Emerging avian pathogenic Escherichia coli strains belonging to clonal groups O111:H4-D-ST2085 and O111:H4-D-ST117 with high virulence-gene content and zoonotic potential

The present study characterizes, for the first time, two emerging avian pathogenic Escherichia coli (APEC) clonal groups of serogroup O111: O111:H4-D-ST117 and O111:H4-D-ST2085. The clonal group O111:H4-D-ST117 was already present in APEC strains isolated between 1991 and 2000, and was still present in strains isolated between 2004 and 2009, showing long time evolution according to the virulence-gene differences and macrorestriction profiles. Among ST117 strains, two virulence profiles could be distinguished: papG II-positive tsh-negative strains which satisfied criteria for extraintestinal pathogenic E. coli (ExPEC), and papG II-negative tsh-positive strains without ExPEC status. Interestingly, we have detected a human septicemic O111:H4-D-ST117 ExPEC strain isolated from a hemocultive in 2000 whose macrorestriction profile showed >85% similarity with four APEC strains of the study. The clonal group O111:H4-D-ST2085 was exclusively detected in 17 APEC strains isolated in 2008 and 2009, and showed short time evolution based on its homogeneity since all were nalidixic acid-resistant, all had ExPEC status, and most carried papG II and tsh genes. From the clinical point of view, O111:H4-D-ST2085 seems a successful clonal group that could be the result of the epidemiological evolution of O111:H4-D-ST117. Due to the increasing prevalence of both clonal groups among clinical APEC isolates, their high virulence-gene content, and zoonotic potential, we suggest them as possible candidates for the development of a future vaccine against avian colibacillosis.     

猪源大肠杆菌O157∶H7毒力差异株的转录组测序分析

为了解大肠杆菌O157∶H7毒力差异株转录组差异,丰富O157∶H7转录组数据信息,本研究采用Illumina HiSeq^TM 2000平台对两株大肠杆菌O157∶H7毒力差异株进行高通量测序,测序数据采用测序评估、基因功能注释等生物信息学方法进行分析。结果发现,经过测序,两个菌株分别获得3 113 118和2 944 912条reads,比对到参考基因组上的reads分别占总reads的83.76%和78.97%。以中等毒力株为参考,在高毒力株中共获得941个差异表达基因,其中上调基因637个,下调基因304个。GO功能注释分析表明,差异表达基因主要与催化活性功能、黏附、转运活性、受体活性、酶调节活性、定位、生化调节、运动等诸多生理生化过程相关;KEGG富集分析发现共有425个基因注释到160个代谢通路中,其中新陈代谢、核糖体、鞭毛合成、嘧啶代谢、糖类代谢、细菌趋化等通路显著富集。此次通过大肠杆菌O157∶H7毒力差异株转录组研究对差异表达基因涉及的信号调控及可能的功能基因进行了探索,丰富了转录组信息,为进一步开展大肠杆菌O157∶H7毒力相关基因的研究及分子调控机制奠定了基础。     

Serotypes and virulence genes of extraintestinal pathogenic Escherichia coli isolates from diseased pigs in China

Extraintestinal pathogenic Escherichia coli (ExPEC) isolates were detected in 315/3127 (10.1%) diseased pigs from 19 provinces of China; the frequency of isolation increased from 3.1% in 2004 to 14.6% in 2007. All isolates were characterised for O serogroups, haemolysis, phenotypic and genotypic antimicrobial resistance, virulence genes and pathogenicity. The most prevalent serogroups were O161, O8, O11, O138, O101 and O26; 83/315 (26.3%) isolates were haemolytic. Forty percent of isolates in phylogenetic groups B2 and D were highly virulent porcine ExPEC strains. Thirty-three putative extraintestinal virulence factor genes that are normally associated with human and/or avian ExPEC strains were widely present in porcine isolates. These results indicate that ExPEC are prevalent in pigs in China and represent a potential public health threat.     

