气雾剂对肉鸡大肠杆菌感染的保护作用

本研究开展了3个试验探讨气雾噬菌体对感染大肠杆菌肉鸡的保护作用。3个试验均包含9个处理组,每组3个重复,每个重复10只鸡。9个处理组中有3个未感染大肠杆菌组,其中1组不做任何处理,另外2组喷雾PBS或噬菌体气雾剂,其余6个组分别在第7、8和10天感染大肠杆菌,并分别进行PBS喷雾或噬菌体气雾剂。致病性大肠杆菌噬菌体是从城市污水处理设施或家禽加工厂分离出来的。试验1:与对照组相比,第7天感染大肠杆菌接受噬菌体喷雾的肉鸡在第1周体重显著降低(P<0.05),与对照组相比,第7天感染大肠杆菌接受PBS喷雾、第8天感染大肠杆菌接受噬菌体喷雾的3周龄肉鸡体重显著降低(P<0.05)。感染大肠杆菌的肉鸡死亡率均显著高于未感染组(P<0.05)。试验2:感染大肠杆菌的肉鸡在第2周的体重均显著低于未感染组(P<0.05),除了第8天感染大肠杆菌的肉鸡,其他感染组均较未感染组显著降低了第3周体重(P<0.05)。第10天感染大肠杆菌的肉鸡接受噬菌体喷雾较接受PBS喷雾显著降低了死亡率(P<0.05)。试验3:第10天感染大肠杆菌的肉鸡接受噬菌体喷雾较对照组显著提高了第1周龄的体重(P<0.05),接受噬菌体喷雾但未感染大肠杆菌的肉鸡死亡率较对照组以及接受PBS喷雾组显著降低(P<0.05)。本试验结果显示,通过气喷噬菌体对保护肉鸡呼吸道感染大肠杆菌具有重要作用,使用孵化场和家禽舍内的现有设备,在气溶胶喷雾剂中使用噬菌体可适用于家禽养殖业,并可替代抗生素控制家禽细菌性疾病。     

Analysis of antibiotic resistance phenotypes and genes of Escherichia coli from healthy swine in Guizhou,China

This study was carried out to investigate the resistance phenotypes and resistance genes of Escherichia coli from swine in Guizhou, China. A total of 47 E. coli strains isolated between 2013 and 2018 were tested using the Kirby–Bauer (K–B) method to verify their resistance to 19 common clinical antimicrobials. Five classes consisting of 29 resistance genes were detected using polymerase chain reaction. The status regarding extended-spectrum β-lactamase (ESBL) and the relationship between ESBL CTX-M-type β-lactamase genes and plasmid-mediated quinolone resistance (PMQR) genes were analysed. A total of 46 strains (97.9%) were found to be multidrug resistant. Amongst them, 27 strains (57.4%) were resistant to more than eight antimicrobials, and the maximum number of resistant antimicrobial agents was 16. Twenty antibiotic resistance genes were detected, including six β-lactamase genes blaTEM (74.5%), blaCTX-M-9G (29.8%), blaDHA (17.0%), blaCTX-M-1G (10.6%), blaSHV (8.5%), blaOXA (2.1%), five aminoglycoside-modifying enzyme genes aac(3′)-IV (93.6%), aadA1 (78.7%), aadA2 (76.6%), aac(3′)-II c (55.3%), aac(6′)-Ib (2.1%) and five amphenicol resistance genes floR (70.2%), cmlA (53.2%), cat2 (10.6%), cat1 (6.4%), cmlB (2.1%), three PMQR genes qnrS (55.3%), oqxA (53.2%), qepA (27.7%) and polypeptide resistance gene mcr-1 (40.4%). The detection rate of ESBL-positive strains was 80.9% (38/47) and ESBL TEM-type was the most abundant ESBLs. The percentage of the PMQR gene in blaCTX-M-positive strains was high, and the detection rate of blaCTX-M-9G was the highest in CTX-M type. It is clear that multiple drug resistant E. coli is common in healthy swine in this study. Extended-spectrum β-lactamase is very abundant in the E. coli strains isolated from swine and most of them are multiple compound genotypes.     

