PCR和核酸探针检测猪源沙门氏菌四环素耐药基因tetC的研究

对沙门氏菌的四环素耐药性进行了检测，结果表明，沙门氏菌对四环素类抗生素产生了广泛的耐药性，耐药率达100％，对其四环素耐药基因tetC进行了扩增，结果获得以质粒为模板的特异性产物，与药敏试验结果阳性符合率75％，具有较高的检出率。用光生物素对PcR产物进行标记，制备核酸探针，采用菌落原位杂交的方法对沙门氏菌进行检测，结果表明13株阳性、3株阴性，杂交结果与PCR结果阳性符合率为93．75％，具有较高的特异性。通过条件的优化，建立的四环素耐药基因tetC的PCR和核酸探针检测技术，为四环素耐药性的分子流行病学监测提供了有效的途径。     

水貂沙门氏菌的分离鉴定及药物敏感性分析

为指导临床合理用药并为治疗患病水貂提供依据,本试验对山东省某水貂养殖场送检的7只疑似患有沙门氏菌病的病死水貂的肝脏和脾脏样品进行细菌分离鉴定及药物敏感性分析,通过分离纯化方法从样品中分离菌株,并采用革兰氏染色、生化鉴定和PCR方法对分离菌株进行鉴定。运用K-B药敏法检测菌株对临床常用药物的敏感性,并通过PCR方法检测菌株耐药基因及Ⅰ类整合子的携带情况。结果显示,本试验分离得到的7株菌均为革兰氏阴性、短小的杆菌;生化反应检测显示,分离菌株葡萄糖、麦芽糖、甘露醇、MR试验、枸橼酸盐、硫化氢试验均表现为阳性,初步鉴定分离菌株为沙门氏菌;PCR产物测序结果进一步表明7株分离菌均为沙门氏菌;药敏试验结果显示,7株沙门氏菌对头孢曲松、左氧氟沙星、氟苯尼考和多黏菌素较敏感,对氨基糖苷类药物、四环素和氨苄西林表现为耐药;耐药基因检测结果显示,7株沙门氏菌共检测出8种耐药基因blaTEM-1、blaCTX-M-1G、aadA1、aac(3′)-Ⅳ、aac(3′)-Ⅱc、aph(4′)-Ⅰa、aph(3′)-Ⅶ和oqxAB,以及基因盒为aadA1、arr-3-aacA4和blaPSE-1的Ⅰ类整合子。综上可知,本试验在送检的7只患病水貂的肝脏和脾脏样品中分离到7株沙门氏菌,分离菌株均为耐药菌株,且主要表现为多重耐药现象;耐药基因呈多样性,且存在位于质粒上的耐药基因扩大了耐药基因的传播范围,增加了细菌的耐药性,为临床用药治疗带来困难。     

水貂沙门氏菌的分离鉴定及药物敏感性分析

为指导临床合理用药并为治疗患病水貂提供依据,本试验对山东省某水貂养殖场送检的7只疑似患有沙门氏菌病的病死水貂的肝脏和脾脏样品进行细菌分离鉴定及药物敏感性分析,通过分离纯化方法从样品中分离菌株,并采用革兰氏染色、生化鉴定和PCR方法对分离菌株进行鉴定。运用K-B药敏法检测菌株对临床常用药物的敏感性,并通过PCR方法检测菌株耐药基因及Ⅰ类整合子的携带情况。结果显示,本试验分离得到的7株菌均为革兰氏阴性、短小的杆菌;生化反应检测显示,分离菌株葡萄糖、麦芽糖、甘露醇、MR试验、枸橼酸盐、硫化氢试验均表现为阳性,初步鉴定分离菌株为沙门氏菌;PCR产物测序结果进一步表明7株分离菌均为沙门氏菌;药敏试验结果显示,7株沙门氏菌对头孢曲松、左氧氟沙星、氟苯尼考和多黏菌素较敏感,对氨基糖苷类药物、四环素和氨苄西林表现为耐药;耐药基因检测结果显示,7株沙门氏菌共检测出8种耐药基因blaTEM-1、blaCTX-M-1G、aadA1、aac(3′)-Ⅳ、aac(3′)-Ⅱc、aph(4′)-Ⅰa、aph(3′)-Ⅶ和oqxAB,以及基因盒为aadA1、arr-3-aacA4和blaPSE-1的Ⅰ类整合子。综上可知,本试验在送检的7只患病水貂的肝脏和脾脏样品中分离到7株沙门氏菌,分离菌株均为耐药菌株,且主要表现为多重耐药现象;耐药基因呈多样性,且存在位于质粒上的耐药基因扩大了耐药基因的传播范围,增加了细菌的耐药性,为临床用药治疗带来困难。     

