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James P Nataro - One of the best experts on this subject based on the ideXlab platform.
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novel aggregative adherence fimbria variant of Enteroaggregative Escherichia Coli
Infection and Immunity, 2015Co-Authors: Nadia Boisen, James P Nataro, Rie Jønsson, Carsten Struve, Håvard Jenssen, Araceli E Santiago, Ramona Valentina Mateiu, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) organisms belong to a diarrheagenic pathotype known to cause diarrhea and can be characterized by distinct aggregative adherence (AA) in a stacked-brick pattern to cultured epithelial cells. In this study, we investigated 118 EAEC strains isolated from the stools of Danish adults with traveler's diarrhea. We evaluated the presence of the aggregative adherence fimbriae (AAFs) by a multiplex PCR, targeting the four known major subunit variants as well as their usher-encoding genes. Almost one-half (49/118) of the clinical isolates did not possess any known AAF major fimbrial subunit, despite the presence of other AggR-related loci. Further investigation revealed the presence of an AAF-related gene encoding a yet-uncharacterized adhesin, termed agg5A. The sequence of the agg5DCBA gene cluster shared fimbrial accessory genes (usher, chaperone, and minor pilin subunit genes) with AAF/III, as well as the signal peptide present in the beginning of the agg3A gene. The complete agg5DCBA gene cluster from a clinical isolate, EAEC strain C338-14, with the typical stacked-brick binding pattern was cloned, and deletion of the cluster was performed. Transformation to a nonadherent E. Coli HB101 and complementation of the nonadherent C338-14 mutant with the complete gene cluster restored the AA adhesion. Overall, we found the agg5A gene in 12% of the 118 strains isolated from Denmark, suggesting that this novel adhesin represents an important variant.
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Chapter 8 – Enteroaggregative Escherichia Coli
Escherichia coli, 2013Co-Authors: Nadia Boisen, Karen Angeliki Krogfelt, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) are among the most prevalent enteric pathogens worldwide. The pathotype has been implicated in endemic diarrhea in both developing and industrialized populations, epidemic diarrhea, and traveler’s diarrhea. A recent outbreak of Shiga toxin-producing EAEC adds a new dimension to the epidemiology of this pathotype. Although the pathogenesis of this pathotype is not fully understood, a number of putative virulence factors have been described. The aggregative adherence fimbriae (AAF) are mucosal adhesins that also elicit inflammatory responses from infected mucosal surfaces. Expression of AAF adhesins is induced by the transcriptional activator AggR, which activates expression of several other secreted, but as yet relatively cryptic, proteins. EAEC-induced histopathology includes exfoliation of enterocytes, which has been linked to the action of serine protease autotransporter toxins. Epidemiologic evidence supports a model of EAEC pathogenesis comprising the concerted action of multiple virulence factors.
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Enteroaggregative Escherichia Coli
The Lancet infectious diseases, 2013Co-Authors: Iruka N. Okeke, Nadia Boisen, James P Nataro, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) are an increasingly important cause of diarrhoea. E. Coli belonging to this category cause watery diarrhoea, which is often persistent and can be inflammatory. EAEC have been implicated in sporadic diarrhoea in children and adults, in both developing and developed countries, and have been identified as the cause of several outbreaks worldwide. EAEC are defined by their ability to adhere to epithelial cells in a characteristic "stacked-brick" pattern but are otherwise highly heterogeneous. Genes that could contribute to the pathogenicity of EAEC encode adhesins, toxins, and other factors, all of which are only partially conserved. Practicable tools are needed to improve diagnosis and identify risk factors. EAEC-infected individuals can be treated with fluoroquinolones but there is a need to examine alternative treatment protocols.
