西藏地区牦牛致病性大肠杆菌的分离鉴定

从西藏地区牦牛自然病例中分离出5株大肠杆菌，通过形态观察、生化试验、血清学鉴定及动物致病性试验，表明5株分离菌是培养特性和生化特性基本一致、具有很强致病力、血清型不同的致病性大肠杆菌。     

禽源大肠杆菌的生物表型特性

对243株禽源大肠杆菌分离株进行血清耐受试验、菌毛化大肠杆菌血凝试验和温度敏感性血凝素试验.在这些分离株中,高度血清耐受、中等血清耐受、轻度血清耐受和血清敏感菌株分别占受试菌株的57.2%(139/243)、28.8%(70/243)、10.3%(25/243)和3.7%(9/243).在37℃细菌培养物与鸡红细胞凝集试验中,甘露糖敏感血凝(MSHA)和甘露糖耐受血凝(MRHA)菌株分别占受试菌株的64.6%(157/243)和5.8%(14/243);与豚鼠红细胞凝集试验中,MSHA和MRHA菌株分别占受试菌株的74.9%(182/243)和2.9%(7/243),其中与鸡红细胞凝集试验MSHA菌株中,MSHA阳性菌株占高致病株的69.5%(132/190),MRHA阳性菌株占低致病株的22.2%(2/9),两者差异极显著(p<0.01).在温度敏感性血凝素试验中,MRHA菌株为112株,占分离株的46.1%,其中O1、O2和O78血清型的高致病株占所在血清型分离株的83%～100%,而其它血清型的高致病株仅占57%左右,差异显著(p<0.05).结果显示禽源大肠杆菌的致病性与其血清耐受能力、鸡红细胞MSHA菌毛的表达和温度敏感性血凝素的表达呈一定的相关关系.     

牛源大肠杆菌对秀丽隐杆线虫的致病性研究

为建立牛源大肠杆菌-秀丽隐杆线虫致病模型，本研究从广西南宁、桂林、柳州等地区收集的牛病料中分离出13株大肠杆菌，继而对这些大肠杆菌进行血清学鉴定及小鼠、秀丽隐杆线虫的致病性试验。采用玻片凝集法鉴定大肠杆菌的O血清型，并将13株大肠杆菌培养液以3.0×10⁹ CFU/mL、0.2 mL/10 g体重给小鼠腹腔注射，同时分别喂食N2野生型秀丽隐杆线虫。结果显示，大肠杆菌的O血清型为O127、O126和O44，其中O126为优势血清型（4/13）。致病性结果显示，有11株大肠杆菌能使小鼠致死（致死率为40%~100%），2株大肠杆菌对小鼠没有致死性（致死率为0）。对小鼠有强致病性的大肠杆菌，对线虫的致死率也较高，死亡率在第3~6天最为显著，半数致死时间为3~4.5 d，最长存活时间为9 d；对小鼠不致死的两株大肠杆菌对线虫的致死率也较低，线虫死亡率下降趋势缓慢，半数致死时间为5~6 d，最长存活时间为10~11 d。肠道细菌计数结果显示，大肠杆菌在线虫体内的数量与时间呈线性关系，大肠杆菌不断破坏线虫的免疫系统，从而导致了线虫的死亡。本研究结果表明，大肠杆菌对线虫和小鼠的致病力试验结果一致，说明成功建立了牛源大肠杆菌-秀丽隐杆线虫致病模型，为牛病防治与临床用药提供了依据。     

河南省鸡源致病性大肠杆菌的分离鉴定

从河南省32个县市的典型大肠杆菌病病变的病、死鸡中,分离到致病性大肠杆菌93株,分别对各菌株进行致病性试验、生化鉴定和血清型鉴定。结果表明:本省致病性大肠杆菌的优势血清型为O78、O1、O2,分别占定型菌株的35.14%、18.92%、13.51%,菌株生化鉴定的结果与其致病力强弱和血清型无一定的相关性。     

