Escherichia albertii, a newly emerging enteric pathogen with poorly defined properties

Whole-genome-based characterization of Escherichia albertii strains isolated from paediatric diarrhoeal cases in Kolkata, India

Escherichia albertii is a Gram-negative facultative anaerobic bacterium that causes diarrhoea in humans. This study shows the isolation of E. albertii from hospitalized paediatric diarrhoeal cases and genome-based characteristics with putative virulence factors and antimicrobial resistance. E. albertii isolates were identified by species-specific PCR, targeting the gene encoding cytolethal distending toxin (Ea-cdt). The genome of E. albertii was sequenced to identify (i) genes encoding virulence factors (ii) antibiotic resistance-encoding genes, including the mobile genetic elements and (iii) core gene-based phylogenetic relationships and pan-genome features. A total of 10 (1.2%) E. albertii isolates were isolated from 854 faecal samples, of which 6 (60%) were found as the sole pathogen and the remaining 4 (40%) were identified along with other pathogens, such as enteroaggregative Escherichia coli, rotavirus and adenovirus. Patients from whom E. albertii was isolated presented cholera-like diarrhoea, i.e. with watery stool (60%) with moderate dehydration (100%), fever (20%) and abdominal pain (20%). The antimicrobial susceptibility testing of E. albertii showed that most of the isolates were susceptible or reduced susceptible to most of the antibiotics except resistance to erythromycin (80%), tetracycline (50%), nalidixic acid (40%), ampicillin (40%), doxycycline (30%) and ceftriaxone (20%). In the whole-genome sequence, E. albertii isolates revealed several virulence-encoding genes, namely the intimin (eae, E. coli attaching and effacing), the cytolethal distending toxin type II subunit A (cdt-IIA), adhesion (paa, porcine attaching- and effacing-associated), non-LEE (locus of enterocyte effacement) encoded effector A (nleA) and antimicrobial resistance genes (ARGs) conferring resistance to tetracycline (tetA, tetR), sulphonamides (sul2), fluoroquinolones (qnrS) and beta-lactamases (bla CTX-M, blaTEM). The SNP-based phylogenetic analysis of 647 whole genomes of E. albertii isolates from the National Center for Biotechnology Information databases did not reveal any comparable clustering pattern based on the biological source and place of isolation. The genome of some of the E. albertii was closely related to those of the isolates from China and the United Kingdom. The PFGE patterns revealed that most of the E. albertii isolates were distinct clones. This study reports on the extensive genome analysis of diarrhoea-associated E. albertii harbouring multiple virulence and ARGs.

Evaluation of a novel modified selective medium cefixime-tellurite-phosphate-xylose-rhamnose MacConkey agar for the isolation of Escherichia albertii from diarrheal stool specimens

It is challenging to isolate Escherichia albertii from clinical specimens. Therefore, a medium that can selectively grow E. albertii and differentiate it from E. coli is earnestly desired. Here, we describe the evaluation of a recently developed selective differential medium, called cefixime-tellurite-phosphate-xylose-rhamnose-MacConkey (CT-PS-XR-MacConkey) medium, which enables the specific growth of E. albertii and differentiation of E. albertii (colorless) from E. coli (red) based on colony color and thus, facilitating the efficient isolation of E. albertii from diarrheal stool. When three E. albertii negative diarrheal stools were inoculated onto CT-PS-XR-MacConkey and xylose-rhamnose-melibiose (XRM) containing MacConkey agars, no colorless colonies were observed on both the media. However, when E. albertii was spiked into these three diarrheal stools, the ratio of colorless colonies to red colonies was higher on CT-PS-XR-MacConkey agar compared to XRM-MacConkey agar in all three samples. Notably, out of 105 Eacdt-gene PCR negative diarrheal stools 56 yielded colorless colonies on MacConkey agar while out of these 56 diarrheal stools, nine yielded colorless colonies on XRM-MacConkey but no colorless colonies were observed on CT-PS-XR-MacConkey agar. Furthermore, evaluation of these two media with five E. albertii positive-stool specimens revealed that the number of red colonies were constantly less, whereas that of colorless colonies were constantly more on CT-PS-XR-MacConkey agar, thus aiding in efficient isolation. Altogether, these results suggest that the CT-PS-XR-MacConkey agar could be a useful selective differential medium for isolation of E. albertii from diarrheal stool specimens.

Development of a novel modified selective medium cefixime-tellurite-phosphate-xylose-rhamnose MacConkey agar for isolation of Escherichia albertii and its evaluation with food samples

Since cefixime and tellurite are known to inhibit most bacteria belonging to Enterobacterales, we found that addition of tellurite inhibited E. albertii growth in Luria Bertani broth but not in tryptic soy broth (TSB), and addition of phosphate and soy peptone enhanced E. albertii growth in TSB in presence of tellurite. Subsequently, to find the positive factor present in TSB, E. albertii growth was examined in tryptone, soy peptone, glucose, or phosphate deficient tryptic soy agar plates. Phosphate, soy peptone, and/or glucose deficiency indeed decreased E. albertii growth. However, none of the substances are specifically present in xylose-rhamnose-melibiose (XRM)-MacConkey agar and thus, not affecting E. albertii growth. Altogether, a novel E. albertii selective differential medium, XRM-MacConkey medium containing cefixime (C), tellurite (T), phosphate (P), and soy peptone (S) (named CT-PS-XR-MacConkey medium), which differentiate E. albertii (colorless) from E. coli (red) by colony color, has been developed. The CT-PS-XR-MacConkey agar was evaluated with 156 bacterial strains including 65 E. albertii. While all E. albertii strains grew as colorless colonies, 54 strains of 9 different genera belonging to 19 different species were unable to grow on this medium. However, rest of these bacterial strains grew either as colorless or as red colonies. Furthermore, spiking experiments using chicken meat as food samples showed that the CT-PS-XR-MacConkey medium is highly selective for E. albertii than XRM-MacConkey agar. Altogether, the results suggest that the CT-PS-XR-MacConkey agar is indeed a useful selective medium for isolation of E. albertii from food samples.

