Prevalence and Characteristics of Salmonella in the Beef Chain in the Republic of Ireland

The study investigated the prevalence, concentration and characteristics of Salmonella spp. in the Irish beef chain. A total of 900 samples including bovine hides, carcasses and ground beef were examined for the pathogen over a 2‐year study (July 2007–June 2009). Salmonella prevalence was low in all sample types; bovine hide (0.75%, 3 of 400); carcasses (0.25%, 1 of 400); and ground beef (3%, 3 of 100). All positive samples contained the pathogen in low concentrations (<10 CFU per cm² or per g). Serovars recovered were S. Dublin from hide and carcasses and S. Braenderup in ground beef. All isolates were susceptible to 13 anti‐microbials. The study highlights that Salmonella can be found at low levels at all stages of beef chain production, processing and retail and that there is a need for multiple hurdle interventions and practices along the beef chain, which will reduce consumer exposure to this pathogen.     

Occurrence,Virulence Genes and Antibiotic Resistance of Enteropathogenic Escherichia coli (EPEC) from Twelve Bovine Farms in the North‐East of Ireland

Cattle faecal samples (n = 480) were collected from a cluster of 12 farms, and PCR screened for the presence of the intimin gene (eae). Positive samples were cultured, and colonies were examined for the presence of eae and verocytotoxin (vtx) genes. Colonies which were positive for the intimin gene and negative for the verocytotoxin genes were further screened using PCR for a range of virulence factors including bfpA, espA, espB, tir ehxA, toxB, etpD, katP, saa, iha, lpfA_{O157/OI‐141} and lpfA_{O157/OI‐154.} Of the 480 faecal samples, 5.8% (28/480) were PCR positive, and one isolate was obtained from each. All 28 isolates obtained were bfpA negative and therefore atypical EPEC (aEPEC). The serotypes detected included O2:H27, O8:H36, O15:H2, O49:H+, O84:H28, O105:H7 and O132:H34 but half of the isolates could not be serogrouped using currently available antisera. Twenty‐two (79%) of the isolates carried the tir gene but only 25% were espB positive, and all other virulence genes tested for were scarce or absent. Several isolates showed intermediate resistance to ciprofloxacin, kanamycin, nalidixic acid, minocycline and tetracycline; full resistance to nalidixic acid or tetracycline with one isolate (O?:H8) displaying resistance to aminoglycosides (kanamycin and streptomycin), quinolones (nalidixic acid) and sulphonamides. This study provides further evidence that cattle are a potential source of aEPEC and add to the very limited data currently available on virulence genes and antibiotic resistance in this pathogenic E. coli group in animals.     

Biosynthetic Modularity Rules in the Bisintercalator Family of Antitumor Compounds

Diverse actinomycetes produce a family of structurally and biosynthetically related non-ribosomal peptide compounds which belong to the chromodepsipeptide family. These compounds act as bisintercalators into the DNA helix. They give rise to antitumor, antiparasitic, antibacterial and antiviral bioactivities. These compounds show a high degree of conserved modularity (chromophores, number and type of amino acids). This modularity and their high sequence similarities at the genetic level imply a common biosynthetic origin for these pathways. Here, we describe insights about rules governing this modular biosynthesis, taking advantage of the fact that nowadays five of these gene clusters have been made public (thiocoraline, triostin, SW-163 and echinomycin/quinomycin). This modularity has potential application for designing and producing novel genetic engineered derivatives, as well as for developing new chemical synthesis strategies. These would facilitate their clinical development.     

Quorum Quenching Agents: Resources for Antivirulence Therapy

The continuing emergence of antibiotic-resistant pathogens is a concern to human health and highlights the urgent need for the development of alternative therapeutic strategies. Quorum sensing (QS) regulates virulence in many bacterial pathogens, and thus, is a promising target for antivirulence therapy which may inhibit virulence instead of cell growth and division. This means that there is little selective pressure for the evolution of resistance. Many natural quorum quenching (QQ) agents have been identified. Moreover, it has been shown that many microorganisms are capable of producing small molecular QS inhibitors and/or macromolecular QQ enzymes, which could be regarded as a strategy for bacteria to gain benefits in competitive environments. More than 30 species of marine QQ bacteria have been identified thus far, but only a few of them have been intensively studied. Recent studies indicate that an enormous number of QQ microorganisms are undiscovered in the highly diverse marine environments, and these marine microorganism-derived QQ agents may be valuable resources for antivirulence therapy.     