Occurrence and characteristics of CS31A antigen-producing Escherichia coli in calves with diarrhoea and septicaemia in Argentina

CS31A is a K88-related non-fimbrial adhesin first described on Escherichia coli strains isolated from diarrhoeic and septicaemic calves. In this report, CS31A antigen was screened by immunological methods and confirmed by PCR among bovine E. coli isolates. In addition, CS31A-producing strains were characterized with respect to different fimbrial antigens, O-serogroup and other properties related to virulence. Faecal or tissue specimens of 100 diarrhoeic or septicaemic calves and 27 older cattle with different pathologies from 71 outbreaks or individual cases that occurred in Buenos Aires province, Argentina, were examined. CS31A + E. coli strains were isolated from 21 (21.0%) calves from 16 outbreaks or individual cases. No CS31A + E. coli was detected in samples from cattle more than 1 year old. Fimbriae F5, F41, F17a and F17b were not detected among the CS31A-producing strains. Three (14.3%) of the CS31A+ E. coli strains expressed the F17c fimbria. All of the 21 isolates exhibited at least one property of septicaemic strains (resistance to serum, production of aerobactin or colicins) but none of them demonstrated heat-stable enterotoxigenic activity. CS31A + E. coli isolates belonged to 10 serogroups, more commonly O8, O7, O17 and O21. The results obtained here confirm the worldwide distribution of CS31A antigen in bovine E. coli strains. However, CS31A + or CS31A + /F17c + E. coli were less frequently isolated than they were in North hemisphere countries.     

青海某区肉鸡致病性大肠杆菌病的病原分离与鉴定

无菌采取病死肉鸡肝、肺、脾、肾等8份病料,进行病原的分离培养与鉴定,分离出致病性大肠杆菌,结合该病的流行病学、临床症状、病理剖检变化和实验室诊断,确诊为肉鸡致病性大肠杆菌病。     

Dermatitis in broilers caused by Escherichia coli: isolation of Escherichia coli from field cases, reproduction of the disease with Escherichia coli O78:K80 and conclusions under consideration of predisposing factors

A dermatitis in broiler chickens, especially on the caudal back, thighs and around the cloaca is observed more frequently in the last years. The skin is swollen at sites of inflammation and a fibrineous plaque extends between muscle and subcutis. No clinical signs are visible in the living flock but the disease causes economical losses because of degrading and rejection of carcasses. Studies of literature and own field observations suggest that Escherichia (E.) coli is involved in the development of the dermatitis. The following serotypes were isolated from field cases: O78:K80 (3X), O2:K56 (2X), O127:K63 (3X), O9:K57 (1X), O140 (2X); two isolates could not be identified. The reproduction of the dermatitis was successful by infection via feather follicles with E. coli O78:K80. The density of broilers kept on farms may contribute to the outbreak of dermatitis by violation of the skin followed by infection of the injuries. Massage of the infected sites by close contact of birds and insufficient hygiene may support the development of the disease.     

Therapeutic efficacy of doxycycline hyclate in experimental Escherichia coli infection in broilers

Treatment of experimentally induced colibacillosis in broilers with doxycycline hyclate through the drinking water was just effective at a dose of 200 mg/kg body weight (1000 ppm). The achieved therapeutic effects were similar to those of tetracycline at the same dose and of flumequine at a dose of 19 mg/kg body weight (100 ppm).     

Experimental reproduction of malabsorption syndrome with different combinations of reovirus, Escherichia coli, and treated homogenates obtained from broilers