Fluoroquinolone-resistant extraintestinal Escherichia coli clinical isolates representing the O15:K52:H1 clonal group from humans and dogs in Australia

Antimicrobial-resistant extraintestinal pathogenic Escherichia coli (ExPEC) impact both human and veterinary medicine. One ExPEC clonal group that has become increasingly multidrug-resistant is serotype O15:K52:H1. Accordingly, we sought O15:K52:H1 strains among fluoroquinolone-resistant (FQ(r)) E. coli clinical isolates from humans (n=582) and dogs (n=120) in Australia. The phylogenetic group D isolates (267/702; 38%) were screened for O15:K52:H1-specific single-nucleotide polymorphisms (SNPs) in fumC and the O15 rfb variant. The 34 so-identified O15:K52:H1 isolates (33 human, 1 canine) underwent antimicrobial susceptibility profiling, virulence genotyping, and macrorestriction profiling. Although susceptibility profiles varied, the 34 isolates were closely related by pulsed-field gel electrophoresis and exhibited typical O15:K52:H1-associated virulence profiles (complete pap operon, F16 papA allele, papG allele II, iha, fimH, sat, fyuA, iutA, kpsMII, ompT). The canine isolate closely resembled human isolates. Thus, O15:K52:H1 strains contribute to the FQ(r) ExPEC population in Australia and may potentially be transferred between humans and dogs.     

Pigeons as a possible reservoir of Shiga toxin 2f-producing Escherichia coli pathogenic to humans

Escherichia coli harboring stx2f which secrete the respective Shiga toxin (Stx) are frequently found in pigeons. In this report we describe the isolation of a stx2f-containing E. coli O128 strain from an 11-month old child with diarrhea and comparison of this strain with stx2f-positive E. coli isolates from droppings of pigeons. The human E. coli O128:NM (nonmotile) isolate had a fliC restriction fragment length polymorphism pattern identical to that in one of the pigeon isolates belonging to the serotype O128:H2. All isolates examined, including that from the patient and five from pigeons, contained the intimin-encoding eae gene in addition to stx2f and all of the strains possessed the gene encoding the major subunit of the long polar fimbriae in enterohemorrhagic E. coli (EHEC) 026. Plasmid-associated virulence genes such as EHEC-hlyA, as well as urease and tellurite resistance-encoding operons were absent from all the strains and this correlated with their lack of hemolytic activity and urease production and tellurite sensitivity. These features, together with the sorbitol fermentation phenotype of Stx2f-producing E. coli, hamper the laboratory diagnosis of these strains. Our data demonstrate that pigeons may be a reservoir of Stx2f-producing E. coli strains associated with human disease.     

Extraintestinal pathogenic Escherichia coli in poultry meat products on the Finnish retail market

Background

Extraintestinal pathogenic Escherichia coli bacteria (ExPEC) exist as commensals in the human intestines and can infect extraintestinal sites and cause septicemia. The transfer of ExPEC from poultry to humans and the role of poultry meat as a source of ExPEC in human disease have been discussed previously. The aim of the present study was to provide insight into the properties of ExPEC in poultry meat products on the Finnish retail market with special attention to their prevalence, virulence and phylogenetic profiles. Furthermore, the isolates were screened for possible ESBL producers and their resistance to nalidixic acid and ciprofloxacin was tested.

Methods

The presence of ExPEC in 219 marinated and non-marinated raw poultry meat products from retail shops has been analyzed. One E. coli strain per product was analyzed further for phylogenetic groups and possession of ten virulence genes associated with ExPEC bacteria (kpsMT K1, ibeA, astA, iss, irp2, papC, iucD, tsh, vat and cva/cv) using PCR methods. The E. coli strains were also screened phenotypically for the production of extended-spectrum β-lactamase (ESBL) and the susceptibility of 48 potential ExPEC isolates for nalidixic acid and ciprofloxacin was tested.

