规模化鹅场致病性大肠杆菌的分离鉴定及耐药性检测

为有效防治鹅大肠杆菌病并分析其耐药性,无菌采集疑似大肠杆菌感染鹅的肝脏、脾脏等组织,进行细菌分离培养、生化鉴定、PCR鉴定、16S rRNA序列比对。结果表明,所分离的细菌为大肠杆菌。通过血清凝集试验,鉴定其主要血清型为O88、O171、O59、O27。应用小鼠对4种血清型代表菌株进行致病性试验,结果分离的菌株致小鼠发病率为92.5%,死亡率为87.5%,表现腹腔有纤维素性渗出物,肝淤血肿大且表面有纤维素性伪膜等病理变化。对代表菌株采用微量肉汤稀释法进行药敏试验,结果显示,分离株对甲氧苄啶、磺胺异恶唑敏感,对黏杆菌素、美罗塔南等11种临床常用药物高度耐药。研究表明,从辽宁省黑山县分离的鹅大肠杆菌具有较强的致病性和较高的耐药性。     

细菌性腹泻仔猪大肠杆菌病流行病学调查

仔猪大肠杆菌病是哺乳仔猪的多发病,严重影响着养猪业的发展.本文调查了50多个母猪繁殖场100多份病料均分离到大肠杆菌,分离率达100%.通过生化试验、药敏试验及血清型鉴定,分离菌株分属于5个血清型,即O2、O5、O8、O101、O4.其中O2型为本次分离的优势血清型,占分离菌株的50%.分离菌株均为耐药菌株,且临床症状典型,这表明大肠杆菌易产生耐药性,其耐药性能转移,菌株易变异的特点.本次调查基本摸清了云南省仔猪大肠杆菌病流行的病原血清型.     

细菌性腹泻仔猪大肠杆菌病流行病学调查

仔猪大肠杆菌病是哺乳仔猪的多发病,严重影响着养猪业的发展.本文调查了50多个母猪繁殖场100多份病料均分离到大肠杆菌,分离率达100%.通过生化试验、药敏试验及血清型鉴定,分离菌株分属于5个血清型,即O2、O5、O8、O101、O4.其中O2型为本次分离的优势血清型,占分离菌株的50%.分离菌株均为耐药菌株,且临床症状典型,这表明大肠杆菌易产生耐药性,其耐药性能转移,菌株易变异的特点.本次调查基本摸清了云南省仔猪大肠杆菌病流行的病原血清型.     

肉鸽大肠杆菌的分离鉴定与耐药性的研究

以南京市郊某肉鸽场病鸽为样本进行细菌分离鉴定,研究肉鸽大肠杆菌的耐药性。从病死鸽体内分离到14株大肠杆菌,鉴定出4种血清型,分别是O2、O18、O78、O101,其中O2型8株,为主要血清型,占血清型总数的66.67%。将分离到的菌株接种20～25日龄雏鸽进行动物回归试验,死亡率达85.17%,说明该分离菌株对雏鸽具有较强的致病性。对分离菌株进行药敏试验,结果表明,14株大肠杆菌对庆大霉素、卡那霉素、头孢拉定3种药物敏感率达100%,对环丙沙星、阿米卡星等13种药物均产生不同程度的耐药,对强力霉素和新霉素2种药物完全耐药。     

徐州地区猪源大肠杆菌血清型调查和耐药检测

旨在研究徐州地区猪源大肠杆菌血清型分布及其耐药性。采集徐州周边猪场病料和样本117份,经分离纯化、PCR鉴定得到102株大肠杆菌。经血清型鉴定,致病性试验和耐药检测,O抗原血清型检出79株,分属18个血清型,其中O15、 O45、O78、O138 4种血清型分别占已定型血清菌株的17.7%、11.4%、13.9%和12.6%,合计占55.6%,为徐州周边地区优势血清型;强毒株25株,占O抗原菌株的31.6%,主要分布在O45、O15、O138 3种血清型;耐药率50%以上的药物多达17种,占到了临床常用药物85%,其中阿莫西林、氨苄西林钠、强力霉素、氟苯尼考、恩诺沙星、乳酸环丙沙星临床耐药尤其严重,高达80%以上。多重耐药菌株至少耐药12种以上,耐药谱型多达8种。研究表明,徐州地区猪源大肠杆菌检出率高,血清型复杂且致病性强,多重耐药现象严重,应结合本地菌株流行特点进行大肠杆菌病的防治。     

仔猪大肠杆菌病流行病学调查

仔猪大肠杆菌病是哺乳仔猪的多发病,严重影响着养猪业的发展。本文调查了50多个母猪繁殖场100多份病料均分离到大肠杆菌,分离率达100%。通过生化试验、药敏试验及血清型鉴定,分离菌株分属于5个血清型,即O2、O5、O8、O101、O4。其中O2型为本次分离的优势血清型,占分离菌株的50%。分离菌株均为耐药菌株,且临床症状典型,这表明大肠杆菌易产生耐药性,其耐药性能转移,菌株易变异的特点。本次调查基本摸清了云南省仔猪大肠杆菌病流行的病原血清型。     

