Mobile genetic elements facilitate the transmission of antibiotic resistance genes in multidrug-resistant Enterobacteriaceae from duck farms

Multidrug-resistant(MDR)Enterobacteriaceae critically threaten duck farming and public health.The phenotypes,genotypes,and associated mobile genetic elements(MGEs)of MDR Enterobacteriaceae isolated from 6 duck farms in Zhejiang Province,China,were investigated.A total of 215 isolates were identified as Escherichia coli(64.65%),Klebsiella pneumoniae(12.09%),Proteus mirabilis(10.23%),Salmonella(8.84%),and Enterobacter cloacae(4.19%).Meanwhile,all isolates were resistant to at least two antibiotics.Most isolates carried tet(A)(85.12%),blaTEM(78.60%)and sul1(67.44%)resistance genes.Gene co-occurrence analysis showed that the resistance genes were associated with IS26 and integrons.A conjugative IncFII plasmid pSDM004 containing all the above MGEs was detected in Proteus mirabilis isolate SDM004.This isolate was resistant to 18 antibiotics and carried the blaNDM-5 gene.MGEs,especially plasmids,are the primary antibiotic resistance gene transmission route in duck farms.These findings provide a theoretical basis for the rational use of antibiotics in farms which are substantial for evaluating public health and food safety.

Meropenem as an Alternative Antibiotic Agent for Suppression of Agrobacterium in Genetic Transformation of Orchid

A case of Meropenem as a novel antibacterial agent to suppress and eliminate Agrobacterium tumefaciens in the Agrobacterium-mediated transformation of orchid protocorm-like bodies （PLBs） has been reported in this article. The in vitro activities of meropenem and four comparator antibacterial agents against three Agrobacterium tumefaciens strains, LBA4404, EHA101, and GV3101, were assessed. In addition, the effect of meropenem on the growth of Dendrobium phalaenopsis PLBs was determined. Compared with other commonly used antibiotics （including ampicillin, carbenicillin, cefotaxime, and cefoperazone）, meropenem showed the highest activity in suppressing all tested A. tumefaciens strains （minimum inhibitory concentration [MIC] 〈 0.5 mg L^-1, which is equal to minimum bactericidal concentration [MBC]）. Meropenem, at all tested concentrations, except for 10 mg L^-1 concentration, had little negative effect on the growth of orchid tissues. The A. tumefaciens strain EHA101 in genetic transformation with vector plG121Hm in infected PLBs of the orchid was visually undetectable after a two-month subculture in 1/2 MS medium with 50 mg L^-1 meropenem and 25 mg L^-1 hygromacin. The expression and incorporation of the transgenes were confirmed by GUS histochemical assay and PCR analysis. Meropenem may be an alternative antibiotic for the effective suppression of A. tumefaciens in genetic transformation.

Adventitious shoot regeneration of Platanus acerifolia Willd. facilitated by Timentin,an antibiotic for suppression of Agrobacterium tumefaciens in genetic transformation

The effects of Timentin and cefotaxime （Cef） on shoot regeneration of the London plane tree （Platanus acerifolia Willd.） and their use for the suppression ofAgrobacterium tumefaciens in Agrobacterium-mediated genetic transformation were compared. Shoot regeneration was significantly reduced on the media with Cef at concentrations from 100 to 500 mg·L^-1. Timentin showed negative effect on plant regeneration at concentrations of 100 and 500 mg·L^-1; however, 300 mg·L^-1 Timentin was shown to facilitate shoot regeneration significantly and the regeneration frequency increased from 64% （control） to 88%. Effective suppression of A. tumefaciens could be obtained with 500 mg·L^-1 Cef, but plant regeneration was completely inhibited at this level. The A. tumefaciens on infected P. acerifolia leaf tissues was visually undetectable after three subcultures on a medium with 300 mg·L^-1 Timentin. Considering the effect of Cef and Timentin on plant regeneration and suppression of Agrobacteria, Timentin at 300 mg·L^-1 is the preferred application in .4. tumefaciens-mediated transformation ofP acerifolia.