Results

E. coli was isolated from 207 (94.5%) of 219 poultry meat products. The most common phylogenetic groups were D (50.7%), A (37.7%), and B2 (7.7%). Based on virulence factor gene PCR, 23.2% of the strains were classified as ExPEC. Two ExPEC strains (1%) belonged to [O1] B2 svg+ (specific for virulent subgroup) group, which has been implicated in multiple forms of ExPEC disease. None of the ExPEC strains was resistant to ciprofloxacin or cephalosporins. One isolate (2.1%) showed resistance to nalidixic acid.

Conclusions

Potential ExPEC bacteria were found in 22% of marinated and non-marinated poultry meat products on the Finnish retail market and 0.9% were contaminated with E. coli [O1] B2 svg+ group. Marinades did not have an effect on the survival of ExPEC as strains from marinated and non-marinated meat products were equally often classified as ExPEC. Poultry meat products on the Finnish retail market may have zoonotic potential.     

Virulence profiles of Shiga toxin 2e-producing Escherichia coli isolated from healthy pig at slaughter

Recently, virulence patterns of Stx2e-producing Escherichia coli from pigs with edema disease and from humans were compared and strains from diseased pigs were reported to be unlikely human pathogens [Sonntag, A.K., Bielaszewska, M., Mellmann, A., Dierksen, N., Schierack, P., Wieler, L.H., Schmidt, M.A., Karch, H., 2005. Shiga toxin 2e-producing Escherichia coli isolates from humans and pigs differ in their virulence profiles and interactions with intestinal epithelial cells. Appl. Environ. Microbiol. 71, 8855-8863]. In the present study, 31 Shiga toxin-producing E. coli (STEC) strains harboring stx2e, which were previously isolated out of fecal samples from healthy pigs at slaughter [Kaufmann, M., Zweifel, C., Blanco, M., Blanco, J.E., Blanco, J., Beutin, L., Stephan, R., 2006. Escherichia coli O157 and non-O157 Shiga toxin-producing Escherichia coli in fecal samples of finished pigs at slaughter in Switzerland. J. Food Prot. 69, 260-266], were characterized by phenotypic and genotypic traits. Nine of the thirty-one sorbitol-positive non-O157 STEC (stx2e) isolated from healthy pigs belonged to serotypes found in STEC isolated from humans, including two serotypes (O9:H-, O26:H-) reported in association with hemolytic-uremic syndrome. Otherwise, the serotypes were different from those isolated from cases of edema disease in pigs. The eae (intimin) gene, which is strongly correlated with severe human disease, was not detected. Moreover, all strains were lacking the genes for enterohemolysin (ehxA), porcine A/E associated protein (paa), STEC autoagglutinating adhesin (saa) and the serin protease EspI (espI). Nine strains tested positive for astA (EAST1), one O141:H17 strain for fedA (F18 fimbrial adhesin) and one O159:H- strain for terF (tellurite resistance). Similar to the Stx2e-producing E. coli isolated from humans, which are mainly lacking further virulence factors, genes of an iron uptake system on the high-pathogenicity island (irp2, fyuA) were detected in three ONT:H10 and ONT:H19 strains from healthy pigs. Consequently, although the isolated strains are unlikely to be associated with severe human diseases, healthy pigs cannot be excluded as a potential source of human infection with Stx2e-producing STEC.     

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

ABSTRACT: 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.     