番鸭源鸭疫里默氏杆菌的分离鉴定及其耐药性分析

为了解番鸭源鸭疫里默氏杆菌的耐药性,本研究对疑似鸭疫里默氏杆菌感染的发病番鸭进行细菌分离培养、革兰氏染色镜检、病鸭病原检测、生化试验、16S rRNA序列分析、PCR鉴定、药敏试验和耐药基因检测。细菌分离结果显示,分离菌在鲜血琼脂培养基上长出表面光滑、边缘整齐、有光泽、半透明的奶油状针尖大小菌落;革兰氏染色镜检呈革兰氏阴性短小杆菌,命名为GZQN201907。GZQN201907生化试验中尿素反应阳性,葡萄糖、麦芽糖、乳糖等生化反应呈阴性。其16S rRNA系统进化树与鸭疫里默氏杆菌处于同一分支;并且分离菌鸭疫里默氏杆菌OmpA基因PCR鉴定结果为阳性。其对头孢呋辛、红霉素、头孢他啶等18种抗菌药耐药,对羧苄西林和环丙沙星中度敏感,对新霉素和复方新诺明敏感。而耐药基因能检测出β-内酰胺类耐药基因VIM、TEM,四环素类耐药基因tetB,大环内酯类耐药基因ermB和ermF。药敏试验与耐药基因检测结果说明,GZQN201907对β-内酰胺类、四环素类、大环内酯类3类药物的耐药表型和耐药基因检测结果一致。动物回归试验中接种GZQN201907的雏鸭在72 h内全部死亡,而对照组雏鸭未出现任何症状,说明GZQN201907对雏鸭有致病力。试验成功分离到1株番鸭源鸭疫里默氏杆菌,为鸭疫里默氏杆菌病的防治奠定基础。     

上海市活禽交易市场鸡群沙门氏菌的分离鉴定与耐药性分析

为了解上海市活禽交易市场鸡群中沙门氏菌的携带情况,我们于2016年对市区的8个活禽交易场所进行了调查。共采集肛门拭子500份,分离培养沙门氏菌,运用诊断血清、VITEK 2Compact和VITEK MS分别对分离菌株进行血清型、生化和质谱鉴定,使用PCR和药敏板分别对分离菌株的耐药基因和耐药性进行检测。结果显示:从500份肛门拭子中分离鉴定出28株沙门氏菌,分离率为5.6%,以肠炎沙门氏菌、印第安纳沙门氏菌和鼠伤寒沙门氏菌为主,说明在市场交易环节应当加强对沙门氏菌的防控;耐药基因检出率较低,仅有喹诺酮类和磺胺类抗生素耐药基因有检出,分别为21.4%和7.1%,I类整合酶基因检出率达到28.6%;从耐药性检测结果看,分离菌株对磺胺类抗生素、头孢噻肟和庆大霉素的耐药率达到50%以上,对环丙沙星、美罗培南、萘啶酸、头孢他啶和氨苄西林的耐药率在40%以下,这些药可用于鸡群沙门氏菌的防控;耐药基因和耐药性之间无明显相关性。     

鸡源大肠杆菌的分离鉴定及耐药特性分析

为了分析鸡源大肠杆菌的耐药特性,对昆明地区3家养鸡场送检的疑似大肠杆菌病的200只鸡进行了剖检,从病鸡肝脏分离出77株病原菌,经常规生化特性鉴定和PCR分子鉴定,确定77株分离株均为大肠杆菌,利用PCR方法对分离株的耐药基因和耐药性进行了研究,同时进行了药敏试验。结果表明:在22种耐药基因中,除β-内酰胺类的OXA、SHV基因未检出外,有14种耐药基因的检出率为100%,其他耐药基因检出率在82.1%以上;在药敏试验中,分离株除对左氧氟沙星的耐药性较低外(48.1%),对试验所用其他药物均具有很强的耐药性(96.1%以上)。说明分离株对抗生素的耐药性更加严重了。     