Attempts to reproduce malabsorption syndrome (MAS) by oral inoculation with several different combinations including intestinal homogenate, reovirus, and hemolytic Escherichia coli obtained from MAS-affected chickens and intestinal homogenate from healthy chickens (healthy homogenate) were performed in 1-day-old specific-pathogen-free (SPF) broilers. The MAS homogenate, serving as a positive control, induced weight gain depression and intestinal lesions such as cystic crypts of Lieberkuhn, villus atrophy, and lymphoid and/or granulocytic infiltration. The healthy homogenate, the formalin-treated MAS homogenate, the formalin-treated healthy homogenate, and phosphate-buffered saline caused neither weight gain depression nor intestinal lesions. We were able to reproduce both weight gain depression and intestinal lesions by inoculation of reovirus either combined with the formalin-treated MAS homogenate or combined with healthy homogenate. Surprisingly, when hemolytic E. coli was added to the combination of reovirus with formalin-treated MAS homogenate, this did not cause weight gain depression although this combination caused the described intestinal lesions. Identical results were obtained with the combination of formalin-treated MAS homogenate with hemolytic E coli or the combination of reovirus with hemolytic E. coli. The intestinal lesions were more severe and developed faster by combinations including reovirus and formalin-treated MAS homogenate. This study indicates that a combination of enteropathogenic reovirus with other agents or substances that are present in an intestinal homogenate from MAS-affected and healthy chickens can induce MAS in SPF broilers. Escherichia coli is not essential for induction of weight gain depression but can play a role in development of intestinal lesions. Furthermore, intestinal lesions alone will not always result in weight gain depression.     

Safety,immunogenicity, and efficacy of two Escherichia coli cya crp mutants as vaccines for broilers

Attenuated derivatives (delta cya delta crp mutants) of an O2 and an O78 avian septicemic Escherichia coli strain were used to immunize broiler chickens by spray to determine the safety, immunogenicity, and efficacy of the derivatives in single- and double-dose regimens. In the safety and immunogenicity studies, groups of 10 chickens were vaccinated by spray (droplet size approximately 20 microm) with the parent E. coli, the mutant organisms, or phosphate-buffered saline (PBS) at 14 days of age and euthanatised 21 days later. There was no deaths or gross pathologic finding in any of the chickens immunized with the vaccine strains. Compared with the levels in chickens exposed to PBS, there were significantly higher levels of immunoglobulin (Ig) G antibody in serum and air sac washings and of IgA antibody in air sac washings in response to the virulent parent strains than to the vaccine strains. In efficacy studies, chickens were immunized with the O2 or the O78 vaccine strain or PBS at day 14 and with the O2 vaccine strain or PBS at days 10 and 14 and challenged with the parent strain 10 days after the last vaccination. There was no significant difference in local IgA and IgG and serum IgG responses between vaccinated and control groups. Chickens vaccinated with the O2 strain, but not the O78 strain, had significantly lower air sac lesion scores compared with those of the unvaccinated groups in both single- and double-dose regimens. We conclude that the mutant O2 strain provided moderate protection against airsacculitis.     

Prevalence and characteristics of intimin- and Shiga toxin-producing Escherichia coli from gulls,pigeons and broilers in Finland

The role of birds as sources of Shiga toxin-and intimin-producing Escherichia coli was studied. Fecal samples from live gulls (n=86), pigeons (n=33) and broiler chickens (n=199) from 23 flocks were analyzed for stx and eae by PCR. No stx positive samples were detected. In contrast, eae E. coli were highly prevalent among gulls (40%), and was also found in pigeons (7%) and chickens (57% of the flocks contaminated). The eae positive isolates were analyzed genetically and O-serogrouped. One isolate from a pigeon was found to have stx (2f). The isolates of gulls differed from those of pigeons and chickens, and all eae E. coli isolates from birds differed from human pathogenic strains by the lack of EHEC-hlyA and bfp/EAF as well as distribution of O-serogroups. Thus, birds cannot be regarded as important carriers of zoonotic stx or eae E. coli in Finland.     

中药提取物恢复耐药大肠杆菌对氨基糖苷类药物敏感性的研究

为考察五倍子、黄芩、黄连、艾叶、鱼腥草5种中药提取物恢复耐药大肠杆菌对氨基糖苷类抗生素敏感性的作用,采用1/2 MIC中药提取物对耐药菌株进行耐药性消除,通过影印培养法筛选出耐药性消除菌落,观察耐药消除率和消除子MIC值变化,并检测质粒及耐药基因rmt B的携带情况。结果表明:5种中药提取物对耐药大肠杆菌均有一定的抑制作用,耐药菌经1/2 MIC作用48 h后,五倍子、黄芩、黄连、艾叶、鱼腥草的耐药消除率分别为20.67%、21.33%、17.33%、16.67%、9.33%;消除子对庆大霉素(GEN)、卡那霉素(KAN)、阿米卡量(AMK)、新霉素(NEO)的MIC值均由高度耐药(512μg/m L)降至敏感(2~4μg/m L);5种中药提取物不能使耐药菌质粒丢失,却能导致耐药基因rmt B丢失。5种中药提取物可能是通过使高度耐氨基糖苷类药物的细菌丢失耐药主效基因来恢复对药物敏感性的。     

