Virulence ofEscherichia coli strains isolated from urine of patients with acute cystitis and from faeces of healthy women

E. coli strains were isolated from the urine of patients with acute cystitis in general practice and from the faeces of a comparable reference group of healthy individuals. These strains were serotyped and tested for virulence in an experimental mouse model. Of 30 cystitis-strains 18 were virulent, and of 30 faeces-strains 15 were virulent. It is concluded that the cystitis-strains were not more often virulent than the faeces-strains. O antigens commonly found among urinaryE. coli isolates were present in 60% of the cystitis-strains and in 37% of the faeces-strains. K antigens commonly found in urinaryE. coli strains were present in 33% of the cystitis-strains and in 12% of the faeces-strains. Neither the presence of common urinary O-antigens, nor the presence of common urinary K antigens could be associated with virulence of the isolated strains. However, it is suggested that certain O and K antigens (O2, O6, K23) may be associated with virulence for the urinary tract.     

Genotyping and PCR detection of potential virulence genes in <Emphasis Type="Italic">Campylobacter jejuni</Emphasis> and <Emphasis Type="Italic">Campylobacter coli</Emphasis> isolates from different sources in Poland

The prevalence of potential virulence markers was determined among the population of Polish Campylobacter jejuni and Campylobacter coli isolates from children, chickens, pigs and dogs. The presence of the flaA, flaB, cdtA, cdtB, cdtC, cdtABC, virB11, and cj0588 genes among 74 C. jejuni and 15 C. coli isolates was detected by PCR. High prevalence of five different putative virulence and toxin genes (flaA, cdtA, cdtB, cdtC, and cj0588) was found among isolates obtained from children, chickens and dogs. The occurrence of these genes among isolates obtained from pigs was significantly different than for strains isolated from other sources. Two methods for genotyping Campylobacter spp. strains were applied — flaA-typing, and ADSRRS-fingerprinting method, which was used for the first time for Campylobacter spp. strains. Similarity of the genetic profiles was demonstrated in strains isolated from chickens and dogs, and in isolates from chickens and children. Strains isolated from pigs, both C. jejuni as well as C. coli, did not group with isolates from other sources.     

Occurrence and genetic association of selected virulence factors in clinicalEscherichia coli isolates

Occurrence ofcnf1+ E. coli pathogenic strains among extraintestinalE. coli isolates was evaluated to explain an impact of cytotoxic necrotizing factor type 1 (CNF1) in human infections. A total of 120E. coli isolates were characterized for presence of virulence factorscnf1- andpap- specific sequences by PCR, and the production of α-hemolysin using blood agar-plate test. Different association patterns among the detected virulence factors were obtained by comparison of various groups of clinicalE. coli isolates. These differences probably reflect a potential impact of CNF1 in the colonization of vaginal environment.     

Assessment of the Significance of Virulence Factors of Uropathogenic Escherichia coli in Experimental Urinary Tract Infection in Mice

Four Escherichia coli strains, isolated from cystitis patients, belonging to serotype O2:H^? and possessing different combinations of urovirulence factors were examined in an experimental pyelonephritis mouse model to assess the relative importance of virulence factors in causation of urinary tract infections (UTI). The results suggest not only that the each virulence factor has a role in causation of UTI but also that the presence of P fimbriae and production of hemolysin significantly reduced the LD₅₀ and ID₅₀ of the strains in the mouse model. The results also demonstrate that the presence of additional virulence factors acts in an additive or synergetic fashion enhancing the cumulative impact of the strain.     

Distribution of additional virulence factors related to adhesion and toxicity in Shiga toxin‐producing Escherichia coli isolated from raw products in Argentina

A total of 73 Shiga toxin‐producing Escherichia coli (STEC) isolates, belonging to 25 serotypes and isolated from raw products in Argentina, were examined for the occurrence of genes responsible for bacterial adhesions to intestine, ehaA (EHEC autotransporter), lpfAO113 (long polar fimbriae), sab (STEC autotransporter [AT] contributing to biofilm formation), ecpA (E. coli common pilus), hcpA (haemorrhagic coli pilus), elfA (E. coli laminin‐binding fimbriae), sfpA (sorbitol‐fermenting EHEC O157 fimbriae plasmid‐encoded) and of the toxigenic gene cdt‐V (cytolethal distending toxin). Our study showed different adhesin profiles that are not linked to one specific serotype and that all analysed isolates possess, besides stx genes, some adherence genes. Several of the isolates contained also multiple toxin genes. The results of the present work alert the presence of genes coding for additional adhesins and cdt‐V toxin in LEE‐negative STEC strains that occur in foods, and this traits could increase their pathogenic potential.

