Investigation on the evolution of Shiga Toxin-converting phages based on whole genome sequencing

Bacteriophages are pivotal elements in the dissemination of virulence genes. The main virulence determinants of Shiga Toxin producing E. coli, Shiga Toxins (Stx), are encoded by genes localized in the genome of lambdoid bacteriophages. Stx comprise two antigenically different types, Stx1 and Stx2, further divided into subtypes. Among these, certain Stx2 subtypes appear to be more commonly occurring in the most severe forms of the STEC disease, haemorrhagic colitis and haemolytic uremic syndrome (HUS). This study aimed at obtaining insights on the evolution of Stx2 bacteriophages, due to their relevance in public health, and we report here on the analysis of the genomic structure of Stx2 converting phages in relation with the known reservoir of the E. coli strains harboring them. Stx2-converting phages conveying the genes encoding different stx2 subtypes have been isolated from STEC strains and their whole genomes have been sequenced, analyzed and compared to those of other Stx2 phages available in the public domain. The phages' regions containing the stx2 genes have been analyzed in depth allowing to make inference on the possible mechanisms of selection and maintenance of certain Stx2 phages in the reservoir. The 'stx regions' of different stx2 gene subtypes grouped into three different evolutionary lines in the comparative analysis, reflecting the frequency with which these subtypes are found in different animal niches, suggesting that the colonization of specific reservoir by STEC strains could be influenced by the Stx phage that they carry. Noteworthy, we could identify the presence of nanS-p gene exclusively in the 'stx regions' of the phages identified in STEC strains commonly found in cattle. As a matter of fact, this gene encodes an esterase capable of metabolizing sialic acids produced by submaxillary glands of bovines and present in great quantities in their gastrointestinal tract

Community-wide outbreak of haemolytic uraemic syndrome associated with Shiga toxin 2-producing Escherichia coli O26:H11 in southern Italy, summer 2013

In summer 2013, an excess of paediatric cases of haemolytic uraemic syndrome (HUS) in a southern region of Italy prompted the investigation of a community-wide outbreak of Shiga toxin 2-producing Escherichia coli (STEC) O26:H11 infections. Case finding was based on testing patients with HUS or bloody diarrhoea for STEC infection by microbiological and serological methods. A case-control study was conducted to identify the source of the outbreak. STEC O26 infection was identified in 20 children (median age 17 months) with HUS, two of whom reported severe neurological sequelae. No cases in adults were detected. Molecular typing showed that two distinct STEC O26:H11 strains were involved. The case-control study showed an association between STEC O26 infection and consumption of dairy products from two local plants, but not with specific ready-to-eat products. E.coli O26:H11 strains lacking the stx genes were isolated from bulk milk and curd samples, but their PFGE profiles did not match those of the outbreak isolates. This outbreak supports the view that infections with Stx2-producing E. coli O26 in children have a high probability of progressing to HUS and represent an emerging public health problem in Europe

Metagenomic Characterization of the Human Intestinal Microbiota in Fecal Samples from STEC-Infected Patients

The human intestinal microbiota is a homeostatic ecosystem with a remarkable impact on human health and the disruption of this equilibrium leads to an increased susceptibility to infection by numerous pathogens. In this study, we used shotgun metagenomic sequencing and two different bioinformatic approaches, based on mapping of the reads onto databases and on the reconstruction of putative draft genomes, to investigate possible changes in the composition of the intestinal microbiota in samples from patients with Shiga Toxin-producing E. coli (STEC) infection compared to healthy and healed controls, collected during an outbreak caused by a STEC O26:H11 infection. Both the bioinformatic procedures used, produced similar result with a good resolution of the taxonomic profiles of the specimens. The stool samples collected from the STEC infected patients showed a lower abundance of the members of Bifidobacteriales and Clostridiales orders in comparison to controls where those microorganisms predominated. These differences seemed to correlate with the STEC infection although a flexion in the relative abundance of the Bifidobacterium genus, part of the Bifidobacteriales order, was observed also in samples from Crohn's disease patients, displaying a STEC-unrelated dysbiosis. The metagenomics also allowed to identify in the STEC positive samples, all the virulence traits present in the genomes of the STEC O26 that caused the outbreak as assessed through isolation of the epidemic strain and whole genome sequencing. The results shown represent a first evidence of the changes occurring in the intestinal microbiota of children in the course of STEC infection and indicate that metagenomics may be a promising tool for the culture-independent clinical diagnosis of the infection

IRIDA-ARIES Genomics, a key player in the One Health surveillance of diseases caused by infectious agents in Italy