鸡源致病性大肠杆菌血清型鉴定及耐药性分析

为了了解山东、河北和河南等省部分地区养殖场鸡源致病性大肠杆菌的血清型及耐药性,试验采用细菌分离和生化鉴定方法对鸡大肠杆菌进行分离和鉴定,通过动物试验确定分离大肠杆菌的致病性,应用血清学方法和药敏试验对致病性大肠杆菌的血清型及耐药性进行研究。结果表明:分离鉴定的119株大肠杆菌中致病性菌株有110株,其中92株致病性菌株能够定型,分别属于15个血清型,有5株出现交叉凝集,O14、O35、O1、O2、O78、O88为优势血清型;分离鉴定的致病性大肠杆菌对环丙沙星、头孢噻肟、头孢哌酮等最敏感,对林可霉素、头孢克肟、卡那霉素、庆大霉素、红霉素的耐药率达60%以上。说明分离的致病性大肠杆菌血清型存在复杂性,对大部分临床常用药物产生了不同程度的耐药。     

三株具有磷霉素抗性禽源大肠杆菌的分离鉴定及其MIC测定

本研究从疑似大肠杆菌感染的病死禽分离3株细菌JE1、IF7和CD11,糖发酵试验、IMViC试验、三糖铁试验等生化试验结果显示符合大肠杆菌生化鉴定指标,判定为大肠杆菌.玻板凝集和试管凝集试验鉴定显示3个分离菌株的血清型分另别为O87、O78、O9.药敏试验结果显示3个分离菌株均具有很强的耐药性,分别对试验的19种药物中的16、10、12种药物具有抵抗力,这3个菌株对兽医临床以前较少使用的磷霉素均表现出了不同程度的耐药性.对磷霉素的MIC测定结果显示,JE1和CD11分别为125 mg/mL和51.2 mg/mL,远高于IF7的1.28 mg/mL.研究结果提示,目前兽医临床已经出现了磷霉素耐药菌株,在药物使用过程中要注意合理用药,防止这种耐药性在细菌中传递.     

泰安地区鸡源致病性大肠杆菌流行病学调查与耐药性分析

正本调查对鸡场采集的疑似鸡大肠杆菌病例的相关病料进行大肠杆菌的分离鉴定,共分离鉴定出14株鸡源大肠杆菌,以微量平板凝集试验鉴定分离菌株的O抗原血清型,分别属于O78、O2和O1等3个血清型,其中O78(6/14)、O2(6/14)为主要流行血清型,占分离菌株总数的85.71%。选取了20种常用治疗肠杆菌病的抗生素对14株鸡源大肠杆菌分离株进行药敏试验,对14株大肠杆菌     

仔猪水肿病病原的分离鉴定及药敏试验

从四川省凉山州盐源县梅雨镇某养猪场采集10份疑似仔猪水肿病的病料。经过细菌分离培养、形态学检查、生化鉴定和致病性试验,分离到8株致病性大肠杆菌。平板凝集试验结果表明,有O138、O139和O141共3种血清型,以O139血清型最多。对这些致病性菌株进行了9种药物的药敏性测定,结果表明：9种药物对所有分离株均有一定的抑菌效果,且不同血清型的大肠杆菌分离株的药物敏感性无显著差异。     

黑龙江 家兔大肠埃希氏菌污染情况的调查

在自１９９６年至１９９９年的４年中，共从腹泻兔群中分离出１５株致病性大肠杆菌，血清型鉴定表示，这１５株大肠杆菌分属于７个血清型，其中以０６８的频率最高，达２０．０％，其次是０７和０１３０，达１３．３％。用试管凝集试验对１９９６年前自黑龙江省部分兔群中采集的血清进行检查，发现以０１３和０７血清型的污染率最高，分别达４８．４％和２４．３％。结果表明，近年来血清型的菌株流行为主，变为最近两年的以０６８等     

A longitudinal study of Shiga-toxigenic Escherichia coli (STEC) prevalence in three Australian diary herds

