Prevalence of virulence genes in Escherichia coli strains recently isolated from young pigs with diarrhea in the US

Enterotoxigenic Escherichia coli (ETEC)-associated post-weaning diarrhea (PWD) is economically one of the most important diseases for the swine industry. Porcine ETEC strains typically express K88 or F18 fimbria and heat-labile (LT) and/or heat-stable (STa, STb) enterotoxins. However, recent studies indicate that EAST1 toxin, adhesin involved in diffuse adherence (AIDA-I) and porcine attaching and effacing-associated factor (paa) may also be expressed by ETEC strains associated with diarrhea. To better understand the virulence factors of E. coli strains that cause PWD, we applied PCR to screen for K88, F18, F41, 987P and K99 fimbrial genes; LT, STa, STb, Stx2e and EAST1 toxic genes; and AIDA-I, paa and EAE adhesin genes in E. coli strains recently isolated from young pigs with PWD in the US. Of 304 E. coli isolates from diarrheic pigs submitted for testing, 175 (57.6%) strains possessed fimbrial genes: K88 (64.6%), F18 (34.3%), F41 (0.57%), K99 (0.57%), 987P (0); toxin genes: LT (57.7%), STb (72.6%), STa (27.4%), STx2e (17.4%), EAST1 (35%); and adhesin genes: AIDA-I (26.9%), paa (60%), EAE (1.1%). All toxin genes except the EAST1 toxin gene, were almost exclusively associated with K88+ or F18+ isolates, and most of these isolates carried multiple toxin genes. The non-fimbrial adhesin paa was found present in over half of the K88+ isolates. A total of 129 (42%) isolates carried no fimbrial genes, including 66 (21.7%) isolates that did not have any of the above virulence genes. These results suggest a broad array of virulence genes associated with PWD in pigs.     

Safety of an attenuated West Nile virus vaccine, live Flavivirus chimera in horses

REASON FOR PERFORMING STUDY: West Nile virus (WNV) infection is endemic and able to cause disease in naive hosts. It is necessary therefore to evaluate the safety of new vaccines. OBJECTIVES: To establish: 1) the safety of a modified live Flavivirus/West Nile virus (WN-FV) chimera by administration of an overdose and testing for shed of vaccine virus and spread to uninoculated sentinel horses; 2) that this vaccine did not become pathogenic once passaged in horses; and 3) vaccine safety under field conditions. METHODS: There were 3 protocols: 1) In the overdose/shed and spread study, horses were vaccinated with a 100x immunogenicity overdose of WN-FV chimera vaccine and housed with sentinel horses. 2) A reversion to virulence study, where horses were vaccinated with a 20x immunogenicity overdose of WN-FV chimera vaccine. Horses in both studies were evaluated for abnormal health conditions and samples obtained to detect virus, seroconversion and dissemination into tissues. 3) In a field safety test 919 healthy horses of various ages, breeds and sex were used. RESULTS: Vaccination did not result in site or systemic reactions in either experimental or field-injected horses. There was no shed of vaccine virus, no detection of vaccine virus into tissue and no reversion to virulence with passage. CONCLUSIONS: WN-FV chimera vaccine is safe to use in horses with no evidence of ill effects from very high doses of vaccine. There was no evidence of reversion to virulence. In addition, administration of this vaccine to several hundred horses that may have been previously exposed to WNV or WNV vaccine resulted in no untoward reactions. POTENTIAL RELEVANCE: These studies establish that this live attenuated Flavivirus chimera is safe to use for immunoprophylaxis against WNV disease in horses.     

Efficacy, duration, and onset of immunogenicity of a West Nile virus vaccine, live Flavivirus chimera, in horses with a clinical disease challenge model

REASON FOR PERFORMING STUDY: West Nile virus (WNF) is a Flavivirus responsible for a life-threatening neurological disease in man and horses. Development of improved vaccines against Flavivirus infections is therefore important. OBJECTIVES: To establish that a single immunogenicity dose of live Flavivirus chimera (WN-FV) vaccine protects horses from the disease and it induces a protective immune response, and to determine the duration of the protective immunity. METHODS: Clinical signs were compared between vaccinated (VACC) and control (CTRL) horses after an intrathecal WNV challenge given at 10 or 28 days, or 12 months post vaccination. RESULTS: Challenge of horses in the immunogenicity study at Day 28 post vaccination resulted in severe clinical signs of WNV infection in 10/10 control (CTRL) compared to 1/20 vaccinated (VACC) horses (P<0.01). None of the VACC horses developed viraemia and minimal histopathology was noted. Duration of immunity (DPI) was established at 12 months post vaccination. Eight of 10 CTRL exhibited severe clinical signs of infection compared to 1 of 9 VACC horses (P<0.05). There was a significant reduction in the occurrence of viraemia and histopathology lesion in VACC horses relative to CTRL horses. Horses challenged at Day 10 post vaccination experienced moderate or severe clinical signs of WNV infection in 3/3 CTRL compared to 5/6 VACC horses (P<0.05). CONCLUSIONS: This novel WN-FV chimera vaccine generates a protective immune response to WNV infection in horses that is demonstrated 10 days after a single vaccination and lasts for up to one year. POTENTIAL RELEVANCE: This is the first USDA licensed equine WNV vaccine to utilise a severe challenge model that produces the same WNV disease observed under field conditions to obtain a label claim for prevention of viraemia and aid in the prevention of WNV disease and encephalitis with a duration of immunity of 12 months.     