Significance and Impact of the Study

Meat products are one of the main vehicles of Shiga toxin‐producing E. coli, and the presence of genes coding for additional adhesins and toxins could increase their pathogenic potential. There is a need for a more detailed characterization of the strains in regard to these extra virulence factors.     

Distribution of PLD and FagA,B, C and D genes in Corynebacterium pseudotuberculosis isolates from sheep and goats with caseus lymphadenitis

Caseous lymphadenits (CL) is a chronic and subclinical disease that affects goats and sheep and, consequently, causes economic losses, especially to small producers. The purpose of this study, through use of Polymerase Chain Reaction (PCR), was to verify the presence of virulence genes of phospholipase D (PLD), integral membrane protein (FagA), iron enterobactin transporter (FagB), ATP binding cytoplasmic membrane protein (FagC) and iron siderophore binding protein (FagD) in 168 isolates of C. pseudotuberculosis obtained from cases of caseous lymphadenitis in goats and sheep. FagA, FagB and PLD genes were detected in all 145 strains isolated from abscesses in superficial lymph nodes and in 23 strains isolated from viscera. The FagC gene was positive in 167 (99.40%) isolates. The FagD gene was detected in 160 (95.23%) isolates. All virulence factors analyzed were found more frequently among isolates collected in the viscera of animals with CL, indicating a multifactorial nature, as well as variations, in the invasive potential of C. pseudotuberculosis strains.     

Virulence factors of Escherichia coli isolated from urine of diabetic women with asymptomatic bacteriuria: correlation with clinical characteristics

Since Escherichia coli isolated from compromised patients with symptomatic urinary tract infections (UTIs) express fewer virulence factors than those isolated from healthy controls, the question arises whether this is also the case for diabetic patients with asymptomatic bacteriuria (ASB). Polymerase chain reaction (PCR) assays were conducted on 111E. coli strains, isolated from the urine of diabetic women with ASB, using primers for the major subunit A and the G-adhesin (I, II, and III) of P fimbriae, type 1 fimbriae, S fimbriae, afimbrial adhesin, cytotoxic necrotizing factor (CNF), and aerobactin. Phenotypically, hemolysis, mannose-sensitive hemagglutination, mannose-resistant hemagglutination and O:K:H-serotypes were determined. Furthermore, we investigated the associations between virulence factors and patient characteristics (including deterioration of renal function). Type 1 fimbriae were the most prevalent virulence factor (86% by genotyping and 59% phenotypically). Except for a lower prevalence of known uropathogenic O-serotypes, we found the same number of virulence factors in our compromised patient group as listed in the literature in noncompromised patients with ASB. Certain virulence factors (type 1 and S fimbriae and CNF) of the causative E. colicorrelated with the risk of a decline in renal function. In conclusion, the number of virulence factors in E. coli isolated from the urine of diabetic women with ASB are comparable with the results found in other (noncompromised) patients with ASB. Furthermore, certain virulence factors of E. colimight contribute to a decline in renal function.     

Virulence of Escherichia coli in acute pyelonephritis,acute cystitis and asymptomatic bacteriuria

E. coli strains were isolated from urine specimens of hospitalised patients with acute pyelonephritis, acute cystitis or asymptomatic bacteriuria (ABU), and tested for virulence in an experimental mouse model. Of 12 pyelonephritisstrains 11 were shown to be virulent and 1 avirulent; of 12 cystitis-strains 4 were virulent and 8 avirulent; of 12 ABU-strains 5 were virulent and 7 avirulent. It is concluded that, while no difference in virulence was found between cystitis-and ABU-strains, pyelonephritis-strains were more often virulent than cystitis-and ABU-strains.No associations could be shown between virulence of the isolated strains and the presence of antibody-coated bacteria in the urine. Common urinary O types were not more often virulent than other O types. No relationship was seen between virulence and the presence of K antigen or the presence of particular K types.     

