A sensitive and specific molecular tool for detection of both typical and atypical enteroaggregative Escherichia coli

A multiplex PCR has been standardized and evaluated for the identification of both typical and atypical enteroaggregative Escherichia coli (EAEC). The assay detecting aaiA, aaiG, aggR and aatA presented 94.8% of sensitivity, 94.3% of specificity and was able to efficiently detect both groups of EAEC among E. coli isolated from stool cultures.

Low-molecular mass comparative proteome of four atypical enteropathogenic Escherichia coli isolates showing different adherence patterns

Atypical enteropathogenic Escherichia coli (aEPEC) are heterogeneous in terms of serotypes, adherence patterns and the presence of non-locus of enterocyte effacement virulence factors. In this study, the low-molecular mass proteomes of four representative aEPEC, comprising three different adhesion phenotypes (localized-like, aggregative and diffuse) and one non-adherent isolate, were analyzed and compared by 2D gel electrophoresis and LC-MS/MS. By mass spectrometry, a total of 59 proteins were identified according to their annotated function, with most of them being involved in metabolism, protection, and transport; some of them still classified as hypothetical proteins. Thus, in this comparative proteomic analysis of low-molecular mass extracted proteins from different aEPEC isolates, the proteins identified are mainly involved in key metabolic pathways. Also, the majority of the hypothetical and filamentous proteins identified in the isolates studied are products of genes originally identified in the genome of enterohemorrhagic E. coli.

The ability of haemolysins expressed by atypical enteropathogenic Escherichia coli to bind to extracellular matrix components

Typical and atypical enteropathogenic Escherichia coli (EPEC) are considered important bacterial causes of diarrhoea. Considering the repertoire of virulence genes, atypical EPEC (aEPEC) is a heterogeneous group, harbouring genes that are found in other diarrheagenic E. coli pathotypes, such as those encoding haemolysins. Haemolysins are cytolytic toxins that lyse host cells disrupting the function of the plasma membrane. In addition, these cytolysins mediate a connection to vascular tissue and/or blood components, such as plasma and cellular fibronectin. Therefore, we investigated the haemolytic activity of 72 aEPEC isolates and determined the correlation of this phenotype with the presence of genes encoding enterohaemolysins (Ehly) and cytolysin A (ClyA). In addition, the correlation between the expression of haemolysins and the ability of these secreted proteins to adhere to extracellular matrix (ECM) components was also assessed in this study. Our findings demonstrate that a subset of aEPEC presents haemolytic activity due to the expression of Ehlys and/or ClyA and that this activity is closely related to the ability of these isolates to bind to ECM components.

Autotransporters and virulence of enteroaggregative E. coli

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen associated with acute and persistent diarrhea in children and adults. EAEC strains are very heterogeneous and the pathogenesis of EAEC diarrhea is complex and not completely understood. Studies have suggested three major features of EAEC pathogenesis: abundant adherence to the intestinal mucosa, elaboration of enterotoxins and cytotoxins, and induction of mucosal inflammation. Here, we discuss the role of the virulence factors involved in these three major features, focusing in the EAEC adhesion including fimbrial and afimbrial factors, EAEC toxins and autotransporter proteins, such as Pet (plasmid encoded toxin) and Pic (protein involved in colonization); both proteins play a role in two EAEC pathogenic features: cytotoxicity and mucosal colonization, including the bacterium-mucus biofilm. Finally we discuss relevant factors involved in the inflammatory process induce by EAEC, such as flagellin, fimbria and regulator factors (AggR). Interestingly, all these factors are not present in all EAEC strain, contributing to EAEC heterogeneity.

A Comparative Study of the Outer Membrane Proteome from an Atypical and a Typical Enteropathogenic Escherichia coli

