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

Enteropathogenic Escherichia coli is a predominant pathotype in healthy pigs in Hubei Province of China

AIM

This study aims to investigate the prevalence of intestinal pathogenic Escherichia coli (InPEC) in healthy pig-related samples and evaluate the potential virulence of the InPEC strains.

METHODS AND RESULTS

A multiplex PCR method was established to identify different pathotypes of InPEC. A total of 800 rectal swab samples and 296 pork samples were collected from pig farms and slaughterhouses in Hubei province, China. From these samples, a total of 21 InPEC strains were isolated, including 19 enteropathogenic E. coli (EPEC) and 2 shiga toxin-producing E. coli (STEC) strains. By whole-genome sequencing and in silico typing, it was shown that the sequence types and serotypes were diverse among the strains. Antimicrobial susceptibility assays showed that 90.48% of the strains were multi-drug resistant. The virulence of the strains was first evaluated using the Galleria mellonella larvae model, which showed that most of the strains possessed medium to high pathogenicity. A moderately virulent EPEC isolate was further selected to characterize its pathogenicity using a mouse model, which suggested that it could cause significant diarrhea. Bioluminescence imaging (BLI) was then used to investigate the colonization dynamics of this EPEC isolate, which showed that the EPEC strain could colonize the mouse cecum for up to 5 days.

Clonal spread of non-O157 Shiga toxigenic Escherichia coli O21:H25 in raw water buffalo milks

AIMS

This study was conducted to investigate the presence of Shiga toxin-producing O157 and non-O157 E. coli in raw water buffalo milk, as well as to determine the virulence gene profiles, phylogroups, sequence types, and serotypes of the isolated strains.

METHODS AND RESULTS

A total of 200 hand-milked raw water buffalo milk samples were collected from 200 different water buffaloes over a period of three months from 20 different farms. Isolation of STEC was performed using CHROMagar STEC. Presence of stx1, stx2, and eaeA genes were investigated by mPCR. Phylogroups and sequence types of E. coli strains were determined by Clermont phylotyping and MLST. Serotyping was performed using PCR or WGS. According to the results, two milk samples obtained from two different farms were found as STEC-positive. All Stx-positive E. coli isolates belonged to phylogenetic group A and were assigned to ST10. WGS results indicated that serotype of two isolates was O21:H25 and average nucleotide identity was detected at 99.99%. Thirteen additional registered E. coli O21:H25 assembled WGS data were obtained from EnteroBase and a phylogenetic tree was constructed.

CONCLUSIONS

With this study, the presence of stx2 harboring E. coli O21:H25 in milk was identified for the first time. Although the identified serotype is considered a non-pathogen seropathotype, we conclude it could play an important role in the environmental circulation of Stx-phages and consequently contribute to the emergence of new STEC-related outbreaks.

Antibiotic Resistance and Virulence Profiles of Escherichia coli Strains Isolated from Wild Birds in Poland

Wild animals are increasingly reported as carriers of antibiotic-resistant and pathogenic bacteria including Enterobacteriaceae. However, the role of free-living birds as reservoirs for potentially dangerous microbes is not yet thoroughly understood. In our work, we examined Escherichia coli strains from wild birds in Poland in relation to their antimicrobial agents susceptibility, virulence and phylogenetic affiliation. Identification of E. coli was performed using MALDI-TOF mass spectrometry. The antibiotic susceptibility of the isolates was determined by the broth microdilution method, and resistance and virulence genes were detected by PCR. E. coli bacteria were isolated from 32 of 34 samples. The strains were most often classified into phylogenetic groups B1 (50%) and A (25%). Resistance to tetracycline (50%), ciprofloxacin (46.8%), gentamicin (34.3%) and ampicillin (28.1%) was most frequently reported, and as many as 31.2% of E. coli isolates exhibited a multidrug resistance phenotype. Among resistance genes, sul2 (31.2% of isolates) and bla_TEM (28.1%) were identified most frequently, while irp-2 (31.2%) and ompT (28.1%) were the most common virulence-associated genes. Five strains were included in the APEC group. The study indicates that wild birds can be carriers of potentially dangerous E. coli strains and vectors for the spread of resistant bacteria and resistance determinants in the environment.

Potential Zoonotic Pathovars of Diarrheagenic Escherichia coli Detected in Lambs for Human Consumption from Tierra del Fuego, Argentina

Diarrheagenic Escherichia coli (DEC) pathovars impact childhood health. The southern region of Argentina shows the highest incidence of hemolytic uremic syndrome (HUS) in children of the country. The big island of Tierra del Fuego (TDF) in Argentina registered an incidence of five cases/100,000 inhabitants of HUS in 2019. This work aimed to establish the prevalence of STEC, EPEC, and EAEC in lambs slaughtered in abattoirs from TDF as well as to characterize the phenotypes and the genotypes of the isolated pathogens. The prevalence was 26.6% for stx+, 5.7% for eae+, and 0.27% for aagR+/aaiC+. Twelve STEC isolates were obtained and belonged to the following serotypes: O70:HNT, O81:H21, O81:HNT, O102:H6, O128ab:H2, O174:H8, and O174:HNT. Their genotypic profiles were stx_1c (2), stx_1c/ehxA (3), stx_2b/ehxA (1), stx_1c/stx_2b (2), and stx_1c/stx₂/ehxA (4). Six EPEC isolates were obtained and corresponded to five serotypes: O2:H40, O32:H8, O56:H6, O108:H21, and O177:H25. All the EPEC isolates were bfpA- and two were ehxA+. By XbaI-PFGE of 17 isolates, two clusters were identified. By antimicrobial susceptibility tests, 8/12 STEC and 5/6 EPEC were resistant to at least one antibiotic. This work provides new data to understand the ecology of DEC in TDF and confirms that ovine are an important carrier of these pathogens in the region.

Pathotypes and Antimicrobial Susceptibility of Escherichia Coli Isolated from Wild Boar (Sus scrofa) in Tuscany

Wild boar are among the most widespread wild mammals in Europe. Although this species can act as a reservoir for different pathogens, data about its role as a carrier of pathogenic and antimicrobial-resistant Escherichia coli are still scarce. The aim of this study was to evaluate the occurrence of antimicrobial-resistant and pathogenic Escherichia coli in wild boar in the Tuscany region of Italy. During the hunting season of 2018-2019, E. coli was isolated from 175 of 200 animals and subjected to antimicrobial resistance tests and PCR for detection of resistance and virulence factor genes. The highest resistance rates were against cephalothin (94.3%), amoxicillin-clavulanic acid (87.4%), ampicillin (68.6%), and tetracycline (44.6%). The most detected resistance genes were blaCMY-2 (54.3%), sul1 (38.9%), sul2 (30.9%), and tetG (24.6%). Concerning genes encoding virulence factors, 55 of 175 isolates (31.4%) were negative for all tested genes. The most detected genes were hlyA (47.4%), astA (29.1%), stx2 (24.6%), eaeA (17.1%), and stx1 (11.4%). E. coli was classified as Shiga toxin-producing E. coli (STEC) (21.7%), enterohemorrhagic E. coli (EHEC) (6.3%), enteroaggregative E. coli (EAEC) (5.1%), and atypical enteropathogenic E. coli (aEPEC) (3.4%). Enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), and typical enteropathogenic E. coli (tEPEC) were not detected. Our results show that wild boars could carry pathogenic and antimicrobial-resistant E. coli, representing a possible reservoir of domestic animal and human pathogens.