Longus: a long pilus ultrastructure produced by human enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) causes an acute cholera-like diarrhoea in both humans and animals. We describe a new pilus termed longus produced by ETEC, which can extend for over 20 microns from the cell surface. Longus is composed of a repeating subunit of 22 kDa and its NH₂-terminal amino acid sequence revealed homology with the toxin-coregulated pilus of Vibrio cholerae, the bundle-forming pilus of enteropathogenic E. coli and type IV pilins of some Gram-negative bacterial pathogens. The longus structural gene (IgA) is encoded in a large plasmid and was cloned in a 5 kb fragment, which proved to be sufficient for pilus production and assembly in E. coli K-12. The presence of IngA was restricted to human ETEC strains. In contrast to other ETEC pili, IngA was widely distributed among ETEC strains independent of their geographical origin, serotype, toxin production, or other pili antigens expressed. Longus is a new member of the type IV pili family, which may represent a highly conserved intestinal colonization factor of ETEC. Common antigenic determinants exist among longus and their pilin subunits, produced by heterologous ETEC. Longus could be significant in the immuno-prophylaxis of diarrhoeal disease caused by ETEC, especially against those strains in which no colonization factors have been identified and that produce heat-stable toxin only.     

Copper,Zinc-Superoxide Dismutase from Clinically Isolated <Emphasis Type="Italic">Escherichia coli</Emphasis>: Cloning,Analysis of <Emphasis Type="Italic">sodC</Emphasis> and Its Possible Role in Pathogenicity

Superoxide dismutase has been discovered within the periplasm of several Gram-negative pathogens. We studied the Cu,Zn-SOD enzyme in Escherichia coli isolated from clinical samples (stool samples) collected from patients suffering from diarrhea. Antibiogram studies of the isolates were carried out to determine the sensitive and resistant strains. The metal co-factor present in the enzyme was confirmed by running samples in native gels and inhibiting with 2 mM potassium cyanide. A 519 bp sodC gene was amplified from resistant and sensitive strains of Escherichia coli. Cloning and sequencing of the sodC gene indicated variation in the protein and amino acid sequences of sensitive and resistant isolates. The presence of sodC in highly resistant Escherichia coli isolates from diarrheal patients indicates that sodC may play role in enhancing the pathogenicity by protecting cells from exogenous sources of superoxide, such as the oxidative burst of phagocytes. The presence of SodC could be one of the factors for bacterial virulence.     

Vaginal versus Obstetric Infection Escherichia coli Isolates among Pregnant Women: Antimicrobial Resistance and Genetic Virulence Profile

Vaginal Escherichia coli colonization is related to obstetric infections and the consequent development of infections in newborns. Ampicillin resistance among E. coli strains is increasing, which is the main choice for treating empirically many obstetric and neonatal infections. Vaginal E. coli strains are very similar to extraintestinal pathogenic E. coli with regards to the virulence factors and the belonging to phylogroup B2. We studied the antimicrobial resistance and the genetic virulence profile of 82 E. coli isolates from 638 vaginal samples and 63 isolated from endometrial aspirate, placental and amniotic fluid samples from pregnant women with obstetric infections. The prevalence of E. coli in the vaginal samples was 13%, which was significant among women with associated risk factors during pregnancy, especially premature preterm rupture of membranes (p<0.0001). Sixty-five percent of the strains were ampicillin-resistant. The E. coli isolates causing obstetric infections showed higher resistance levels than vaginal isolates, particularly for gentamicin (p = 0.001). The most prevalent virulence factor genes were those related to the iron uptake systems revealing clear targets for interventions. More than 50% of the isolates belonged to the virulent B2 group possessing the highest number of virulence factor genes. The ampicillin-resistant isolates had high number of virulence factors primarily related to pathogenicity islands, and the remarkable gentamicin resistance in E. coli isolates from women presenting obstetric infections, the choice of the most appropriate empiric treatment and clinical management of pregnant women and neonates should be carefully made. Taking into account host-susceptibility, the heterogeneity of E. coli due to evolution over time and the geographical area, characterization of E. coli isolates colonizing the vagina and causing obstetric infections in different regions may help to develop interventions and avoid the aetiological link between maternal carriage and obstetric and subsequent puerperal infections.     