腹泻犊牛大肠杆菌血清型抗菌药物耐药性耐药基因鉴定及脉冲场凝胶电泳分型

本试验对2011年由哈尔滨周边地区采集的263份腹泻犊牛的肛拭子进行大肠杆菌的分离鉴定,并通过小鼠致病性试验鉴定出26株致病性大肠杆菌,用Kirby-Bauer法开展对12种药物的药敏试验,PCR检测了我国流行广泛的9种耐药基因,脉冲场凝胶电泳(PFGE)进行基因分型.检测结果,该地区主要流行的致病性血清型为O26、O78和O15,所有致病性菌株都存在多重耐药现象,其中阿莫西林-棒酸、链霉素、四环素、复方新诺明的耐药率达到了100％,共检出7种耐药基因,检出率符合我国平均分布趋势,且检出率基本上与耐药表型相一致.PFGE结果显示,该地区存在致病性菌株的克隆传播.     

15株临床分离耐药大肠杆菌耐氟喹诺酮类抗生素基因的检测与序列分析

15株动物源性耐氟喹诺酮类药物大肠杆菌进行PCR检测、测序、WDNASIS软件分析gyrA基因中的氟喹诺酮耐药决定区(QRDR)、AcrA以及编码与质粒介导的氟喹诺酮类药物耐药机制相关的qnrA、qnrB、qnrS、qepA和aac(6′)-Ib-cr基因。结果表明,15株耐药菌中,QRDR基因在其编码第72、75、83位或第87位氨基酸均发生突变;AcrA基因未检测到氨基酸的突变;qnrS、qepA和aac(6′)-Ib-cr耐药基因阳性菌各检测到1株,序列分析表明不存在氨基酸突变。QRDR基因编码的氨基酸4个位点发生突变,其中Ser83→Leu和Asp87→Asn 2个基因的突变均与文献报道的突变相同,双突变的7个菌株均表现为高度耐氟喹诺酮类抗生素,表明gyrA基因为大肠杆菌耐氟喹诺酮类抗生素的一个重要机制。高度耐氟喹诺酮类抗生素的菌株中有2株没有检测到氨基酸突变的存在,但是aac-(6′)-Ib-cr基因和qnrS检测为阳性,表明质粒介导的喹诺酮类耐药也可单独导致菌株的耐药。存有一个菌株gyrA基因编码的氨基酸发生突变Ser83→Leu,AcrA基因和qnrA、qnrB、qnrS、qepA和aac(6′...     

畜禽大肠埃希氏杆菌的药敏性调查

从梅州地区多个养殖场的动物肠道和排泄物中分别分离出10株鸡源性大肠埃希氏杆菌和8株猪源性大肠埃希氏杆菌,分别对11种较新的抗生素进行药敏性试验。结果表明:诺氟沙星、环丙沙星和阿米卡星的抑菌效果最强;其次为痢特灵、头孢噻吩、氯霉素及卡那霉素;克林霉素、青霉素、氨苄西林和苯唑西林无抑菌作用。     

Serogrouping,phylotyping, and virulence genotyping of commensal and avian pathogenic Escherichia coli isolated from broilers in Hamedan,Iran