兔病毒性出血症病毒西藏分离株毒力的测定

对一株兔病毒性出血症病毒(RHDV)西藏株进行血凝性、特异性、致病性及毒力鉴定。结果表明:此株RHDV血凝价高达10240以上;RHDV抗血清可特异性抑制该株病毒对人“O”型红细胞的凝集;RHDV的最小致死量为10-5/mL。说明此分离株是一株具有高致病力的RHDV强毒株。     

四川阿坝州牦牛源溶血性大肠杆菌血清型鉴定及毒力相关基因检测

为了解牦牛源溶血性大肠杆菌血清型及毒力相关基因,本研究从四川阿坝州采集的牦牛鼻腔棉拭子中分离鉴定溶血性大肠杆菌,并通过玻板凝集结合试管凝集试验鉴定其血清型,采用PCR方法检测大肠杆菌的4个溶血素基因及其它7个毒力相关基因。结果显示,从临床健康的牦牛鼻腔中分离鉴定出74株溶血性大肠杆菌,分离率为19.2%(74/386)。O血清型鉴定结果显示,74株牦牛源溶血性大肠杆菌中已确定O血清型的菌株有60株,共24种O血清型,其余14株未能定型。PCR检测与溶血素相关的4个基因携带率分别为96.0%(hly A)、86.5%(hly E)、14.9%(ehly)和2.7%(ehx);有4种溶血素基因组合,分别为hly A~+(96.0%),hly E~+(86.5%),hly A/hly E双阳性(80.9%),ehx/hly E双阳性(2.7%);其它毒力相关基因的检出率分别为93.2%(irp2)、93.2%(fyu A)和2.7%(stx2);LT、STa、STb和K99基因未检出。研究结果表明,溶血性大肠杆菌存在于临床健康牦牛鼻腔内,血清型复杂且无优势血清型,大肠杆菌溶血素相关基因和高致病性毒力岛相关基因携带率高。本研究首次对四川阿坝州牦牛源溶血性大肠杆菌的血清型和毒力相关基因进行了研究,提示在牦牛中存在溶血性大肠杆菌的潜在威胁。     

兔出血症病毒西藏野毒分离株的鉴定

对西藏农牧学院分离的一株兔出血症病毒(RHDV)西藏野毒进行血凝性、特异性和致病性进行鉴定。结果表明,此株RHDV野毒血凝价高达10240以上;RHDV抗血清可特异性抑制该株病毒对人“O”型红细胞的凝集;西藏株RHDV的最小致死量为10^-5／mL,是一株具有高致病力的RHDV强毒株。     

盐城地区鹅大肠杆菌的致病性试验

从盐城地区临诊上有典型鹅大肠杆菌病变的病、死鹅和鹅炕坊的死胚蛋中分离培养出256株大肠杆菌。为了解这些鹅大肠杆菌的致病性情况,用不同地区、不同血清型的51株分离株做致病性试验。所测分离株对1日龄鹅均有致病性。3个优势血清型分离株中,对1日龄鹅高度致病者占77.8%,中度致病者占16.7%。低度致病者占5.5%。试验表明我们所获得的大肠杆菌分离株均为致病性。     

致羔羊腹泻大肠杆菌血清型鉴定与耐药性分析

为了分析白城地区致羔羊腹泻大肠杆菌流行的血清型与耐药性,从采集的腹泻羔羊粪便样品127份中分离鉴定得到了56株为致病性大肠杆菌。采用玻板凝集法和K-B药敏纸片法分别检测56株致病性大肠杆菌分离株的血清型分布和耐药性情况。结果显示,56株致病性大肠杆菌分离株属于9个血清型,致病性大肠杆菌分离株以O119、O101、O24为流行的优势血清型;56株致病性大肠杆菌分离株且呈现多重耐药性,对头孢克肟、头孢曲松两种药物的耐药率最低,在12.4%~28.6%之间;对阿米卡星、新霉素、多西环素等7种药物的耐药率在50.0%~78.6%之间;对大观霉素、环丙沙星、氧氟沙星等5种药物的耐药率在82.1%~96.4%之间。     

