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1.
In this study, we tested the capability of enterobacterial repetitive intergenic consensus (ERIC) and repetitive extragenic palindromic (REP) polymerase chain reaction (PCR) to detect genetic diversity among Escherichia coli strains isolated from chickens bearing clinical signs of colibacillosis and compared the genotypes so obtained with the O:H serotypes and virulence of those strains. The DNAs from 50 avian E. coli strains and from E. coli ATCC 25922 were used to amplify ERIC and REP sequences. DNA from avian strains produced from 8 to 17 bands by ERIC-PCR and from 6 to 20 bands by REP-PCR; E. coli ATCC produced 11 bands by both methods. ERIC and REP-PCR showed good discriminating power, and the dendograms based on the different patterns revealed extensive genetic diversity among the avian strains. Those strains were allocated into four major clonal clusters, each one with 60% of similarity by ERIC and REP-PCR, and those clusters corresponded to strains with different degrees of pathogenicity. However, 56% of the pathogenic strains (28/50) belonged to two out of three major clonal clusters, and 86% of the nonpathogenic strains tended to group in one cluster and one subgroup. The 32 serotypes detected were distributed in all clusters, and within a serogroup, different DNA fingerprints were observed; however, strains with same serotypes tended to form clusters with similarity coefficients greater than 80%. These results suggest that no specific serotype and genotype is responsible for colibacillosis and that REP and ERIC-PCR are reproducible techniques that can improve the studies needed to clarify the pathways to the pathogenesis of colibacillosis.  相似文献   

2.
Here we describe the application of a random amplified polymorphic DNA (RAPD) analysis for molecular genetic typing avian pathogenic Escherichia coli (APEC) strains. The RAPD technique was shown to be highly reproducible. Stable banding patterns with a high discriminatory capacity were obtained using two different primers. Overall, 55 E. coli strains were analyzed with a RAPD technique. The RAPD analysis showed that the E. coli strains isolated from poultry in Thailand and Sweden could be grouped into 50 of RAPD types by using these two different primer sets. Most of these different E. coli RAPD types were not geographically restricted. There was, as expected, a tendency of higher genetic relationship among E. coli strains isolated from the same farm. It is suggested that the RAPD technique may provide a rapid, low cost, simple and powerful tool to study the clonal epidemiology of avian E. coli infections.  相似文献   

3.
Colibacillosis caused by avian pathogenic Escherichia coli (APEC) is a leading cause of economic loss to the poultry industry worldwide. The ability of APEC to cause disease is determined by certain virulence markers, some of which are located on pathogenicity islands (PAls). We recently described one such PAI in an APEC O1:K1 strain (APEC-O1). This PAI, termed PAI I(APEC-O1), carries the genes of the pap operon, a region similar to the tia invasion determinant of enterotoxigenic E coli; ireA, a gene that encodes an iron-responsive element; and a novel 1.5-kb region, ORF 54. Here, the occurrence of six selected loci of PAI I(APEC-O1) (papA, papC, papG, ireA, tia, and ORF 54) among APEC and fecal E. coli strains from apparently healthy chickens (avian commensal E. coli) was determined using polymerase chain reaction (PCR) techniques. None of the commensal E. coli was positive for all six traits, whereas 7.2% of the APEC isolates were positive for all the traits. Although there was no significant difference in the occurrence of ORF 54 among APEC and commensal E. coli, tia, ireA, papC, and papG genes were predominantly present in APEC rather than in avian commensal E. coli. papA was detected in only 6.3% of APEC, perhaps because of the presence of allelic variants of the gene. Additionally, the presence of all six traits was tested with PCR in APEC isolates collected in the 1980s, and these results were compared with those obtained with the APEC isolated in the 1990s. There was no significant difference in the occurrence of tia, ireA, papC, papG, and ORF 54 between APEC isolates collected during the different decades. However, papA was more frequently present in APEC from the 1980s than it was in APEC from the 1990s. Phylogenetic group of an isolate did not correlate with pathogenicity or the presence of PAI traits, except that more APEC of the low-pathogenicity group belonged to the phylogenetic group B1. However, PAI traits occurred more frequently in isolates belonging to the intermediate- and high-pathogenicity groups than in isolates of low pathogenicity.  相似文献   