Isolation and Detection of the Emerging Pathogen Escherichia albertii in Clinical Stool Samples and the Potential Transmission by Meat Samples in Retail

The significance of Escherichia albertii as a foodborne pathogen is increasingly acknowledged, but the assessment of its occurrence and transmission remains challenging due to the lack of validation of selective isolation, detection, and identification methods. The aim of the present study was to examine its presence on various meat samples at the retail level in order to assess a potential foodborne transmission and its occurrence in clinical stool samples. First, the evaluation and selection of a selective enrichment broth and isolation medium, combined with an optimized identification by MALDI-TOF MS, as well as a suitable DNA extraction method and a PCR-based detection strategy were developed. After the evaluation of existing isolation strategies and the formulation of an adapted enrichment and isolation medium, 100% isolation specificity was not achieved. An identity confirmation of suspected colonies remains necessary. A total of 292 samples, including 45 beef fillet, 51 minced beef, 50 pork fillet, 30 minced pork, 30 chicken carcass, 51 chicken fillet, and 35 minced chicken samples were examined. Samples were all collected at the retail level, including supermarkets and local butcheries. Escherichia albertii was isolated from two chicken fillets (3.9%) and additionally detected in one minced chicken (4.5%) and two other chicken fillet (4.5%) samples by a PCR assay. All beef and pork samples tested negative for its presence, but transmission through these meat types cannot be excluded, as it potentially correlates with the level of fecal contamination that was significantly higher on poultry products. With other hygienic conditions and processing steps applied, the presence of E. albertii on food can therefore differ in other parts of the world. Escherichia albertii was present in 0.4% of the 2419 clinical stool samples examined. The future development of a chromogenic isolation medium, as well as further extensive epidemiologic approaches and a genomic comparison of human, food, and animal isolates, could enhance the assessment of the emerging pathogen status and its potential as a foodborne hazard.

Escherichia albertii as a Potential Enteropathogen in the Light of Epidemiological and Genomic Studies

Escherichia albertii is a new enteropathogen of humans and animals. The aim of the study was to assess the prevalence and pathogenicity of E. albertii strains isolated in northeastern Poland using epidemiological and genomic studies. In 2015-2018, a total of 1154 fecal samples from children and adults, 497 bird droppings, 212 food samples, 92 water samples, and 500 lactose-negative E. coli strains were tested. A total of 42 E. albertii strains were isolated. The PCR method was suitable for their rapid identification. In total, 33.3% of E. albertii isolates were resistant to one antibiotic, and 16.7% to two. Isolates were sensitive to cefepime, imipenem, levofloxacin, gentamicin, trimethoprim/sulfamethoxazole, and did not produce ESBL β-lactamases. High genetic variability of E. albertii has been demonstrated. In the PFGE method, 90.5% of the strains had distinct pulsotypes. In MLST typing, 85.7% of strains were assigned distinct sequence types (STs), of which 64% were novel ST types. Cytolethal distending toxin (CDT) and Paa toxin genes were found in 100% of E. albertii isolates. Genes encoding toxins, IbeA, CdtB type 2, Tsh and Shiga (Stx2f), were found in 26.2%, 9.7%, 1.7%, and 0.4% of E. albertii isolates, respectively. The chromosome size of the tested strains ranged from 4,573,338 to 5,141,010 bp (average 4,784,003 bp), and at least one plasmid was present in all strains. The study contributes to a more accurate assessment of the genetic diversity of E. albertii and the potential threat it poses to public health.

The genomic epidemiology of Escherichia albertii infecting humans and birds in Great Britain

Escherichia albertii is a recently identified gastrointestinal bacterial pathogen of humans and animals which is typically misidentified as pathotypes of diarrhoeagenic Escherichia coli or Shigella species and is generally only detected during genomic surveillance of other Enterobacteriaceae. The incidence of E. albertii is likely underestimated, and its epidemiology and clinical relevance are poorly characterised. Here, we whole genome sequenced E. albertii isolates from humans (n = 83) and birds (n = 79) isolated in Great Britain between 2000 and 2021 and analysed these alongside a broader public dataset (n = 475) to address these gaps. We found human and avian isolates typically (90%; 148/164) belonged to host-associated monophyletic groups with distinct virulence and antimicrobial resistance profiles. Overlaid patient epidemiological data suggested that human infection was likely related to travel and possibly foodborne transmission. The Shiga toxin encoding stx2f gene was associated with clinical disease (OR = 10.27, 95% CI = 2.98-35.45 p = 0.0002) in finches. Our results suggest that improved future surveillance will further elucidate disease ecology and public and animal health risks associated with E. albertii.

Occurrence and Characteristics of Escherichia albertii in Wild Birds and Poultry Flocks in Switzerland

Escherichia albertii, a zoonotic pathogen, has sporadically been associated with infectious diarrhea in humans. Poultry and wild birds are considered potential reservoirs. We assessed the occurrence of E. albertii in 280 fecal samples from wild birds (n = 130) and pooled fecal samples collected at slaughterhouse level from poultry flocks (n = 150) in Switzerland. Using an E. albertii-specific PCR targeting the Eacdt gene, 23.8% (31/130) of the samples from wild birds, but not from the pooled poultry fecal samples, tested positive for Eacdt. The positive samples originated from 11 bird species belonging to eight families. Strain isolation was attempted on the PCR-positive samples by subculturing the broth cultures onto xylose–MacConkey plates. Isolation was possible on 12 of the 31 Eacdt-PCR-positive samples. Whole-genome sequencing revealed that the strains belonged to nine distinct sequence types, with ST13420 and ST5967 being represented by two and three isolates, respectively. All strains harbored the eae gene, while two strains were also positive for stx2f. Our study thus shows that E. albertii is present in the Swiss wild bird population, which can potentially act as a source of this pathogen to humans, other animals, and the environment.

