Drugs from bugs: the use of insects as a valuable source of transgenes with potential in modern plant protection strategies

Transgenic expression of antimicrobial peptides in crops has become a novel approach among the strategies to combat phytopathogens in modern plant protection measures. The first antimicrobial transgenes of insect origin, modified cecropins, have been demonstrated to confer resistance of several transgenic cultivars against both bacterial and fungal phytopathogens. Insects represent a promising reservoir for antimicrobial peptides to engineer disease resistant crops. The increasing knowledge about the potent insect innate immunity may help to develop a novel strategy in sustainable agriculture. Several approaches are presently under investigation to prevent evolution of phytopathogens that can overcome disease resistance in transgenic crops expressing an insect antimicrobial peptide. Pathogen-induced expression of insect antimicrobial peptides in crops and combined multiple expression of different antimicrobial peptides along with proteinase inhibitors from insects may prevent selection of resistant phytopathogens. The potential of insect antimicrobial peptides as transgenes to render disease resistant crops has just started to be explored and may provide tools to be ahead of the evolutionary adaptability of phytopathogens.     

Occurrence and antimicrobial resistance of Salmonella serovars in apparently healthy slaughtered sheep and goats of central Ethiopia

The present study was undertaken to determine the occurrence, distribution and antimicrobial resistance pattern of Salmonella serovars in apparently healthy slaughtered sheep and goats in central Ethiopia. A total 1224 samples consisting of faeces, mesenteric lymph nodes, liver, spleen, and abdominal and diaphragmatic muscle samples were collected from 104 sheep and 100 goats. Salmonella was isolated from 12 of 104 (11.5%) sheep and 3 of 100 (3%) goats. Of the total 624 and 600 samples examined from sheep and goats, 18 (2.9%) and 4 (0.7%), respectively, were Salmonella positive. The 22 Salmonella isolates belonged to 9 different serovars. The common serovars isolated were S. typhimurium, followed by S. heidelberg, S. reading, S. give, and S. poona. Seven of the 22 isolates (31.8%) were multidrug-resistant to various antimicrobials.     

Quantification and evaluation of antimicrobial drug use in group treatments for fattening pigs in Belgium

To control the emergence of antimicrobial resistance, knowledge of antimicrobial drug consumption is essential. Because consumption data are not available in Belgium, a study was conducted between March and October 2003 to investigate the antimicrobial drug consumption in pigs, using the treatment incidence based on the animal daily dose pig (ADDpig), the treatment incidence based on the used daily dose pig (UDDpig) (number of ADDpig or UDDpig/1000 pigs at risk/day), and the ratio UDDpig/ADDpig.

The sampling frame consisted of 821 pig herds that (a) used a closed or semi-closed production system, (b) were located in the most dense pig areas of Belgium, and (c) had at least 150 sows and 600 fattening pigs each. Of 50 randomly selected herds, all group treatments with antimicrobial drugs, applied to fattening pigs that were within 2 weeks of slaughter (median age 187 days), were collected retrospectively.

The treatment incidence based on ADDpig for all oral and injectable antimicrobial drugs was 178.1 per 1000 pigs at risk per day. The treatment incidence based on UDDpig shows that in reality fewer pigs were treated, namely 170.3 per 1000 pigs at risk per day. Proportionally, the most often applied oral antimicrobial drugs were: doxycycline, amoxicillin, combination trimethoprim-sulphonamides and polymyxin E. The most often applied injectable antimicrobial drugs were long-acting amoxicillin and ceftiofur. The distribution of the UDDpig/ADDpig ratio per antimicrobial drug shows that 50–75% of the oral formulations were underdosed. Injectable formulations were almost always overdosed (>90%).     

