khuzestan, over a period of 6 months and were evaluated by cultivation in selective media (CT-SMAC) and multiplex PCR.

RESULTS

Two isolates were identified as E. coli using biochemical tests, none of them were toxigenic E. coli O157:H7 as determined by multiplex PCR. Using direct PCR on milk samples, 45 samples contained at least one gene of the studied genes in this investigation (rfb, flic, stx1, stx2). With direct PCR, 2 milk samples were positive for toxigenic O157:H7.

CONCLUSION

E. coli O157:H7 is present in this region and so the necessity for strict compliance of health standards is recommended. This is the first study on O157: H7 E. coli milk contamination in Khuzestan province. Based on these results, direct PCR is more accurate than indirect PCR.

Identification of virulence factors and antibiotic resistance markers using bacterial genomics

In recent years, the number of multidrug-resistant bacteria has increased rapidly and several epidemics were signaled in different regions of the world. Faced with this situation that presents a major global public health concern, the development and the use of new and rapid technologies is more than urgent. The use of the next-generation sequencing platforms by microbiologists and infectious disease specialists has allowed great progress in the medical field. Here, we review the usefulness of whole-genome sequencing for the detection of virulence and antibiotic resistance associated genes.

Virulence Gene Regulation in Escherichia coli

Escherichia colicauses three types of illnesses in humans: diarrhea, urinary tract infections, and meningitis in newborns. The acquisition of virulence-associated genes and the ability to properly regulate these, often horizontally transferred, loci distinguishes pathogens from the normally harmless commensal E. coli found within the human intestine. This review addresses our current understanding of virulence gene regulation in several important diarrhea-causing pathotypes, including enteropathogenic, enterohemorrhagic,enterotoxigenic, and enteroaggregativeE. coli-EPEC, EHEC, ETEC and EAEC, respectively. The intensely studied regulatory circuitry controlling virulence of uropathogenicE. coli, or UPEC, is also reviewed, as is that of MNEC, a common cause of meningitis in neonates. Specific topics covered include the regulation of initial attachment events necessary for infection, environmental cues affecting virulence gene expression, control of attaching and effacing lesionformation, and control of effector molecule expression and secretion via the type III secretion systems by EPEC and EHEC. How phage control virulence and the expression of the Stx toxins of EHEC, phase variation, quorum sensing, and posttranscriptional regulation of virulence determinants are also addressed. A number of important virulence regulators are described, including the AraC-like molecules PerA of EPEC, CfaR and Rns of ETEC, and AggR of EAEC;the Ler protein of EPEC and EHEC;RfaH of UPEC;and the H-NS molecule that acts to silence gene expression. The regulatory circuitry controlling virulence of these greatly varied E. colipathotypes is complex, but common themes offerinsight into the signals and regulators necessary forE. coli disease progression.

High-level Multi-Resistant and Virulent Escherichia coli in Abeokuta, Nigeria

Multi-resistant Escherichia coli (E. coli) strains co-harboring virulence genes is a cause of high morbidity in Abeokuta, Nigeria. This study was designed to determine some virulent factors among enteropathogenic E. coli in Abeokuta, Nigeria. Approximately non-repetitive 102 isolates of E. coli were recovered from clinical samples from two health facilities in Abeokuta. Biotyping using API and antibiotic susceptibility was determined, and eae and flic genes were assayed by PCR. Antibiotic resistance relatedness was performed by DendroUPGMA. Results showed that 48.0% and 52.0 % were intestinal and extra-intestinal E. coli, ampicillin recorded 100% resistance, amoxycilli/clavulanic acid 64.7%, cotrimoxazole 57.8% and 56.8% resistance against cefotaxime, at MIC >16 ug/mL, 100%, 57.8%, and 50% have MIC50 to ampicillin, tetracycline, and ceftazidime, while 74.5% and 48.0% have MIC90 to ampicillin and ceftazidime. Significant rates of 4.9%, 7.8%, and 9.8% flic, eae, and flic/eae genes were found in intestinal isolates, while 2.9%, 2.0%, and 3.9% were found in extra-intestinal (P < 0.05). Two major clades of the resistant isolates reveal significant antibiotic relatedness among intestinal and extra-intestinal isolates, at 54% resistance similarities with very high multi-antibiotic resistance index of 1.0 (MARI). A high rate of undetected virulent E. coli pathotypes with high resistance could trigger unprecedented morbidity and mortality, mostly among children and the elderly.