4.
Forty-nine avian pathogenic Escherichia coli (APEC) strains obtained from chickens suffering from septicemia (24), swollen head syndrome (14) and omphalitis (11), isolated from individuals in different regions of Brazil and from different outbreaks, were studied for their adhesion to trachea epithelial cells, fimbrial expression and hemagglutination capacity to different erythrocyte types. These results were compared with their content of fimbriae-related genes as detected by polymerase chain reaction (PCR) using specific pair of primers. The aim of these assays was to determine the importance of expression of adhesins in the pathogenic strains and to evaluate the presence of adhesin genes either previously described or not yet recognized for APEC strain. Thirty commensal strains isolated from poultry showing no signs of any of the above diseases were used to compare the results with the pathogenic isolates. The PCR assay demonstrated that septicaemic and swollen head syndrome strains had the highest number of adhesion-related genes of recognized importance in pathogenicity. Using different media for growth conditions, 40 different D-mannose resistant haemagglutination patterns were observed in this study, what indicates the expression of a great variability of surface agglutinins in these bacterial strains. Our results also showed that adhesion, whether D-mannose resistant (MRA) or D-mannose sensitive (MSA), is a characteristic observed in both pathogenic and commensal strains. Several strains with positive adherence had no genetic sequences related to the studied adhesin genes what indicates that our APEC strains probably possess a genome with adhesins genes besides those describe elsewhere and that have not yet been described.  相似文献   

5.
The virulence factors of avian pathogenic Escherichia coli (APEC) isolated in Japan were investigated. Serogroups O, serotypes K1 and K5, and genes cva C, iss, iutA, papA, tsh, and usp, which have been thought to be related to virulence, were examined for their association with E. coli strains isolated from diseased and healthy chickens. The frequently recognized serogroups O1, O2, and O78 were found in 56 of 125 (44.8%) strains of diseased chickens (APEC) versus 13 of 100 (13.0%) strains of healthy chickens (commensal E. coli), a significant difference at risk ratio < 0.01. Although iss, iutA, and tsh were widely distributed in the APEC irrespective of O serogroup, papA, usp, and the K1 serotype were detected in serogroup O2 of APEC. The kfiD gene related to the K5 capsule and VT, LT, and ST genes related to exotoxins were not detected in any strains examined.  相似文献   

6.
为调查山东省禽源致病性大肠杆菌流行的血清型及耐药性,从山东部分地区的45家养禽场分离到致病性大肠杆菌96株,应用微量平板凝集试验进行了血清型鉴定,共鉴定出18种血清型,其中优势血清型6种,分别为O78、O2、O15、O18、O143、O88,占定型致病性菌株的64％。抗菌药物敏感性试验发现,96株大肠杆菌对20种药物有不同程度的耐药性。75％以上的菌株对氨苄青霉素、阿莫西林、土霉素等5种抗菌药耐药,50％以上的菌株对卡那霉素、多西环素、环丙沙星等7种抗菌药表现为耐药;所有分离株存在多重耐药现象,75％的受检菌对9种或9种以上的被测药物耐药。结果表明,O78、O2、O15、O18、O143、O886种血清型是山东省部分地区近年来禽源致病性大肠杆菌的优势血清型,且禽源致病性大肠杆菌的耐药现象严重,有必要加强耐药性检测,以指导兽医临床合理使用抗菌药物。  相似文献   