溶藻弧菌对水产动物致病性及其防治的研究进展

溶藻弧菌是一种常见的海洋伺机性病原体,是引起人类、水生动物细菌性疾病的重要病原之一。与其它病原微生物一样,弧菌的致病性与其产生的多种毒力因子息息相关,毒力基因是产生各种毒力因子的物质基础。本文对溶藻弧菌的病原学、致病机理及其防治等方面的最新研究成果进行了综述。     

可食性抗菌膜的研制及其在草莓保鲜中的应用

[目的]研制出可用于草莓的抑茵保鲜的可食性果蔬保鲜抗菌膜.[方法]先用浓度为80％的乙醇溶液分别提取大黄、地榆、丁香和肉桂,然后进行中草药抑茵试验探索其对草莓灰霉菌的抑菌效果;再以膜的力学性能、吸水率、水蒸气透过率以及抑菌性能为依据,分别确定海藻酸钠的浓度、交联剂的种类、交联剂溶液的浓度、交联时间和丁香与海藻酸钠的比例;最后,将可食性抗菌膜处理草莓后,分别测定草莓腐烂率、失重率、呼吸强度和维生素等指标的变化,来探索抗茵膜的保鲜效果.[结果]试验表明,丁香和肉桂具有广普抑菌性,其中丁香的抑菌性最佳,尤其对草莓灰霉菌的抑菌效果最好;海藻酸钠的浓度为2％,交联剂为4％的CaCl2、交联20 min以及丁香与海藻酸钠比例为7:43时抗菌膜具有最佳的物理和抑菌性能;保鲜组草莓烂果率、失重率、呼吸强度和维生素等指标的变化速度均低于空白对照组,保鲜效果较好,草莓在室温下能保存3d,比空白对照组能延长保存2d.[结论]可食性果蔬保鲜膜制作工艺简单、成本低、保鲜效果好、易降解、可食用、对环境无污染,是一种极具开发潜力的果蔬保鲜膜.     

南川升麻的化学成分和抗菌活性研究

[目的]研究南川升麻化学成分的抗菌活性。[方法]采用回流提取法提取升麻根茎中的化合物,然后依次用石油醚、乙酸乙酯和正丁醇萃取,乙酸乙酯部位经硅粗胶拌样后进行硅胶层析,然后用氯仿-无水甲醇(10∶0→0∶10,V/V)梯度洗脱,通过薄层层析检测合并相同的部分,并取3、4和5化合物进行抑菌试验。[结果]从南川升麻的干燥根茎中分离得到6个化合物,其中3个为环菠萝蜜烷型三萜,通过光谱和质谱分析将他们的结构分别鉴定为异阿魏酸(1)、阿魏酸(2)、25-O-乙酰升麻醇(3)、兴安升麻苷C(4)、12β-羟基升麻醇(5)和β-谷甾醇(6)。[结论]首次从该植物中分离得到1～6化合物,其中3、4和5化合物都有较好的抗菌活性。     

亚胺培南与头孢曲松联合药敏试验

研究亚胺培南与头孢曲松钠,对革兰氏阴性菌大肠杆菌与革兰氏阳性菌四联球菌联合体外抗菌效果。采用8×8棋盘法测定不同浓度的亚胺培南与头孢曲松钠组合对于大肠杆菌与四联球菌的抗菌效果,并且计算FIC值。通过本次试验研究显示,联合用药大大减少了亚胺培南与头孢曲松钠的用量。亚胺培南对于大肠杆菌可以增效8倍,对于四联球菌增效4倍。头孢曲松钠对于大肠杆菌和四联球菌可以增效16倍。亚胺培南与头孢曲松钠对于两菌用药FIC值均小于0.5,呈协同作用。     

Structure-function studies of Bubalus bubalis lingual antimicrobial peptide analogs