Plant variety and soil type influence Escherichia coli O104:H4 strain C227/11ϕcu adherence to and internalization into the roots of lettuce plants

Human disease outbreaks caused by pathogenic Escherichia coli are increasingly associated with the consumption of contaminated fresh produce. Internalization of enteroaggregative/enterohemorrhagic E. coli (EAEC/EHEC) strains into plant tissues may present a serious threat to public health. In the current study, the ability of the fluorescing Shiga toxin-negative E. coli O104:H4 strain C227/11ϕcu/pKEC2 to adhere to and to internalize into the roots of Lactuca sativa and Valerianella locusta grown in diluvial sand (DS) and alluvial loam (AL) was investigated. In parallel, the soil microbiota was analyzed by partial 16S rRNA gene sequencing. The experiments were performed in a safety level 3 greenhouse to simulate agricultural practice. The adherence of C227/11ϕcu/pKEC2 to the roots of both plant varieties was increased by at least a factor three after incubation in DS compared to AL. Compared to V. locusta, internalization into the roots of L. sativa was increased 12-fold in DS and 108-fold in AL. This demonstrates that the plant variety had an impact on the internalization ability, whereas for a given plant variety the soil type also affected bacterial internalization. In addition, microbiota analysis detected the inoculated strain and showed large differences in the bacterial composition between the soil types.

Truncated Class 1 Integron Gene Cassette Arrays Contribute to Antimicrobial Resistance of Diarrheagenic Escherichia coli

Class 1 integrons (c1-integrons) are associated with multidrug resistance in diarrheagenic Escherichia coli (DEC). However, little is known about gene cassettes located within these c1-integrons, particularly truncated c1-integrons, in DEC strains. Therefore, the aims of the present study were to reveal the relationship between antimicrobial resistance and the presence of truncated c1-integrons in DEC isolates derived from human stool samples in Japan. A total of 162 human stool-derived DEC isolates from Japan were examined by antimicrobial susceptibility testing, PCR-based gene detection, and next-generation sequencing analyses. Results showed that 44.4% (12/27) of c1-integrons identified in the DEC isolates harbored only intI1 (an element of c1-integrons) and were truncated by IS26, Tn3, or IS1-group insertion sequences. No difference in the frequency of antimicrobial resistance was recorded between intact and truncated c1-integron-positive DEC isolates. Isolates containing intact/truncated c1-integrons, particularly enteroaggregative E. coli isolates, were resistant to a greater number of antimicrobials than isolates without c1-integrons. aadA and dfrA were the most prevalent antimicrobial resistance genes in the intact/truncated c1-integrons examined in this study. Therefore, gene cassettes located within these intact/truncated c1-integrons may only play a limited role in conferring antimicrobial resistance among DEC. However, DEC harboring truncated c1-integrons may be resistant to a greater number of antimicrobials than c1-integron-negative DEC, similar to strains harboring intact c1-integrons.

Predictors of Enteric Pathogens in the Domestic Environment from Human and Animal Sources in Rural Bangladesh

Fecal indicator organisms are measured to indicate the presence of fecal pollution, yet the association between indicators and pathogens varies by context. The goal of this study was to empirically evaluate the relationships between indicator Escherichia coli, microbial source tracking markers, select enteric pathogen genes, and potential sources of enteric pathogens in 600 rural Bangladeshi households. We measured indicators and pathogen genes in stored drinking water, soil, and on mother and child hands. Additionally, survey and observational data on sanitation and domestic hygiene practices were collected. Log10 concentrations of indicator E. coli were positively associated with the prevalence of pathogenic E. coli genes in all sample types. Given the current need to rely on indicators to assess fecal contamination in the field, it is significant that in this study context indicator E. coli concentrations, measured by IDEXX Colilert-18, provided quantitative information on the presence of pathogenic E. coli in different sample types. There were no significant associations between the human fecal marker (HumM2) and human-specific pathogens in any environmental sample type. There was an increase in the prevalence of Giardia lamblia genes, any E. coli virulence gene, and the specific E. coli virulence genes stx1/2 with every log10 increase in the concentration of the animal fecal marker (BacCow) on mothers' hands. Thus, domestic animals were important contributors to enteric pathogens in these households.

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

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

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.

Pro-inflammatory capacity of Escherichia coli O104:H4 outbreak strain during colonization of intestinal epithelial cells from human and cattle

In 2011, Germany was struck by the largest outbreak of hemolytic uremic syndrome. The highly virulent E. coli O104:H4 outbreak strain LB226692 possesses a blended virulence profile combining genetic patterns of human adapted enteroaggregative E. coli (EAEC), rarely detected in animal hosts before, and enterohemorrhagic E. coli (EHEC), a subpopulation of Shiga toxin (Stx)-producing E. coli (STEC) basically adapted to the ruminant host. This study aimed at appraising the relative level of adaptation of the EAEC/EHEC hybrid strain LB226692 to humans and cattle. Adherence and invasion of the hybrid strain to intestinal (jejunal and colonic) epithelial cells (IEC) of human and bovine origin was compared to that of E. coli strains representative of different pathovars and commensal E. coli by means of light and electron microscopy and culture. Strain-specific host gene transcription profiles of selected cytokines and chemokines as well as host-induced transcription of bacterial virulence genes were assessed. The release of Stx upon host cell contact was quantified. The outbreak strain's immunomodulation was assessed by cultivating primary bovine macrophages with conditioned supernatants from IEC infection studies with E. coli, serving as model for the innate immunity of the bovine gut. The outbreak strain adhered to IEC of both, human and bovine origin. Electron microscopy of infected cells revealed the strain's particular affinity to human small IEC, in contrast to few interactions with bovine small IEC. The outbreak strain possessed a high-level of adhesive power, similar to human-associated E. coli strains and in contrast to bovine-associated STEC strains. The outbreak strain displayed a non-invasive phenotype, in contrast to some bovine-associated E. coli strains, which were invasive. The outbreak strain provoked some pro-inflammatory activity in human cells, but to a lower extent as compared to other pathotypes. In contrasts to bovine-associated E. coli strains, the outbreak strain induced marked pro-inflammatory activity when interacting with bovine host cells directly (IEC) and indirectly (macrophages). Among stx2-positive strains, the human-pathogenic strains (LB226692 and EHEC strain 86-24) released higher amounts of Stx compared to bovine-associated STEC. The findings imply that the outbreak strain is rather adapted to humans than to cattle. However, the outbreak strain's potential to colonize IEC of both host species and the rather mixed reaction patterns observed for all strains under study indicate, that even STEC strains with an unusual genotype as the EHEC O104:H4 outbreak strain, i.e. with an EAEC genetic background, may be able to conquer other reservoir hosts.