盐城地区鹅大肠菌的致病性试验

从盐城地区临诊上有典型鹅大肠杆菌病变的病、死鹅和鹅炕坊的死胚蛋中分离培养出256株大肠杆菌。为了解这些鹅大肠杆菌的致病性情况,用不同地区、不同血清型的51株分离株做致病性试验。所测分离株对1日龄鹅均有致病性。3个优势血清型分离株中,对1日龄鹅高度致病者占77.8%,中度致病者占16.7%。低度致病者占5.5%。试验表明我们所获得的大肠杆菌分离株均为致病性。     

Differentiation of pathogenic and nonpathogenic Escherichia coli isolated from poultry

Twenty-one isolates of Escherichia coli recovered from chickens and turkeys were evaluated for pathogenicity in 1-week-old chicks. Fifteen produced coli-septicemia (pathogenic) and six were innocuous (nonpathogenic). Both pathogenic and nonpathogenic E. coli were tested for their ability to selectively absorb Congo red (CR) dye incorporated into agar medium. Eight of 15 pathogenic E. coli (somatic antigen types O1, O78, O11, O88, and OX9) absorbed the dye and produced red colonies (CR+) between 48 to 72 hours of incubation. All serotypes of E. coli with homologous somatic antigen O78 were CR+, while those of O2 antigen were CR- (white colonies). Five of six nonpathogenic E. coli also were CR+. In contrast to pathogenic E. coli, however, nonpathogenic isolates absorbed CR early, between 18 to 24 hours of incubation. Although CR dye binding did not correlate well with pathogenicity, it may be an identifiable property of some serotypes of E. coli.     

Virulence factors of Escherichia coli isolated from cows with acute mastitis

A total of 184 Escherichia coli isolates recovered from cows with acute mastitis were examined for recognized pathogenic mechanisms and virulence factors commonly found in pathogenic groups of E coli. A modification of the Eng procedure (for detecting complement deficiencies in serum) was used to test for resistance to different animal sera. The Sereny test (for invasiveness), infant mouse test (for heat-stable enterotoxin), and Y-1 adrenal tumor cell assay (for heat-labile enterotoxin) were used. Hemagglutination tests, using rabbit, sheep, and guinea pig RBC, were done with and without added mannose. All of the 184 isolates were serum resistant in all tested sera. None of the isolates was invasive. Only 1 isolate was positive for heat-stable enterotoxin and 2 cultures were positive for heat-labile enterotoxin. Multiple patterns of hemagglutination were observed. The majority of the isolates exhibited both mannose-sensitive and mannose-resistant hemagglutinins with guinea pig and rabbit RBC. A few strains were positive only in mannose-sensitive or mannose-resistant hemagglutination tests. A few strains were negative in all hemagglutination tests. Based on our results, E. coli from cows with acute mastitis lack the virulence factors commonly observed in other E coli groups associated with disease. Serum resistance was the only characteristic that could be related to virulence.     

仔猪腹泻致病性大肠杆菌分型鉴定及耐药性分析

为了解贵州省规模化养猪场腹泻仔猪致病性大肠杆菌流行情况及耐药性变化,本研究运用凝集试验、PCR和药敏纸片琼脂扩散法等方法对分离的78株致病性大肠杆菌进行血清型、毒力基因及耐药性分析。结果显示,78株致病性大肠杆菌以O138、O87血清型为主,占定型菌株的60.8%;其中62株致病性大肠杆菌检出毒力基因,检出率为79.5%,可分为8种毒力基因类型,分属肠致病性大肠杆菌（EPEC）、肠产毒性大肠杆菌（ETEC）和肠聚集性大肠杆菌（EAEC）,毒力基因eaeA、elt和escV检出率较高,分别为38.5%、28.2%和21.8%;分离到的致病性大肠杆菌对β-内酰胺类药物高度耐药,均为多重耐药株,耐药种类可达8种以上。结果表明,当前贵州省规模化养猪场腹泻仔猪致病性大肠杆菌的毒力基因检出率较高且基因型复杂,耐药性严重。本试验结果可为规模化养猪场防控仔猪腹泻提供基础资料及理论依据。     