Characterization of the Emerging Enteropathogen Escherichia Albertii Isolated from Urine Samples of Patients Attending Sapporo Area Hospitals, Japan

Recently, Escherichia albertii has been identified as a causative agent of diarrhea in humans and is often misidentified as diarrheagenic Escherichia coli (DEC), a lactose-nondegrading bacterium. In this study, we performed biochemical characterization, gene possession status, drug susceptibility testing, and sequencing analysis of the strains detected in urine samples. One urea-degrading strain was detected in terms of biochemical characteristics, but was found to be nonurea-degrading by another method, leading to conflicting results. All target strains possessed the E. albertii-specific gene, the DEC common gene eae, and the E. coli 16S rRNA gene. In the drug susceptibility test, all urine-derived strains were sensitive to tetracycline (TC), whereas the JCM 17328 strain was resistant to TC, suggesting that TC is effective against urine-derived E. albertii strains. In 16S rRNA sequencing analysis, the E. albertii strains were ranked at the top of homology, but not in the top one, making it difficult to differentiate them from other strains. In summary, if a suspected lactose-nondegrading E. coli strain was isolated from a urine sample, it could be differentiated from E. albertii by the presence of E. albertii-specific genes.

Microbiology and Epidemiology of Escherichia albertii—An Emerging Elusive Foodborne Pathogen

Escherichia albertii, a close relative of E. coli, is an emerging zoonotic foodborne pathogen associated with watery diarrhea mainly in children and immunocompromised individuals. E. albertii was initially classified as eae-positive Hafnia alvei, however, as more genetic and biochemical information became available it was reassigned to its current novel taxonomy. Its infections are common under conditions of poor hygiene with confirmed transmission via contaminated water and food, mainly poultry-based products. This pathogen has been isolated from various domestic and wild animals, with most isolates being derived from birds, implying that birds among other wild animals might act as its reservoir. Due to the absence of standardized isolation and identification protocols, E. albertii can be misidentified as other Enterobacteriaceae. Exploiting phenotypes such as its inability to ferment rhamnose and xylose and PCR assays targeting E. albertii-specific genes such as the cytolethal distending toxin and the DNA-binding transcriptional activator of cysteine biosynthesis encoding genes can be used to accurately identify this pathogen. Several gaps exist in our knowledge of E. albertii and need to be bridged. A deeper understanding of E. albertii epidemiology and physiology is required to allow the development of effective measures to control its transmission and infections. Overall, current data suggest that E. albertii might play a more significant role in global infectious diarrhea cases than previously assumed and is often overlooked or misidentified. Therefore, simple, and efficient diagnostic tools that cover E. albertii biodiversity are required for effective isolation and identification of this elusive agent of diarrhea.

Molecular Study of Escherichia albertii in Pediatric Urinary Tract Infections

Background:

There are insufficient data about the presence ofE. albertiias a causative organism in urinary tract infection in pediatric patients. Objective: The present study aimed to detectE. albertiiby polymerase chain reaction (PCR) for detection ofuidA, mdh,andlysPgenes among isolatedE.colifrom children with urinary tract infection.

Methods:

The present study was a cross-sectional retrograde study which was carried out on 100 isolates of phenotypically confirmedE.colidetected in urine samples of children suffering from urinary tract infection. The isolates were subjected to molecular identification by PCR foruidA, mdh,andlysPgenes.

Results:

E. albertiiwas identified by PCR in 7% of the isolates andE.coliwas identified in 93% of the isolates. TwomdhandlysPgenes were detected forE. albertiiand theuidAgene forE. coli.E. albertiiisolates had marked resistance to gentamicin (71.4%), followed by resistance to ciprofloxacin (57.1%), meropenem and imipenem (42.9% each) and ESBL activity by double discs method was reported in 57.1% of the isolates. However, none of the isolates had shown resistance to nalidixic acid and only one isolate had resistance to norfloxacin. There was a statistically insignificant difference between resistance to the used antibiotics such as aztreonam (P=0.083), ampicillin/clavulanate (P=0.5), ciprofloxacin (P=0.69), gentamicin (P=0.3) and ceftazidime (P=1.00).

Conclusion:

The present study highlights the emergence ofE. albertiias a pathogen associated with urinary tract infections in children. There is marked antibiotic resistance of this pathogen, especially toward extended spectrum beta-lactams antibiotics. The identification method depends mainly on genetic studies. Further longitudinal studies with large number of patients are required to verify the accurate prevalence of this bacterium.