Pathogen genomics is transforming surveillance of infectious diseases, deepening our understanding of evolution and diffusion of etiological agents, host-pathogen interactions and antimicrobial resistance. This discipline is playing an important role in the development of One Health Surveillance with public health experts of various disciplines integrating methods applied to pathogen research, monitoring, management and prevention of outbreaks. Especially with the notion that foodborne diseases may not be transmitted by food only, the ARIES Genomics project aimed to deliver an Information System for the collection of genomic and epidemiological data to enable genomics-based surveillance of infectious epidemics, foodborne outbreaks and diseases at the animal-human interface. Keeping in mind that the users of the system comprised persons with expertise in a wide variety of domains, the system was expected to be used with a low learning curve directly by the persons target of the analyses' results, keeping the information exchange chains as short as possible. As a result, the IRIDA-ARIES platform (https://irida.iss.it/) provides an intuitive web-based interface for multisectoral data collection and bioinformatic analyses. In practice, the user creates a sample and uploads the Next-generation sequencing reads, then an analysis pipeline is launched automatically performing a series of typing and clustering operations fueling the information flow. Instances of IRIDA-ARIES host the Italian national surveillance system for infections by Listeria monocytogenes (Lm) and the surveillance system for infections by Shigatoxin-producing Escherichia coli (STEC). As of today, the platform does not provide tools to manage epidemiological investigations but serves as an instrument of aggregation for risk monitoring, capable of triggering alarms on possible critical situations that might go unnoticed otherwise

A cross-sectional study in four provinces of Mozambique: Diarrheagenic Escherichia coli in Mozambique

Funding Information: The National Surveillance of Diarrhea was supported by a Senior Fellowship awarded to Nilsa de Deus by the European Foundations Initiative for African Research into Neglected Tropical Diseases (EFINTD, grant number 98539), the World Health Organization, a Master Fellowship funded by the Italian Agency for Development Cooperation (AICS) project AID10524, Deutsche Forschungsgemeinschaft (DFG, grant number JO369/5–1)—where Adilson Fernando Loforte Bauhofer and Assucênio Chissaque are fellows, GAVI (Global Alliance for Vaccines and Immunization) through Health System Strengthening (HSS), and Fundo Nacional de Investigação (FNI). The protocol was approved by the National Bioethics Committee for Health of Mozambique (IRB00002657, reference number: 348/CNBS/13), and each caregiver gave written informed consent to authorize their child's participation. The authors want to thank the parents or guardians who consented to their children's enrollment in the surveillance program. The authors acknowledge Dr. Octávio Jossai, the National Reference Laboratory of Microbiology team, all the focal points, and the provincial field teams who helped to conduct this study. Funding Information: The National Surveillance of Diarrhea was supported by a Senior Fellowship awarded to Nilsa de Deus by the European Foundations Initiative for African Research into Neglected Tropical Diseases (EFINTD, grant number 98539), the World Health Organization, a Master Fellowship funded by the Italian Agency for Development Cooperation (AICS) project AID10524, Deutsche Forschungsgemeinschaft (DFG, grant number JO369/5–1)—where Adilson Fernando Loforte Bauhofer and Assucênio Chissaque are fellows, GAVI (Global Alliance for Vaccines and Immunization) through Health System Strengthening (HSS), and Fundo Nacional de Investigação (FNI). Publisher Copyright: © 2022Objectives: Analyze the frequency of diarrheagenic Escherichia coli (DEC) pathotypes and their antimicrobial resistance profiles among children aged <15 years with diarrhea in four Mozambican provinces. Methods: A cross-sectional hospital-based surveillance program of diarrhea was implemented in Maputo, Sofala, Zambézia, and Nampula. A single stool sample was collected from each child from May 2014 to May 2017. Culture methods and biochemical characterization were performed to detect E. coli strains. DEC pathotypes were determined by conventional polymerase chain reaction targeting specific virulence genes. Antimicrobial susceptibility was assessed by the Kirby–Bauer method. Results: From 723 specimens analyzed by culture, 262 were positive for E. coli. A total of 208 samples were tested by polymerase chain reaction for DEC identification, of which 101 (48.6%) were positive for a DEC pathotype. The predominant pathotypes were enteroaggregative (66.3%, 67/101), enteropathogenic (15.8%, 16/101), enterotoxigenic (13.9%, 14/101), and enteroinvasive E. coli (4.0%, 4/101). No Shiga toxin–producing E. coli was identified. Regardless of the province, the most frequent pathotype was enteroaggregative E. coli. Isolated DEC presented high frequency of resistance to ampicillin (97.8%), tetracycline (68.3%), chloramphenicol (28.4%), nalidixic acid (19.5%), and gentamicin (14.4%). Conclusion: Children with diarrhea in Mozambique had DEC and higher resistance to ampicillin and tetracycline.publishersversionpublishe

Whole-Genome Characterization and Strain Comparison of VT2f-Producing Escherichia coli Causing Hemolytic Uremic Syndrome.