兔源金黄色葡萄球菌的耐药性及耐药基因分析

为了解四川地区规模化兔场金黄色葡萄球菌(S.aureus)的耐药情况,本研究从四川地区部分规模化兔场共分离鉴定出41株S.aureus,采用纸片扩散法对分离株进行了耐药表型鉴定,同时采用PCR方法对相关耐药基因进行了检测。药敏试验结果显示:分离株对β-内酰胺类、氨基糖苷类、四环素类和大环内脂类药物的耐药率分别为87.80%、97.56%、78.05%和56.10%,对多肽类、喹诺酮类及磺胺类耐药率较低。耐药基因检测结果显示:所有分离株均检测到耐药基因,并且29株分离株具有多重耐药性,其中耐药基因mec A、tet、erm、aac(6')/aph(2')、ant(4',4')及aph(3')-III的检出率分别为75.61%、70.73%、46.34%、92.68%、80.49%及53.66%。结合耐药表型与耐药基因结果分析显示兔源S.aureus的耐药表型与耐药基因检出率基本呈正相关。本研究通过检测41株兔源S.aureus对临床常用抗生素的耐药性及相关耐药基因,初步掌握了四川地区规模化兔场S.aureus的耐药情况,为该地区规模化兔场预防及治疗葡萄球菌病临床合理用药提供了依据。     

北京地区鸭源大肠杆菌耐药表型和Tet aac耐药基因的检测

从北京地区肉鸭养殖场的发病鸭样本中分离鉴定出30株大肠杆菌,并进行药敏试验和四环素耐药基因Tet和氨基糖苷类耐药基因aac的PCR检测,初步探究肉鸭源大肠杆菌的耐药情况。通过药敏试验,发现鸭源大肠杆菌对青霉素类、四环素类和氨基糖苷类抗生素均表现出耐药性,甚至出现多重耐药。同时对其耐药基因进行PCR检测发现,5种四环素耐药基因Tet的检出率为96. 7%。其中Tet(B)阳性率最高,为63. 3%,Tet(A)、Tet(C)、Tet(M)的阳性率分别为60. 0%、30. 0%、13. 3%,未检出Tet(K)。2种氨基糖苷类耐药基因acc的检出率为50. 0%,其中aac(3)-Ⅱc的阳性率为26. 7%,aac(6’)-Ⅰb的阳性率为36. 7%。本研究获得了北京地区鸭源大肠杆菌耐药性以及携带耐药基因的相关数据,为指导养殖户的临床用药及耐药性监测提供了数据参考。     

苏北及周边地区水禽致病性大肠杆菌的分离鉴定及耐药性分析

为研究近年来禽致病性大肠杆菌(APEC)的耐药性,本研究室于2018年～2019年对江苏北部及周边地区228份水禽组织病料样品(鸭头、鸭肝样品;鹅头、鹅肝样品)进行了细菌分离培养和APEC的PCR鉴定。对分离到的APEC菌株采用K-B纸片法进行药敏试验;同时对其碳青霉烯类、β-内酰胺类、氨基糖苷类、磺胺类、粘菌素类、喹诺酮类、四环素类7大类共计16种耐药基因进行了PCR检测。结果显示,在分离到的细菌中,共鉴定出50株APEC菌株。药敏试验结果显示,APEC分离菌株对四环素、氨苄西林、氟苯尼考耐药性较强,耐药菌株分别占100%、96%、86%;对头孢噻肟、恩诺沙星、链霉素、氧氟沙星中等耐药,耐药菌株分别占76%、70%、58%、36%;对美罗培南、呋喃妥因、丁胺卡那霉素的耐药性较低,耐药菌株仅分别占4%、4%、6%。其中多重耐药性较严重,耐4、5、6、7种抗生素的现象较普遍。在对其β-内酰胺类的耐药基因检测中,CTX-M、TEM、SHV的检出率分别为60%、58%、20%;氨基糖苷类:ant(3')-I a、aac(3')-I b的检出率分别为0,50%(25/50);磺胺类sul I的检出率为82%(41/50);粘菌素类mcr-1的检出率为6%(3/50);喹诺酮类:qnrB、parC的检出率分别为68%(34/50)、98%(49/50);四环素类:tetA、tetB的检出率分别为66%(33/50)、10%(5/50)。值得注意的是,从50株APEC分离菌中,鉴定出3株携带粘菌素类耐药基因mcr-1和2株携带碳青霉烯类耐药基因NDM的APEC,进一步经改良Hoge试验检测该2株菌均产碳青霉烯酶。表明这两株菌均耐美罗培南等碳青霉烯类抗生素,也进一步表明分离的APEC耐药情况的严重性。本研究为养禽场相关疫病的用药提供了参考依据。     