Characterization of Diarrheagenic Escherichia coli Isolated in Organic Waste Products (Cattle Fecal Matter, Manure and, Slurry) from Cattle's Markets in Ouagadougou, Burkina Faso

Cattle farming can promote diarrheal disease transmission through waste, effluents or cattle fecal matter. The study aims to characterize the diarrheagenic Escherichia coli (DEC) isolated from cattle feces, manure in the composting process and slurry, collected from four cattle markets in Ouagadougou. A total of 585 samples (340 cattle feces, 200 slurries and 45 manures in the composting process) were collected from the four cattle markets between May 2015 and May 2016. A multiplex Polymerase Chain Reaction (PCR), namely 16-plex PCR, was used to screen simultaneously the virulence genes specific for shiga toxin-producing E. coli (STEC), enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC) and enteroaggregative E. coli (EAEC). DEC was detected in 10.76% of samples. ETEC was the most prevalent (9.91%). STEC and EAEC have been observed with the same rate (0.51%). ETEC were detected in 12.64% of cattle feces, in 6.66% of manure in the composting process and in 5% of slurry. STEC were detected in 0.58% of cattle feces and in 2.22% of manure in the composting process. EAEC was detected only in 1% of slurry and in 2.22% of manure in the composting process. ETEC strains were identified based on estIa gene and/or estIb gene and/or elt gene amplification. Of the 58 ETEC, 10.34% contained astA, 17.24% contained elt, 3.44% contained estIa and 79.31% contained estIb. The two positive EAEC strains contained only the aggR gene, and the third was positive only for the pic gene. The results show that effluent from cattle markets could contribute to the spreading of DEC in the environment in Burkina Faso.

Diarrheagenic Escherichia coli

Most Escherichia coli strains live harmlessly in the intestines and rarely cause disease in healthy individuals. Nonetheless, a number of pathogenic strains can cause diarrhea or extraintestinal diseases both in healthy and immunocompromised individuals. Diarrheal illnesses are a severe public health problem and a major cause of morbidity and mortality in infants and young children, especially in developing countries. E. coli strains that cause diarrhea have evolved by acquiring, through horizontal gene transfer, a particular set of characteristics that have successfully persisted in the host. According to the group of virulence determinants acquired, specific combinations were formed determining the currently known E. coli pathotypes, which are collectively known as diarrheagenic E. coli. In this review, we have gathered information on current definitions, serotypes, lineages, virulence mechanisms, epidemiology, and diagnosis of the major diarrheagenic E. coli pathotypes.

Fitness of Enterohemorrhagic Escherichia coli (EHEC)/Enteroaggregative E. coli O104:H4 in Comparison to That of EHEC O157: Survival Studies in Food and In Vitro

In 2011, one of the world's largest outbreaks of hemolytic-uremic syndrome (HUS) occurred, caused by a rare Escherichia coli serotype, O104:H4, that shared the virulence profiles of Shiga toxin-producing E. coli (STEC)/enterohemorrhagic E. coli (EHEC) and enteroaggregative E. coli (EAEC). The persistence and fitness factors of the highly virulent EHEC/EAEC O104:H4 strain, grown either in food or in vitro, were compared with those of E. coli O157 outbreak-associated strains. The log reduction rates of the different EHEC strains during the maturation of fermented sausages were not significantly different. Both the O157:NM and O104:H4 serotypes could be shown by qualitative enrichment to be present after 60 days of sausage storage. Moreover, the EHEC/EAEC O104:H4 strain appeared to be more viable than E. coli O157:H7 under conditions of decreased pH and in the presence of sodium nitrite. Analysis of specific EHEC strains in experiments with an EHEC inoculation cocktail showed a dominance of EHEC/EAEC O104:H4, which could be isolated from fermented sausages for 60 days. Inhibitory activities of EHEC/EAEC O104:H4 toward several E. coli strains, including serotype O157 strains, could be determined. Our study suggests that EHEC/EAEC O104:H4 is well adapted to the multiple adverse conditions occurring in fermented raw sausages. Therefore, it is strongly recommended that STEC strain cocktails composed of several serotypes, instead of E. coli O157:H7 alone, be used in food risk assessments. The enhanced persistence of EHEC/EAEC O104:H4 as a result of its robustness, as well as the production of bacteriocins, may account for its extraordinary virulence potential.

IMPORTANCE

In 2011, a severe outbreak caused by an EHEC/EAEC serovar O104:H4 strain led to many HUS sequelae. In this study, the persistence of the O104:H4 strain was compared with those of other outbreak-relevant STEC strains under conditions of fermented raw sausage production. Both O157:NM and O104:H4 strains could survive longer during the production of fermented sausages than E. coli O157:H7 strains. E. coli O104:H4 was also shown to be well adapted to the multiple adverse conditions encountered in fermented sausages, and the secretion of a bacteriocin may explain the competitive advantage of this strain in an EHEC strain cocktail. Consequently, this study strongly suggests that enhanced survival and persistence, and the presumptive production of a bacteriocin, may explain the increased virulence of the O104:H4 outbreak strain. Furthermore, this strain appears to be capable of surviving in a meat product, suggesting that meat should not be excluded as a source of potential E. coli O104:H4 infection.