7.
One hundred and forty-three Pasteurella spp. strains and 10 unclassified strains obtained from free ranging poultry, dogs and cats were investigated by extended phenotypic characterization. One hundred and forty-nine of these strains were selected for further studies using ribotyping and REA-typing to evaluate the role of dogs and cats in Pasteurella multocida transmission. Seven and six type strains were included for comparison in phenotyping and genotyping, respectively. Eleven clusters and six unclustered strains were revealed by phenotyping. Ribotyping outlined 12 clusters and six unclustered strains. A correlation between clusters obtained by phenotyping and ribotyping was demonstrated which indicated that a genetic basis exists for clusters outlined by quantitative evaluation of phenotypic data. Similarities and differences in hosts, phenotype, ribotype, and zone of isolation were demonstrated among Pasteurella strains investigated. Isolates of P. multocida from ducks were shown to be clonal by both phenotyping and ribotyping. These strains were identical to one of the chickens strains. REA-typing, however, showed that the chicken strain was different underlining that exchange of clones of P. multocida between avian species rarely happens under village conditions. Management practise in the villages suggest the potential for exchange of P. multocida between poultry and animals kept in contact. The present findings, however, did not indicate that clones of P. multocida are widely exchanged between poultry and other animal species, even though close contact exists. In the present investigation exchange of clones of P. multocida was only demonstrated among animals belonging to the same species. Caution is drawn to the use of ribotyping as the sole method for epidemiological typing and tracing of P. multocida. The present results also underline the importance of proper phenotyping in the identification of P. multocida and related species.  相似文献   

8.
Ninety-five avian pathogenic Escherichia coli (APEC) isolates recovered from diagnosed cases of avian colibacillosis from North Georgia between 1996 and 2000 were serotyped and examined for typical virulence-factors, susceptibility to antimicrobials of human and veterinary significance, and genetic relatedness. Twenty different serotypes were identified, with O78 being the most common (12%). The majority of the avian E. coli isolates (60%), however, were non-typeable with standard O antisera. Eighty-four percent of isolates were PCR positive for the temperature-sensitive hemagglutinin (tsh) gene and 86% positive for the increased serum survival (iss) gene. Multiple antimicrobial-resistant phenotypes (> or =3 antimicrobials) were observed in 92% of E. coli isolates, with the majority of isolates displaying resistance to sulfamethoxazole (93%), tetracycline (87%), streptomycin (86%), gentamicin (69%), and nalidixic acid (59%). Fifty-six E. coli isolates displaying resistance to nalidixic acid were co-resistant to difloxacin (57%), enrofloxacin (16%), gatifloxacin (2%), and levofloxacin (2%). DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Tyr, Asp87-Gly, Asp87-Ala), gyrB (Glu466-Asp, Asp426-Thr), and parC (Ser80-Ile, Ser80-Arg). No mutations were observed in parE. Twelve of the quinolone-resistant E. coli isolates were tolerant to cyclohexane, a marker for upregulation of the acrAB multi-drug resistance efflux pump. Quinolone-resistant isolates were further genetically characterized via ribotyping. Twenty-two distinct ribogroups were identified, with 61% of isolates clustering into four major ribogroups, indicating that quinolone resistance has emerged among multiple avian pathogenic E. coli serogroups and chromosomal backgrounds.  相似文献   

9.
Vacuolating cytotoxin produced by avian pathogenic Escherichia coli   总被引：2，自引：0，他引：2  
The purpose of this study was to determine whether avian pathogenic Escherichia coli produced cytotoxic activity. Culture supernatants of 20 E. coli strains isolated from cellulitis lesions in chickens, five E. coli strains from avian septicemia, five from swollen head syndrome, and five from the feces of healthy chickens were incubated with primary chicken embryo fibroblast (CEF) cells, primary chicken kidney (PCK) cells, a quail fibroblast cell line (QT-35), and four mammalian cell lines (human epithelioid cervical carcinoma, African green monkey kidney, Chinese hamster ovary, and human larynx epidermoid carcinoma). Cytotoxicity was observed with supernatants from the 30 avian pathogenic strains on the two primary chicken cells (CEF and PCK). The highest dilution of culture supenatant that induced cytotoxic changes in 50% of the cells was 1/64. Supernatants from the five strains from normal feces were noncytotoxic, and none of the supernatants was cytotoxic for the QT-35 or the four mammalian cell lines. The cytotoxic effect, which was observed as early as 2 hr after exposure of the cells, was maximal at 6 hr and was evident as vacuolation, morphologically indistinguishable from that previously reported for culture supernatants of Helicobacter pylori. Like the activity in H. pylori, the cytotoxicity of the avian pathogenic strains was destroyed by heating at 70 C for 30 min and by exposure to proteolytic enzymes and was retained by filtration with a 100,000 molecular weight cut-off ultrafilter. Supernatants of two vacuolating cytotoxin-positive cultures of H. pylori failed to induce vacuolation of the CEF and PCK cells but caused the characteristic vacuolation in HeLa and Vero cells. The observations suggest that avian pathogenic E. coli produce a cytotoxin that is similar to the cytotoxin of H. pylori but may be specific for avian cells.  相似文献   