Clonal Diversity of Escherichia Coli Isolates from Marketed Beef in East Malaysia

Summary Escherichia coli, including Shiga-like toxin producing E. coli (STEC), serogroup O157:H7 and E. coli O157, were isolated from raw beef marketed in Sarawak and Sabah, East Malaysia. Molecular subtyping by pulsed-field gel electrophoresis (PFGE) was performed on 51 confirmed E. coli isolates. Of the 51 isolates, five were E. coli O157:H7, four E. coli O157, two non-O157 STEC and 40 other E. coli isolates (non-STEC). Digestion of chromosomal DNA from these E. coli isolates with restriction endonuclease XbaI (5′-TCTAGA-3′), followed by PFGE, produced 45 restriction endonuclease digestion profiles (REDPs) of 10–18 bands. E. coli O157:H7 isolates from one beef sample were found to have identical PFGE profiles. In contrast, E. coli serogroup O157 from different beef samples displayed considerable differences in their PFGE profiles. These suggested that E. coli isolates of both serogroups were not closely related. A large variety of PFGE patterns among non-STEC isolates were observed, demonstrating a high clonal diversity of E. coli in the beef marketed in East Malaysia. The distance matrix values (D), calculated showed that none of the pathogenic E. coli strains displayed close genetic relationship with the non-STEC strains. Based on the PFGE profiles, a dendrogram was generated and the isolates were grouped into five PFGE clusters (A–E). From the dendrogram, the most related isolates were E. coli O157:H7, grouped within cluster B. The STEC O157:H7 beef isolates were more closely related to the clinical E. coli O157:H7 isolate than the E. coli O157:H7 reference culture, EDL933. Cluster A, comprising many of other E. coli isolates was shown to be the most heterogeneous. PFGE was shown to possess high discriminatory power in typing pathogenic and non-pathogenic E. coli strains, and useful in studying possible clonal relationship among strains.     

Characterization of uropathogenic E. coli O25b-B2-ST131, O15:K52:H1, and CGA: Neutrophils apoptosis,serum bactericidal assay,biofilm formation,and virulence typing

Pathogenic and drug-resistant strains of Escherichia coli (E. coli) O25b-B2-ST131, O15:H1-D-ST393, and CGA (clonal group A) clonal groups have spread worldwide. This study aimed at determining E. coli epidemic clonal groups, their virulence factors, biofilm formation, neutrophils apoptosis, and antimicrobial resistance pattern of uropathogenic E. coli. A total of 95 CTX-M-1-producing E. coli clinical isolates were enrolled. E. coli O25b-B2-ST131, CGA, and O15:K52:H1 were identified by serotyping and phylogrouping and allele-specific polymerase chain reaction-based assay. Antibiotic susceptibility, biofilm formation, hemolysis, and human serum bactericidal assay were performed. Neutrophil apoptosis was assayed by flow cytometry. Nine E. coli clonal groups including six O25b-B2-ST131 strains, two CGA, and one O15:K52:H1-D-ST393 strains were detected. One O25b-B2-ST131 isolate was a strong biofilm-producer. Three ST131 isolates had type I fimbriae. Furthermore, all the CGA and O15:K52:H1 and three of ST131 isolates harbored the P fimbriae. The virulence genes ompT, fimH, and traT were detected among all the clonal groups. The apoptosis was induced by O25b-B2-ST131, CGA, and O15:K52:H1 E. coli. There was no significant difference regarding apoptosis induction among clonal groups. Furthermore, the presence of the cdt, usp, and vat genes was significantly associated with the apoptosis of neutrophils by O25b-B2-ST131, CGA, and O15:K52:H1-D-ST393 clonal groups.     

Phylogenetic groups,virulence genes and quinolone resistance of integron-bearing <Emphasis Type="Italic">Escherichia coli</Emphasis> strains isolated from a wastewater treatment plant

We investigated phylogenetic affiliation, occurrence of virulence genes and quinolone resistance in 109 integron-containing strains of Escherichia coli isolated from a wastewater treatment plant. Selection for integron-bearing strains caused a shift toward phylogroup D, which was most numerous, followed by A, B1 and B2. Phylogroups D and B2, both of which are reported to include virulent extraintestinal pathotypes, made up 50.5% of all isolates and were present in every stage of wastewater treatment, including final effluent. Diarrheagenic pathotypes made up 21% of the strains. The average virulence factor genes score was low (1.40) and the range was from 0 to 5. Quinolone and fluoroquinolone resistance was observed in 56.0% and 50.4% of the strains, respectively; however, it was not associated with virulence factor score. Although the average virulence factor score was low, 17.4% of strains had three and more virulence genes. They were isolated mostly from raw sewage, but 30% of them were cultured from final effluent. Release of multiresistant integron-bearing E. coli strains with virulence traits into the environment may create potential threat and be of public health concern.     