Characterization of virulence factors and phylogenetic group determination of Escherichia coli isolated from diarrheic and non-diarrheic calves from Brazil

This study aimed to detect virulence factors, pathovars, and phylogenetic groups of Escherichia coli strains obtained from feces of calves with and without diarrhea up to 70 days old and to determine the association between occurrence of diarrhea, phylogenetic groups, and pathovars. Phylo-typing analysis of the 336 E. coli strains isolated from calves with Clermont method showed that 21 (6.25 %) belong to phylogroup A, 228 (67.85 %) to phylogroup B1, 2 (0.6 %) to phylogroup B2, 5 (1.49 %) to phylogroup C, 57 (16.96 %) to phylogroup E, and 3 (0.9 %) to phylogroup F. Phylogroup D was not identified and 20 strains (5.95 %) were assigned as "unknown." The distribution of phylogenetic groups among pathovars showed that NTEC belong to phylogroups B1 (17) and C (4); EPEC to phylogroups B1 (6) and E (8); STEC to phylogroups A (5), B1 (56), B2 (2), C (1), and E (15); EHEC to phylogroups B1 (95) and E (5); and ETEC to phylogroups A (3), B1 (7), and E (10). The EAST-1 strains were phylogroups A (13), B1 (47), E (19), and F (3); E. coli strains of "unknown" phylogroups belonged to pathovars EPEC (1), EHEC (2), STEC (7), and EAST-1 strains (6). ETEC was associated with diarrhea (P = 0.002). Our study did not find association between the phylogenetic background and occurrence of diarrhea (P = 0.164) but did find some relationship in phylogenetic group and pathovar. The study showed that EHEC and STEC are classified as phylogroup B1, EAST-1 phylogroup A, ETEC, and EPEC phylogroup E.

Experimental Infection of Calves with Escherichia coli O104:H4 outbreak strain

In 2011, a severe outbreak of hemolytic-uremic syndrome was caused by an unusual, highly virulent enterohemorrhagic E. coli (EHEC) O104:H4 strain, which possessed EHEC virulence traits in the genetic background of human-adapted enteroaggregative E. coli. To determine magnitude of fecal shedding and site of colonization of EHEC O104:H4 in a livestock host, 30 (ten/strain) weaned calves were inoculated with 10¹⁰ CFU of EHEC O104:H4, EHEC O157:H7 (positive control) or E. coli strain 123 (negative control) and necropsied (4 or 28 d.p.i.). E. coli O157:H7 was recovered until 28 d.p.i. and O104:H4 until 24 d.p.i. At 4 d.p.i., EHEC O104:H4 was isolated from intestinal content and detected associated with the intestinal mucosa. These results are the first evidence that cattle, the most important EHEC reservoir, can also carry unusual EHEC strains at least transiently, questioning our current understanding of the molecular basis of host adaptation of this important E. coli pathovar.

Genome sequencing and comparative genomics provides insights on the evolutionary dynamics and pathogenic potential of different H-serotypes of Shiga toxin-producing Escherichia coli O104

BACKGROUND

Various H-serotypes of the Shiga toxin-producing Escherichia coli (STEC) O104, including H4, H7, H21, and H¯, have been associated with sporadic cases of illness and have caused food-borne outbreaks globally. In the U.S., STEC O104:H21 caused an outbreak associated with milk in 1994. However, there is little known on the evolutionary origins of STEC O104 strains, and how genotypic diversity contributes to pathogenic potential of various O104 H-antigen serotypes isolated from different ecological niches and/or geographical regions.

RESULTS

Two STEC O104:H21 (milk outbreak strain) and O104:H7 (cattle isolate) strains were shot-gun sequenced, and the genomes were closed. The intimin (eae) gene, involved in the attaching-effacing phenotype of diarrheagenic E. coli, was not found in either strain. Examining various O104 genome sequences, we found that two "complete" left and right end portions of the locus of enterocyte effacement (LEE) pathogenicity island were present in 13 O104 strains; however, the central portion of LEE was missing, where the eae gene is located. In O104:H4 strains, the missing central portion of the LEE locus was replaced by a pathogenicity island carrying the aidA (adhesin involved in diffuse adherence) gene and antibiotic resistance genes commonly carried on plasmids. Enteroaggregative E. coli-specific virulence genes and European outbreak O104:H4-specific stx2-encoding Escherichia P13374 or Escherichia TL-2011c bacteriophages were missing in some of the O104:H4 genome sequences available from public databases. Most of the genomic variations in the strains examined were due to the presence of different mobile genetic elements, including prophages and genomic island regions. The presence of plasmids carrying virulence-associated genes may play a role in the pathogenic potential of O104 strains.

CONCLUSIONS

The two strains sequenced in this study (O104:H21 and O104:H7) are genetically more similar to each other than to the O104:H4 strains that caused an outbreak in Germany in 2011 and strains found in Central Africa. A hypothesis on strain evolution and pathogenic potential of various H-serotypes of E. coli O104 strains is proposed.

Evaluation of a PCR targeting fimbrial subunit gene (fimA) for rapid and reliable detection of Enteroaggregative Escherichia coli recovered from human and animal diarrhoeal cases

The present study describes the utility of a chromosomal associated fimbrial subunit gene (fimA) for screening 'typical' as well as 'atypical' Enteroaggregative Escherichia coli (EAEC) by PCR and its possible role as a promising molecular marker for rapid detection of 'typical' and 'atypical' EAEC pathotype.

Detection of pathogenic Escherichia coli in samples collected at an abattoir in Zaria, Nigeria and at different points in the surrounding environment

Pathogenic Escherichia coli can be released with the wastes coming from slaughterhouses into the environment, where they can persist. We investigated the presence of diarrheagenic E. coli in specimens taken at an abattoir located in the Zaria region, Nigeria, in samples of water from the river Koreye, where the effluent from the abattoir spills in, and vegetable specimens taken at a nearby farm. All the isolated E. coli were assayed for the production of Shiga toxins (Stx) by using the Ridascreen verotoxin Immunoassay and by PCR amplification of genes associated with the diarrheagenic E. coli. Three strains from the rectal content of two slaughtered animals and a cabbage were positive for the presence of the Stx-coding genes. Additionally we have isolated one Enteroaggregative E. coli (EAggEC) from the abattoir effluent and two Subtilase-producing E. coli from the slaughterhouse’s effluent and a sample of carrots. Our results provide evidence that pathogenic E. coli can contaminate the environment as a result of the discharge into the environment of untreated abattoir effluent, representing a reservoir for STEC and other diarrheagenic E. coli favouring their spread to crops.