Antimicrobial peptides expressed on different epithelial lining are major components of the innate immune system. Based on the deduced amino acid sequence of Bubalus bubalis lingual antimicrobial peptide (LAP) cDNA (Accession No. DQ458768), five overlapping peptides LAP^23–55, LAP^42–64, LAP^21–64, LAP^1–26 and LAP^1–64 were synthesized using solid phase fluorenylmethoxycarbonyl (Fmoc) chemistry. Circular Dichroism spectroscopy of synthesized peptides revealed predominantly β-structure for LAP^23–55, LAP⁴²⁻⁶⁴ and LAP^21–64 with less α-helix in different solutions. Quantitation of secondary structure indicated the highest β-structure for all these three peptides in membrane mimetic SDS solution. The helicogenic solvent TFE could not induce helix in LAP^23–55 however TFE induced helical propensity was observed in LAP^42–64 and LAP^21–64. The quantitation of secondary structure indicated the highest ordered structure for LAP^23–55 followed by LAP^42–64 and LAP^21–64. The antibacterial activity of LAP^23–55 was found to be more potent against Staphylococcus aureus, Listeria monocytogens, Escherichia coli and Salmonella typhimurium followed by LAP^42–64 and LAP^21–64. Minimum inhibitory concentration (MIC) also showed similar trend with lowest value for LAP^23–55 followed by LAP^42–64 and LAP^21–64. Haemolysis and cytotoxicity was observed above 3 fold for LAP^21–64, above six fold for LAP^23–55 and LAP^42–64 of their MIC. The LAP^1–26 and LAP^1–64 could not produce any characteristic CD spectra and did not show any antimicrobial activity, indicating that N- terminal of the peptide negates the antimicrobial activity.     

The effect of rehabilitation of northern elephant seals (Mirounga angustirostris) on antimicrobial resistance of commensal Escherichia coli

The aim of this study was to determine if antimicrobial drug use increases resistance of commensal gastrointensinal Escherichia coli of wild northern elephant seals (Mirounga angustirostris) treated in rehabilitation, and, if so, identify the risk factors involved. Minimum inhibitory concentration (MIC) levels of twelve antimicrobial drugs were determined for 289 E. coli isolates from 99 seals sampled at admission and 277 isolates obtained at release from rehabilitation using broth microdilution. Prevalence of E. coli antimicrobial resistance, MIC(50), MIC(90), and clustering of MIC values were determined for seals and the data were analyzed using Fisher's exact test, ordinal logistic regression and negative binomial regression. At release from rehabilitation 77.8% of the seals had antimicrobial resistant E. coli compared to 38.4% of the seals at admission. The MIC(90) for amoxicillin-clavulanic acid, chloramphenicol, enrofloxacin, ticarcillin-clavulanic acid, and trimethoprim-saulfamethoxazole were at levels considered to be sensitive at admission but they increased to levels of resistance at release. E. coli were grouped into four clusters by their MIC values, with increasing levels of resistance going from Cluster 1 to 4. A primary risk factor associated with the probability of a seal having E. coli in Clusters 3 and 4 was time in rehabilitation, regardless of whether the animal received treatment with antimicrobial drugs, suggesting nosocomial infection. The results of this study provide evidence that increased levels of hygiene and appropriate use of antimicrobial therapy might be important in the rehabilitation of wild animals to prevent rise in the prevalence of antimicrobial resistant bacteria.     

The anatomical distribution and antimicrobial susceptibility of yeast species isolated from healthy dogs

The aim of this work was to identify the predominant yeast species present at different anatomical sites in healthy dogs and to determine their in vitro antimicrobial susceptibility using a broth microdilution assay. Samples were collected from the preputial, vaginal, oral and perianal mucosae and the isolates cultured were identified according to their morphological characteristics and biochemical profile. Malassezia pachydermatis was the most commonly isolated yeast, followed by Candida parapsilosis, Candida tropicalis, Candida albicans, Saccharomyces cerevisiae and Rhodotorula spp.Minimum inhibitory concentrations of the azole derivatives ketoconazole, itraconazole and fluconazole against Candida spp. were 0.03–16 μg/mL, 0.06 to >16 μg/mL and 0.5–64 μg/mL, respectively and Candida isolates were sensitive to caspofungin and amphotericin B. Although all isolates of M. pachydermatis were sensitive to itraconazole, fluconazole, ketoconazole and amphotericin B, they were found to be resistant to caspofungin. The study has highlighted that Candida spp., M. pachydermatis, S. cerevisiae and Rhodotorula spp. are part of the normal canine surface microbiota and some of these organisms exhibit in vitro resistance to commonly used antimicrobials.