This study compared the proteomic profile of outer membrane proteins (OMPs) from one strain of atypical enteropathogenic Escherichia coli (aEPEC) and one of typical EPEC (tEPEC). The OMPs fractions were obtained using sarcosine extraction, and analyzed by one- and two-dimensional gel electrophoresis (1DE and 2DE, respectively). The 1DE OMPs analysis of typical and atypical EPEC evidenced similar patterns; however, the 2DE OMP profile from the aEPEC revealed more protein spots in the 40- to 70-kDa region. 2DE image analysis identified 159 protein spots in both strains whereas 53 protein spots were observed only in tEPEC and 128 were observed only in aEPEC. Remarkably, 41.5% of aEPEC spots showed higher levels of expression compared to tEPEC, some of which with two, others four or even five times more. Twenty-four selected spots were identified using MALDI-TOF mass spectrometry and they corresponded to proteins involved in cell structure and metabolism, as well as in gene regulation. Some of these proteins showed similarity with proteins identified in other E. coli pathotypes. Besides, the differential expression of some proteins in aEPEC may suggest that it could be related to their features that ascertain the adaptation to distinct environments and the worldwide spread distribution of these pathogens.

Cloning approach and functional analysis of anti-intimin single-chain variable fragment (scFv)

Background

Intimin is an important virulence factor involved in the pathogenesis of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic Escherichia coli (EHEC). Both pathogens are still important causes of diarrhea in children and adults in many developing and industrialized countries. Considering the fact that antibodies are important tools in the detection of various pathogens, an anti-intimin IgG2b monoclonal antibody was previously raised in immunized mice with the conserved sequence of the intimin molecule (int_388-667). In immunoblotting assays, this monoclonal antibody showed excellent specificity. Despite good performance, the monoclonal antibody failed to detect some EPEC and EHEC isolates harboring variant amino acids within the 338-667 regions of intimin molecules. Consequently, motivated by its use for diagnosis purposes, in this study we aimed to the cloning and expression of the single-chain variable fragment from this monoclonal antibody (scFv).

Findings

Anti-intimin hybridoma mRNA was extracted and reversely transcripted to cDNA, and the light and heavy chains of the variable fragment of the antibody were amplified using commercial primers. The amplified chains were cloned into pGEM-T Easy vector. Specific primers were designed and used in an amplification and chain linkage strategy, obtaining the scFv, which in turn was cloned into pAE vector. E. coli BL21(DE3)pLys strain was transformed with pAE scFv-intimin plasmid and subjected to induction of protein expression. Anti-intimin scFv, expressed as inclusion bodies (insoluble fraction), was denatured, purified and submitted to refolding. The protein yield was 1 mg protein per 100 mL of bacterial culture. To test the functionality of the scFv, ELISA and immunofluorescence assays were performed, showing that 275 ng of scFv reacted with 2 mg of purified intimin, resulting in an absorbance of 0.75 at 492 nm. The immunofluorescence assay showed a strong reactivity with EPEC E2348/69.

Conclusion

This study demonstrated that the recombinant anti-intimin antibody obtained is able to recognize the conserved region of intimin (Int_388-667) in purified form and the EPEC isolate.

HeLa-cell adherence patterns and actin aggregation of enteropathogenic Escherichia coli (EPEC) and Shiga-toxin-producing E. coli (STEC) strains carrying different eae and tir alleles

A collection of 69 eae-positive strains expressing 29 different intimin types and eight tir alleles was characterized with respect to their adherence patterns to HeLa cells, ability to promote actin accumulation in vitro, the presence of bfpA alleles in positive strains, and bundle-forming pilus (BFP) expression. All of the nine typical enteropathogenic Escherichia coli (tEPEC) studied harbored the enteropathogenic E. coli adherence factor (EAF) plasmid, as shown by PCR and/or EAF probe results. In addition, they were positive for bfpA, as shown by PCR, and BFP expression, as confirmed by immunofluorescence (IFL) and/or immunoblotting (IBL) assays. Localized adherence (LA) was exclusively displayed by those nine tEPEC, while localized-adherence-like (LAL) was the most frequent pattern among atypical EPEC (aEPEC) and Shiga-toxinproducing E. coli (STEC). All LA and LAL strains were able to cause attaching and effacing (AE) lesions, as established by means of the FAS test. There was a significant association between the presence of tir allele alpha1 and bfpA-positive strains, and consequently, with the LA pattern. However, intimin type or bfpA was not associated with the adherence pattern displayed in HeLa cells. Among the eight bfpA alleles detected, a new type (beta10; accession number FN391178) was identified in a strain of serotype O157:H45, and a truncated variant (beta3.2-t; accession number FN 391181) in four strains belonging to different pathotypes.