中药与抗菌药物联用对猪源大肠杆菌耐药性的抑制作用

为了探讨中药与抗菌药物联用对大肠杆菌耐药性的作用效果，本研究对河南部分地区采集的样品（50份）进行分离鉴定、生化试验及致病性试验，对分离鉴定后的致病性猪大肠杆菌选用12种中药采用K-B法进行耐药性检测，将筛选出来的中药与抗生素进行中西联用对致病性大肠杆菌做体外抑菌试验，并分析中西药联用对大肠杆菌的抑制作用。结果显示，采集的50份样品有23株菌符合大肠杆菌的分离培养特性和生化特性，且23株菌均为致病性大肠杆菌；通过耐药性检测，23株试验菌株对测试的中药均有不同程度的耐药性，其中试验菌株对甘草耐药率最高（82.6%），其次为生地（78.2%），而对黄柏（17.3%）和白头翁（21.7%）耐药性较低，具有一定的敏感性；体外抑菌试验结果发现，中药与抗生素联用均有不同程度的抑菌效果，其中黄柏、白头翁与抗菌药物联用的抑菌效果最明显。以上结果说明中药与抗菌药物联用不仅可以抑制大肠杆菌的耐药性，还可以延缓大肠杆菌耐药性的产生。     

Escherichia coli challenge in chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex.

Relative sensitivity to Escherichia coli challenge was evaluated in white leg-horn chickens that had been selected for high antibody (HA) or low antibody (LA) response and that differed in haplotypes at the major histocompatibility complex (MHC). Assessments were made of relative body-weight change and of heart and air-sac lesions after inoculation of 10(6), 10(5), or 10(4) E. coli via the posterior thoracic air sac. As has previously been reported, chicks from line HA were more sensitive to E. coli than those from line LA. Lesion scores were 1.58 +/- 0.12 in line HA and 1.02 +/- 0.12 in line LA (mean +/- S.E.), and ranged from 0.99 +/- 0.14 with the lowest dose of E. coli to 1.79 +/- 0.15 for the highest dose. Relative body-weight change to 72 hours after inoculation was greater in line LA (7.5 +/- 0.5) than in line HA (4.4 +/- 0.8). There was no apparent resistance or susceptibility conferred to chickens in either the HA or LA genetic background as a result of haplotypes present at the MHC.     

规模化猪场大肠杆菌的耐药性监测及血清流行病学调查

为了调查猪致病性大肠杆菌的耐药性及流行血清型 ,从湖北、河南、江西、安徽、浙江等省的 33个猪场采集 32 1份仔猪黄、白痢病料进行细菌的分离和生化鉴定 ,结果分离到大肠杆菌 30 2株 ,其中致病性大肠杆菌 2 76株。对 112株致病性大肠杆菌进行了 15种抗生素敏感性试验 ,发现分离菌株对 15种药物均有不同程度的耐药性 :青霉素 G对其完全没有抑制作用 ;先锋霉素 抑制作用最强 (97.3% ) ,其次为呋喃妥因 (78.6 % )、痢特灵 (71.4 % )、环丙沙星(6 8.8% )、诺氟沙星 (6 5 .1% )。 112株菌中 ,有 4 7种耐药谱型 ,多数为 6耐以上的菌株 (80株 ) ,占供试菌株的 71.4 %。应用微量平板凝集试验 ,对分离的 2 76株致病菌进行了血清型鉴定 ,鉴定共有 72种血清型 ,其中优势血清型 10种 ,占能定型分离致病菌株的 5 3.7%。     