Verotoxigenic Escherichia coli infections in humans cause disease ranging from uncomplicated intestinal illnesses to bloody diarrhea and systemic sequelae, such as hemolytic uremic syndrome (HUS). Previous research indicated that pigeons may be a reservoir for a population of verotoxigenic E. coli producing the VT2f variant. We used whole-genome sequencing to characterize a set of VT2f-producing E. coli strains from human patients with diarrhea or HUS and from healthy pigeons. We describe a phage conveying the vtx2f genes and provide evidence that the strains causing milder diarrheal disease may be transmitted to humans from pigeons. The strains causing HUS could derive from VT2f phage acquisition by E. coli strains with a virulence genes asset resembling that of typical HUS-associated verotoxigenic E. coli

Identification and functional analysis of virulence determinants of Verocytotoxin-producing Escherichia coli (VTEC)

Verocytotoxin(VT)-producing Escherichia coli (VTEC) are important zoonotic pathogens whose natural reservoir is the gastrointestinal tract of ruminants. The transmission of the infections mainly occurs via the ingestion of contaminated food of animal origin. VTEC pathogenicity relies on the production of the VTs and on the action of accessory virulence factors constituting the virulome, which has not been completely identified yet. The main objective of this piece of research was the identification of the genomic structures forming the VTEC virulome. An additional goal was the analysis of their distribution in different VTEC sub-populations. Finally, a function for some of the factors identified and involved in the pathogenetic mechanism has been proposed. The work presented here has been largely based on the genomic comparison of VTEC strains isolated from human and animal sources and held in the collections of the EU RL VTEC and of the collaborating institutions Statens Serum Institut (Copenhagen, DK) and University of Extremadura (Caceres, ES). This approach led to the identification and characterisation of two pathogenicity islands (PAIs) proposed to be part of the virulome of VTEC strains commonly isolated from cases of human disease. The two PAIs harbour genes encoding factors involved in the colonization (adfO, OI-57, Chapter 4 and tia, SE-PAI, Chapter 3) or specifying an allelic variant of the Subtilase cytotoxin (subAB2, SE-PAI, Chapter 3). The identification and characterization of the open reading frames carried by the two PAIs allowed making inference on the function of the encoded proteins and on their role in the pathogenetic process. As a matter of fact, the tia and shiA genes (SE-PAI, Chapter 3) have been proposed to be part of the colonization machinery of VTEC strains lacking the ability to cause attaching-and-effacing (A/E) lesions on the intestinal mucosa, a typical feature of the VTEC associated with the most severe forms of the infection. The products of genes homologues to tia and shiA have been in fact described respectively to have a role in the process of cell invasion used by some enterotoxigenic E. coli strains or in the attenuation of host inflammatory response upon infection of another invasive enteric pathogen: Shigella flexneri. The genomic approach has also been used to investigate on the VT-producing Enteroaggregative E. coli O104:H4 that caused an outbreak in Germany in 2011. This peculiar VTEC is characterised by a rare combination of virulence traits from Enteroaggregative E. coli (EAEC) and VTEC, two different E. coli pathotypes responsible for enteric infections in low-income areas and common in industrialized countries respectively. Before the German outbreak, VTEC O104:H4 had been isolated in a few sporadic cases of infection, sometimes with an epidemiological connection with travel in North Africa. Similarly, the strain that caused the German outbreak was introduced into the EU with fenugreek seeds produced in Egypt. These observations, together with the genomic stability observed for some of the VTEC O104 strain (Chapter 5), led to the hypothesis that such chimeric strains may have emerged in developing countries. The high loads of enteric pathogens causing diarrhoea and lack of wastewater treatment in these geographic regions, cause the diffuse faecal contamination of the environment, particularly of the aquatic ecosystem often shared with ruminants, facilitating the exchange of mobile genetic elements between human and animal E. coli pathotypes and leading to the formation of new combinations of virulence features such as those characterising the VT-producing EAEC O104:H4

Metagenomic Characterization of the Human Intestinal Microbiota in Fecal Samples from STEC-Infected Patients

Contains fulltext : 190030.pdf (publisher's version ) (Open Access

Production of the Subtilase AB5 Cytotoxin by Shiga Toxin-Negative Escherichia coli▿

The subtilase cytotoxin (SubAB) is an AB5 toxin described in certain Shiga toxin (Stx)-producing Escherichia coli (STEC) strains that usually lack the locus for enterocyte effacement (LEE). We report for the first time the production of SubAB by two Stx-negative E. coli strains, isolated from unrelated cases of childhood diarrhea. The characterization of the SubAB-coding genes showed a 90% nucleotide sequence similarity with that of the prototype subAB, located on the virulence plasmid of the STEC O113 strain 98NK2 (pO113). In both strains, subAB was physically associated with tia, an invasion genetic determinant of enterotoxigenic E. coli. The strains were negative for the saa gene, encoding an adhesin located on pO113 and present in many of the SubAB-positive strains described so far. PCR screening of 61 STEC and 100 Stx-negative E. coli strains in our collection revealed the presence of subAB in five LEE-negative STEC strains but not in the Stx-negative strains. subAB was contiguous to tia in three of the positive strains, which were all negative for saa. These results indicate that SubAB production is not restricted to STEC and suggest that a subAB-tia putative pathogenicity island is involved in the dissemination of subAB genes, as an alternative to plasmid pO113