腹泻犬肠道分离菌的鉴定及耐药性分析

本试验从9例有腹泻症状的病犬分离菌株并进行16S rDNA鉴定、药敏试验及耐药基因检测,分离得到12株菌株,经鉴定有8株大肠杆菌、3株绿脓杆菌和1株粪肠球菌。药敏试验显示,12株分离菌对临床常用的3大类抗菌药物均产生了耐药性,对氨苄西林、庆大霉素和恩诺沙星耐药率较高。β-内酰胺酶耐药基因bla_(TEM)和bla_(SHV)检出率均为100%;ESBL-抗生素耐药基因bla_(CTX-M-8)的检出率为83.3%。氨基糖苷类耐药基因aac(3)-Ⅱ、aac(6’)-Ib、aacC2检出率分别为100%、66.7%、41.7%。氟喹诺酮类耐药基因qnrS和qepA的检出率分别为83.3%、58.3%。因此,药敏试验与耐药基因检测结果均表明犬腹泻分离菌株对临床常用3大类药物均已产生耐药性,且存在多重耐药现象。     

番鸭源鸭疫里默氏菌大环内脂类药物的耐药基因检测与分析

为了解莆田市番鸭源鸭疫里默氏菌对大环内酯类药物的耐药性和相关耐药基因携带情况,对本实验室分离鉴定的49株番鸭源鸭疫里默氏菌菌株采用K-B纸片扩散法进行药敏试验,提取菌株基因组DNA,采用PCR方法对大环内酯类药物的ermA、ermB、ermC、ermF、ereD等5种耐药基因进行检测,阳性产物送公司测序并对序列进行分析...     

鸡柔嫩艾美耳球虫不同抗药性虫株的种内多态性研究

应用RAPD技术进行柔嫩艾美耳球虫4个单一抗药性虫株与1个敏感株的基因组DNA多态性分析，发现4个抗药性虫株及敏感株之间的相似值均大于99%；OPAO3引物对抗盐霉素株扩增出一条约500bp的特异条带，OPH02引物对抗克球粉株和抗盐霉素株均扩增出了约1kb的第三条主带，这些特异条带的出现很可能与球虫抗药性基因有关，有可能用于抗药性虫株的诊断与鉴定。     

From parasite genomes to one healthy world: Are we having fun yet?

In 1990, the Human Genome Sequencing Project was established. This laid the ground work for an explosion of sequence data that has since followed. As a result of this effort, the first complete genome of an animal, Caenorhabditis elegans was published in 1998. The sequence of Drosophila melanogaster was made available in March, 2000 and in the following year, working drafts of the human genome were generated with the completed sequence (92%) being released in 2003. Recent advancements and next-generation technologies have made sequencing common place and have infiltrated every aspect of biological research, including parasitology. To date, sequencing of 32 apicomplexa and 24 nematode genomes are either in progress or near completion, and over 600k nematode EST and 200k apicomplexa EST submissions fill the databases. However, the winds have shifted and efforts are now refocusing on how best to store, mine and apply these data to problem solving. Herein we tend not to summarize existing X-omics datasets or present new technological advances that promise future benefits. Rather, the information to follow condenses up-to-date-applications of existing technologies to problem solving as it relates to parasite research. Advancements in non-parasite systems are also presented with the proviso that applications to parasite research are in the making.     