An 8bp indel in exon 1 of Ghrelin gene associated with chicken growth

Ghrelin, acts as the endogenous ligand for growth hormone secretagogues receptor (GHS-R), is a novel growth hormone (GH) releasing peptide with reported effects on food intake in chickens. In this study, an 8 bp indel polymorphism in exon 1 of the chicken Ghrelin (cGHRL) gene was genotyped in a F(2) designed full-sib population to analyze its associations with chicken growth and carcass traits. Later, mRNA level in the proventriculus was determined by real-time PCR to reveal the expression feature of cGHRL gene. Result showed that this 8 bp indel was significantly associated with body weight at the age of 28 days (BW28) and 56 days (BW56), eviscerated weight (EW) and leg muscle weight (LMW) (P<0.05), highly significantly associated with hatch weight (HW), BW14, 21, 35, 42, 49, 90 and body length (BL), dressed weight (DW), eviscerated weight with giblet (EWG), wing weight (WW), breast muscle weight (BMW) and head and neck weight (HNW) (P<0.01). Meanwhile, A allele (with 'CTAACCTG') was positive for chicken growth as individuals with AA genotype had the highest value of all traits. Analysis on cGhrelin mRNA level revealed that it differed significantly among individuals with three genotypes (P<0.05). Individuals with AB genotype had the highest mRNA level, whereas that of AA had the lowest one. It was concluded that this 8 bp indel of cGHRL gene was significantly associated with most body weight and body composition traits, and negative effect of endogenous Ghrelin on chicken growth were indicated by this study.     

Characterization,phylogenetic analyses and pathogenicity of Bipolaris setariae associated with brown stripe disease on sugarcane in Yunnan,China

Brown stripe disease is a severe foliar fungal disease of sugarcane worldwide and is widespread in all sugarcane planting areas in China. Brown stripe is a major disease that seriously affects the output and quality of the sugarcane industry in Yunnan Province, China's second-largest sugar base, while the pathogen of this disease remains not yet fully understood. To address this, we isolated and identified the fungi associated with 68 leaf samples showing typical symptoms of brown stripe from 22 sugarcane varieties in different areas of Yunnan Province. A total of 113 isolates were obtained, which were morphologically similar. Of these, 64 representative isolates were sequenced for the internal transcribed spacer region (ITS), GAPDH and EF-1α loci. All representative isolates grouped with the type strain of Bipolaris setariae in the phylogenetic trees inferred with individual and concatenated sequences of ITS, GAPDH and EF1-α. Pathogenicity test results showed that B. setariae strains were able to induce typical symptoms of brown stripe. The results obtained in this study clarify that only B. setariae is associated with sugarcane brown stripe in Yunnan, China. It is recorded here for the first time as a pathogen causing sugarcane brown stripe in Yunnan, and it is able to infect many major cultivars and new varieties, posing a new threat to the sugar industry in Yunnan Province. In addition, these results provide the scientific basis for the future breeding of disease-resistant varieties and effective prevention and control of sugarcane brown stripe disease.     

二化螟dsRNA降解酶基因的克隆与表达分析

为解析二化螟Chilo suppressalis体内参与降解双链RNA(double-stranded RNA,dsRNA)的关键核酸酶的功能,克隆二化螟不同的非专一性核酸酶（non-specific nuclease,NUC）基因,并对这些基因进行生物信息学分析和组织定量表达分析,同时对dsRNA降解酶（dsRNA degrading nuclease,dsRNase）活力的组织分布进行研究。结果显示,共克隆获得5个NUC基因,其中有4个编码dsRNase亚家族基因（CsdsRNase1～CsdsRNase4）和1个编码Endonuclease G亚家族基因（CsEndoG）。5个NUC基因的开放阅读框核苷酸序列长度范围为828～1 338 bp,编码275～445个氨基酸残基,其分子量大小为31.68～49.57 kD,预测等电点为5.48～9.42。CsdsRNase1和CsdsRNase2含有信号肽序列,两者相似度极高,且与家蚕Bombyx mori和斜纹夜蛾Spodoptera litura中具有dsRNA降解酶活力的dsRNase同源聚类;CsdsRNase1和CsdsRN...     