10.
To investigate the distribution and characteristic of E. coli in the microbial-fermentation bed of piggery, litters with different levels of fermentation were used for the isolation, identification and drug sensitivity test of E. coli, to analyze the pathogenicity and drug susceptibility of E. coli in the microbial-fermentation bed of piggery. The results showed that, E. coli could be isolated only from litters with low degree of fermentation (0<△E≤7.63), and totally 41 strains were isolated from litters with 10-5 dilution, but none from litters with higher degree of fermentation (△E>7.63). The number of E. coli reduced along with the fermentation of litters. Among the 41 strains of E. coli, 15 were intestinal pathogenic strains, 9 of which had astA gene (22%), and 2 strains had sepA gene (4.8%). 11 strains were resistant to doxycycline, accounted for 27% of the total.The two strains containing sepA gene had strong resistance to doxycycline. In conclusion, the microbial-fermentation bed fermentation bed had a inhibitory effect on E. coli which promoted the application of fermentation bed and reusing of litters.  相似文献   

11.
为了研究微生物发酵床不同发酵等级垫料中大肠杆菌的分布及其特性,试验采集了微生物发酵床猪舍不同发酵程度的垫料,进行大肠杆菌的分离鉴定和药敏试验,分析了发酵床中大肠杆菌的致病性和抗生素抗性。试验结果表明,在10-5稀释倍数下,仅在垫料发酵级别为一级的垫料中,即垫料使用时间较短、发酵程度较低（0<△E≤7.63）的条件下,分离到41株大肠杆菌;而在发酵程度较高的垫料中,即垫料发酵程度二级以上（△E>7.63）的环境中未分离到大肠杆菌。随着发酵的进行,发酵床中大肠杆菌数量逐渐减少。41株大肠杆菌中含有致泻性大肠杆菌15株,其中具有热稳定肠毒素（astA）基因的大肠杆菌9株,占总数的22%,含耐药性因子（sepA）基因的大肠杆菌2株,占总数的4.8%;耐强力霉素的大肠杆菌11株,占总数的27%。含有sepA基因的大肠杆菌具有强耐药性。从以上结果来看,微生物发酵床对猪舍大肠杆菌具有抑制作用,可为发酵床的推广应用及垫料再利用提供一定依据。  相似文献   

12.
Based on recently published prevalence data of virulence-associated factors in avian pathogenic Escherichia coli (APEC) and their roles in the pathogenesis of colibacillosis, we developed a multiplex polymerase chain reaction (PCR) as a molecular tool supplementing current diagnostic schemes that mainly rely on serological examination of strains isolated from diseased birds. Multiple isolates of E. coli from clinical cases of colibacillosis known to possess different combinations of eight genes were used as sources of template DNA to develop the multiplex PCR protocol, targeting genes for P-fimbriae (papC), aerobactin (iucD), iron-repressible protein (irp2), temperature-sensitive hemagglutinin (tsh), vacuolating autotransporter toxin (vat), enteroaggregative toxin (astA), increased serum survival protein (iss), and colicin V plasmid operon genes (cva/cvi). In order to verify the usefulness of this diagnostic tool, E. coli strains isolated from fecal samples of clinically healthy chickens were also included in this study, as were uropathogenic (UPEC), necrotoxigenic, and diarrhegenic E. coli strains. The application of the multiplex PCR protocol to 14 E. coli strains isolated from septicemic poultry showed that these strains harbored four to eight of the genes mentioned above. In contrast, those isolates that have been shown to be nonpathogenic for 5-wk-old chickens possessed either none or, at most, three of these genes. We found only one enterohemorrhagic (EHEC), one enteropathogenic (EPEC), and two enterotoxic (ETEC) E. coli strains positive for irp2, and another two ETEC strains positive for astA. As expected, UPEC isolates yielded different combinations of the genes iss, papC, iucD, irp2, and a sequence similar to vat. However, neither the colicin V operon genes cva/cvi nor tsh were amplified in UPEC isolates. The multiplex PCR results were compared with those obtained by DNA-DNA-hybridization analyses to validate the specificity of oligonucleotide primers, and the protocol was concluded to be a useful, sensitive, and rapid assay system to detect avian pathogenic E. coli and differentiate them from nonpathogenic strains and those belonging to other pathotypes.  相似文献   