Hemagglutination, hydrophobicity, enterotoxigenicity, and drug-resistance characteristics of avian Escherichia coli

A total of 35 Escherichia coli isolates obtained from necropsy materials of hens with septicemia in the Konya region of Turkey were examined for hemagglutination (HA), cell-surface hydrophobicity, enterotoxigenicity, and drug resistance. HA tests were performed on live cultures with human (group A), bovine, avian (chicken), and guinea pig erythrocytes with and without mannose. Nine HA patterns were observed. Of the 35 isolates, 62.8% exhibited mannose sensitive hemagglutination (MSHA), 8.6% exhibited mannose resistant hemagglutination (MRHA), and 28.6% did not hemagglutinate. Of the isolates, 85.7% were hydrophobic by a salt aggregation test (SAT). Only three isolates were enterotoxigenic by a suckling mouse assay. The majority of the isolates were resistant to chloramphenicol, tetracycline, streptomycin, ampicillin, erythromycin, and trimethoprim + sulfamethoxazole but were highly sensitive to gentamicin and nalidixic acid.     

Prediction of chicken embryo lethality with the avian Escherichia coli traits complement resistance,colicin V production,and presence of the increased serum survival gene cluster (iss)

Differentiating between virulent and avirulent avian Escherichia coli isolates continues to be a problem for poultry diagnostic laboratories and the study of colibacillosis in poultry. The ability of a laboratory to conduct one simple test that correlates with virulence would simplify studies in these areas; however, previous studies have not enabled researchers to establish such a test. In this study, the occurrence of certain phenotypic and genotypic traits purported to contribute to avian E. coli virulence in 20 avian E. coli isolates was correlated with the results of embryo challenge studies. This analysis was undertaken in an effort to determine which trait(s) best identified each avian E. coli isolate as virulent or avirulent. Traits selected were complement resistance, production of colicin V (ColV), motility, type F1 pili expression, presence of the temperature-sensitive hemagglutinin gene (tsh), and presence of the increased serum survival genetic locus (iss). ColV production, complement resistance, and presence of the iss genetic element were the three traits most highly correlated with high embryo lethality. A logistic regression model was used to predict the embryo lethality results on the basis of the most frequent isolate characteristics. Results indicate that ColV, complement resistance, and if are significant predictor variables for the percentage of embryo lethality resulting from challenge with a specific avian E. coli isolate. However, no single trait has the ability to predict virulent isolates 100% of the time. Such results suggest the possibility that the embryo lethality assay may prove to be the one test needed to determine if an avian E. coli isolate is virulent.     

Antimicrobial susceptibility and molecular characterization of avian pathogenic Escherichia coli isolates

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.     

藏香猪源大肠埃希菌致病性和血清型检测及药敏试验

为了解四川省藏香猪源大肠埃希菌致病性、血清型及耐药性情况,从四川省藏香猪养殖场中无菌采集腹泻仔猪肝脏、肛拭子及粪便等组织病料253份中,分离得到155株大肠埃希菌。采用人工感染小鼠致病性试验、玻板凝集试验和KB药敏纸片法分别测定155株大肠埃希菌分离菌株的致病性、血清型及耐药性。结果显示,小鼠致病性试验表明155株分离菌中120株有致病性;玻板凝集试验表明120株致病性大肠埃希菌分离株属于14个血清型,以O111、O147、O109和O119为主要流行的优势血清型;耐药性试验表明120株致病性大肠埃希菌分离株对阿莫西林、氨苄西林、新霉素、磺胺间甲氧嘧啶4种药物耐药较严重,耐药率在94.2%~98.3%之间,对庆大霉素、氟苯尼考、多西环素等6种药物耐药率在44.2%~85.0%之间,对其他药物耐药率在15.0%~37.5%之间。说明该地区藏香猪源致病性大肠埃希菌血清型呈多样性分布,耐药性严重。