Epilepsy in Border Collies: Clinical Manifestation, Outcome, and Mode of Inheritance

Background: There is a lack of data on idiopathic epilepsy (IE) in Border Collies (BCs) in the veterinary literature.
Hypothesis: Genetic epilepsy occurs in BCs and is frequently characterized by a severe clinical course and poor response to medical treatment.
Animals: Forty-nine BCs diagnosed with IE.
Methods: Medical records, seizure data, treatment data, and pedigree information of affected dogs were collected. Cases were classified phenotypically as affected or not affected; mild, moderate, or severe clinical course; active epilepsy (AE) or remission; and drug resistant or not drug resistant.
Results: Clinical manifestations were classified as having a moderate (33%) or severe clinical course (49%), characterized by a high prevalence of cluster seizures and status epilepticus. Survival time was significantly decreased in dogs <2 years of age at seizure onset, and in dogs with a severe clinical course. Drug resistance was apparent in 71% of 24 dogs treated with ≥2 antiepileptic drugs. The epilepsy remission rate was 18%. Median age at onset was significantly higher and initial seizure frequency was significantly lower in dogs with remission compared with dogs with AE. Pedigree analyses indicated a strong genetic founder effect in the appearance of epilepsy, resembling autosomal recessive inheritance.
Conclusion and Clinical Importance: The present study confirms the occurrence of genetically mediated epilepsy with a frequent severe clinical course and drug resistance in BCs. The results provide information about the long-term prognosis of IE in BCs for veterinarians and concerned owners, and may benefit breeders as well.     

柔嫩艾美耳球虫野外抗药性虫株的RAPD分析

用RAPD方法对柔嫩艾美耳球虫（Eimeria tenella）的8个分别来源于黑龙江、北京、四川、甘肃和广东的中山、新会、东莞以及广州近郊的江村镇的野外分离虫株和2个药物敏感性虫株进行了遗传多态性分析。同时用9种抗球虫药物即马杜霉素（5mg/kg）、盐霉素（60mg/kg）、莫能霉素（120mg/kg）、拉沙菌素（90mg/kg）、克球多（150mg/kg）、常山酮（3mg/kg）、氯氢苯乙氰（1mg/kg）、尼卡巴嗪（125mg/kg）和球痢灵（125mg/kg）分别对8个野不进行抗药性试验，8个虫株对上述药物均有不同程度的抗药性。RAPD分析表明：10个样品都有相似而清晰的主带，每个泳道有5－13条带不等，大小为0.18-2.10kb。它们之间的相似率（SI）大于40.58%，最大的为90.72%，这种相似率属种内变异水平。根据SI值可把10个样品划分为3个类群：广东虫株类群，群内比较，平均SI值为76.60%；广东省外虫株类群，群内比较的平均SI值72.14%；敏感株类群，其间的SI值为89.27%。在另一方面，广东株与广东省外株、敏感株之间比较，其SI的平均值分别仅为63.03%和47.25%，说明柔嫩艾美耳球虫抗药性虫株之间有遗传差异法。     

Colistin resistance and plasmid-mediated mcr genes in Escherichia coli and Salmonella isolated from pigs,pig carcass and pork in Thailand,Lao PDR and Cambodia border provinces

BackgroundColistin and carbapenem-resistant bacteria have emerged and become a serious public health concern, but their epidemiological data is still limited.ObjectivesThis study examined colistin and carbapenem resistance in Escherichia coli and Salmonella from pigs, pig carcasses, and pork in Thailand, Lao PDR, and Cambodia border provinces.MethodsThe phenotypic and genotypic resistance to colistin and meropenem was determined in E. coli and Salmonella obtained from pigs, pig carcasses, and pork (n = 1,619). A conjugative experiment was performed in all isolates carrying the mcr gene (s) (n = 68). The plasmid replicon type was determined in the isolates carrying a conjugative plasmid with mcr by PCR-based replicon typing (n = 7). The genetic relatedness of mcr-positive Salmonella (n = 11) was investigated by multi-locus sequence typing.ResultsColistin resistance was more common in E. coli (8%) than Salmonella (1%). The highest resistance rate was found in E. coli (17.8%) and Salmonella (1.7%) from Cambodia. Colistin-resistance genes, mcr-1, mcr-3, and mcr-5, were identified, of which mcr-1 and mcr-3 were predominant in E. coli (5.8%) and Salmonella (1.7%), respectively. The mcr-5 gene was observed in E. coli from pork in Cambodia. Two colistin-susceptible pig isolates from Thailand carried both mcr-1 and mcr-3. Seven E. coli and Salmonella isolates contained mcr-1 or mcr-3 associated with the IncF and IncI plasmids. The mcr-positive Salmonella from Thailand and Cambodia were categorized into two clusters with 94%–97% similarity. None of these clusters was meropenem resistant.ConclusionsColistin-resistant E. coli and Salmonella were distributed in pigs, pig carcasses, and pork in the border areas. Undivided-One Health collaboration is needed to address the issue.     