Pilus Biogenesis in Lactococcus lactis: Molecular Characterization and Role in Aggregation and Biofilm Formation

The genome of Lactococcus lactis strain IL1403 harbors a putative pilus biogenesis cluster consisting of a sortase C gene flanked by 3 LPxTG protein encoding genes (yhgD, yhgE, and yhhB), called here pil. However, pili were not detected under standard growth conditions. Over-expression of the pil operon resulted in production and display of pili on the surface of lactococci. Functional analysis of the pilus biogenesis machinery indicated that the pilus shaft is formed by oligomers of the YhgE pilin, that the pilus cap is formed by the YhgD pilin and that YhhB is the basal pilin allowing the tethering of the pilus fibers to the cell wall. Oligomerization of pilin subunits was catalyzed by sortase C while anchoring of pili to the cell wall was mediated by sortase A. Piliated L. lactis cells exhibited an auto-aggregation phenotype in liquid cultures, which was attributed to the polymerization of major pilin, YhgE. The piliated lactococci formed thicker, more aerial biofilms compared to those produced by non-piliated bacteria. This phenotype was attributed to oligomers of YhgE. This study provides the first dissection of the pilus biogenesis machinery in a non-pathogenic Gram-positive bacterium. Analysis of natural lactococci isolates from clinical and vegetal environments showed pili production under standard growth conditions. The identification of functional pili in lactococci suggests that the changes they promote in aggregation and biofilm formation may be important for the natural lifestyle as well as for applications in which these bacteria are used.     

Detection of virulent Escherichia coli O157 strains using multiplex PCR and single base sequencing for SNP characterization

Aims: To compare 167 Norwegian human and nonhuman Escherichia coli O157:H7/NM (nonmotile) isolates with respect to an A/T single nucleotide polymorphism (SNP) in the tir gene and to detect specific SNPs that differentiate STEC O157 into distinct virulence clades (1–3 and 8). Methods and Results: We developed a multiplex PCR followed by single base sequencing for detection of the SNPs, and examined the association among SNP genotype, virulence profile (stx and eae status), multilocus variable number of tandem repeats analysis (MLVA) profile and clinical outcome. We found an over‐representation of the T allele among human strains compared to nonhuman strains, including 5/6 haemolytic‐uraemic syndrome cases. Fourteen strains belonged to clade 8, followed by two clade 2 strains. No clade 1 nor 3 isolates were observed. stx1 in combination with either stx2_EDL933 or stx2c were frequently observed among human strains, whereas stx2c was dominating in nonhuman strains. MLVA indicated that only single cases or small outbreaks with E. coli O157 have been observed in Norway through the years 1993–2008. Conclusion: We observed that the tir‐255 A/T SNP and the stx status were different between human and nonhuman O157 strains. No major outbreaks were observed, and only a few strains were differentiated into the virulence clades 2 and 8. Significance and Impact of the Study: The detection of virulence clade‐specific SNPs enables the rapid designation of virulent E. coli O157 strains, especially in outbreak situations.     

Detection of<Emphasis Type="Italic">pap</Emphasis>-,<Emphasis Type="Italic">sfa</Emphasis>- and<Emphasis Type="Italic">afa</Emphasis>-specific DNA sequences in<Emphasis Type="Italic">Escherichia coli</Emphasis> strains isolated from extraintestinal material

P-fimbriae, S-fimbriae and AFA-adhesins are virulence factors responsible for adherence ofEscherichia coli strains to extraintestinal host-cell surface. Detection ofpap-,sfa- andafa-specific sequences performed by PCR revealed 74%pap ⁺, 65%sfa ⁺, and 8.3%afa ⁺ strains in a group of 84 extraintestialE. coli isolates. Detection in a group of fecal strains showed 29%pap ⁺, 21%sfa ⁺ and 4%afa ⁺ strains.pap together withsfa were found as the most frequent combination (56%) among extraintestinal isolates probably due to localization ofpap-andsfa-operons on a common pathogenicity island. The occurrence ofafa-specific sequence among 56 urine strains was 11%, although noafa ⁺ strain was detected among 28 gynecological isolates. No strains with detected adhesin operons were found among twenty (24%) extraintestinalE. coli strains.     