Investigation of the Domestic Reservoirs of Diarrheagenic Escherichia coli in Diarrhea Case Households of Urban Bangladesh

This study collected rectal swabs from diarrheal patients and in-house environmental samples from low-income households in Dhaka City, Bangladesh, over a 4-month period and investigated these to determine the domestic transmission pathways of Escherichia coli-associated diarrhea. The environmental samples included swabs from four frequently touched surfaces, drinking water and food. Both the rectal swabs and environmental samples were examined for virulence genes characteristic of diarrheagenic E. coli pathotypes by PCR. In addition, each sample was cultured for E. coli, and the strains were analyzed for virulence profile and subjected to multilocus sequence typing (MLST). The results showed that 31% (73 of 233) of all samples including rectal swabs and household samples were positive for one or more of the diarrheagenic E. coli virulence factors. PCR analyses showed that 28% (10/36) of the rectal swabs, 43% (58/136) of household swabs, 9% (3/32) of the food, and 7% (2/29) of the water samples were positive for various virulence genes. 6 Out of the 36 rectal swab samples and associated household samples were shown to have similar E. coli pathotypic genes, and the drinking vessel surface was identified as the major source of contamination. EAEC and CTEC were the most commonly identified pathotypes in the cultured isolates. The phylogenetic tree constructed by MLST data showed that the diarrheagenic isolates were clustered in several diversified lineages. This study supports the hypothesis that there are high-risk hotspots, particularly those surfaces associated with food consumption, for diarrheagenic E. coli contamination within the household environments of Bangladesh.

Detection of Escherichia Albertii in Urinary and Gastrointestinal Infections in Kermanshah, Iran

Background: Escherichia albertii has been recently isolated from the feces of people with gastroenteritis as a pathogen that causes diarrhea. Due to insufficient information on the phenotypic and biochemical characteristics of E. albertii, it is difficult to distinguish it from other species of the Enterobacteriaceae family and, therefore, it is mistakenly identified as Escherichia coli or even Hafnia alvei. Objective: The present study which was conducted for the first time in Iran aimed to identify E. albertii in samples from individuals afflicted with urinary and gastrointestinal infections by using the polymerase chain reaction (PCR) method. The required samples were obtained from clinical laboratories in Kermanshah. Materials and Methods: Firstly, a total of 60 urinary and 40 fecal samples identified as E. coli in clinical laboratories were re-evaluated in terms of specific phenotypic and biochemical characteristics of E. coli. Then, two lysP and mdh genes were detected for E. albertii, and the uidA gene was found for E. coli by PCR using specific primers pairs. Results: The results from phenotypic and biochemical tests indicated that all samples shared common characteristics with E. coli. However, PCR findings demonstrated that out of 100 samples, 6 samples (6%) contained specific genes of E. coli while 94 remaining samples (94%) showed the uidA gene. Out of the given 6 samples, 5 samples carried urinary tract infections and only one showed gastrointestinal infection. Conclusion: Our study findings revealed that E. albertii could have been considered as one of the causes for urinary and gastrointestinal infections in Iran, and that it was mistakenly identified as E. coli in clinical laboratories.

Isolation and Identification of Escherichia albertii in Broiler Chickens From Kermanshah

Background: F Escherichia albertii is generally recognized as a human pathogen with a limited number of strains. It has also been identified as a cause of mortality among birds. The clinical significance and prevalence of E. albertii are somewhat unknown. Objectives: The aim of the present study was to isolate and identify E. albertii as a causative agent of respiratory infections in broilers. Materials and Methods: During a three-month period (Winter 2018), 200 samples of the air sacs of 100 chickens with suspected colibacillosis were collected. Routine biochemical tests were performed and suspected isolates of E. albertii were selected for polymerase chain reaction (PCR). Results: A total of 68 suspected samples of E. albertii and Escherichia coli were isolated. Further, E. coli was detected in all the suspected samples using species-specific sequences of E. coli (uidA) and E. albertii (mdh and lysP). Conclusion: Escherichia albertii was not identified as a cause of respiratory infection in broilers.

Escherichia albertii Pathogenesis

Escherichia albertii is an emerging enteropathogen of humans and many avian species. This bacterium is a close relative of Escherichia coli and has been frequently misidentified as enteropathogenic or enterohemorrhagic E. coli due to their similarity in phenotypic and genetic features, such as various biochemical properties and the possession of a type III secretion system encoded by the locus of enterocyte effacement. This pathogen causes outbreaks of gastroenteritis, and some strains produce Shiga toxin. Although many genetic and phenotypic studies have been published and the genome sequences of more than 200 E. albertii strains are now available, the clinical significance of this species is not yet fully understood. The apparent zoonotic nature of the disease requires a deeper understanding of the transmission routes and mechanisms of E. albertii to develop effective measures to control its transmission and infection. Here, we review the current knowledge of the phylogenic relationship of E. albertii with other Escherichia species and the biochemical and genetic properties of E. albertii, with particular emphasis on the repertoire of virulence factors and the mechanisms of pathogenicity, and we hope this provides a basis for future studies of this important emerging enteropathogen.

A review on antimicrobial botanicals, phytochemicals and natural resistance modifying agents from Apocynaceae family: Possible therapeutic approaches against multidrug resistance in pathogenic microorganisms