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characterization of the aggr regulon in Enteroaggregative Escherichia Coli
Infection and Immunity, 2013Co-Authors: Nicholas P Morin, Araceli E Santiago, Robert K Ernst, Stacey J Guillot, James P NataroAbstract:AggR is a transcriptional regulator of Enteroaggregative Escherichia Coli (EAEC) and has been proposed as the defining factor for typical EAEC strains. Expression of multiple putative virulence factors, including the aggregative adherence fimbriae (AAF), dispersin, the dispersin translocator Aat, and the Aai type VI secretion system, have been found to be regulated by AggR. Here, we confirm the existence of at least 44 AggR-regulated genes using DNA microarray and real-time quantitative reverse transcription-PCR (qRT-PCR); these genes include chromosomal and plasmid-borne loci and 19 previously unsuspected genes. Two previously uncharacterized virulence plasmid-encoded open reading frames (ORFs) (designated ORF3 and ORF4) exhibit significant identity with isoprenoid biosynthesis genes of Bacteria and Archaea. The predicted ORF4 product is closely related to isopentenyl isomerase (IDI) enzymes, whereas the predicted product of the adjacent ORF3 exhibits an aspartate-rich region that is common among trans-isoprenyl phosphate synthases. We show that mutations in these ORFs confer changes in bacterial surface properties. AggR coordinately controls expression of a large number of EAEC genes.
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Enteroaggregative Escherichia Coli disrupts epithelial cell tight junctions
Infection and Immunity, 2010Co-Authors: Maura C Strauman, Erik J. Boll, Susan M. Harrington, Jill M Harper, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) is responsible for inflammatory diarrhea in diverse populations, but its mechanisms of pathogenesis have not been fully elucidated. We have used a previously characterized polarized intestinal T84 cell model to investigate the effects of infection with EAEC strain 042 on tight junction integrity. We find that infection with strain 042 induces a decrease in transepithelial electrical resistance (TER) compared to uninfected controls and to cells infected with commensal E. Coli strain HS. When the infection was limited after 3 h by washing and application of gentamicin, we observed that the TER of EAEC-infected monolayers continued to decline, and they remained low even as long as 48 h after the infection. Cells infected with the afimbrial mutant strain 042aafA exhibited TER measurements similar to those seen in uninfected monolayers, implicating the aggregative adherence fimbriae II (AAF/II) as necessary for barrier dysfunction. Infection with wild-type strain 042 induced aberrant localization of the tight junction proteins claudin-1 and, to a lesser degree, occludin. EAEC-infected T84 cells exhibited irregular shapes, and some cells became elongated and/or enlarged; these effects were not observed after infection with commensal E. Coli strain HS or 042aafA. The effects on tight junctions were also observed with AAF/I-producing strain JM221, and an afimbrial mutant was similarly deficient in inducing barrier dysfunction. Our results show that EAEC induces epithelial barrier dysfunction in vitro and implicates the AAF adhesins in this phenotype.
Karen Angeliki Krogfelt - One of the best experts on this subject based on the ideXlab platform.
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The wax moth Galleria mellonella as a novel model system to study Enteroaggregative Escherichia Coli pathogenesis.
Virulence, 2017Co-Authors: Rie Jønsson, Carsten Struve, Håvard Jenssen, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) comprise of a large, diverse group of diarrheagenic E. Coli defined by their characteristically ‘stacked brick’ pattern on HEp-2 cells.1 EAEC was first ass...
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novel aggregative adherence fimbria variant of Enteroaggregative Escherichia Coli
Infection and Immunity, 2015Co-Authors: Nadia Boisen, James P Nataro, Rie Jønsson, Carsten Struve, Håvard Jenssen, Araceli E Santiago, Ramona Valentina Mateiu, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) organisms belong to a diarrheagenic pathotype known to cause diarrhea and can be characterized by distinct aggregative adherence (AA) in a stacked-brick pattern to cultured epithelial cells. In this study, we investigated 118 EAEC strains isolated from the stools of Danish adults with traveler's diarrhea. We evaluated the presence of the aggregative adherence fimbriae (AAFs) by a multiplex PCR, targeting the four known major subunit variants as well as their usher-encoding genes. Almost one-half (49/118) of the clinical isolates did not possess any known AAF major fimbrial subunit, despite the presence of other AggR-related loci. Further investigation revealed the presence of an AAF-related gene encoding a yet-uncharacterized adhesin, termed agg5A. The sequence of the agg5DCBA gene cluster shared fimbrial accessory genes (usher, chaperone, and minor pilin subunit genes) with AAF/III, as well as the signal peptide present in the beginning of the agg3A gene. The complete agg5DCBA gene cluster from a clinical isolate, EAEC strain C338-14, with the typical stacked-brick binding pattern was cloned, and deletion of the cluster was performed. Transformation to a nonadherent E. Coli HB101 and complementation of the nonadherent C338-14 mutant with the complete gene cluster restored the AA adhesion. Overall, we found the agg5A gene in 12% of the 118 strains isolated from Denmark, suggesting that this novel adhesin represents an important variant.