13.
The molecular biology and epidemiology of 150 avian pathogenic Escherichia coli strains (APEC) isolated from septicemic poultry in Germany was investigated by serotyping, pulsed field gel electrophoresis (PFGE), and polymerase chain reaction (PCR). Only 49.6% of the isolates could be grouped to serogroups O1, O2, and O78. Macrorestriction analyses data revealed two large clonal groups (clusters I and II) among the APEC strains with a similarity of 60.9% to each other. An association between restriction pattern and serogroup or origin of the strains was only present in a few subgroups of each clusters I and II, but was not evident. In contrast, our data revealed distinct combinations of virulence-associated genes in that 51.2% of the O2-strains harboured a combination of the genes fyuA, irp2, iucD, tsh, vat, fimC, and colV and 36.4% of the O78-strains possessed the same gene combination with exception of vat. With 34 different gene combinations the non-O1, -O2, -O78 isolates revealed a higher variability in their virulence gene pattern than O1-, O2-, and O78-strains with 6, 13, and 9 patterns, respectively. Our data indicate only a limited association between the virulence gene pattern and the serogroup of APEC strains and question the sensitivity of O-typing for APEC identification without the application of further diagnostic tools. Although a limited number of APEC clones exist, horizontal gene transfer seems to be common in these pathogens. These findings strengthen further research on the population structure of APEC and may be the reason for the lack of clear definition of this common E. coli pathotype.  相似文献   

14.
A collection of 1601 extraintestinal and intestinal Escherichia coli isolated from chickens, turkeys and ducks, in Belgium, France and Spain, was hybridised with gene probes specific for fimbrial and afimbrial adhesins (F17, F18, S , Bfp, Afa, Cs31A, Intimin , Aida-1) of intestinal, urinary and invasive E. coli of mammals and with a probe specific for the P (Pap/Prs) fimbrial adhesin of urinary and invasive E. coli of mammals and birds. Three hundred and eighty-three strains (23.9%) were P-positive, 76 strains (4.8%) were Afa-positive, 75 strains (4.7%) were F17-positive, 67 strains (4.2%) were S-positive, 23 (1.4%) were Intimin-positive, and all were F18-, Cs31A-, Aida1- and Bfp-negative. The 75 F17-positive strains harboured different major subunit A-encoding gene variants, but the f17Ac variant was the most frequent (52 strains, 69.3%) and seven strains (9.3%) were not typeable. The f17G gene variant coding for the GII adhesin was the most frequent (56 strains, 75.0%), whereas the f17GI gene variant was present in four strains (5%) and 15 strains (20.0%) were not typeable. All Afa-positive strains harboured the afa-8 variant. The 23 Intimin-positive E. coli tested positive for the beta-variant (16 strains; 69.6%) or for the gamma-variant (seven strains; 30.4%) of the eae gene. Chicken and turkey E. coli were more frequently probe-positive (43.6 and 43.1%, respectively) than duck E. coli (31.5%) and extraintestinal E. coli were also more frequently probe-positive (48.4%) than intestinal strains (18.5%). Different combinations of probe positive hybridisation results were observed in 72 of the 540 probe-positive E. coli (13.3%). The most frequent combinations were between AfaE-8 and F17 probes (47 strains; 8.7%) and between P and S probes (13 strains; 2.4%). Although f17- and afa-8-related DNA sequences can be plasmid-located in mammalian E. coli, they were not in avian E. coli. Besides the P fimbrial adhesins, F17 and S fimbrial and Afa-VIII and Intimin afimbrial adhesins may thus represent colonisation factors of avian pathogenic E. coli.  相似文献   