Characterization and biofilm forming ability of diarrhoeagenic enteroaggregative Escherichia coli isolates recovered from human infants and young animals

Enteroaggregative Escherichia coli (EAEC) is an important pathotype that causes infection in humans and animals. EAEC isolates (n=86) recovered from diarrhoeal cases in human infants (37) and young animals (49) were characterized as 'typical' and/or 'atypical' EAEC strains employing PCR for virulence associated genes (cvd432, aaiA, astA, pilS, irp2, ecp, pic, aggR, aafA, aggA, and agg3A). Besides, biofilm formation ability of human and animal EAEC isolates was assessed using microtiter plate assay. In addition, the transcriptional profile of biofilm associated genes (fis and ecp) was also evaluated and correlated with biofilm formation assay for few selected EAEC isolates of human and animal origins. Overall, a diverse virulence gene profile was observed for the EAEC isolates of human and animal origins as none of the EAEC isolates revealed the presence of all the genes that were targeted. Nine 'typical' EAEC isolates were identified (6 from humans and 3 from animals) while, the majority of the isolates were 'atypical' EAEC strains. Isolation and identification of three 'typical' EAEC isolates from animals (canines) appears to be the first report globally. Further, based on the observations of the biofilm formation assay, the study suggested that human EAEC isolates in particular were comparatively more biofilm producers than that of the animal EAEC isolates. The fis gene was highly expressed in majority of 'typical' EAEC isolates and the ecp gene in 'atypical' EAEC isolates.

Slaughterhouse effluent discharges into rivers not responsible for environmental occurrence of enteroaggregative Escherichia coli

Enteroaggregative Shiga-toxin-producing Escherichia coli strains were responsible for a massive outbreak in Europe in 2011, and had been previously isolated from French patients. The objective of this study was to investigate the presence of enteroaggregative E. coli (EAEC) in slaughterhouse effluents (wastewater, slurry, sludge and effluents), and in river waters near these slaughterhouses. A total of 10,618 E. coli isolates were screened by PCR for the presence of EAEC-associated genetic markers (aggR, aap and aatA). None of these markers was detected in E. coli isolated from slaughterhouse samples. A unique enteroaggregative E. coli (EAEC) O126:H8 was detected in river water sampled upstream from slaughterhouse effluent discharge. These results confirmed that animals might not be reservoirs of EAEC, and that further studies are required to evaluate the role of the environment in the transmission of EAEC to humans.

Recent advances in understanding enteric pathogenic Escherichia coli

Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.

Detection of Escherichia coli O104 in the feces of feedlot cattle by a multiplex PCR assay designed to target major genetic traits of the virulent hybrid strain responsible for the 2011 German outbreak

A multiplex PCR was designed to detect Escherichia coli O104:H4, a hybrid pathotype of Shiga toxigenic and enteroaggregative E. coli, in cattle feces. A total of 248 fecal samples were tested, and 20.6% were positive for serogroup O104. The O104 isolates did not carry genes characteristic of the virulent hybrid strain.

Chromogenic agar medium for detection and isolation of Escherichia coli serogroups O26, O45, O103, O111, O121, and O145 from fresh beef and cattle feces

Non-O157 Shiga toxin-producing Escherichia coli (STEC) strains are clinically important foodborne pathogens. Unlike E. coli O157:H7, these foodborne pathogens have no unique biochemical characteristics to readily distinguish them from other E. coli strains growing on plating media. In this study, a chromogenic agar medium was developed in order to differentiate among non-O157 STEC strains of serogroups O26, O45, O103, O111, O121, and O145 on a single agar medium. The ability of this chromogenic agar medium to select and distinguish among these pathogens is based on a combination of utilization of carbohydrates, b -galactosidase activity, and resistance to selective agents. The agar medium in combination with immunomagnetic separation was evaluated and successfully allowed for the detection and isolation of these six serogroups from artificially contaminated fresh beef. The agar medium in combination with immunomagnetic separation also allowed successful detection and isolation of naturally occurring non-O157 STEC strains present in cattle feces. Thirty-five strains of the top six non-O157 STEC serogroups were isolated from 1,897 fecal samples collected from 271 feedlot cattle. This chromogenic agar medium could help significantly in routine screening for the top six non-O157 STEC serogroups from beef cattle and other food.

Enteroaggregative Escherichia coli O78:H10, the cause of an outbreak of urinary tract infection

In 1991, multiresistant Escherichia coli O78:H10 strains caused an outbreak of urinary tract infections in Copenhagen, Denmark. The phylogenetic origin, clonal background, and virulence characteristics of the outbreak isolates, and their relationship to nonoutbreak O78:H10 strains according to these traits and resistance profiles, are unknown. Accordingly, we extensively characterized 51 archived E. coli O78:H10 isolates (48 human isolates from seven countries, including 19 Copenhagen outbreak isolates, and 1 each of calf, avian, and unknown-source isolates), collected from 1956 through 2000. E. coli O78:H10 was clonally heterogeneous, comprising one dominant clonal group (61% of isolates, including all 19 outbreak isolates) from ST10 (phylogenetic group A) plus several minor clonal groups (phylogenetic groups A and D). All ST10 isolates, versus 25% of non-ST10 isolates, were identified by molecular methods as enteroaggregative E. coli (EAEC) (P < 0.001). Genes present in >90% of outbreak isolates included fimH (type 1 fimbriae; ubiquitous in E. coli); fyuA, traT, and iutA (associated with extraintestinal pathogenic E. coli [ExPEC]); and sat, pic, aatA, aggR, aggA, ORF61, aaiC, aap, and ORF3 (associated with EAEC). An outbreak isolate was lethal in a murine subcutaneous sepsis model and exhibited characteristic EAEC "stacked brick" adherence to cultured epithelial cells. Thus, the 1991 Copenhagen outbreak was caused by a tight, non-animal-associated subset within a broadly disseminated O78:H10 clonal group (ST10; phylogenetic group A), members of which exhibit both ExPEC and EAEC characteristics, whereas O78:H10 isolates overall are phylogenetically diverse. Whether ST10 O78:H10 EAEC strains are both uropathogenic and diarrheagenic warrants further investigation.

Escherichia coli O104:H4 outbreak from sprouted seeds

From May to July 2011, one of the largest reported outbreaks of haemolytic uraemic syndrome (HUS) and bloody diarrhoea caused by the Shiga toxin-producing Escherichia coli (STEC) O104:H4 occurred in Germany and France. The hypothetical origin of the outbreak strain was a combined enteroaggregative E. coli and an enterohaemorrhagic E. coli with the ability to resist multi-antibiotics and produce Shiga-toxin 2. The combination of aggregative ability, antibiotic resistance and the production of Shiga-toxin 2 significantly affected the severity of the symptoms presented. Since humans may be the primary reservoir, it is likely that contamination could have occurred through contact with infected individuals. Farm food safety management, and hand hygiene training programmes are crucial to primary production to prevent or reduce risks of contamination.