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Epidemiology and Clinical Manifestations of Enteroaggregative Escherichia Coli
Clinical microbiology reviews, 2014Co-Authors: Betina Hebbelstrup Jensen, Karen Angeliki Krogfelt, Carsten Struve, Katharina E. P. Olsen, Andreas PetersenAbstract:SUMMARY Enteroaggregative Escherichia Coli (EAEC) represents a heterogeneous group of E. Coli strains. The pathogenicity and clinical relevance of these bacteria are still controversial. In this review, we describe the clinical significance of EAEC regarding patterns of infection in humans, transmission, reservoirs, and symptoms. Manifestations associated with EAEC infection include watery diarrhea, mucoid diarrhea, low-grade fever, nausea, tenesmus, and borborygmi. In early studies, EAEC was considered to be an opportunistic pathogen associated with diarrhea in HIV patients and in malnourished children in developing countries. In recent studies, associations with traveler9s diarrhea, the occurrence of diarrhea cases in industrialized countries, and outbreaks of diarrhea in Europe and Asia have been reported. In the spring of 2011, a large outbreak of hemolytic-uremic syndrome (HUS) and hemorrhagic Colitis occurred in Germany due to an EAEC O104:H4 strain, causing 54 deaths and 855 cases of HUS. This strain produces the potent Shiga toxin along with the aggregative fimbriae. An outbreak of urinary tract infection associated with EAEC in Copenhagen, Denmark, occurred in 1991; this involved extensive production of biofilm, an important characteristic of the pathogenicity of EAEC. However, the heterogeneity of EAEC continues to complicate diagnostics and also our understanding of pathogenicity.
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Role of Enteroaggregative Escherichia Coli Virulence Factors in Uropathogenesis
Infection and immunity, 2013Co-Authors: Erik J. Boll, Nadia Boisen, Carsten Struve, Bente Olesen, Steen Gustav Stahlhut, Karen Angeliki KrogfeltAbstract:A multiresistant clonal Escherichia Coli O78:H10 strain qualifying molecularly as Enteroaggregative Escherichia Coli (EAEC) was recently shown to be the cause of a community-acquired outbreak of urinary tract infection (UTI) in greater Copenhagen, Denmark, in 1991. This marks the first time EAEC has been associated with an extraintestinal disease outbreak. Importantly, the outbreak isolates were recovered from the urine of patients with symptomatic UTI, strongly implying urovirulence. Here, we sought to determine the uropathogenic properties of the Copenhagen outbreak strain and whether these properties are conferred by the EAEC-specific virulence factors. We demonstrated that through expression of aggregative adherence fimbriae, the principal adhesins of EAEC, the outbreak strain exhibited pronouncedly increased adherence to human bladder epithelial cells compared to prototype uropathogenic strains. Moreover, the strain was able to produce distinct biofilms on abiotic surfaces, including urethral catheters. These findings suggest that EAEC-specific virulence factors increase uropathogenicity and may have played a significant role in the ability of the strain to cause a community-acquired outbreak of UTI. Thus, inclusion of EAEC-specific virulence factors is warranted in future detection and characterization of uropathogenic E. Coli.
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Enteroaggregative Escherichia Coli
The Lancet infectious diseases, 2013Co-Authors: Iruka N. Okeke, Nadia Boisen, James P Nataro, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) are an increasingly important cause of diarrhoea. E. Coli belonging to this category cause watery diarrhoea, which is often persistent and can be inflammatory. EAEC have been implicated in sporadic diarrhoea in children and adults, in both developing and developed countries, and have been identified as the cause of several outbreaks worldwide. EAEC are defined by their ability to adhere to epithelial cells in a characteristic "stacked-brick" pattern but are otherwise highly heterogeneous. Genes that could contribute to the pathogenicity of EAEC encode adhesins, toxins, and other factors, all of which are only partially conserved. Practicable tools are needed to improve diagnosis and identify risk factors. EAEC-infected individuals can be treated with fluoroquinolones but there is a need to examine alternative treatment protocols.