Characteristics of alpha-hemolytic strains of Escherichia coli isolated from dogs with gastroenteritis

Twenty-four hemolysin producing (Hly+) strains of Escherichia coli isolated from dogs with gastroenteritis were investigated for their virulence markers and their phenotypic properties. The strains were distributed over eleven known E. coli O-serogroups and most of them were heterogeneous for their phenotypes. All strains were found to produce alpha-hemolysin which was detected by Southern hybridization and colony immunoblotting using a specific gene probe and a monoclonal antibody. Eight strains were carrying plasmids encoding alpha-hemolysin sequences (hly-plasmids) and 16 strains carried chromosomal hly-determinants. Twelve of the strains showed enterotoxic activities which were tested for in different assays. Among these, three O42:H37 and two O70:H-strains carrying hly-plasmids were found to harbour other plasmids encoding the heat-stable enterotoxin STA1. The other seven strains showing enterotoxicity in the ileal loop or the suckling mouse assay were negative for STA1, STA2, or LT. None of the 24 strains were positive for invasiveness or for production of Vero (Shiga-like) toxins. The production of alpha-hemolysin was closely associated with the production of cytotoxic necrotizing factor (CNF), which was detected in 17 of 24 strains. Of these, 16 elaborated CNF1 and one strain produced an unknown CNF type. Surprisingly, all strains carrying ST-plasmids and six of eight strains carrying hly-plasmids were negative for CNF. Thus, in canine E. coli strains CNF production seems to be closely associated with production of chromosomally encoded alpha-hemolysin whereas hly-plasmids are more often associated with ST-producing, CNF negative isolates.     

Study on Seasonal Impact to the Distribution of Bovine E.coli O157: H7 in Xinjiang

To study the impact of season to the distribution of bovine E.coli O157:H7,samples of anus swabs (399),feces (68),water (29) and feed (43) were collected in the spring, summer,autumn and winter from A,B and C farms of Xinjiang. After enrichment by EC broth, SMAC and MUG selective culture were then performed. Finally,PCR was used for identification and virulence gene detection of isolated strains. A total of 5 E.coli O157:H7 strains were isolated from 539 samples from three farms (0.93%,5/539), 2 of them were from spring (1.44%,2/139),1 from autumn(0.56%,1/180),2 from winter (1.38%,2/145) and no strains were isolated from summer samples. One strain were isolated from anus swab samples in farm B (0.69%,1/145) and one were isolated from anus swabs (0.66%,1/152) and three strains were isolated from feed samples in farm C (20.00%,3/15),and no target strains were isolated from water samples. The distribution of bovine E. coli O157:H7 had obvious seasonal characteristics.One E.coli O157:H7 strain of farm B was isolated from autumn and four of farm C were from isolated spring (2 strain) and winter (2 strain),and the isolation rate of E. coli O157:H7 in spring and winter were higher than that in summer and autumn. In conclusion,under the special climate characteristics and feeding mode in Xinjiang,to prevent and control the spreading of E. coli O157:H7 of cattle,we must pay great attention on hygiene management of pens at cold season, specially avoiding the feed contaminated by feces.     

Prevalence and deletion types of the pathogenicity island ETT2 among Escherichia coli strains from oedema disease and colibacillosis in pigs

Piglet pathogenic Escherichia coli encoding Shigatoxin 2e and F18 adhesins are the etiological agents of oedema disease as well as of non-oedema disease colibacillosis. In order to reveal virulence differences among this pathogen, the presence of the pathogenicity island (PAI) E. coli type three secretion system 2 (ETT2) was examined. Using PCR and Southern blot techniques for the identification of the right, the middle, and the left region of this 29.9kb large genetic element, the entire ETT2 was found among E. coli O138:H(-), O139:H1, and O147:H6 strains originated from cases of oedema disease in Germany between 1995 and 2001 and belonging to various clonal types. In contrast, non-oedema disease E. coli isolates (e.g. O8:H19, 101:H(-), O141:H4) contain deleted subtypes of ETT2. These deletions cover the translocon part of the putative ETT2-encoded type III secretion apparatus. It is suggested that the entire ETT2 is associated with a particular virulence trait of piglet oedema disease E. coli (EDEC).     