Clonal relationship among atypical enteropathogenic Escherichia coli strains isolated from different animal species and humans

Forty-nine typical and atypical enteropathogenic Escherichia coli (EPEC) strains belonging to different serotypes and isolated from humans, pets (cats and dogs), farm animals (bovines, sheep, and rabbits), and wild animals (monkeys) were investigated for virulence markers and clonal similarity by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The virulence markers analyzed revealed that atypical EPEC strains isolated from animals have the potential to cause diarrhea in humans. A close clonal relationship between human and animal isolates was found by MLST and PFGE. These results indicate that these animals act as atypical EPEC reservoirs and may represent sources of infection for humans. Since humans also act as a reservoir of atypical EPEC strains, the cycle of mutual infection of atypical EPEC between animals and humans, mainly pets and their owners, cannot be ruled out since the transmission dynamics between the reservoirs are not yet clearly understood.

Differentiation of typical and atypical enteropathogenic Escherichia coli using colony immunoblot for detection of bundle-forming pilus expression

AIMS

The aim of study was to develop a colony immunoblot assay to differentiate typical from atypical enteropathogenic Escherichia coli (EPEC) by detection of bundle-forming pilus (BFP) expression.

METHODS AND RESULTS

Anti-BFP antiserum was raised in rabbits and its reactivity was confirmed by immunoelectron microscopy and by immunoblotting recognizing bundlin, the major pilus repeating subunit. The bacterial isolates tested in the colony immunoblot assay were grown in different media. Proteins from bacterial isolates were transferred to nitrocellulose membrane after treatment with phosphate buffer containing Triton X-100, EDTA and sodium chloride salts. When 24 typical EPEC and 96 isolates including, 72 atypical EPEC, 13 Gram-negative type IV-expressing strains and 11 enterobacteriaceae were cultivated in Dulbecco's Modified Eagle's Medium agar containing fetal bovine serum or in blood agar in the presence of CaCl(2) , they showed a positivity of 92 and 83%, and specificity of 96 and 97%, respectively.

CONCLUSION

The assay enables reliable identification of BFP-expressing isolates and contributes to the differentiation of typical and atypical EPEC.

SIGNIFICANCE AND IMPACT OF THE STUDY

The colony immunoblot for BFP detection developed in this study combines the simplicity of an immunoserological assay with the high efficiency of testing a large number of EPEC colonies.

The dispersin-encoding gene (aap) is not restricted to enteroaggregative Escherichia coli

The presence of the enteroaggregative Escherichia coli (EAEC) virulence genes aatA, aap, and aggR was assayed in strains of different diarrheagenic E. coli pathotypes and nonpathogenic E. coli. The dispersin-encoding gene (aap) was detected in EAEC, diffusely adherent E. coli, and nonpathogenic E. coli, demonstrating that molecular diagnostics of EAEC based on aap detection may identify non-EAEC strains.

Identification of enteropathogenic and enterohaemorrhagic Escherichia coli strains by immunoserological detection of intimin

AIMS

To evaluate the sensitivity and specificity of polyclonal and monoclonal antibodies (Mabs) against intimin in the detection of enteropathogenic and enterohaemorrhagic Escherichia coli isolates using immunoblotting.

METHODS AND RESULTS

Polyclonal and Mabs against the intimin-conserved region were raised, and their reactivities were compared in enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC) isolates using immunoblotting analysis. In comparison with rat antiserum, rabbit anti-intimin IgG-enriched fraction had a stronger recognition pattern to a wide spectrum of intimin types in different EPEC and EHEC serotypes. On the other hand, murine monoclonal IgG2b specific to intimin, with dissociation constant of 1.3x10(-8) mol l(-1), failed in the detection of some of these isolates.

CONCLUSION

All employed antibodies showed 100% specificity, not reacting with any of the eae-negative isolates. The sensitivity range was according to the employed antisera, and 97% for rabbit anti-intimin IgG-enriched fraction, followed by 92% and 78% sensitivity with rat antisera and Mab.

SIGNIFICANCE AND IMPACT OF THE STUDY

The rabbit anti-intimin IgG-enriched fraction in immunoblotting analysis is a useful tool for EPEC and EHEC diagnoses.