15.
Five distinct lipopolysaccharide (LPS) core types, namely R1-R4 and K12 have been identified in Escherichia coli. The aims of this study were to determine, primarily by means of PCR, the distribution of those oligosaccharide core types among avian pathogenic E. coli and their relationship to phylogenetic groups. To identify putative avian pathogenic E. coli, serum resistance and the presence of three virulence genes encoding temperature sensitive haemagglutinin (tsh), increased serum survival (iss) and colicin V (cvaC) were determined. Of the 143 clinical isolates examined 62% possessed the R1 core, 22% were R3, 13% were R4 and 3% were R2. Fifty commensal isolates consisted of 58% with R1 core, 38% with R3 core, 4% with R4 core, and none with R2. None of the isolates were of K12 core type. The distribution of core oligosaccharide types in clinical and commensal isolates were not statistically significant (P=0.51). Three genes, tsh, iss and cvaC were found in E. coli of all four core types. The genes tsh (P<0.001) and iss (P=0.03412) were significantly associated with the R4 core oligosaccharide type. The isolates containing R4 core type LPS were mainly confined to phylogenetic group D. The widespread R1 core type showed less ability to possess virulence genes and 83% were in the phylogenetic group A. Results of this study indicated that E. coli with R1, R2, R3 and R4 were important in causing infections in chickens and further, the E. coli with R4 core type were less common among commensals, possessed more virulence genes and were related to phylogenetic groups pathogenic for poultry.  相似文献   

16.
Escherichia coli is a common avian pathogen mainly associated with extraintestinal infections such as yolk sac infection (YSI). The aim of this study was to determine the serotypes and the presence of some virulence genes of E. coli strains isolated from different samples in a vertically integrated poultry operation in Mexico. Two hundred sixty-seven E. coli isolates from different samples were serotyped using rabbit serum against the 175 somatic (O) and 56 flagellar (H) antigens of the typing schema. Virulence genes were determined by colony blot hybridization, using DNA probes for st, eae, agg1, agg2, bfp, lt, cdt, slt, and ipaH diarrhea-associated virulence factors. The serogroup of 85% of the strains was determined; O19 (12%), 084 (9%), 08 (6%), and 078 (5%) were the most common. Using the complete antigenic formula (O and H), O19:NM (n = 31) was the serotype most frequently isolated from dead-in-shell embryos and in broilers that had died on the fourth, fifth, sixth, and seventh days after hatch. One hundred ten strains (41.2%) hybridized with one or more of the used probes. Of these, ipaH (72%), eae (30%), and cdt (27%) were the most common. Considering the origin of the respective isolates, 40% of the broiler farm strains were positive for at least one probe. Results show that some avian E. coli strains isolated in Mexico are included in avian pathogenic E. coli serotypes not previously reported, suggesting that they could be specific for this geographic area. The wide distribution of the ipaH gene among nonmotile strains suggests that this invasiveness trait could be important in YSI pathogenesis. On the other hand, some other genes could contribute to E. coli virulence during YSI.  相似文献   

17.
Haemolysin is one type of virulence factor that assists in the pathogenesis of Escherichia coli. Currently, hemolytic activity in E. coli has been attributed to haemolysin genes found in either uropathogenic or enterohemorrhagic E. coli. Both haemolysins are classified as RTX toxins because they both have repeats in toxin domains and share similar operon organization, sequence homology, and mechanisms of action. Haemolytic avian E. coli isolates, however, lack either E. coli haemolysin gene. To investigate the avian E. coli haemolysin, a genomic library was made from an avian pathogenic E. coli. A haemolytic clone that was isolated was shown to contain homology with sheA, an E. coli K- 12 gene which causes haemolysis when present in high copy number. The cloned haemolysin gene, hlyE, lacked the conserved amino acid sequence and accessory genes common to all RTX toxins. DNA hybridizations and polymerase chain reaction amplifications showed that the nucleotide sequences homologous to hlyE were not present in a collection of three O157: H7 E. coli, five haemolytic canine uropathogenic E. coli, one haemolytic O26 E. coli, and three haemolytic avian pathogenic E. coli. Thus we have identified a new E. coli haemolysin distinct from the RTX haemolysins and have shown that some avian pathogenic E. coli possess a haemolysin with no apparent homology to hlyE or RTX haemolysins.  相似文献   