Accelerated emergence of drug- resistant pathogenic microbes, their unbeatable virulence and a gradual loss of efficacy of currently used antimicrobial agents over the last decade, have expanded the scope of herbal medicine to combat this emerging challenge to have a wide spectrum of activity to develop effective medicines with lesser untoward side effects. Plant-based natural products should be of utmost interest to today's pharmaceutical industries since they are a primary source of new chemical entities directed at new drug targets. Apocynaceae or 'Dogbane' family has attained a global reputation as a source of some life-saving plant-derived products and novel compounds. Members of this family have also been extensively investigated against several nosocomial pathogenic microbes through in vitro and in vivo experimental settings. Several plant-derived components obtained from members of this family have also exhibited remarkable microbial growth inhibitory properties. Popular and widely accepted international databases such as PubMed, Science Direct, ResearchGate, Scopus, Google Scholar, JSTOR and more were searched using the various search strings such as Apocynaceae, antimicrobials, multidrug resistance, resistance modifying agents and pathogenic microorganisms were used in various combinations to retrieve several citations related to the topic. The current review encompasses recent developments in experimental studies and phytochemical analyses which correlates with antimicrobial efficacy of selected Apocynaceous plants along with synergistic mechanism and structural details. The present review recognizes and leverages the importance of Apocynaceae plants, which could be of significant interest in the development of more effective and less toxic antimicrobial drugs which may surmount multidrug resistance. Three different paradigm models harnessing clinical antimicrobial resistance (AMR) including the plant family Apocynaceae, Gram-positive and Gram-negative bacterial species have been broadly discussed in this review. In a nutshell, the present review represents a comprehensive account on the antimicrobials and resistance modifying agents obtained from the members of the plant family Apocynaceae and derived phytochemicals. It also gives an insight into the underlying mode of action of these phytochemicals against an array of pathogenic bacteria, their mechanism of antibiosis, plant parts from which the phytochemicals were isolated or the extracts was prepared with a critical discussion on the botanically-derived antibiotics as a template for antimicrobial drug development.

Phenotypic characterization and virulence-related properties of Escherichia albertii strains isolated from children with diarrhea in Brazil

Escherichia albertii are emerging enteropathogens, whose identification is difficult, as they share biochemical characteristics and some virulence-related genes with diarrheagenic Escherichia coli (DEC). Studies on phylogeny, phenotypic characteristics and potential virulence factors of human E. albertii strains are scarce. In this study, we identified by multiplex PCR five E. albertii among 106 strains isolated from diarrheic children in São Paulo, Brazil, which were previously classified as atypical enteropathogenic E. coli. All strains were investigated regarding their phylogeny, biochemical properties, virulence-related properties, antimicrobial resistance and presence of putative virulence-related genes. All strains belonged to different E. albertii lineages and adhered to and produced attaching and effacing lesions on HeLa cells. Three strains invaded Caco-2 cells, but did not persist intracellularly, and three formed biofilms on polystyrene surfaces. All strains were resistant to few antibiotics and only one carried a self-transmissible resistance plasmid. Finally, among 38 DEC and 18 extraintestinal pathogenic E. coli (ExPEC) virulence-related genes searched, six and three were detected, respectively, with paa and cdtB being found in all strains. Despite the limited number of strains, this study provided additional knowledge on human E. albertii virulence potential, showing that they share important virulence factors with DEC and ExPEC.

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

A straightforward sequential synthetic strategy has been developed for the synthesis of a pentasaccharide repeating unit corresponding to the cell wall O-antigen of the Escherichia albertii O4 strain in very good yield with the desired configuration at the glycosidic linkages using thioglycosides and trichloroacetimidate derivatives as glycosyl donors and perchloric acid supported over silica (HClO4/SiO2) as a solid supported protic acid glycosyl activator. The expected configuration at the glycosidic linkages was achieved using a reasonable selection of protecting groups in the manosaccharide intermediates.

Transcriptional and posttranscriptional regulation of the locus of enterocyte effacement in Escherichia albertii

The diarrheic bacterium Escherichia albertii is a recent addition to the attaching and effacing (A/E) morphotype of pathogens. A/E pathogens cause disease by tightly attaching to intestinal cells, destroying their actin-rich microvilli, and triggering re-localization and repolymerization of actin at the bacterial-host interface to form actin-filled membranous protrusions, termed A/E lesions, beneath the adherent bacterium. The locus of enterocyte effacement (LEE) is required for the biogenesis of these lesions. Whereas regulation of the LEE has been intensively investigated in EPEC and EHEC, it remains cryptic in E. albertii. In this study we characterized the very first transcriptional and posttranscriptional regulators of the LEE in this emerging pathogen. Our results suggest that Ler and GrlA globally activate transcription from the LEE, whereas GrlR negatively regulates the LEE. Additionally, we demonstrate that the RNA chaperone Hfq posttranscriptionally represses the LEE by specifically targeting the 5' UTR of grlR. In summary, our findings provide the very first glimpse of the regulatory landscape of the LEE in E. albertii - a bacterium that has been implicated in multiple diarrheal outbreaks worldwide.

Non-biogroup 1 or 2 Strains of the Emerging Zoonotic Pathogen Escherichia albertii, Their Proposed Assignment to Biogroup 3, and Their Commonly Detected Characteristics

Escherichia albertii, a zoonotic enteropathogen, is responsible for outbreaks of disease in humans. Identifying strains of E. albertii by phenotypic characterization tests is difficult because of its poorly defined properties. Screening its phenotypic characteristics is, nevertheless, a necessary prerequisite for further genetic analysis of its properties, and species-specific polymerase chain reaction (PCR) analysis can be used to type the pathogen. While two E. albertii biogroups (1 and 2) have been described, strains with characteristics divergent from both biogroups have been reported worldwide. The aim of the present study was to evaluate the characteristics of non-biogroup 1 or 2 strains, and discern the characteristics common to all of the E. albertii strains from this study. Altogether, 107/414 field isolates were selected for examination based on pulsed-field gel electrophoresis analysis. The 107 strains were isolated from 92 sources, including humans and pigeon feces, other wild birds, and retail chicken livers. All strains were then examined using various culture-based, biochemical (API 50CHE tests, API Zym test, and others) and molecular (virulence gene screening, multi-locus sequence analysis) testing methods. Our results revealed that all field strains (n = 107) showed non-biogroup 1 or 2 characteristics, with multiple sequence differences. Variations in indole production and the lysine decarboxylase activity profiles among the isolates made identification of E. albertii very difficult. Therefore, we propose that non-biogroup 1 or 2 of E. albertii should be assigned to biogroup 3 to make screening of them easier in public health and clinical laboratory settings. Clearly, having group criteria for indole-negative/lysine-positive, indole-positive/lysine-negative, and indole-positive/lysine-positive E. albertii biogroups 1, 2, and 3 strains, respectively, should provide for more accurate identification of E. albertii isolates. Based on our findings, we recommend that isolates displaying phenotype mobility-negativity (sulfide-indole-motility medium, 37°C), hydrogen sulfide production-negativity (triple sugar iron medium), acid production-negativity from xylose, negative β-glucuronidase activity properties, and showing indole production and lysine decarboxylase activity profiles in accordance with one of the three biogroups, should be further assessed using an E. albertii-specific PCR assay.