Nadia Boisen - One of the best experts on this subject based on the ideXlab platform.
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novel aggregative adherence fimbria variant of Enteroaggregative Escherichia Coli
Infection and Immunity, 2015Co-Authors: Nadia Boisen, James P Nataro, Rie Jønsson, Carsten Struve, Håvard Jenssen, Araceli E Santiago, Ramona Valentina Mateiu, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) organisms belong to a diarrheagenic pathotype known to cause diarrhea and can be characterized by distinct aggregative adherence (AA) in a stacked-brick pattern to cultured epithelial cells. In this study, we investigated 118 EAEC strains isolated from the stools of Danish adults with traveler's diarrhea. We evaluated the presence of the aggregative adherence fimbriae (AAFs) by a multiplex PCR, targeting the four known major subunit variants as well as their usher-encoding genes. Almost one-half (49/118) of the clinical isolates did not possess any known AAF major fimbrial subunit, despite the presence of other AggR-related loci. Further investigation revealed the presence of an AAF-related gene encoding a yet-uncharacterized adhesin, termed agg5A. The sequence of the agg5DCBA gene cluster shared fimbrial accessory genes (usher, chaperone, and minor pilin subunit genes) with AAF/III, as well as the signal peptide present in the beginning of the agg3A gene. The complete agg5DCBA gene cluster from a clinical isolate, EAEC strain C338-14, with the typical stacked-brick binding pattern was cloned, and deletion of the cluster was performed. Transformation to a nonadherent E. Coli HB101 and complementation of the nonadherent C338-14 mutant with the complete gene cluster restored the AA adhesion. Overall, we found the agg5A gene in 12% of the 118 strains isolated from Denmark, suggesting that this novel adhesin represents an important variant.
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Role of Enteroaggregative Escherichia Coli Virulence Factors in Uropathogenesis
Infection and immunity, 2013Co-Authors: Erik J. Boll, Nadia Boisen, Carsten Struve, Bente Olesen, Steen Gustav Stahlhut, Karen Angeliki KrogfeltAbstract:A multiresistant clonal Escherichia Coli O78:H10 strain qualifying molecularly as Enteroaggregative Escherichia Coli (EAEC) was recently shown to be the cause of a community-acquired outbreak of urinary tract infection (UTI) in greater Copenhagen, Denmark, in 1991. This marks the first time EAEC has been associated with an extraintestinal disease outbreak. Importantly, the outbreak isolates were recovered from the urine of patients with symptomatic UTI, strongly implying urovirulence. Here, we sought to determine the uropathogenic properties of the Copenhagen outbreak strain and whether these properties are conferred by the EAEC-specific virulence factors. We demonstrated that through expression of aggregative adherence fimbriae, the principal adhesins of EAEC, the outbreak strain exhibited pronouncedly increased adherence to human bladder epithelial cells compared to prototype uropathogenic strains. Moreover, the strain was able to produce distinct biofilms on abiotic surfaces, including urethral catheters. These findings suggest that EAEC-specific virulence factors increase uropathogenicity and may have played a significant role in the ability of the strain to cause a community-acquired outbreak of UTI. Thus, inclusion of EAEC-specific virulence factors is warranted in future detection and characterization of uropathogenic E. Coli.
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Enteroaggregative Escherichia Coli
The Lancet infectious diseases, 2013Co-Authors: Iruka N. Okeke, Nadia Boisen, James P Nataro, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) are an increasingly important cause of diarrhoea. E. Coli belonging to this category cause watery diarrhoea, which is often persistent and can be inflammatory. EAEC have been implicated in sporadic diarrhoea in children and adults, in both developing and developed countries, and have been identified as the cause of several outbreaks worldwide. EAEC are defined by their ability to adhere to epithelial cells in a characteristic "stacked-brick" pattern but are otherwise highly heterogeneous. Genes that could contribute to the pathogenicity of EAEC encode adhesins, toxins, and other factors, all of which are only partially conserved. Practicable tools are needed to improve diagnosis and identify risk factors. EAEC-infected individuals can be treated with fluoroquinolones but there is a need to examine alternative treatment protocols.