Atypical enteropathogenic Escherichia coli genomic background allows the acquisition of non-EPEC virulence factors

Atypical enteropathogenic Escherichia coli (aEPEC) has been associated with infantile diarrhea in many countries. The clonal structure of aEPEC is the object of active investigation but few works have dealt with its genetic relationship with other diarrheagenic E. coli (DEC). This study aimed to evaluate the genetic relationship of aEPEC with other DEC pathotypes. The phylogenetic relationships of DEC strains were evaluated by multilocus sequence typing. Genetic diversity was assessed by pulsed-field gel electrophoresis (PFGE). The phylogram showed that aEPEC strains were distributed in four major phylogenetic groups (A, B1, B2 and D). Cluster I (group B1) contains the majority of the strains and other pathotypes [enteroaggregative, enterotoxigenic and enterohemorrhagic E. coli (EHEC)]; cluster II (group A) also contains enteroaggregative and diffusely adherent E. coli; cluster III (group B2) has atypical and typical EPEC possessing H6 or H34 antigen; and cluster IV (group D) contains aEPEC O55:H7 strains and EHEC O157:H7 strains. PFGE analysis confirmed that these strains encompass a great genetic diversity. These results indicate that aEPEC clonal groups have a particular genomic background--especially the strains of phylogenetic group B1--that probably made possible the acquisition and expression of virulence factors derived from non-EPEC pathotypes.

An overview of atypical enteropathogenic Escherichia coli

The enteropathogenic Escherichia coli (EPEC) pathotype is currently divided into two groups, typical EPEC (tEPEC) and atypical EPEC (aEPEC). The property that distinguishes these two groups is the presence of the EPEC adherence factor plasmid, which is only found in tEPEC. aEPEC strains are emerging enteropathogens that have been detected worldwide. Herein, we review the serotypes, virulence properties, genetic relationships, epidemiology, reservoir and diagnosis of aEPEC, including those strains not belonging to the classical EPEC serogroups (nonclassical EPEC serogroups). The large variety of serotypes and genetic virulence properties of aEPEC strains from nonclassical EPEC serogroups makes it difficult to determine which strains are truly pathogenic.

Production and characterization of rabbit polyclonal sera against Shiga toxins Stx1 and Stx2 for detection of Shiga toxin-producing Escherichia coli

STEC has emerged as an important group of enteric pathogens worldwide. In this study, rabbit polyclonal Stx1 and Stx2 antisera were raised and employed in the standardization of immunoassays for STEC detection. Using their respective antisera, the limit of detection of the toxin was 35.0 pg for Stx1 and 5.4 pg for Stx2. By immunoblotting, these antisera recognized both toxin subunits. Cross-reactivity was observed in the A subunit, but only Stx2 antiserum was able to neutralize the cytotoxicity of both toxins in the Vero cell assay. Six stx-harboring E. coli isolates were analyzed for their virulence traits. They belonged to different serotypes, including the O48:H7, described for the first time in Brazil. Only three strains harbored eae, and the e-hly gene and hemolytic activity was detected in five strains. Three isolates showed new stx2 variants (stx(2v-ha) and stx(2vb-hb)). The ELISA assay detected all six isolates, including one VCA-negative isolate, while the immunodot assay failed to detect one isolate, which was VCA-positive. In contrast, the colony-immunoblot assay detected only one VCA-positive isolate. Our results demonstrate that among the immunoassays developed in this study, the immunodot, and particularly the ELISA, appear as perspective for STEC detection in developing countries.

Immunization of mice with Lactobacillus casei expressing intimin fragments produces antibodies able to inhibit the adhesion of enteropathogenic Escherichia coli to cultivated epithelial cells

Enteropathogenic Escherichia coli (EPEC) are frequently isolated as a cause of infantile diarrhea in developing countries. Its pathogenicity is distinguished by histopathological alterations at the site of infection, known as attaching and effacing (A/E) lesions, in which bacterial virulence factors and host proteins participate. Intimin, a bacterial adhesin expressed by all EPEC described to date, is responsible for the intimate adherence of the bacteria to host cells and is essential for the formation of A/E lesions. Mucosal vaccination may represent an efficacious intervention to prevent EPEC infection and lower morbidity and mortality rates. Strategies for mucosal vaccinations that use lactic acid bacteria for the delivery of heterologous antigens rely on their safety profile and ability to stimulate the immune system. In the present work, we have constructed Lactobacillus casei strains expressing different fragments of intimin beta, a subtype that is frequently expressed by EPEC strains. Mucosal immunization of mice with L. casei expressing intimin fragments induced specific systemic and mucosal antibodies. These antibodies were able to recognize native intimin on the surface of EPEC and to inhibit in vitro EPEC binding to epithelial cells.