Effect of new ethyl and methyl carbamates on Rhipicephalus microplus larvae and adult ticks resistant to conventional ixodicides

The effects of six new synthetic carbamates on fully engorged females of four Rhipicephalus microplus strains (one reference strain susceptible to conventional ixodicides, two strains multiresistant to ixodicides and one tick field isolate) were compared. In addition, the effect of two other new synthetic carbamates was tested on larvae from the same strains. The first six tested carbamates reduced egg laying and inhibited egg hatching in the four studied strains (P < 0.05). Compared with untreated females, the eggs produced by the treated engorged female ticks of all strains had a dark, dry, opaque appearance and were less adherent. The remaining two tested carbamates induced larval mortality in all of the evaluated strains. The three studied R. microplus strains displayed 50% resistance ratios (RR₅₀) of less than 2 when compared to the susceptible reference strain. These results demonstrate that both carbamates with a larvicidal effect and carbamates that inhibit egg laying and embryo development are efficacious against tick strains that are resistant to commercial ixodicides, no cross resistance was observed.     

奶牛乳腺炎无乳链球菌的分离鉴定与耐药性分析

奶牛乳腺炎是奶牛养殖业的常见疾病,而无乳链球菌是乳腺炎的重要病原体之一。本试验从江苏和河北地区的规模化奶牛场中共收集67份乳腺炎奶样,经分离培养和鉴定,共分离出33株无乳链球菌。药敏试验表明:河北地区和江苏地区奶牛场的分离株对阿莫西林、头孢氨苄等β-内酰胺类药物以及恩诺沙星等喹诺酮类药物高度敏感,而对链霉素、庆大霉素、卡那霉素以及丁胺卡那等氨基糖苷类药物均表现出较高的耐药性。此外,河北地区分离株对四环素、多西环素这两种药物比较敏感,但在江苏地区无乳链球菌对这两种药物表现出了较强的耐药性,耐药率均高达74.1%。说明不同地区的无乳链球菌耐药情况有一定的差异。本研究结果可为临床上用抗生素预防和治疗乳腺炎提供参考。     

Drug resistant Tuberculosis: A review

Tuberculosis (TB) was announced as a global emergency in 1993. There was an alarming counter attack of TB worldwide. However, when it was known that TB can be cured completely, the general public became ignorant towards the infection. The pathogenic organism Mycobacterium tuberculosis continuously evolved to resist the antagonist drugs. This has led to the outbreak of resistant strain that gave rise to “Multi Drug Resistant-Tuberculosis” and “Extensively Drug Resistant Tuberculosis” that can still be cured with a lower success rate. While the mechanism of resistance proceeds further, it ultimately causes unmanageable totally drug resistant TB (TDR-TB). Studying the molecular mechanisms underlying the resistance to drugs would help us grasp the genetics and pathophysiology of the disease. In this review, we present the molecular mechanisms behind Mycobacterium tolerance to drugs and their approach towards the development of multi-drug resistant, extremely drug resistant and totally drug resistant TB.     

豫北地区猪源大肠杆菌耐药性及基因多态性分析

为了解豫北地区规模化养殖场猪源大肠杆菌的耐药性及基因多态性,对分离的21株猪源大肠杆菌进行药物敏感实验,采用PCR技术对其耐药基因进行检测,RAPD技术进行基因多态性分析。结果表明:豫北地区规模化养殖场分离的猪源性大肠杆菌菌株对常见16种抗生素存在不同情况的耐药性。其中对四环素、红霉素、麦迪霉素、阿莫西林、磺胺异恶唑、环丙沙星、新生霉素、复方新诺明、恩诺沙星、甲氧苄啶的耐药率均为100%,对庆大霉素、洛美沙星的耐药率为85%以上,对其他药物的耐药率相对较低;PCR检测得到8种耐药基因的条带;对菌株进行RAPD分析得到7种不同的基因型。大肠杆菌极易产生耐药性,耐药基因广泛存在于耐药菌株中,但耐药表型与耐药基因之间无绝对相关性。豫北地区猪源大肠杆菌感染多重耐药十分严重,严重影响了该地区猪源大肠杆菌病的诊治和预防。