The Evasive Enemy: Insights into the Virulence and Epidemiology of the Emerging Attaching and Effacing Pathogen Escherichia albertii

The diarrheic attaching and effacing (A/E) pathogen Escherichia albertii was first isolated from infants in Bangladesh in 1991, although the bacterium was initially classified as Hafnia alvei Subsequent genetic and biochemical interrogation of these isolates raised concerns about their initial taxonomic placement. It was not until 2003 that these isolates were reassigned to the novel taxon Escherichia albertii because they were genetically more closely related to E. coli, although they had diverged sufficiently to warrant a novel species name. Unfortunately, new isolates continue to be mistyped as enteropathogenic E. coli (EPEC) or enterohemorrhagic E. coli (EHEC) owing to shared traits, most notably the ability to form A/E lesions. Consequently, E. albertii remains an underappreciated A/E pathogen, despite multiple reports demonstrating that many provisional EPEC and EHEC isolates incriminated in disease outbreaks are actually E. albertii Metagenomic studies on dozens of E. albertii isolates reveal a genetic architecture that boasts an arsenal of candidate virulence factors to rival that of its better-characterized cousins, EPEC and EHEC. Beyond these computational comparisons, studies addressing the regulation, structure, function, and mechanism of action of its repertoire of virulence factors are lacking. Thus, the paucity of knowledge about the epidemiology, virulence, and antibiotic resistance of E. albertii, coupled with its misclassification and its ability to develop multidrug resistance in a single step, highlights the challenges in combating this emerging pathogen. This review seeks to synthesize our current but incomplete understanding of the biology of E. albertii.

Diarrhoeagenic Escherichia coli and Escherichia albertii in Brazil: pathotypes and serotypes over a 6-year period of surveillance

Diarrhoeagenic Escherichia coli (DEC) is a leading cause of infectious diarrhoea worldwide. In recent years, Escherichia albertii has also been implicated as a cause of human enteric diseases. This study describes the occurrence of E. coli pathotypes and serotypes associated with enteric illness and haemolytic uremic syndrome (HUS) isolated in Brazil from 2011 to 2016. Pathotypes isolated included enteropathogenic E. coli (EPEC), enteroaggregative E. coli (EAEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC) and Shiga toxin-producing E. coli (STEC). PCR of stool enrichments for DEC pathotypes was employed, and E. albertii was also sought. O:H serotyping was performed on all DEC isolates. A total of 683 DEC and 10 E. albertii strains were isolated from 5047 clinical samples. The frequencies of DEC pathotypes were 52.6% (359/683) for EPEC, 32.5% for EAEC, 6.3% for ETEC, 4.4% for EIEC and 4.2% for STEC. DEC strains occurred in patients from 3 months to 96 years old, but EPEC, EAEC and STEC were most prevalent among children. Both typical and atypical isolates of EPEC and EAEC were recovered and presented great serotype heterogeneity. HUS cases were only associated with STEC serotype O157:H7. Two E. albertii isolates belonged to serogroup O113 and one had the stx2f gene. The higher prevalence of atypical EPEC in relation to EAEC in community-acquired diarrhoea in Brazil suggests a shift in the trend of DEC pathotypes circulation as previously EAEC predominated. This is the first report of E. albertii isolation from active surveillance. These results highlight the need of continuing DEC and E. albertii surveillance, as a mean to detect changes in the pattern of pathotypes and serotypes circulation and provide useful information for intervention and control strategies.

Twenty-seven years of screening for Shiga toxin-producing Escherichia coli in a university hospital. Brussels, Belgium, 1987-2014

Objective

Since 1987 all fecal samples referred to the clinical microbiology laboratory of the UZ Brussel were screened for the presence of Shiga toxin-producing E. coli (STEC). In this study all STEC strains isolated over a period of 27 years (1987–2014) were reexamined to achieve deeper insight in the STEC infections in our patient population.

Methods

A total of 606 STEC strains from 604 patients were subjected to molecular methods for shiga toxin (stx) subtyping, detection of additional virulence genes, typing of the O-serogroups, and phylogenetic relatedness assessment of STEC O157:H7/H-.

Results

Since the introduction of PCR in 1991 the annual positivity rates varied between 1.1% and 2.7%. The isolation rate of STEC O157:H7/H- remained stable over the years while the isolation rate of non-O157 serotypes increased, mainly since 2011. The majority of the patients were children. Uncomplicated- and bloody diarrhea were the most prevalent gastrointestinal manifestations (respectively 51.9% and 13.6%), 4.3% of the strains were related to the hemolytic uremic syndrome (HUS), and 30.2% of the patients showed none of these symptoms. The strains were very diverse; they belonged to 72 different O-serovars and all stx subtypes except stx1d and stx2g were identified. Out of the 23 stx2f-positives one was associated with HUS and one belonged to the E. albertii species. As seen in other studies, the frequency of strains of the O157:H7/H- serotype and strains carrying stx2a, eaeA and ehxA was higher in patients with HUS.