Uropathogenic Escherichia coli (UPEC) strains may carry virulence properties of diarrhoeagenic E. coli

To analyze whether Escherichia coli strains that cause urinary tract infections (UPEC) share virulence characteristics with the diarrheagenic E. coli (DEC) pathotypes and to recognize their genetic diversity, 225 UPEC strains were examined for the presence of various properties of DEC and UPEC (type of interaction with HeLa cells, serogroups and presence of 30 virulence genes). No correlation between adherence patterns and serogroups was observed. Forty-five serogroups were found, but 64% of the strains belonged to one of the 12 serogroups (O1, O2, O4, O6, O7, O14, O15, O18, O21, O25, O75, and O175) and carried UPEC virulence genes (pap, hly, aer, sfa, cnf). The DEC genes found were: aap, aatA, aggC, agg3C, aggR, astA, eae, ehly, iha, irp2, lpfA(O113), pet, pic, pilS, and shf. Sixteen strains presented aggregative adherence and/or the aatA sequence, which are characteristics of enteroaggregative E. coli (EAEC), one of the DEC pathotypes. In summary, certain UPEC strains may carry DEC virulence properties, mostly associated to the EAEC pathotype. This finding raises the possibility that at least some faecal EAEC strains might represent potential uropathogens. Alternatively, certain UPEC strains may have acquired EAEC properties, becoming a potential cause of diarrhoea.

Fimbriae of uropathogenicProteus mirabilis

Proteus mirabilis is a common causative agent of cystitis and pyelonephritis in patients with urinary catheters or structural abnormalities of the urinary tract. Several types of fimbriae, which are potentially involved in adhesion to the uroepithelium, can be expressed simultaneously by P. mirabilis: mannose-resistant/Proteus-like (MR/P) fimbriae, P. mirabilis fimbriae (PMF), uroepithelial cell adhesin (UCA), renamed by some authors nonagglutinating fimbriae (NAF), and ambient-temperature fimbriae (ATF). Proteus mirabilis is a common cause of biofilm formation on catheter material and MR/P fimbriae are involved in this process. The considerable serious pathology caused by P. mirabilis in the urinary tract warrants the development of a prophylactic vaccine, and several studies have pointed to MR/P fimbriae as a potential target for immunization. This article reviews P. mirabilis fimbriae with regard to their participation in uropathogenesis, biofilm formation and as vaccine targets.

Aggregative adherence of uropathogenic Proteus mirabilis to cultured epithelial cells

Proteus mirabilis is an important cause of urinary tract infection (UTI) in patients with complicated urinary tracts. Thirty-five strains of P. mirabilis isolated from UTI were examined for the adherence capacity to epithelial cells. All isolates displayed the aggregative adherence (AA) to HEp-2 cells, a phenotype similarly presented in LLC-MK(2) cells. Biofilm formation on polystyrene was also observed in all strains. The mannose-resistant Proteus-like fimbriae (MR/P), Type I fimbriae and AAF/I, II and III fimbriae of enteroaggregative Escherichia coli were searched by the presence of their respective adhesin-encoding genes. Only the MR/P fimbrial subunits encoding genes mrpA and mrpH were detected in all isolates, as well as MR/P expression. A mutation in mrpA demonstrated that MR/P is involved in aggregative adherence to HEp-2 cells, as well as in biofilm formation. However, these phenotypes are multifactorial, because the mrpA mutation reduced but did not abolish both phenotypes. The present results reinforce the importance of MR/P as a virulence factor in P. mirabilis due to its association with AA and biofilm formation, which is an important step for the establishment of UTI in catheterized patients.