Enteroaggregative Escherichia coli pathotype: a genetically heterogeneous emerging foodborne enteropathogen

Until now, a common feature that defines the enteroaggregative Escherichia coli (EAEC) strains is the ability to produce a 'stacked-brick' appearance on epithelial cells, but it does not distinguish between pathogenic and nonpathogenic strains. Numerous adhesins, toxins, and proteins associated with virulence have been described, as well as multiple factors contributing to EAEC-induced inflammation. None of these factors are found in all EAEC isolates, and no single factor has ever been implicated in EAEC virulence. The European outbreak of Shiga-toxin-producing EAEC raises its pathogenic potential and interest on finding the true pathogenic factors that may define this pathotype. EAEC were first associated with persistent diarrhea in infants from developing countries, since then they have increasingly been linked as a cause of acute and persistent diarrhea in young infants and children in developing and industrialized countries, individuals infected with human immunodeficiency virus, as a cause of acute diarrhea in travelers from industrialized regions, and with foodborne outbreaks. A major effect of EAEC infection is on the malnourished children in developing countries. Here, we will discuss the EAEC public health relevance and their complexity because of the strain heterogeneity regarding their pathogenesis, identification, diagnosis, lineage, epidemiology, and clinical manifestations.

Prevalence of diarrheagenic Escherichia coli virulence genes in the feces of slaughtered cattle, chickens, and pigs in Burkina Faso

We investigated the prevalence of the virulence genes specific for five major pathogroups of diarrheagenic Escherichia coli (DEC) in primary cultures from feces of animals slaughtered for human consumption in Burkina Faso. For the study, 704 feces samples were collected from cattle (n = 304), chickens (n = 350), and pigs (n = 50) during carcass processing. The presence of the virulence-associated genes in the mixed bacterial cultures was assessed using 16-plex polymerase chain reaction (PCR). Virulence genes indicating presence of DEC were detected in 48% of the cattle, 48% of the chicken, and 68% of the pig feces samples. Virulence genes specific for different DECs were detected in the following percentages of the cattle, chicken, and pig feces samples: Shiga toxin-producing E. coli (STEC) in 37%, 6%, and 30%; enteropathogenic E. coli (EPEC) in 8%, 37%, and 32%; enterotoxigenic E. coli (ETEC) in 4%, 5%, and 18%; and enteroaggregative E. coli (EAEC) in 7%, 6%, and 32%. Enteroinvasive E. coli (EIEC) virulence genes were detected in 1% of chicken feces samples only. The study was the first of its kind in Burkina Faso and revealed the common occurrence of the diarrheal virulence genes in feces of food animals. This indicates that food animals are reservoirs of DEC that may contaminate meat because of the defective slaughter and storage conditions and pose a health risk to the consumers in Burkina Faso.

O157:H7 and O104:H4 Vero/Shiga toxin-producing Escherichia coli outbreaks: respective role of cattle and humans

An enteroaggregative Verotoxin (Vtx)-producing Escherichia coli strain of serotype O104:H4 has recently been associated with an outbreak of haemolytic-uremic syndrome and bloody diarrhoea in humans mainly in Germany, but also in 14 other European countries, USA and Canada. This O104:H4 E. coli strain has often been described as an enterohaemorrhagic E. coli (EHEC), i.e. a Vtx-producing E. coli with attaching and effacing properties. Although both EHEC and the German O104:H4 E. coli strains indeed produce Vtx, they nevertheless differ in several other virulence traits, as well as in epidemiological characteristics. For instance, the primary sources and vehicles of typical EHEC infections in humans are ruminants, whereas no animal reservoir has been identified for enteroaggregative E. coli (EAggEC). The present article is introduced by a brief overview of the main characteristics of Vtx-producing E. coli and EAggEC. Thereafter, the O104:H4 E. coli outbreak is compared to typical EHEC outbreaks and the virulence factors and host specificity of EHEC and EAggEC are discussed. Finally, a renewed nomenclature of Vtx-producing E. coli is proposed to avoid more confusion in communication during future outbreaks and to replace the acronym EHEC that only refers to a clinical condition.

Outbreak of Shiga toxin-producing Escherichia coli (STEC) O104:H4 infection in Germany causes a paradigm shift with regard to human pathogenicity of STEC strains

An outbreak that comprised 3,842 cases of human infections with enteroaggregative hemorrhagic Escherichia coli (EAHEC) O104:H4 occurred in Germany in May 2011. The high proportion of adults affected in this outbreak and the unusually high number of patients that developed hemolytic uremic syndrome makes this outbreak the most dramatic since enterohemorrhagic E. coli (EHEC) strains were first identified as agents of human disease. The characteristics of the outbreak strain, the way it spread among humans, and the clinical signs resulting from EAHEC infections have changed the way Shiga toxin-producing E. coli strains are regarded as human pathogens in general. EAHEC O104:H4 is an emerging E. coli pathotype that is endemic in Central Africa and has spread to Europe and Asia. EAHEC strains have evolved from enteroaggregative E. coli by uptake of a Shiga toxin 2a (Stx2a)-encoding bacteriophage. Except for Stx2a, no other EHEC-specific virulence markers including the locus of enterocyte effacement are present in EAHEC strains. EAHEC O104:H4 colonizes humans through aggregative adherence fimbrial pili encoded by the enteroaggregative E. coli plasmid. The aggregative adherence fimbrial colonization mechanism substitutes for the locus of enterocyte effacement functions for bacterial adherence and delivery of Stx2a into the human intestine, resulting clinically in hemolytic uremic syndrome. Humans are the only known natural reservoir known for EAHEC. In contrast, Shiga toxin-producing E. coli and EHEC are associated with animals as natural hosts. Contaminated sprouted fenugreek seeds were suspected as the primary vehicle of transmission of the EAHEC O104:H4 outbreak strain in Germany. During the outbreak, secondary transmission (human to human and human to food) was important. Epidemiological investigations revealed fenugreek seeds as the source of entry of EAHEC O104:H4 into the food chain; however, microbiological analysis of seeds for this pathogen produced negative results. The survival of EAHEC in seeds and the frequency of human carriers of EAHEC should be investigated for a better understanding of EAHEC transmission routes.

Epidemic profile of Shiga-toxin-producing Escherichia coli O104:H4 outbreak in Germany

BACKGROUND

We describe an outbreak of gastroenteritis and the hemolytic-uremic syndrome caused by Shiga-toxin-producing Escherichia coli in Germany in May, June, and July, 2011. The consumption of sprouts was identified as the most likely vehicle of infection.

METHODS

We analyzed data from reports in Germany of Shiga-toxin-producing E. coli gastroenteritis and the hemolytic-uremic syndrome and clinical information on patients presenting to Hamburg University Medical Center (HUMC). An outbreak case was defined as a reported case of the hemolytic-uremic syndrome or of gastroenteritis in a patient infected by Shiga-toxin-producing E. coli, serogroup O104 or serogroup unknown, with an onset of disease during the period from May 1 through July 4, 2011, in Germany.