Over a 12 month period, 588 cattle faecal samples and 147 farm environmental samples from three dairy farms in southeast Queensland were examined for the presence of Shiga-toxigenic Escherichia coli (STEC). Samples were screened for Shiga toxin gene (stx) using PCR. Samples positive for stx were filtered onto hydrophobic grid membrane filters and STEC identified and isolated using colony hybridisation with a stx-specific DNA probe. Serotyping was performed to identify serogroups commonly associated with human infection or enterohaemorrhagic Escherichia coli (EHEC). Shiga-toxigenic Escherichia coli were isolated from 16.7% of cattle faecal samples and 4.1% of environmental samples. Of cattle STEC isolates, 10.2% serotyped as E. coli O26:H11 and 11.2% serotyped as E. coli O157:H7, and the E. coli O26:H11 and E. coli O157:H7 prevalences in the cattle samples were 1.7 and 1.9%, respectively. Prevalences for STEC and EHEC in dairy cattle faeces were similar to those derived in surveys within the northern and southern hemispheres. Calves at weaning were identified as the cattle group most likely to be shedding STEC, E. coli O26 or E. coli O157. In concurrence with previous studies, it appears that cattle, and in particular 1-14-week-old weanling calves, are the primary reservoir for STEC and EHEC on the dairy farm.     

临床型乳房炎奶牛致病性大肠杆菌血清型研究

为有效防治乳房炎以及进一步研究致病性大肠杆菌的危害性,本研究对呼和浩特市某奶牛场16头患临床型乳房炎的奶牛进行采样分析了致病性大肠杆菌。结果表明,在16份粪样、乳样中致病性大肠杆菌的检出率分别为100%和68.75%,血样中未检出致病性大肠杆菌。经动物试验表明,所检出的致病菌均有强致病力。在血清型鉴定中,粪样中分离鉴定出致病性大肠杆菌为O51、O55、O127、O7、O91、O101、O112、O92、O142血清型较多;乳样中分离出的致病性大肠杆菌为O55、O101、O112、O134、O51、O53、O78、O91、O126、O128、O158血清型较多。且粪样中分离出的致病性大肠杆菌42种血清型,乳样中分离出的致病性大肠杆菌33种血清型中具有25种血清型相同,分别为:O8、O35、O44、O51、O55、O61、O62、O65、O69、O80、O91、O92、O95、O96、O98、O99、O100、O101、O112、O120、O127、O134、O142、O153、O158。因此可见,作为环境性病原菌,大肠杆菌侵入乳房而引发了奶牛乳房炎。     

Escherichia coli O157 in Dutch domesticated rabbits

Enterohaemorrhagic Escherichia coli (EHEC) has been detected in both wild and domesticated rabbits in other countries. The aim of this study was to determine whether the most pathogenic E. coli serotype, O157:H7, occurs in the Dutch domesticated rabbit population and thus could form a public health risk. To this end, faecal samples were collected from rabbits from two rabbit farms and 741 rabbits of different breeds and origin and analysed for E. coli O157:H7, using a combination of enrichment, immunomagnetic separation, selective culture, and PCR. E. coli O157:H7 was not detected in any of the samples. The results indicate that Dutch domesticated rabbits probably do not play a role in the infection of humans with E. coli O157:H7.     

Escherichia coli in the rumen and colon of slaughter cattle,with particular reference to E. coli O157

The distribution of Escherichia coli O157 and of total E. coli was surveyed in the digestive tract of cattle under 30 months of age, slaughtered between August 1999 and May 2000 in three abattoirs in southern England. Samples were taken from the dorsal and ventral rumen wall, the rumen contents, the colon wall and colon contents, and from faeces or caudal rectal contents. Gut wall samples were processed by vortex-mixer to release loosely adherent bacteria, and by Stomacher to release firmly attached bacteria. E. coli O157 was detected by immunomagnetic separation followed by growth on selective culture media. The numbers of E. coli were higher in the colon than the rumen, and most were located in the digesta phase, rather than associated with the gut wall. The number of E. coli found in the gut and in faeces decreased during the winter months. E. coli O157 was detected more frequently in the colon than in the rumen, but the majority of detections(7/8) were in samples of rumen wall.     

Sensitivity of methods for the isolation of Escherichia coli O157 from naturally infected bovine faeces

At present, no standard protocol has been described to detect the presence of Escherichia coli O157 in cattle faeces. Therefore, the sensitivity of 26 different isolation methods was determined in order to recommend a method of choice. Faeces samples from 17 different beef cattle at a farm previously found positive for E. coli O157 were subdivided into a total of 40 samples. It was not known whether the 17 cattle shed E. coli O157 at the time of sampling. At another farm where cattle have been found negative for E. coli O157 on different occasions, five faeces samples were collected. Two methods yielded the highest sensitivity (74%): 6h enrichment in modified tryptone soya broth supplemented with novobiocin (mTSBn) followed by an immunomagnetic separation (IMS) with (i) Dynal beads or (ii) Captivate beads and selective plating on Rainbow agar (RA) plates. Enrichment for 6h was significantly better than 24h enrichment. Only after 24h, buffered peptone water (BPw) was significantly better than mTSBn. A sensitivity of 82% was obtained only when the two most sensitive tests were done simultaneously. Because none of the tests gave 100% sensitivity, it can be concluded that isolation rates of E. coli O157 from bovine faeces using only one of the tested procedures results in an underestimation of the incidence of E. coli O157 in cattle. Performing more than one test on the samples must be considered.     