Enteropathogenic Escherichia coli (EPEC): Does it have a role in colorectal tumourigenesis? A Prospective Cohort Study

BACKGROUND

Despite the characterization of many aetiologic genetic changes. The specific causative factors in the development of sporadic colorectal cancer remain unclear. This study was performed to detect the possible role of Enteropathogenic Escherichia coli (EPEC) in developing colorectal carcinoma.

PATIENTS AND METHOD

Fresh biopsy specimens have been obtained from the colonic mucosa overlying the colorectal cancer as well as from the colon of the healthy controls. Culture, genotyping and virulence of EPEC were done using (nutrient broth culture, and PCR). Strains biochemically identified as Escherichia coli were selected from the surface of a MacConkey's plate and were serogrouped by slide agglutination tests.

RESULTS

From January 2011 to June 2014, 213 colorectal cancer patients (Group 1) and 248 healthy controls (Group 2) were prospectively enrolled in this study. EPEC was positive in 108 (50.7%) in group 1 and 51 (20.6%) in group 2 (P = 0.0001). A significant difference between both groups was observed regarding serotyping, genotyping (eae gene) and virulence category (P = 0.0001). A significant difference between the 2 subgroups of colorectal cancer cases was observed regarding genotyping (eae, bfb genes) and virulence category.

CONCLUSION

The incidence EPEC was higher significantly in patients with colorectal cancer. E. coli in patients with colorectal cancer significantly differed serotypically and genotypically from the E. coli in normal population. E. coli colonization of the colonic mucosa may be a cause colorectal cancer.

The RpoE Stress Response Pathway Mediates Reduction of the Virulence of Enteropathogenic Escherichia coli by Zinc

Zinc supplements are an effective clinical treatment for infantile diarrheal disease caused by enteric pathogens. Previous studies demonstrated that zinc acts on enteropathogenic Escherichia coli (EPEC) bacteria directly to suppress several virulence-related genes at a concentration that can be achieved by oral delivery of dietary zinc supplements. Our in vitro studies showed that a micromolar concentration of zinc induced the envelope stress response and suppressed virulence in EPEC, providing a possible mechanistic explanation for zinc's therapeutic action. In this report, we investigated the molecular and physiological changes in EPEC induced by zinc. We found that micromolar concentrations of zinc reduced the bacterial growth rate without affecting viability. We observed increased membrane permeability caused by zinc. Zinc upregulated the RpoE-dependent envelope stress response pathway and suppressed EPEC virulence gene expression. RpoE alone was sufficient to inhibit virulence factor expression and to attenuate attaching and effacing lesion formation on human host cells. By mutational analysis we demonstrate that the DNA-binding motif of RpoE is necessary for suppression of the LEE1, but not the LEE4, operon. Predictably, inhibition of the RpoE-mediated envelope stress response in combination with micromolar concentrations of zinc reduced EPEC viability. In conclusion, zinc induces the RpoE and stress response pathways in EPEC, and the alternate sigma factor RpoE downregulates EPEC LEE and non-LEE virulence genes by multiple mechanisms.

Activation of intestinal epithelial Stat3 orchestrates tissue defense during gastrointestinal infection

Gastrointestinal infections with EHEC and EPEC are responsible for outbreaks of diarrheal diseases and represent a global health problem. Innate first-line-defense mechanisms such as production of mucus and antimicrobial peptides by intestinal epithelial cells are of utmost importance for host control of gastrointestinal infections. For the first time, we directly demonstrate a critical role for Stat3 activation in intestinal epithelial cells upon infection of mice with Citrobacter rodentium – a murine pathogen that mimics human infections with attaching and effacing Escherichia coli. C. rodentium induced transcription of IL-6 and IL-22 in gut samples of mice and was associated with activation of the transcription factor Stat3 in intestinal epithelial cells. C. rodentium infection induced expression of several antimicrobial peptides such as RegIIIγ and Pla2g2a in the intestine which was critically dependent on Stat3 activation. Consequently, mice with specific deletion of Stat3 in intestinal epithelial cells showed increased susceptibility to C. rodentium infection as indicated by high bacterial load, severe gut inflammation, pronounced intestinal epithelial cell death and dissemination of bacteria to distant organs. Together, our data implicate an essential role for Stat3 activation in intestinal epithelial cells during C. rodentium infection. Stat3 concerts the host response to bacterial infection by controlling bacterial growth and suppression of apoptosis to maintain intestinal epithelial barrier function.