RESULTS

A total of 3816 cases (including 54 deaths) were reported in Germany, 845 of which (22%) involved the hemolytic-uremic syndrome. The outbreak was centered in northern Germany and peaked around May 21 to 22. Most of the patients in whom the hemolytic-uremic syndrome developed were adults (88%; median age, 42 years), and women were overrepresented (68%). The estimated median incubation period was 8 days, with a median of 5 days from the onset of diarrhea to the development of the hemolytic-uremic syndrome. Among 59 patients prospectively followed at HUMC, the hemolytic-uremic syndrome developed in 12 (20%), with no significant differences according to sex or reported initial symptoms and signs. The outbreak strain was typed as an enteroaggregative Shiga-toxin-producing E. coli O104:H4, producing extended-spectrum beta-lactamase.

CONCLUSIONS

In this outbreak, caused by an unusual E. coli strain, cases of the hemolytic-uremic syndrome occurred predominantly in adults, with a preponderance of cases occurring in women. The hemolytic-uremic syndrome developed in more than 20% of the identified cases.

No evidence of the Shiga toxin-producing E. coli O104:H4 outbreak strain or enteroaggregative E. coli (EAEC) found in cattle faeces in northern Germany, the hotspot of the 2011 HUS outbreak area

BACKGROUND

Ruminants, in particular bovines, are the primary reservoir of Shiga toxin-producing E. coli (STEC), but whole genome analyses of the current German ESBL-producing O104:H4 outbreak strain of sequence type (ST) 678 showed this strain to be highly similar to enteroaggregative E. coli (EAEC). Strains of the EAEC pathotype are basically adapted to the human host. To clarify whether in contrast to this paradigm, the O104:H4 outbreak strain and/or EAEC may also be able to colonize ruminants, we screened a total of 2.000 colonies from faecal samples of 100 cattle from 34 different farms - all located in the HUS outbreak region of Northern Germany - for genes associated with the O104:H4 HUS outbreak strain (stx2, terD, rfbO104, fliCH4), STEC (stx1, stx2, escV), EAEC (pAA, aggR, astA), and ESBL-production (blaCTX-M, blaTEM, blaSHV).

RESULTS

The faecal samples contained neither the HUS outbreak strain nor any EAEC. As the current outbreak strain belongs to ST678 and displays an en-teroaggregative and ESBL-producing phenotype, we additionally screened selected strains for ST678 as well as the aggregative adhesion pattern in HEp-2 cells. However, we were unable to find any strains belonging to ST678 or showing an aggregative adhesion pattern. A high percentage of animals (28%) shed STEC, corroborating previous knowl-edge and thereby proving the validity of our study. One of the STEC also harboured the LEE pathogenicity island. In addition, eleven animals shed ESBL-producing E. coli.

CONCLUSIONS

While we are aware of the limitations of our survey, our data support the theory, that, in contrast to other Shiga-toxin producing E. coli, cattle are not the reservoir for the O104:H4 outbreak strain or other EAEC, but that the outbreak strain seems to be adapted to humans or might have yet another reservoir, raising new questions about the epidemiology of STEC O104:H4.

A rapid procedure for the detection and isolation of enterohaemorrhagic Escherichia coli (EHEC) serogroup O26, O103, O111, O118, O121, O145 and O157 strains and the aggregative EHEC O104:H4 strain from ready-to-eat vegetables

Human infections with Enterohaemorrhagic Escherichia coli strains (EHEC) as agents of Haemorrhagic Colitis (HC) and Haemolytic Uraemic Syndrome (HUS) are frequently associated with the consumption of EHEC contaminated foodstuffs of different origins. EHEC O26, O103, O111, O118, O121, O145 and O157 strains are responsible for the majority of HC and HUS cases worldwide. In May 2011, the emerging aggregative EHEC O104:H4 strain caused a large outbreak with high HUS incidence in northern Germany. Contaminated sprouted seeds were suspected to be the vehicles of transmission. The examination of vegetables retailed for raw consumption revealed low numbers of E. coli (<100 cfu/g) together with high titres of Enterobacteriaceae and Pseudomonas (approx. 5.6 × 10⁷ cfu/g). Specific methods of EHEC detection adapted to vegetables are not yet published. Therefore, we have developed a rapid and sensitive method for detecting low EHEC contamination in vegetables (1-10 cfu/25 g) with artificially EHEC contaminated ready-to-eat salads. A 6-hour enrichment period in BRILA-broth was sufficient to detect 1-10 EHEC from spiked samples after plating 0.1 ml portions of enrichment culture on selective TBX-agar and CHROMagar STEC plates that were incubated at 44 °C overnight. Unlike EHEC strains, the growth of bacteria of the plant flora was substantially inhibited at 44 °C. DNA for real-time PCR detection of EHEC characteristic genes (stx(1), stx(2), eae, ehxA, and O-antigen associated) was prepared with bacteria grown on TBX-agar plates. The storage of EHEC inoculated salad samples for 72 h at 6 °C resulted in a significant reduction (mean value 14.6%) of detectable EHEC, suggesting interference of EHEC with the resident plant microflora. CHROMagar STEC was evaluated as a selective medium for the detection of EHEC strains. Growth on CHROMagar STEC was closely associated with EHEC O26:[H11], O111:[H8], O118:H16, O121:[H19], O145:[H28], O157:[H7] and aggregative EHEC O104:H4 strains and with the presence of the terB gene (tellurite resistance). TerB sequences were found in 87.2% of 235 EHEC but only in only 12.5% of 567 non-EHEC strains. EHEC strains which did not grow on CHROMagar STEC were negative for terB as frequently observed with EHEC O103:H2 (52.9%) and sorbitol-fermenting O157:NM strains (100%). The enrichment and detection method was applied in the examination of sprouted seeds incriminated as vehicles in the EHEC O104:H4 outbreak in Germany. Aggregative EHEC O104:H4 could be detected and isolated from a sample of sprouted seeds which was suspected as vector of transmission of EHEC O104 to humans.

Molecular characterization of uropathogenic and diarrheagenic Escherichia coli pathotypes

In this study diarrheagenic and uropathogenic Escherichia coli (UPEC) strains were comparatively characterized according to serotype, hemolytic activity, protein polymorphism among housekeeping enzymes, phylogenetic group and urovirulence genes. Intra-serogroup/serotype variations were observed. Hemolytic activity was detected in 100%, 93%, 67% and 39% of UPEC, EAEC, EPEC and ETEC strains, respectively. The alpha-hemolytic phenotype was observed in all pathogenic groups while beta-hemolytic phenotype was less frequent. PCR phylotyping revealed higher prevalence of diarrheagenic E. coli in groups A and D while uropathogenic strains were mainly found in subgroup B2. Amplification assays revealed that 74%, 45% and 22% of UPEC, EAEC and EPEC strains, respectively, carried at least one of the urovirulence sequences. The molecular typing system revealed a pathotype-specific clonal group distribution and showed a closer relationship between the EAEC and UPEC. Additionally, the occurrence of urovirulence traits, especially those related to iron acquisition, was more frequent among EAEC and UPEC than among the other E. coli pathotypes. This observation is of special value considering that the EAEC pathotype constitutes an emerging group of enteropathogens, particularly, in developing countries, and information on their pathogenic and phylogenetic characteristics is still scarce.