In the present study, 100 Avian-Pathogenic Escherichia coli (APEC) isolates from colibacillosis-suspected broilers and 100 Avian Faecal Escherichia coli (AFEC) isolates from healthy broilers in Iran were examined by PCR for confirmation of their serogroups and phylogenetic background, and their association with ten virulence-associated genes (VAG) including fimC, iutA, chuA, sitA, iss, cvaA/B, hylA, stx1, stx2, and yjaA. Serogroups O78, O1, O2 and O18 were the prominent strains including 54 % of the APEC and 23 % of the AFEC strains. At phylotyping, the majority of APEC strains belonged to phylogenetic group E (22 %) while for the AFEC strains, half of the isolates were not assigned to any group but the predominant phylogroup was E (27 %). Virulence genotyping, revealed that the predominant VAGs were iutA (97 %), fimC (87 %) and iss (84 %) among APEC strains, and fimC (95 %), iss (93 %) and sitA (87 %) in AFEC strains. This is the first time that phylogroup E is described as predominant phylogroup among APEC strains also, this is the first report on the presence of the stx1 gene in APEC strains isolated from broilers in Iran. The results of the present study indicate that VAGs are more prevalent in APEC strains belonging to O2 and O78 serogroups, also phylogroups E and D have more frequency of VAGs than other phylogroups. Therefore, the APEC strains belonging to O2 and O78 serogroups and phylogroups E and D probably have more pathogenicity to broilers.     

Effects of mannanoligosaccharide and fructooligosaccharide on the response of broilers to pathogenic Escherichia coli challenge

1. The effects of mannanoligosaccharide (MOS, Bio-Mos, Alltech Inc.) on the growth performance and digestive system, particularly gut microflora, were tested and compared with fructooligosaccharide (FOS, Raftilose P95, Orafti) using 1-d-old birds in an Escherichia coli challenge model. The experiment lasted for 3 weeks and zinc bacitracin (ZnB) was used as a positive control. 2. Dietary MOS had positive effects on body weight gain (BWG) or/and feed conversion efficiency (FCE) of the challenged birds compared to the negative control at the end of weeks 1 and 3. Similar results were obtained for ZnB treatment. In contrast, FOS supplementation improved only the BWG of the challenged birds at 21 d of age. Within the unchallenged birds, a large improvement in BWG was noticed for FOS treatment at the end of the experiment, with the BWG of birds on ZnB and MOS treatments being intermediate. The FCE of the unchallenged birds was not affected by the dietary additives. 3. The addition of MOS reduced the number of mucosa-associated coliforms in the jejunum of the challenged birds on d 7. On d 21, FOS tended to increase the number of jejunal mucosa-associated lactobacilli in both the challenged and unchallenged birds. The number of Clostridium perfringens in the gut lumen was reduced by only ZnB. 4. Dietary MOS reduced the jejunal crypt depth of birds on d 7, regardless of the challenge. The FOS supplement did not affect the gut morphology, however, the concentration of lactic acid in the ileum was increased and, depending on the challenge, the intestinal pH was decreased by FOS at different ages. 5. In conclusion, the effects of MOS or FOS on the composition and activities of gut microflora and mucosal morphology of birds were related to E. coli challenge as well as the age of birds, which may be involved in the observed different growth-improving effects of the tested dietary additives.     

河北省犊牛腹泻大肠杆菌致病性及耐药性分析

为确定河北省犊牛腹泻大肠杆菌的致病性与耐药性,本研究对2018年1月至2019年6月期间从河北省石家庄、保定、承德、唐山、廊坊的部分肉牛场腹泻犊牛样品中分离到的50株大肠杆菌进行了致病性试验、药物敏感性试验、毒力基因和耐药基因检测。结果显示:50株分离菌均对小鼠具有致病性,致病菌占比100%(50/50)。毒力基因fyuA、irp2、eaeA、ler检出率分别为68.0%、66.0%、34.0%、34.0%。50株分离菌均对15种抗生素中的2种及以上表现为耐药,对10种及以上抗生素耐药的菌株占比达34%(17/50);分离菌对土霉素、磺胺对甲氧嘧啶、磺胺间甲氧嘧啶、替米考星4种药物表现为高度耐药,耐药率分别为90%、90%、94%、100%。除四环素类tetD基因检出率为0外,其它耐药基因均有检出,其中四环素类tetC、氨基糖苷类aadA1、喹诺酮类gyrA、gyrB基因检测率高达100%。试验的50株大肠杆菌均具有较强的毒力和多重耐药性。本研究为河北省大肠杆菌所致犊牛腹泻病的防治提供了实验依据。