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Chapter 8 – Enteroaggregative Escherichia Coli
Escherichia coli, 2013Co-Authors: Nadia Boisen, Karen Angeliki Krogfelt, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) are among the most prevalent enteric pathogens worldwide. The pathotype has been implicated in endemic diarrhea in both developing and industrialized populations, epidemic diarrhea, and traveler’s diarrhea. A recent outbreak of Shiga toxin-producing EAEC adds a new dimension to the epidemiology of this pathotype. Although the pathogenesis of this pathotype is not fully understood, a number of putative virulence factors have been described. The aggregative adherence fimbriae (AAF) are mucosal adhesins that also elicit inflammatory responses from infected mucosal surfaces. Expression of AAF adhesins is induced by the transcriptional activator AggR, which activates expression of several other secreted, but as yet relatively cryptic, proteins. EAEC-induced histopathology includes exfoliation of enterocytes, which has been linked to the action of serine protease autotransporter toxins. Epidemiologic evidence supports a model of EAEC pathogenesis comprising the concerted action of multiple virulence factors.
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genomic characterization of Enteroaggregative Escherichia Coli from children in mali
The Journal of Infectious Diseases, 2012Co-Authors: Nadia Boisen, Myron M. Levine, Flemming Scheutz, David A Rasko, Julia C Redman, Soren Persson, Jakub K Simon, Karen L Kotloff, Samba O Sow, Boubou TambouraAbstract:Background. Enteroaggregative Escherichia Coli (EAEC) is a cause of epidemic and sporadic diarrhea, yet its role as an enteric pathogen is not fully understood. Methods. We characterized 121 EAEC strains isolated in 2008 as part of a case-control study of moderate to severe acute diarrhea among children 0–59 months of age in Bamako, Mali. We applied multiplex polymerase chain reaction and comparative genome hybridization to identify potential virulence factors among the EAEC strains, coupled with classification and regression tree modeling to reveal combinations of factors most strongly associated with illness. Results. The gene encoding the autotransporter protease SepA, originally described in Shigella species, was most strongly associated with diarrhea among the EAEC strains tested (odds ratio, 5.6 [95% confidence interval, 1.92–16.17]; P = .0006). In addition, we identified 3 gene combinations correlated with diarrhea: (1) a clonal group positive for sepA and a putative hemolysin; (2) a group harboring the EAST-1 enterotoxin and the flagellar type H33 but no other previously identified EAEC virulence factor; and (3) a group carrying several of the typical EAEC virulence genes. Conclusion. Our data suggest that only a subset of EAEC strains are pathogenic in Mali and suggest that sepA may serve as a valuable marker for the most virulent isolates.
Iruka N. Okeke - One of the best experts on this subject based on the ideXlab platform.
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Enteroaggregative Escherichia Coli
The Lancet infectious diseases, 2013Co-Authors: Iruka N. Okeke, Nadia Boisen, James P Nataro, Karen Angeliki KrogfeltAbstract:Enteroaggregative Escherichia Coli (EAEC) are an increasingly important cause of diarrhoea. E. Coli belonging to this category cause watery diarrhoea, which is often persistent and can be inflammatory. EAEC have been implicated in sporadic diarrhoea in children and adults, in both developing and developed countries, and have been identified as the cause of several outbreaks worldwide. EAEC are defined by their ability to adhere to epithelial cells in a characteristic "stacked-brick" pattern but are otherwise highly heterogeneous. Genes that could contribute to the pathogenicity of EAEC encode adhesins, toxins, and other factors, all of which are only partially conserved. Practicable tools are needed to improve diagnosis and identify risk factors. EAEC-infected individuals can be treated with fluoroquinolones but there is a need to examine alternative treatment protocols.
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Enteroaggregative Escherichia Coli related to uropathogenic clonal group A.
Emerging infectious diseases, 2007Co-Authors: Faith Wallace-gadsden, James R. Johnson, John Wain, Iruka N. OkekeAbstract:Enteroaggregative Escherichia Coli (EAEC) are heterogeneous, diarrheagenic E. Coli. Of EAEC strains from Nigeria, 10 independent antimicrobial-resistant isolates belonged to the multilocus sequence type 69 clonal complex, to which uropathogenic E. Coli clonal group A belongs. This finding suggests a recent common ancestor for these distinct groups of pathogenic E. Coli.