病原菌多重耐药与生物膜表型和毒力因子的相关性

本文旨在研究导尿管相关尿路感染病原菌多重耐药与生物膜表型和毒力因子的相关性。选取2018年1月至2019年12月于沈阳市第四人民医院住院期间出现导尿管相关尿路感染的患者为研究对象,收集尿液培养标本,使用全自动微生物鉴定仪和纸片扩散法进行菌株鉴定和药敏试验。根据药敏试验结果,将大肠埃希菌分为多重耐药组和非多重耐药组。紫外分光光度法测定多重耐药组和非多重耐药组大肠埃希菌的生物膜附着力。PCR法分析多重耐药组和非多重耐药组参与大肠埃希菌4种毒力因子(黏附素、保护素、细胞毒素、铁载体)编码的16种基因表达水平。 共收集156例患者的尿液,并从尿液培养标本中分离出病原菌172株,其中大肠埃希菌97株（56.7%）占比最多。药敏试验结果显示,多重耐药组大肠埃希菌对各类抗菌药物的耐药率均超过60%。与非多重耐药组相比,多重耐药组大肠埃希菌生物膜阳性率差异有统计学意义（P<0.05）,附着力强度等级差异也有统计学意义（P<0.05）。多重耐药组大肠埃希菌与黏附素相关4种毒力基因fimH、sfa、afa、iha表达明显高于非多重耐药组,差异具有统计学意义(P<0.05)。导尿管相关尿路感染病原菌的多重耐药与毒力因子参与产生强附着力生物膜表型有关。     

Diarrheal and Environmental Isolates of Aeromonas spp. Produce a Toxin Similar to Shiga-Like Toxin 1

Diarrheal and environmental isolates of 39 strains of Aeromonas spp. were studied for detection of virulence factors. Although these 39 strains did not produce either heat-labile or heat-stable enterotoxins, culture filtrates of 31 strains produced cytopathic effects on Vero cells. Among these, culture filtrates of three strains of Aeromonas hydrophila and one strain of Aeromonas caviae could be neutralized by Escherichia coli O157:H7 Shiga-like toxin 1 antiserum. A single band of plasmid DNA of 2.14 kbp was isolated from these strains of Aeromonas spp. and E. coli O157:H7, which could be amplified by the polymerase chain reaction (PCR), employing oligonucleotide primers from the Shiga-like toxin 1 (SLT1) gene of E. coli O157:H7. E. coli HB 101 cells when transformed with the same plasmid showed cytopathic effects on Vero cells, which indicates that the SLT 1 homolog gene(s) of Aeromonas spp. is plasmid encoded. These results suggest that Aeromonas spp. may also produce Shiga-like toxin 1, or at least a cytotoxin with some homology with the Shiga-like toxin 1 of E. coli O157:H7.     

反刍动物产志贺毒素大肠杆菌的分离鉴定和致病潜力分析

产志贺毒素大肠杆菌（Shiga toxin-producing Escherichia coli,STEC）是重要的食源性病原,而STEC往往以正常菌群的形式存在于牛羊等反刍动物肠道。[目的] 本研究对牛羊粪便样品中的STEC分离和鉴定并对分离株进行致病潜力分析。从江苏、云南和河北等地共分离到羊源STEC菌株11株,牛源STEC菌株1株,另新疆农业大学佟盼盼组馈赠牛源菌株10株。[方法] 通过细菌选择培养及特异性基因stx1和stx2的检测进行分离鉴定;并通过Vero细胞毒性试验、溶血活性试验和毒力因子的检测分析STEC分离株的致病潜力。[结果] 分离到羊源分离株11株,分离率17.5%（11/63）;分离得到牛源分离株1株,分离率0.7%（1/134）;11株羊源分离株中有5株对Vero细胞具有强的毒性,3株有溶血活性;11株牛源分离株中有5株对Vero细胞具有强的毒性,3株有溶血活性。11株羊源STEC分离株eae基因携带率为63.6%（7/11）,而11株牛源STEC分离株eae基因携带率仅为9.0%（1/11）。[结论] 结果表明羊源STEC菌株的分离率和致病潜力高于牛源菌株,所以,除牛外,羊作为STEC菌株宿主也应该得到更多的重视。