蓝鳃太阳鱼诺卡氏菌的分离鉴定及药敏分析

为探明患结节病蓝鳃太阳鱼的病因,从蓝鳃太阳鱼(Lepomis macrochirus)脾脏结节处分离获得一病原菌SD1810。通过菌落形态、细菌生理生化鉴定和16S rRNA基因序列分析,确定所得菌株为鰤鱼诺卡氏菌(Nocardia seriolae)。人工回归感染试验结果显示,注射浓度为2.8×107 CFU/mL的菌液能使蓝鳃太阳鱼患病致死,发病症状与原感染鱼相似。从死亡太阳鱼体内可重新分离到与SD1810形态特征、生理生化指标相一致的病菌。对分离获得的鰤鱼诺卡氏菌进行药敏试验分析,结果表明,鰤鱼诺卡氏菌SD1810对红霉素、利福平、庆大霉素、氯霉素、阿米卡星、氟苯尼考等10种抗生素极其敏感,对头孢唑啉,诺氟沙星,青霉素、氨苄青霉素和阿莫西林等6种抗生素具有耐药性。     

Antibiotic Resistance in two Water Reclamation Systems for Space Applications

The purpose of this research was to evaluate the antibiotic resistance in two water reclamation systems developed from space missions. The first system is a small-scale water reclamation system operated at Johnson Space Center designed to reclaim wastewater during long-term space missions. The second system was a scaled-down version of the Johnson Space Center system operated at Texas Tech University. Antibiotic resistance patterns to 10 antibiotics were investigated before and after controlled doses of amoxicillin were added to the water reclamation systems. The results of this study indicate that bacteria in all systems were resistant to many antibiotics including beta-lactam antibiotics and a beta-lactam, beta-lactamase inhibitor combination, amoxicillin with clavulanic acid.     

两种抗菌素油剂防治奶牛干奶期乳房炎的疗效比较

以杭州乳房炎诊断法(HMT)、细菌学检验和临床检查结果为依据,综合判断PC-805和TA-125两种抗菌素油剂对干奶期乳房炎的防治效果。66头受试奶牛随机分成两组,第一组35头136个乳区于停奶当天经由乳头管注入20ml PC-805;第二组31头121个乳区以同样方法注入20ml TA-125。第一组牛在干奶前有72个乳区为HMT强阳性(++、+++),至产后降为11个,转阴率为84.7％;第二组牛在干奶前HMT强阳性乳区为66个,产后降至6个,转阴率为90.9％。第一、二组HMT强阳性乳区的细菌转阴率分别为57.4％和68.4％,除去新感染后则分别为70.5％和75.4％。这两种制剂对链球菌感染的效果较好,而对葡萄球菌的作用较差,第一组牛在千奶期间的临床发病率为2.9％,第二组为1.7％。尽管TA-125的疗效较好,但统计结果表明这两种制剂对HMT和细菌转阴率以及临床发病率方面均无显著差异(P>0.05)。     

辣木内生真菌产生抗菌物质的生物学特性研究

从辣木(Moringa sp.)中分离得到一株内生真菌(Aspergillus sp.),其发酵液对金黄色葡萄球菌和绿脓杆菌的生长有很强的抑制作用。曲霉ly14发酵液抑菌效果的最适碳源是麦芽糖,最适氮源是玉米浆,最适初始pH为5,最适装液量为50 mL和最适培养时间160 h,但生长因子(叶酸和VB12除外)和无机盐离子并不促进发酵夜得抑菌效果。     

复方中药多糖对断奶仔猪生长性能和激素水平的影响

试验选用(28±2)日龄体重为(8.5±0.5)kg的"杜长大"三元杂交断奶仔猪60头,随机分为6组,每组10头,分别饲喂基础日粮、基础日粮 0.3%复方中药多糖、基础日粮 0.6%复方中药多糖、基础日粮 0.9%复方中药多糖、基础日粮 0.6%白术多糖、基础日粮 100 mg/kg金霉素,试验期为14天.结果表明,随着复方中药多糖用量的增加,断奶仔猪的日增重和激素水平(胰岛素、生长激素、三碘甲腺原氨酸、四碘甲腺原氨酸)明显提高,料肉比降低;饲喂白术多糖和抗生素的仔猪也表现出优于单喂基础日粮仔猪的趋势.根据试验结果认为,0.9%复方中药多糖的添加效果最好.     

生长点点滴法在筛选鉴定转基因植株中的应用

对转化体 (种子或幼苗 )筛选的培养基筛选法和生长点点滴筛选法进行了比较分析。结果表明 ,在 4d苗龄的转化芥菜幼苗生长点点滴 80 0 mg/L 的潮霉素 ,获得了转基因植株 ,PCR检测结果表明 ,两种筛选方法的筛选结果一致。生长点点滴法的优点是 ,转基因幼苗不易污染 ,且成活率高。