Conclusions

The characteristics and trends of STEC infection seen in our patient population are similar to those noted in other countries. STEC infections in our hospital are mainly sporadic, and a substantial portion of the patients were asymptomatic carriers. Human STEC Stx2f infection was less rare than previously assumed and we report the first Belgian STEC stx2f HUS case and stx2f positive E. albertii infection.

Modulation of Host Cell Processes by T3SS Effectors

Two of the enteric Escherichia coli pathotypes-enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)-have a conserved type 3 secretion system which is essential for virulence. The T3SS is used to translocate between 25 and 50 bacterial proteins directly into the host cytosol where they manipulate a variety of host cell processes to establish a successful infection. In this chapter, we discuss effectors from EPEC/EHEC in the context of the host proteins and processes that they target-the actin cytoskeleton, small guanosine triphosphatases and innate immune signalling pathways that regulate inflammation and cell death. Many of these translocated proteins have been extensively characterised, which has helped obtain insights into the mechanisms of pathogenesis of these bacteria and also understand the host pathways they target in more detail. With increasing knowledge of the positive and negative regulation of host signalling pathways by different effectors, a future challenge is to investigate how the specific effector repertoire of each strain cooperates over the course of an infection.

Characterization of four Escherichia albertii isolates collected from animals living in Antarctica and Patagonia

Escherichia albertii is a recently discovered species with a limited number of well characterized strains. The aim of this study was to characterize four of the E. albertii strains, which were among 41 identified Escherichia strains isolated from the feces of living animals on James Ross Island, Antarctica, and Isla Magdalena, Patagonia. Sequencing of 16S rDNA, automated ribotyping, and rep-PCR were used to identify the four E. albertii isolates. Phylogenetic analyses based on multi-locus sequence typing showed these isolates to be genetically most similar to the members of E. albertii phylogroup G3. These isolates encoded several virulence factors including those, which are characteristic of E. albertii (cytolethal distending toxin and intimin) as well as bacteriocin determinants that typically have a very low prevalence in E. coli strains (D, E7). Moreover, E. albertii protein extracts caused cell cycle arrest in human cell line A375, probably because of cytolethal distending toxin activity.

Structure and gene cluster of the O-antigen of Escherichia albertii O1 resembling the O-antigen of Pseudomonas aeruginosa O5

The O-specific polysaccharide (O-antigen) was obtained by mild acid degradation of the lipopolysaccharide of Escherichia albertii serotype O1 strain SP20140089 and studied by sugar analysis along with 1D and 2D ¹H and ¹³C NMR spectroscopy. The following structure was established for the trisaccharide repeating unit of the O-polysaccharide: →4)-β-d-ManpNAc3NAcA-(1 → 4)-β-d-GlcpNAm3NAcA-(1 → 3)-α-d-GlcpNAc-(1→ where ManNAc3NAcA and GlcNAm3NAcA indicate 2,3-diacetamido-2,3-dideoxymannuronic acid and 2-acetimidoylamino-3-acetamido-2,3-dideoxyglucuronic acid, respectively. While showing some similarity with O-polysaccharide structures of a group of Pseudomonas aeruginosa serotypes (O2, O5, O16, O18, and O20), that of E. albertii O1 is unique among known bacterial polysaccharide structures. The gene cluster for biosynthesis of the O1-antigen was sequenced and functions of the genes were predicted by comparison with sequences in the available databases, including those involved in the synthesis of nucleotide precursors of 2,3-diamino-2,3-dideoxyhexuronic acid derivatives in P. aeruginosa O5.

Defining the Genome Features of Escherichia albertii, an Emerging Enteropathogen Closely Related to Escherichia coli

Escherichia albertii is a recently recognized close relative of Escherichia coli. This emerging enteropathogen possesses a type III secretion system (T3SS) encoded by the locus of enterocyte effacement, similar to enteropathogenic and enterohemorrhagic E. coli (EPEC and EHEC). Shiga toxin-producing strains have also been identified. The genomic features of E. albertii, particularly differences from other Escherichia species, have not yet been well clarified. Here, we sequenced the genome of 29 E. albertii strains (3 complete and 26 draft sequences) isolated from multiple sources and performed intraspecies and intragenus genomic comparisons. The sizes of the E. albertii genomes range from 4.5 to 5.1 Mb, smaller than those of E. coli strains. Intraspecies genomic comparisons identified five phylogroups of E. albertii. Intragenus genomic comparison revealed that the possible core genome of E. albertii comprises 3,250 genes, whereas that of the genus Escherichia comprises 1,345 genes. Our analysis further revealed several unique or notable genetic features of E. albertii, including those responsible for known biochemical features and virulence factors and a possibly active second T3SS known as ETT2 (E. coli T3SS 2) that is inactivated in E. coli. Although this organism has been observed to be nonmotile in vitro, genes for flagellar biosynthesis are fully conserved; chemotaxis-related genes have been selectively deleted. Based on these results, we have developed a nested polymerase chain reaction system to directly detect E. albertii. Our data define the genomic features of E. albertii and provide a valuable basis for future studies of this important emerging enteropathogen.

Conventional and molecular methods in the diagnosis of community-acquired diarrhoea in children under 5 years of age from the north-eastern region of Poland

OBJECTIVES

The purpose of this study was to determine the main causative agents of community-acquired acute diarrhoea in children using conventional methods and PCR.

METHODS

Stool samples were collected from 100 children under 5 years of age with acute diarrhoea during the autumn-winter period of 2010-2011. Rotaviruses and adenoviruses were detected by the stool antigen immunoassay, and Salmonella spp, Campylobacter spp, Shigella spp, Yersinia enterocolitica, Yersinia pseudotuberculosis, Clostridium difficile, enterotoxigenic Bacteroides fragilis (ETBF), and diarrhoeagenic Escherichia coli were detected by culture methods and PCR.