Enteroaggregative Escherichia coli from humans and animals differ in major phenotypical traits and virulence genes

Enteroaggregative Escherichia coli (EAEC) is characterized by the expression of the aggregative adherence pattern to cultured epithelial cells. In this study, we determined the phenotypic and genotypic relationships among 86 EAEC strains of human and animal (calves, piglets and horses) feces. Serotypes and the presence of EAEC virulence markers were determined, and these results were associated with ribotyping. Strains harboring aggR (typical EAEC) of human origin were found carrying several of the searched markers, while atypical EAEC harbored none or a few markers. The strains of animal origin were classified as atypical EAEC (strains lacking aggR) and harbored only irp2 or shf. Strains from humans and animals belonged to several different serotypes, although none of them prevailed. Sixteen ribotypes were determined, and there was no association with virulence genes profiles or serotypes. Relationship was not found among the strains of this study, and the assessed animals may not represent a reservoir of human pathogenic typical EAEC.

Antibody response against plasmid-encoded toxin (Pet) and the protein involved in intestinal colonization (Pic) in children with diarrhea produced by enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) is an emerging cause of pediatric and adult travellers diarrhea. The mechanism by which EAEC induce diarrhea is not completely known. Two serine protease autotransporter proteins, named Pet and Pic have been identified in EAEC strains. Pet has enterotoxic and cytotoxic activities, while the role of Pic in pathogenesis may lie on its mucinolytic activity. Little is known about Pet and Pic biological activities in vivo. In this study the antibody responses against these autotransporter proteins in convalescent children is investigated. Fifteen (83%) children showed specific antibodies against Pet or Pic in their sera. IgG and IgM antibodies were the main isotype found. Specific antibodies against Pic, but not against Pet, were detected in sera from age-matched control group. These data show that specific anti-Pet and anti-Pic antibodies are produced during the course of a natural EAEC infection in children.

Detection of LEE 4 region-encoded genes from different enteropathogenic and enterohemorrhagic Escherichia coli serotypes

The LEE 4 genes sepL, espA, espD, espB, and espF were detected in 50 strains of typical and atypical enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli by PCR. sepL was amplified in 90%, espA in 94%, espB in 50%, espD in 40%, and espF in 78% of all strains, employing prototype EPEC-based primers. With O26:H(-)-based primers, espB was detected in all O26 strains, and O157:H7-specific primers amplified espD and espB among all O55:H7 and O157:H7 strains. Our results indicated that espA and sepL should be more conserved between different EPEC and EHEC serotypes, while espB, espD, and espF should be more diverse. Apparently this variation is related to serogroup or serotype, but sequencing assays are necessary to confirm such conservation/diversity and their association with serogroup or serotype. Secreted protein analyses of espA, espD, and espB PCR-negative strains demonstrated that their encoded proteins present distinct immunological types, reflecting the genetic variability of those genes.

Virulence factors of Escherichia coli strains belonging to serogroups O127 and O142

A total of 102 Escherichia coli strains belonging to serogroups O127 and O142 were examined for genotypic and phenotypic characteristics. The most frequent serotypes found were O127:H21, O127:H40 and O142:H34. The virulence properties were evaluated by adhesion to HeLa cells and hybridization with gene probes for diarrhoeagenic E. coli. Most strains in the two serogroups were categorized as enteropathogenic E. coli, but enteroaggregative E. coli was also detected in both serogroups. All strains that carried the eae sequence presented the LEE region inserted in selC. Five ribotypes were detected in serogroup O127 and four in serogroup O142 and a correlation between serotypes and ribotypes was observed mainly in serogroup O142.

Role of type I fimbriae in the aggregative adhesion pattern of enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) is distinguished by its characteristic aggregative adherence (AA) pattern to cultured epithelial cells. In this study we investigated the role of type I fimbriae (TIF) in the AA pattern to HEp-2 cells and in biofilm formation. Accentuation of this pattern was observed when the adherence assay was performed in the absence of mannose. This effect was observed in the prototype EAEC strain 042 (O44:H18), O128:H35 strains and for other EAEC serotypes. Antiserum against TIF decreased AA by 70% and 90% for strains 042 and 18 (O128:H35 prototype strain), respectively. A non-polar knockout of fimD, the TIF usher, in strains 042 and 18 resulted in inhibition of the accentuated AA pattern of approximately 80% and 70% respectively, and biofilm formation diminution of 49% for 042::fimD and 76% for 18::fimD. Our data evidence a role for TIF in the AA pattern and in EAEC biofilm formation, demonstrating that these phenotypes are multifactorial.