Uropathogenic virulence factors in isolates of Escherichia coli from clinical cases of canine pyometra and feces of healthy bitches

Escherichia coli is commonly isolated in canine pyometra, but little is known of the virulence factors that may be involved in the precipitation of this disease. The aim of this study was to compare the prevalence of uropathogenic virulence factor (UVF) genes in E. coli isolates from canine pyometra and from feces of healthy bitches to evaluate their role in the pathogenesis of pyometra. E. coli from 23 cases of canine pyometra and from the feces of 24 healthy bitches were analyzed, by polymerase chain reaction, for UVF genes associated with canine and human urinary tract infections (UTIs). The prevalences of UVFs in E. coli from canine pyometra were similar to that in canine and human uropathogenic E. coli. The prevalence of pap was greater (P=0.036) for E. coli from pyometra (52%) than for fecal isolates (21%), and the papGIII allele was present in all pap-containing isolates. The prevalences of genes for alpha-haemolysin and cytotoxic necrotising factor 1 were not significantly higher (P=0.075) in E. coli from pyometra than from feces. The proportion of pyometra strains with >or=3 UVFs was higher (P=0.039) than that of fecal strains, suggesting that possession of >or=3 UVF genes enhances the pathogenicity of the strain. Our findings demonstrate that E. coli associated with canine pyometra are similar to uropathogenic strains, and that operons that encode P fimbriae, alpha-haemolysin and cytotoxic necrotising factor 1 probably enhance the virulence and pathogenicity of the strain in the canine genital tract.     

Comparative genomics of multiple plasmids from APEC associated with clonal outbreaks demonstrates major similarities and identifies several potential vaccine-targets

Avian pathogenic Escherichia coli (APEC) is associated with several types of extraintestinal infections, collectively known as colibacillosis. A heterogeneous population structure has hindered development of vaccines protective against all APEC. Recently, however, the existence of different APEC subpathotypes have been suggested, which are defined by specific disease syndromes and associated virulence genes. A collection of 14 APEC isolates representing clonal outbreaks of salpingitis accompanied by peritonitis and sepsis were characterized in the present study. All the strains carried large plasmids and the aim of the study was to investigate the similarity of these by sequencing, annotating and comparative analysis to identify potential vaccine targets. In addition, a comparison with gene content of human extraintestinal E. coli (ExPEC) subtypes was conducted. Results obtained demonstrated highly similar plasmid contents of the 14 APEC strains, despite the diversity of their chromosomal background. All 14 APEC carried the colicin V operon and numerous virulence genes. These included iss, traT, hlyF, eitABC, ompT, iroBCDEN, sitABCD, iutA and lucABCD. Several of these are shared with human ExPEC, implicating a possible zoonotic potential. Despite a diverse chromosomal background, it was concluded that the plasmid content of virulence genes are highly similar for the investigated APEC subpathotype. Based on their frequency, protein uniformity and subcellular localization iroN, iutA, iss, traT, ompT and etsC are suggested as vaccine-candidates. Experimental studies are, however, necessary to determine the protective potential of the candidates against the APEC subpathotype characterized by salpingitis, peritonitis and possibly septicaemia.     

The Ins and Outs of siderophore mediated iron uptake by extra-intestinal pathogenic Escherichia coli

Extraintestinal pathogenic E. coli (ExPEC) are responsible for many infectious diseases in livestock, such as airsacculitis in poultry, acute mastitis in dairy animals and neonatal septicaemia and urinary tract infections (UTI) in pigs and cattle. In their animal hosts, ExPEC have to cope with low iron availability. By using different strategies, ExPEC strains are able to retrieve iron sequestered by host proteins. One of these strategies is the use of siderophores, which are small secreted molecules with high affinity for iron. ExPEC are known to synthesize up to four different types of siderophores: enterobactin, salmochelins, yersiniabactin and aerobactin. Steps required for iron acquisition by siderophores include (1) siderophore synthesis in the cytoplasm, (2) siderophore secretion, (3) ferri-siderophore reception, (4) ferri-siderophore internalization and (5) iron release in the cytoplasm. Each siderophore has specific properties and may be differentially regulated to provide different advantages, potentially allowing ExPEC to adapt to different environmental conditions or to overcome host innate immunity. Iron acquisition by siderophores plays a significant role in ExPEC virulence and, as it requires outer membrane receptors, it constitutes an interesting target for the development of vaccines that could be used to limit the number of infectious diseases due to ExPEC in livestock.     