18.
试验对新疆克拉玛地区106头健康成年荷斯坦奶牛的新鲜粪便进行了致病性大肠杆菌的分离鉴定、分型及遗传进化分析,初步掌握了调查地区奶牛致病性大肠杆菌的流行情况。参考USDA检测法,对106份粪便样品选择性增菌,分别利用麦康凯和伊红美蓝琼脂培养基对大肠杆菌进行分离纯化鉴别,通过PCR方法鉴定,获得55株大肠杆菌分离株,对这些分离株进行致病性大肠杆菌血清型鉴定、系统进化群及多位点序列分型（multilocus sequence typing,MLST）分析,利用goeBURST和Mega 7.0生物学软件进行聚类和进化研究,并进行流行病学分析。结果显示,106头健康荷斯坦奶牛的新鲜粪便中大肠杆菌的检出率为51.89%,55株大肠杆菌分离株共鉴定出9种与致病性相关的血清型,检出率为54.55%,其中肠致病性大肠杆菌（EPEC）、肠侵袭性大肠杆菌（EIEC）和肠产毒性大肠杆菌（ETEC）血清型检出率分别为21.82%、18.81%和14.55%,优势血清型为O142∶K86（B）和O124∶K72（均为10.91%）,前者属于肠致病性大肠杆菌,后者属于肠侵袭性大肠杆菌,而肠出血性大肠杆菌（EHEC）血清型检出率为0;系统发育群结果表明,55株大肠杆菌中B1群所占比例最高,为70.91%,其次为A群,占21.82%,D群所占比例较少,占7.27%,B2群未检测出;MLST分析可知,分离株中存在24个ST型,其中优势ST型为ST154（18.18%）;进化树分析显示有7个进化分支。结果表明,新疆克拉玛依地区健康成年奶牛粪便大肠杆菌多样性丰富,不仅存在多种致病性大肠杆菌,而且大肠杆菌菌株之间还存在一定的进化关系。因此,健康成年奶牛粪便也具有潜在的安全风险,应加强对奶牛粪便致病性大肠杆菌的检测和监控。  相似文献   

19.
In this study we sequenced and analysed the fimH and fimA genes of 24 avian pathogenic Escherichia coli (APEC) isolates, in order to investigate their possible conserved nature. Additional parameters (serotype, presence of aerobactin receptor, expression of F1 pili and virulence for chickens) were investigated to look for correlations with the obtained sequences. The sequence analysis demonstrated that FimH is highly conserved among all investigated APEC strains (>99% homology), whereas the major subunit FimA is less conserved, presenting 6 variable regions distributed along the protein. A hydrophilicity analysis suggested several variable domains of FimA to be potential epitopes. We were able to classify the investigated strains into three main groups, on the basis of the amino-acid sequences of the variable regions. This grouping was consistent throughout all variable regions and was independent of serotype, leading to an improved classification of the F1 pili. No correlation was found between the fimH and fimA sequences and the following parameters: avian species, organ of isolation, serotype, presence of aerobactin receptor and virulence for chickens. This study elucidated the molecular structure and the degree of conservation of FimH and FimA among various avian pathogenic E. coli strains.  相似文献   

20.
Fifty avian (chicken) pathogenic Escherichia coli strains (APEC) isolated from individuals suffering from omphalitis, septicaemia and swollen head syndrome, and 30 strains isolated from healthy chickens were studied regarding their biological characteristics such as serogroups, haemolysin, colicin, cytotoxin, toxin and siderophore production, adhesion capacity to in vitro cultivated cells, and absorption of Congo red dye. Serotyping demonstrated that most of the omphalitis and normal strains were untypable, whereas most of the septicaemic strains were either untypable or rough. There was no prevalent serogroup among the pathogenic strains studied. The capacity for adhesion and invasion of in vitro cultured cells (HeLa, HEp-2, KPCC), as well as the agglutination of different types of red blood cells and the LD50 of each strain were also evaluated. No correlation was observed between the biological characteristics and pathogenicity, except that colicin was characteristically produced by swollen head syndrome E. coli strains. No correlation was found between adhesion or haemagglutination patterns and pathogenicity. Only six of the 50 strains revealed invasive capacity and the strain that best invaded the cell lines was the one with the lowest LD50.  相似文献   

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