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Heterogeneous Virulence of Enteroaggregative Escherichia Coli Strains Isolated from Children in Southwest Nigeria
The Journal of infectious diseases, 2000Co-Authors: Iruka N. Okeke, Adebayo Lamikanra, John R. Czeczulin, Filip Dubovsky, James B. Kaper, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) has been implicated in acute and persistent diarrhea, and most strains harbor a member of a partially-conserved plasmid family (called pAA). We studied EAEC isolated from Nigerian children aged
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heterogeneous virulence of Enteroaggregative Escherichia Coli strains isolated from children in southwest nigeria
The Journal of Infectious Diseases, 2000Co-Authors: Iruka N. Okeke, Adebayo Lamikanra, John R. Czeczulin, Filip Dubovsky, James B. Kaper, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) has been implicated in acute and persistent diarrhea, and most strains harbor a member of a partially-conserved plasmid family (called pAA). We studied EAEC isolated from Nigerian children aged <5 years to elucidate the roles of plasmid and chromosomal EAEC loci. We tested a total of 131 EAEC strains isolated from acute diarrhea case patients and control subjects for hybridization with 8 pAA plasmid-derived and 2 chromosomal gene probes, for several in vitro phenotypes and for resistance to antimicrobial agents. Using by multiple logistic regression, we found genes encoding the AAF/II fimbriae to be strongly associated with diarrhea in this population. EAEC strains appear to be of heterogeneous virulence, and data suggest that AAF/II may be a marker for pathogenic strains.
Ian R. Henderson - One of the best experts on this subject based on the ideXlab platform.
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Interaction of Enteroaggregative Escherichia Coli with salad leaves
Environmental microbiology reports, 2009Co-Authors: Cedric N. Berger, James P Nataro, Robert K. Shaw, Fernando Ruiz-perez, Ian R. Henderson, Mark J. Pallen, Gad FrankelAbstract:Enteroaggregative Escherichia Coli (EAEC) are important human pathogens. However, their environmental reservoir is unknown. As fresh salad leaves are increasingly recognized as an important environmental vector for human pathogens, we investigated leaf attachment capability of EAEC strains. We found that binding of clinical EAEC isolates to leaves from Eruca vesicaria (commonly known as rocket or arugula) can be divided into high, moderate and low adherent phenotypes. Using the prototype EAEC strain 042 to investigate the underlining mechanisms involved in leaf attachment, we found small attached bacterial aggregates over the entire leaf surface and dense bacterial attachment to the guard cell of the stomata. An aaf 042 mutant lost the ability to bind the epidermis while retaining stomatal adherence. In contrast, a fliC 042 mutant retained the ability to bind the epidermis but lost stomatal tropism. These results show that multiple adherence factors are involved in the interaction of EAEC with leaves, that EAEC uses similar colonization factors to bind mucosal and leaf surfaces and that fresh produce might be an important reservoir of EAEC strains.
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A novel dispersin protein in Enteroaggregative Escherichia Coli
The Journal of clinical investigation, 2002Co-Authors: Jalaluddin Sheikh, John R. Czeczulin, Susan M. Harrington, Ian R. Henderson, Susan Hicks, Alan D. Phillips, Chantal Le Bouguénec, Pierre Gounon, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) is a diarrheal pathogen defined by its characteristic aggregative adherence (AA) to HEp-2 cells in culture. We have previously shown that EAEC strains secrete a 10-kDa protein that is immunogenic in a human EAEC challenge model. We report here that this protein is encoded by a gene (called aap) lying immediately upstream of that encoding the AggR transcriptional activator, and that aap is under AggR control. The product of aap has a typical signal sequence and is secreted to the extracellular milieu, where it remains noncovalently attached to the surface of the bacterium. EAEC aap mutants aggregate more intensely than the wild-type parent in a number of assays, forming larger aggregates and fewer individual bacteria. Infection of colonic biopsies with wild-type EAEC strain 042 and its aap mutant revealed more dramatic autoagglutination of the mutant compared with the wild-type parent. Our data suggest that the aap gene product participates in formation of a surface coat that acts to disperse the bacteria, thus partially counteracting aggregation mediated by aggregative adherence fimbriae. We have therefore named the aap gene product "dispersin," and we propose that it may be representative of a functional class of colonization factors. Since dispersin is expressed in vivo, is highly immunogenic, and is present in most EAEC strains, it holds considerable promise as an EAEC immunogen.