RESULTS

Overall, enteropathogens were identified in 73% of the children. Bacteria, viruses, and mixed infections were noted in 37%, 24%, and 12% of diarrhoeal cases, respectively. The most common enteric pathogens were rotaviruses (31%), followed by C. difficile (17%), Campylobacter jejuni (13%), Salmonella spp (11%), and atypical enteropathogenic Escherichia coli (aEPEC) strains (10%). Compared with culture methods, PCR increased the overall detection frequency of the bacterial enteropathogens by 4%.

CONCLUSIONS

The high prevalence of Campylobacter jejuni suggests that the number of campylobacteriosis cases in Poland may be underestimated; this pathogen should be investigated routinely in children with diarrhoea. Moreover, C. difficile might be considered a causative or contributing agent of diarrhoea in 14.8% of children aged >1 year.

Prevalence of eae-positive, lactose non-fermenting Escherichia albertii from retail raw meat in China

Escherichia albertii is a newly emerging enteric pathogen that has been associated with gastroenteritis in humans. Recently, E. albertii has also been detected in healthy and sick birds, animals, chicken meat and water. In the present study, the prevalence and characteristics of the eae-positive, lactose non-fermenting E. albertii strains in retail raw meat in China were evaluated. Thirty isolates of such strains of E. albertii were identified from 446 (6·73%) samples, including duck intestines (21·43%, 6/28), duck meat (9·52%, 2/21), chicken intestines (8·99%, 17/189), chicken meat (5·66%, 3/53), mutton meat (4·55%, 1/22) and pork meat (2·44%, 1/41). None was isolated from 92 samples of raw beef meat. Strains were identified as E. albertii by phenotypic properties, diagnostic PCR, sequence analysis of the 16S rRNA gene, and housekeeping genes. Five intimin subtypes were harboured by these strains. All strains possessed the II/III/V subtype group of the cdtB gene, with two strains carrying another copy of the I/IV subtype group. Pulsed-field gel electrophoresis showed high genetic diversity of E. albertii in raw meats. Our findings indicate that E. albertii can contaminate various raw meats, posing a potential threat to public health.

Detection of Escherichia albertii from chicken meat and giblets

Escherichia albertii occasionally causes food-borne outbreaks of gastroenteritis in humans; however, little is known about the vehicle of transmission. To screen retail chicken products for the presence of E. albertii, 104 retail chicken products were investigated. Portions of enrichment cultures that were PCR-positive for E. albertii (n=3) were sub-cultured on agar medium. Only 2 strains obtained from 2 chicken giblet samples were identified as E. albertii by multi locus sequence typing. Antimicrobial susceptibility testing showed that 1 strain was resistant to streptomycin and sulfisoxazole. Both strains harbored the virulence genes cdt and eae. This study is the first description of E. albertii isolation from retail food, suggesting that chicken products are a potential vehicle of E. albertii transmission.

Evaluating the occurrence of Escherichia albertii in chicken carcass rinses by PCR, Vitek analysis, and sequencing of the rpoB gene

Escherichia albertii is a recently described species that has been associated with gastroenteritis in humans and with healthy and ill birds. Most recently, it has been identified as the causative agent in a food-borne outbreak in Japan. The distribution and clinical importance of E. albertii are not well studied because its importance is unclear. Culture methods for clinical isolation frequently miss E. albertii or incorrectly identify it as Shigella spp., Escherichia coli, or Hafnia alvei. This study was designed to determine if E. albertii could be recovered from chicken carcass rinses collected at slaughter during a 1-year period from November 2009 until October 2010. Colonies were isolated from chicken carcass rinses and tested by PCR for the presence or absence of clpX, lysP, mdh, intimin (eae), Shiga toxins 1 and 2 (stx1, stx2, and stx2f), heat-stable enterotoxin A (staA), and cytolethal distending toxins 1 and 2 (cdtB) genes. Sixty-five isolates were analyzed by sequencing a section of the rpoB gene. Analysis of the rpoB gene sequences revealed 14 fixed differences between E. albertii and other, closely related organisms. The fixed differences found in the rpoB gene could aid in future discrimination of E. albertii from closely related bacteria.

First Complete Genome Sequence of Escherichia albertii Strain KF1, a New Potential Human Enteric Pathogen

Escherichia albertii has been recently recognized as an emerging human and bird enteric pathogen. Here, we report the first complete chromosome nucleotide sequence of a clinical isolate of E. albertii strain KF1, which may provide information about the pathogenic potential of this new species and the mechanisms of evolution of enteropathogenic Escherichia spp.

Isolation of human pathogen Escherichia albertii from faeces of seals (Leptonychotes weddelli) in James Ross Island, Antarctica

A set of nine gram-negative fermenting rods biochemically identified as Escherichia coli was isolated from faeces of seals. These bacteria were characterized by phenotypic classification, 16S rDNA sequence analyses, automated ribotyping, study of whole-cell protein profiles by SDS-PAGE and finally by bacteriocin production. The results of our polyphasic taxonomic study supported the recognition of P4652, P4653 and P4740 isolates as true members of Escherichia albertii species – probably a major enteric human pathogen. To our best knowledge, this is the first evidence showing that E. albertii produces bacteriocin, colicin D. Obtained data unambiguously showed incon-venience of commercial identification systems to distinguish both Escherichia species due to missing data of E. albertii in the commercial databases. The results of Escherichia isolates taxonomy suggest seals as a novel source of human and animal pathogen,E. albertii in the Antarctic region.