Comparative infectivity for axenic and specific-pathogen-free chickens of O2 Escherichia coli strains with or without virulence factors

Adhesion to epithelial respiratory cells, iron acquisition, and production of K1 polysaccharide capsules have been proposed as potential virulence factors of avian Escherichia coli. These factors were studied by inoculating groups of axenic or specific-pathogen-free (SPF) chickens intratracheally with O2 E. coli strains after previous challenge with a wild strain of infectious bronchitis virus (IBV). In all experiments, the association between IBV and an E. coli strain endowed with the three virulence factors previously mentioned resulted in the most severe pathological effects, as measured by mortality, weight gains, lesions, and reisolation of E. coli from internal organs. An E. coli strain devoid of virulence factors was able only to induce mild pathological effects restricted to the respiratory tract when combined with IBV. Both E. coli strains were more invasive in axenic chickens than in SPF chickens. These results confirm the probable involvement of the three factors studied in the pathogenic properties of avian E. coli. This model can be used to assess the role of virulence factors, by comparing pairs of positive and negative isogenic strains.     

Serotypes, virulence genes and intimin types of verotoxin-producing Escherichia coli and enteropathogenic E. coli isolated from healthy dairy goats in Spain

Faecal samples from 222 healthy dairy goats on 12 farms in Spain, as well as bulk tank milk samples of these farms, were screened for the presence of verotoxin-producing Escherichia coli (VTEC) and enteropathogenic E. coli (EPEC). VTEC and EPEC were isolated in 47.7 and 7.7% of the animals, respectively. VTEC were isolated more frequently from adults and replacement animals than from goat kids. In contrast, EPEC were detected more frequently from goat kids than from replacement animals and adults. VTEC or EPEC strains were not detected in the bulk tank milk samples. Although a selective enrichment protocol was used, the serotype O157:H7 was not detected. The most frequent serotypes among the 106 VTEC strains isolated from goats were O5:H-, O76:H19, O126:H8, O146:H21, ONT:H- and ONT:H21. None VTEC strain was eae-positive. The absence of the eae gene in the VTEC strains could indicate that these strains are less virulent for humans that the classical eae-positive enterohaemorrhagic E. coli types. However, 16% of VTEC strains isolated from healthy goats belonged to serotypes associated with haemolytic uraemic syndrome in humans. The ehxA gene was detected in 84.9 and 52.9% of the VTEC and EPEC from goats, respectively. The beta1, theta/gamma2 and zeta were the most frequent intimin types among the 17 EPEC strains studied and the most prevalent serotypes of these strains were O156:H25 and O177:H11. Our data show that in Spain healthy goats are an important reservoir of VTEC and EPEC, and a potential source of infection for humans.     

Serotypes and virulence genes of bovine Shigatoxigenic Escherichia coli (STEC) isolated from a feedlot in Argentina