A systematic review and meta-analysis of the epidemiology of pathogenic Escherichia coli of calves and the role of calves as reservoirs for human pathogenic E. coli

Escherichia coli bacteria are the most common causes of diarrhea and septicemia in calves. Moreover, calves form a major reservoir for transmission of pathogenic E. coli to humans. Systematic reviews and meta-analyses of publications on E. coli as calf pathogens and the role of calves as reservoir have not been done so far. We reviewed studies between 1951 and 2013 reporting the presence of virulence associated factors (VAFs) in calf E. coli and extracted the following information: year(s) and country of sampling, animal number, health status, isolate number, VAF prevalence, serotypes, diagnostic methods, and biological assays. The prevalence of VAFs or E. coli pathotypes was compared between healthy and diarrheic animals and was analyzed for time courses. Together, 106 papers with 25,982 E. coli isolates from 27 countries tested for VAFs were included. F5, F17, and F41 fimbriae and heat-stable enterotoxin (ST) – VAFs of enterotoxigenic E. coli (ETEC) were significantly associated with calf diarrhea. On the contrary, ETEC VAF F4 fimbriae and heat-labile enterotoxin as well as enteropathogenic (EPEC), Shiga toxin-producing (STEC), and enterohemorrhagic E. coli (EHEC) were not associated with diarrhea. The prevalence increased overtime for ST-positive isolates, but decreased for F5- and STEC-positive isolates. Our study provides useful information about the history of scientific investigations performed in this domain so far, and helps to define etiological agents of calf disease, and to evaluate calves as reservoir hosts for human pathogenic E. coli.

Oral infection with enteropathogenic Escherichia coli triggers immune response and intestinal histological alterations in mice selected for their minimal acute inflammatory responses

Enteropathogenic Escherichia coli (EPEC), a leading cause of infant diarrhea, is an important public health problem in Brazil and other developing countries. In vitro assays of bacterial adhesion to cultured cells are important tools for studying bacterial pathogenicity but do not reproduce all the events that occur in natural infections. In this study, the effects of oral infection with EPEC on mice selected for their minimal acute inflammatory response (AIR min) were evaluated. Mice were orally infected with EPEC and variations in body weight, bacterial shedding and antibody production observed. The infected animals developed seric and secretory anti-EPEC antibodies; however, neither mortality nor diarrhea was observed. Light microscopy of their intestines demonstrated histological modifications that were not present in controls. However, electron microscopy did not show bacteria attached to the intestinal epithelia to form attaching and effacing lesions, characteristic of EPEC in humans. The bacteria were detected in Peyer's patches and intestinal contents up to 5 hr post-infection. When human anti-EPEC secretory immunoglobulin A or avian immunoglobulin Y antibodies were administered to infected animals, they developed minor histological alterations compared with non-treated animals. In summary, it was found that EPEC triggers immune responses and intestinal histological alterations but does not produce evidence of diarrheal disease in mice infected by the oral route. This study of EPEC experimental infection provides a better understanding of the effects of antibodies on bacterial infections and may provide a suitable model for the design and testing of immunobiological products for active or passive immunization.

A systematic review and meta-analysis of the epidemiology of pathogenic Escherichia coli of calves and the role of calves as reservoirs for human pathogenic E. coli

Escherichia coli bacteria are the most common causes of diarrhea and septicemia in calves. Moreover, calves form a major reservoir for transmission of pathogenic E. coli to humans. Systematic reviews and meta-analyses of publications on E. coli as calf pathogens and the role of calves as reservoir have not been done so far. We reviewed studies between 1951 and 2013 reporting the presence of virulence associated factors (VAFs) in calf E. coli and extracted the following information: year(s) and country of sampling, animal number, health status, isolate number, VAF prevalence, serotypes, diagnostic methods, and biological assays. The prevalence of VAFs or E. coli pathotypes was compared between healthy and diarrheic animals and was analyzed for time courses. Together, 106 papers with 25,982 E. coli isolates from 27 countries tested for VAFs were included. F5, F17, and F41 fimbriae and heat-stable enterotoxin (ST) - VAFs of enterotoxigenic E. coli (ETEC) were significantly associated with calf diarrhea. On the contrary, ETEC VAF F4 fimbriae and heat-labile enterotoxin as well as enteropathogenic (EPEC), Shiga toxin-producing (STEC), and enterohemorrhagic E. coli (EHEC) were not associated with diarrhea. The prevalence increased overtime for ST-positive isolates, but decreased for F5- and STEC-positive isolates. Our study provides useful information about the history of scientific investigations performed in this domain so far, and helps to define etiological agents of calf disease, and to evaluate calves as reservoir hosts for human pathogenic E. coli.