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Enteroaggregative Escherichia Coli virulence factors in traveler s diarrhea strains
The Journal of Infectious Diseases, 2000Co-Authors: Jordi Vila, Ian R. Henderson, Martha Vargas, Joaquim Gascon, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) is associated with diarrhea in Spanish travelers to developing countries. In this study, the polymerase chain reaction was used to test EAEC isolates for genes encoding putative virulence factors, including EAEC adhesins, the plasmid-encoded toxin (Pet), a heat-stable enterotoxin (EAST), and Shigella enterotoxins 1 and 2 (ShET1 and ShET2), Findings included a low prevalence of genes for Pet (4.3%), ShET2 (4.3%), and the adherence factor AAF/II (8.7%), The overlapping genes encoding the ShET1 and the Pic mucinase were present in most EAEC strains tested (56.5%); however, some strains that carried this locus did not produce both proteins, as determined by Western immunoblot. Surprisingly, ShET1 and ShET2 genes were also found in other E. Coli pathotypes, as was the EAST toxin locus. These findings underscore the heterogeneity of EAEC strains and suggest that the ShET1 may be an important virulence factor in traveler's diarrhea.
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Characterization of Pic, a Secreted Protease of Shigella flexneri and Enteroaggregative Escherichia Coli
Infection and immunity, 1999Co-Authors: Ian R. Henderson, Carlos Eslava, John R. Czeczulin, Fernando R. Noriega, James P NataroAbstract:We have identified and characterized a secreted protein, designated Pic, which is encoded on the chromosomes of Enteroaggregative Escherichia Coli (EAEC) 042 and Shigella flexneri 2457T. The product of the pic gene is synthesized as a 146.5-kDa precursor molecule which is processed at the N and C termini during secretion, allowing the release of a mature protein (109.8 kDa) into the culture supernatant. The deduced amino acid sequence of Pic shows high homology to autotransporter proteins, particularly a subgroup termed the SPATEs (serine protease autotransporters of the Enterobacteriaceae). Present in all members of this subgroup is a motif similar to the active sites of certain serine proteases. Pic catalyzes gelatin degradation, which can be abolished by disruption of the predicted proteolytic active site. Functional analysis of the Pic protein implicates this factor in mucinase activity, serum resistance, and hemagglutination. Our data suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.
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pet an autotransporter enterotoxin from Enteroaggregative Escherichia Coli
Infection and Immunity, 1998Co-Authors: Carlos Eslava, John R. Czeczulin, Alejandro Cravioto, Ian R. Henderson, Fernando Navarrogarcia, James P NataroAbstract:Enteroaggregative Escherichia Coli (EAEC) is an emerging cause of diarrheal illness. Clinical data suggest that diarrhea caused by EAEC is predominantly secretory in nature, but the responsible enterotoxin has not been described. Work from our laboratories has implicated a ca. 108-kDa protein as a heat-labile enterotoxin and cytotoxin, as evidenced by rises in short-circuit current and falls in tissue resistance in rat jejunal tissue mounted in an Ussing chamber. Here we report the genetic cloning, sequencing, and characterization of this high-molecular-weight heat-labile toxin. The toxin (designated the plasmid-encoded toxin [Pet]) is encoded on the 65-MDa adherence-related plasmid of EAEC strain 042. Nucleotide sequence analysis suggests that the toxin is a member of the autotransporter class of proteins, characterized by the presence of a conserved C-terminal domain which forms a β-barrel pore in the bacterial outer membrane and through which the mature protein is transported. The Pet toxin is highly homologous to the EspP protease of enterohemorrhagic E. Coli and to EspC of enteropathogenic E. Coli, an as yet cryptic protein. In addition to its potential role in EAEC infection, Pet represents the first enterotoxin within the autotransporter class of secreted proteins. We hypothesize that other closely related members of this class may also produce enterotoxic effects.