Grazing-fed cattle were previously demonstrated to be reservoir of non-O157 Shigatoxigenic Escherichia coli (STEC) serotypes in Argentina. The acid-resistance of some STEC strains makes it reasonable to assume the presence in feedlot of particular STEC serotypes. Fifty-nine animals were sampled every 2 weeks during 6 months by rectal swabs. Twenty-seven of 59 animals (45.8%) were shown to be Stx2(+); 3/59 (5.1%) carried Stx1(+) and 7/59 (11.9%) were Stx1(+) Stx2(+). Among 44 STEC isolates, 31 isolates were associated to 10 O serogroups (O2, O15, O25, O103, O145, O146, O157, O171, O174, O175) and 13 were considered non-typable (NT). Six H antigens (H2, H7, H8, H19, H21, H25) were distributed in 21 isolates whereas 23 were non-mobile (H-). Seventeen of 44 strains (38.6%) were eaeA(+) and 14 (31.8%) harbored the 60MDa plasmid. The megaplasmid (Mp) and eaeA gene were simultaneously found in a limited number of serotypes belonging to the enterohaemorrhagic E. coli (EHEC). E. coli O157:H7 strains, isolated from four (6.8%) animals, corresponded to the Stx2(+), eaeA(+), Mp(+) pattern. Three O157:H7 strains belonged to phage type 4 and the other strain was atypical. Many serotypes isolated from grain-fed cattle (O2:H25, O15:H21, O25:H19, O145:H-, O146:H-, O146:H21, O157:H7, O175:H8) also differed from those isolated by us previously from grazing animals. The serotypes O15:H21, O25:H19 and O175:H8 had not been identified at present as belonging to STEC. This work provides new data for the understanding of the ecology of STEC in grain-fed cattle and confirms that cattle are an important reservoir of STEC.     

Investigation of domestic animals and pets as a reservoir for intimin- (eae) gene positive Escherichia coli types

Domestic animals belonging to seven different species (cattle, sheep, dogs, cats, pigs, chicken and goats) were investigated as natural reservoirs for attaching and effacing Escherichia coli (AEEC). For this, 2165 E. coli strains from faeces of 803 animals were examined for the presence of the intimin -(eae) gene as a characteristic of AEEC strains. Ten percent of the animals were found to excrete AEEC, most frequently found in sheep (19.2%) and pigs (17.6), followed by cattle (10.4%), dogs (7.2%), cats (6.5%) and poultry (2.3%). The 97 AEEC strains from animals were grouped into 44 serotypes. Only four E. coli serotypes (O2:H8, O26:[H11], O109:[H25] and O145:[H28] were found in more than one animal host species. AEEC O26:[H11] strains were most frequently isolated (13.4%) being present in cattle, poultry, pigs and sheep. A search for virulence markers associated with enterohemorrhagic E. coli (EHEC) revealed Shiga-toxin genes in three (3.1%) AEEC strains from sheep. Bundle forming pili genes as a trait of typical enteropathogenic E. coli (EPEC) were detected in four (4.1%) strains from dogs and cats. The remaining 90 AEEC strains were classified as atypical EPEC. Typing of intimin genes revealed intimin beta being present in 51.5% of the strains, followed by intimins theta (23.7%), epsilon (6.2%), kappa (5.2%), zeta (5.2%), alpha, eta and iota (each 1.0%). Our data indicate that domestic animals and pets constitute an important natural reservoir of AEEC strains, and some of these (O26:[H11], O103:H2, O128:H2, O145:[H28] and O177:[H11]) are known to occur as pathogens in humans.     

Serum resistance and aerobactin iron uptake in avian Escherichia coli mediated by conjugative 100-megadalton plasmid.

A total of 115 strains of Escherichia coli isolated from chickens with colisepticemia in Japan were examined for chicken lethality and virulence factors. It was found that serum resistance and aerobactin-mediated iron uptake are the most prevalent characteristics in these strains. Among them, S-20, a representative virulent strain of serotype O2, was further studied. S-20 harbored a conjugative 100-megadalton (Mdal) plasmid, designated pKI100. Curing and reintroduction experiments showed that pKI100 encodes both serum resistance and aerobactin-mediated iron uptake, and the diminished virulence of the pKI100-cured strain was fully restored by the reintroduction of the plasmid. These results demonstrated that pKI100 is the virulence plasmid of the S-20 strain, and that serum resistance and aerobactin-mediated iron uptake are the virulence factors in E. coli strains which cause avian colibacillosis.