Antibiotic resistance in Escherichia coli O157 isolated between 1998 and 2003 in The Netherlands

Little is known about the antibiotic resistance of E. coli O157 in The Netherlands. In this study, 218 human and 247 nonhuman samples, isolated between 1998 and 2003, were tested for antimicrobial resistance. About 5.5% of E. coli O157 isolates from human samples were resistant, as were about 4.00% of E. coli O157 isolates from non-human samples. These figures are lower than those reported in the literature. Class I integrons were found in six multiresistant isolates. This type of integron is also found in commensal E. coli in food animals and Salmonella spp. One of the integron-positive isolates contained the beta-lactamase bla(TEM-1b) and an extended spectrum beta-lactamase (ESBL), which belongs to the group 2 CTX-M enzymes. This is the first report of these beta-lactamases in E. coli O157 isolated from chicken.     

Testing of a Chemiluminescence Enzyme Immunoassay for selective detection of E. Coli O157 from ground beef samples

The aim of this study was to evaluate a Chemiluminescence Enzyme Immunoassay (CLIA) developed for the detection of E. coli O157:H7, using different E. coli O157 serotypes. The sensitivity and specificity of the kit were determined from the tenfold dilutions of the 24-hour broth cultures of the test strains. According to the results obtained in this trial, the sensitivity of the kit is 10(3)-10(4) cells ml-1, and it is specific for E. coli O157. Twenty-five g ground raw beef samples were prepared and inoculated with E. coli O157:H7 at different CFU g-1. The samples were incubated in 225 ml of modified E. coli broth with novobiocin (mEC + n) at 42 degrees C for 4 h and the immunoassays were performed following the instructions of the manufacturer. According to the results obtained by the CLIA test 10(1)-10(2) E. coli O157 g-1 can be detected from the sample. So this kit seems to be suitable for screening the samples before selective cultivation of E. coli O157:H7.     

Feeding supplemental dried distiller's grains increases faecal shedding of Escherichia coli O157 in experimentally inoculated calves

Escherichia coli O157 is an important foodborne pathogen and asymptomatic cattle serve as major reservoirs for human infection. We have shown a positive association between feeding distiller's grains and E. coli O157 prevalence in feedlot cattle. The objective of this study was to determine the effect of feeding dried distiller's grain (DDG) on faecal shedding of E. coli O157 in calves experimentally inoculated with E. coli O157. Holstein calves (five per treatment group), fed steam-flaked corn-based high-grain diets supplemented with 0% (control) or 25% DDG, were orally inoculated with a five-strain mixture (6 x 10(9) CFU/calf) of nalidixic acid-resistant (NalR) E. coli O157. Faecal samples were taken three times per week for 6 weeks to determine the prevalence and concentration of Nal E. coli O157. At the end of the study (day 43), calves were euthanized and necropsied. Ruminal, caecum, colon, and rectal contents, and rectoanal mucosal swab (RAMS) samples were collected at necropsy to determine NalR E. coli O157 concentration. There was a trend for an interaction between treatment and faecal sampling day. The concentration of NalR E. coli O157 in the faeces was significantly higher in faecal samples from calves fed DDG compared with control calves on days 35, 37, 39 and 42. At necropsy, the concentration of NalR E. coli O157 was higher in the caecum (P = 0.01), colon (P = 0.03) and rectum (P = 0.01) from calves fed DDG compared with control animals. The number of sites at necropsy positive for NalR E. coli O157 was higher in calves fed DDG compared with calves in the control treatment (P < 0.001). Our results indicate that E. coli O157 gut persistence and faecal prevalence increased in calves fed DDG, which potentially have important implications for food safety.     

Occurrence and virulence patterns of E. coli O26, O103, O111 and O145 in slaughter cattle

The study attempted to investigate the occurrence of non-O157 E. coli serogroups O26, O103, O111 and O145 in cattle at slaughter and to determine the virulence potential of these isolates. A total of 399 fecal samples were analyzed by selective plating and E. coli isolates were characterized by polymerase chain reaction (PCR) for the genes vtx1, vtx2, eae and EHEC hlyA. Immunomagnetic separation (IMS) is required to increase the efficiency of the isolation procedure. E. coli O26, O103, O111 and O145 were recovered from 24 (6%) fecal samples. E. coli O26 and O103 seemed to be more abundant in slaughter cattle than E. coli O111 and O145. Sixteen out of the 24 isolates harbored vtx genes. All vtx-positive isolates harbored one or more additional virulence factors. Six out of the 8 vtx-negative isolates harbored eae and/or EHEC hlyA, whereas 2 strains harbored none of the tested virulence genes.