光源、性别及光处理时间对草地贪夜蛾趋光行为的影响

为研发高效、精准的监测防控设备,利用八臂行为选择装置系统测定不同光源、性别和光处理时间下草地贪夜蛾Spodoptera frugiperda的趋光行为。结果显示,在紫外光（波长365 nm）、紫光（波长420～430 nm）、蓝光（波长465～475 nm）、绿光（波长525～535 nm）、黄光（波长585～595 nm）和红光（波长655～665 nm）6种波长光源下,草地贪夜蛾混合种群（雌雄成虫比为1∶1）对紫外光光源的趋光选择率最高,为25.61%,显著高于其他处理,其次为紫光和蓝光光源,趋光选择率分别为16.30%和8.82%,对红光的趋光选择率最低,为4.76%。在紫外光刺激下,草地贪夜蛾雌成虫的趋光选择率显著高于混合种群（雌雄成虫比为1∶1）,在红光刺激下,雄成虫的趋光选择率显著高于雌成虫。另外,在紫外光刺激下,光处理时间60 min草地贪夜蛾雌成虫的趋光选择率显著高于其他处理。表明光源与性别因素均影响草地贪夜蛾的趋光行为,光处理时间对草地贪夜蛾的趋光行为影响较小,且与光源及性别因素有关。     

广东省稻菜轮作区中牛筋草对十种除草剂的抗性水平及靶基因序列分析

为明确广东省稻菜轮作区中牛筋草对10种常用除草剂的抗性水平及抗性分子机制,采用整株生物测定法测定广东省稻菜轮作区内8个牛筋草种群P1～P8对草甘膦、草铵膦和乙酰辅酶A羧化酶(acetyl-CoA carboxylase,ACCase)抑制剂类等10种除草剂的抗性水平,并进一步分析P1和P8种群相关靶标酶基因5-烯醇丙酮酰莽草酸-3-磷酸合酶(5-enolpyruvyl-shikimate-3-phosphate synthase,EPSPS)、谷氨酰胺合成酶(glutamine synthetase,GS)和ACCase的部分功能区序列特征。结果显示,牛筋草P1～P8种群对草甘膦抗性指数为敏感种群的5.9倍～17.7倍,其中P8种群对草甘膦的抗性水平最高;8个种群对草铵膦也产生了不同程度的抗性,抗性指数为敏感种群的2.3倍～14.2倍,其中P1种群抗性最高。牛筋草P1和P8种群均对ACCase抑制剂类除草剂精喹禾灵、氰氟草酯和噁唑酰草胺产生了交互抗性;P1种群ACCase基因在第2 041位氨基酸处发生突变,该突变在牛筋草种群中首次发现;而P8种群ACCase基因则在第2 027位氨基...     

四种替代药剂对梨火疫病菌的抑制活性及其田间防效

为筛选农用链霉素替代药剂,以其为对照药剂,测定春雷霉素、中生菌素、噻霉酮和噻菌铜这4种常用细菌病害防治药剂对梨火疫病菌Erwinia amylovora的抑制活性、对梨火疫病的田间防效及不同药剂处理后梨中的农药残留,并对这4种药剂的作物安全性进行评价。结果表明,中生菌素、噻霉酮和春雷霉素对梨火疫病菌有抑制作用,抑制中浓度EC50分别为1.60、6.64和60.57 mg/L,中生菌素的抑制效果高于链霉素。在连续2年田间试验中,中生菌素1 000倍液和春雷霉素400倍液对梨火疫病的保护效果和治疗效果均达90.33%以上,噻霉酮500倍液和噻菌铜200倍液对梨火疫病的保护效果均达100.00%,治疗效果均超过86.97%,与对照药剂农用链霉素2 000倍液的效果相当。所有药剂处理后均未检出中生菌素、春雷霉素、高效氯氰菊酯和农用链霉素的农药残留,而噻虫嗪、阿维菌素和矮壮素虽有检出,但其残留量均低于国家限量标准。花期前后、幼果期和果实膨大期施药,中生菌素、春雷霉素、噻霉酮和噻菌铜对梨花、叶片、枝梢及果实生长均无不良影响。综合来看,中生菌素、春雷霉素、噻霉酮和噻菌铜均可作为农用链霉素的替代药剂,...