Characterization of typical and atypical enteroaggregative escherichia coli in Kagoshima, Japan: biofilm formation and acid resistance

EAEC is increasingly recognized as an emerging enteric pathogen. Typical EAEC expressing the AggR regulon have been proven to be an important cause of childhood diarrhea in industrialized countries as well as in the developing world, while atypical EAEC without this regulon have not been thoroughly investigated. To investigate the bacteriological characteristics of EAEC, including both typical and atypical strains in Kagoshima, Japan, 2417 E. coli strains from Japanese children with diarrhea were screened by a quantitative biofilm assay to detect possible EAEC strains, resulting in the identification of 102 (4.2%) of these strains by the HEp-2 cell adherence test. Virulence gene patterns, PFGE analysis and O-serogrouping demonstrated the heterogeneity of the EAEC. The EAEC strains were classified into two groups: typical EAEC with aggR (74.5%, 76/102) and atypical EAEC without aggR (25.5%, 26/102). There was no significant difference between the typical EAEC strains (median OD(570)= 0.73) and the atypical strains (median OD(570)= 0.61) in biofilm formation (P= 0.17). Incidences of resistance against ampicillin, cefotaxime and tetracycline were significantly higher in the typical EAEC strains than the atypical EAEC strains (84.2% vs. 53.8%, 36.8% vs. 7.7% and 93.4% vs. 73.1%, respectively, P < 0.05). The typical EAEC strains showed significantly higher resistance ratios against HCl and lactate than the atypical strains (94.7% vs. 61.5% and 92.1% vs. 57.7%, respectively, P < 0.001). To investigate the pathogenicity of not only typical but also atypical EAEC, further bacteriological and epidemiologic studies including atypical EAEC are needed.

Molecular typing and virulence of enteroaggregative Escherichia coli strains isolated from children with and without diarrhoea in Rio de Janeiro city, Brazil

Enteroaggregative Escherichia coli (EAEC) strains have been implicated as emerging aetiological agents of diarrhoea worldwide. In the present study, 43 EAEC strains were serotyped and characterized according to random amplification of polymorphic DNA profiles, PFGE, multilocus enzyme electrophoresis (MLEE) and the presence of putative virulence genes (hly, aero, kps, fim, aggA, aafA, aggR, astA, she, aap, shf and pet). The EAEC strains consisted of a diversity of serotypes including eight O-non-typable and 35 O-typable strains arranged into 21 O : H combinations. Amplification of specific genes revealed that all strains carried at least two of the virulence sequences investigated. fim, aggR and aap were the most frequent genes in both groups studied. hly, aero and aggA sequences were more prevalent in the diarrhoeal group. kps occurred exclusively in strains isolated from symptomatic children and showed strong association with diarrhoeal disease. The molecular approaches used to investigate the relatedness among EAEC strains revealed a high degree of polymorphism, suggesting that these micro-organisms have a non-clonal origin. A closer relationship was observed among EAEC strains sharing O : H types. No significant clustering could be identified related to the virulence traits investigated; however, the she locus showed clonal distribution by MLEE typing. These results are in accordance with previous findings in revealing the conservation of particular EAEC factors, despite the high degree of diversity related to both genotypic and phenotypic markers.

Enteroaggregative Escherichia coli associated with a foodborne outbreak of gastroenteritis

This study investigated two foodborne outbreaks of gastroenteritis that occurred 10 days apart among individuals who had meals at the restaurant of a farm holiday resort. Mild gastrointestinal symptoms were reported and none of the patients needed hospitalization. Mean incubation times were 45 and 33 h, and the overall attack rates were 43.5 and 58.3%, respectively. Stool sample examination was negative for common enteric pathogens in both outbreaks. Specimens from 13 people involved in the second outbreak and 3 restaurant staff were examined for diarrhoeagenic Escherichia coli. An enteroaggregative E. coli (EAEC) strain of serotype O92:H33 was isolated from six participants and one member of staff. In particular, the EAEC strain was isolated from five of the six cases of diarrhoea examined. The strain showed an aggregative pattern of adherence to HEp-2 cells, did not produce a biofilm and possessed the virulence-related genes aat, aggR, aap and set1A, but not the astA gene. A retrospective cohort study indicated a pecorino cheese made with unpasteurized sheep milk as the possible source (P<0.001). Samples of the cheese had E. coli counts higher than 10(6) c.f.u. g(-1), but the outbreak EAEC strain was not isolated. This report confirms that EAEC infections are probably underdiagnosed because of the limited availability of laboratories capable of identifying this group of pathogenic E. coli.

Association of putative pathogenicity genes with adherence characteristics and fimbrial genotypes in typical enteroaggregative Escherichia coli from patients with and without diarrhoea in the United Kingdom

The aim of this study was to compare genotypic characteristics seen in typical EAggEC isolated during a study of intestinal infectious disease from cases and controls, and to identify which genes, or combinations of genes, were most associated with diarrhoeal disease. We also investigated the association of genotype with certain characteristics, such as presence of fimbrial genes and adherence to Hep-2 cells. The aafC gene, encoding the usher for AAFII, was the only gene significantly associated with patients with diarrhoea (P < 0.005), and the aggC gene, which encodes the usher for AAFI, was the only gene significantly associated with the healthy control group (P < 0.002). Putative virulence genes significantly associated with aggregative adherence included aafC, aggR, pet, pic and astA. The shf, pet and astA genes were all more likely to be associated with type II fimbriae than with type I. We conclude that in addition to presence and absence of certain genes, studies of EAggEC pathogenicity should investigate the combinations and associations of putative virulence factors.

Distinct pathotypes of O113 Escherichia coli strains isolated from humans and animals in Brazil

Two distinct diarrheagenic Escherichia coli pathotypes, enteroaggregative E. coli (EAEC) and Shiga toxin-producing E. coli, were observed in association with O113 strains isolated from human and nonhuman sources in Brazil, respectively. The O113 strains from human diarrhea belonged to a diversity of serotypes, and nine (53%) of them harbored virulence traits of typical EAEC.