Genetic Diversity,Antibiotic Resistance,and Pathogenicity of Aeromonas Species from Food Products in Shanghai,China

Objective Aeromonas has recently been recognized as an emerging human pathogen.Aeromonasassociated diarrhea is a phenomenon occurring worldwide.This study was designed to determine the prevalence,genetic diversity,antibiotic resistance,and pathogenicity of Aeromonas strains isolated from food products in Shanghai.Methods Aeromonas isolates(n=79)collected from food samples were analyzed using concatenated gyrB-cpn60 sequencing.The antibiotic resistance of these isolates was determined using antimicrobial susceptibility testing.Pathogenicity was assessed usingβ-hemolytic,extracellular protease,virulence gene detection,C.elegans liquid toxicity(LT),and cytotoxicity assays.Results Eight different species were identified among the 79 isolates.The most prevalent Aeromonas species were A.veronii[62(78.5%)],A.caviae[6(7.6%)],A.dhakensis[3(3.8%)],and A.salmonicida[3(3.8%)].The Aeromonas isolates were divided into 73 sequence types(STs),of which 65 were novel.The isolates were hemolytic(45.6%)and protease-positive(81.0%).The most prevalent virulence genes were act(73.4%),fla(69.6%),aexT(36.7%),and ascV(30.4%).The results of C.elegans LT and cytotoxicity assays revealed that A.dhakensis and A.hydrophila were more virulent than A.veronii,A.caviae,and A.bivalvium.Antibiotic resistance genes[tetE,blaTEM,tetA,qnrS,aac(6)-Ib,mcr-1,and mcr-3]were detected in the isolates.The multidrug-resistance rate of the Aeromonas isolates was 11.4%,and 93.7%of the Aeromonas isolates were resistant to cefazolin.Conclusion The taxonomy,antibiotic resistance,and pathogenicity of different Aeromonas species varied.The Aeromonas isolates A.dhakensis and A.hydrophila were highly pathogenic,indicating that food-derived Aeromonas isolates are potential risks for public health and food safety.The monitoring of food quality and safety will result in better prevention and treatment strategies to control diarrhea illnesses in China.

Helicobacter pylori vs immune system or antibiotics

Helicobacter pylori(H. pylori) infection has often no clinical signs and is one of the most common bacterial infections. All infected subjects have histology of active chronic gastritis. In some cases patients develop peptic ulcer and minority of them develop gastric cancer. Gastric cancer is multifactorial disease,thus various progressions of H. pylori infection and disease are dependent on the host genetic factors,the characteristics of the individual's immune response,environmental factors,and different bacterial virulence factors of the individual bacterial strains. Eradication of the bacteria plays a crucial role in the treatment of these cases however antibiotic therapy does not always help. Bacteria often develop resistance to antibiotics so we recommend that not only screening for H. pylori also the strain determination should have some diagnostic value,especially in the patients who already developed gastritis. Furthermore,for such patients assessment of disease progression(atrophic or metaplastic gastritis) could be followed by polymorphism determination. Until now we cannot predict the disease based only on single polymorphism. Bacteria successfully neutralize the responses of the immune systems using different enzymes or even components of the host immune response. However,the influence of immune system and its components could represent new ways of treatments and could help to eradicate the infection.

Impact of Genetic Diversity of Uropathogenic Escherichia coli and Klebsiella pneumoniae Strains on the Dissemination of Extended Spectrum Beta-Lactam Resistance Genes in Côte d’Ivoire

The increase and spread of bacterial resistance to extended-spectrum beta-lactam antibiotics are reported in many infections and are a real public health problem worldwide. Drug pressure is a factor that favors the emergence of a population of better adapted bacteria. However, there is no literature highlighting the genetic diversity and evolutionary structure of E. coli and K. pneumoniae in an environment with high selection pressure in Côte d’Ivoire. The objective of this study was to evaluate the genetic diversity of E. coli and K. pneumoniae strains circulating at the HKB Hospital in Abobo and at the Daloa Regional Hospital and its impact on the dissemination of extended spectrum beta-lactam resistance genes. A total of 39 strains isolated from the urinary tract of infected patients, including 30 strains of E. coli and 9 strains of K. pneumoniae were studied. A total of 39 strains isolated from the urinary tract of infected patients, including 30 strains of E. coli and 9 strains of K. pneumoniae were studied. From genomic DNA extracts, ESBL resistance genes were amplified by PCR and sequenced, in addition to genetic typing by ERIC-PCR. The data obtained were submitted to genetic and bioinformatics analyses. The results have shown a genetic diversity important in E. coli and K. pneumoniae with diversity indexs (SID) ranging from 0.5 to 0.77. The genetic structure of the bacterial species studied has shown a clonal distribution of strains with clones expressing TEM-9 and CTX-M-15 variants. Also, this clonal structure was correlated with the spread of resistance genes in E. coli and K. pneumoniae. The spread of resistant clones is a factor that might limit the fight against antibiotic resistance.

Genetic factors determining the host response to Helicobacter pylori

INTRODUCTIONThe strongest evidence that H.pylori infection isthe cause of peptic ulcer is that treatment withantibiotics as the only regimen,is not only effectivefor the clearance and eradication of the infection,but more importantly for the healing of the ulcer orthe remission of gastric lymphoma.However,it isstill a matter of controversy and research as to

Early Identification of Stable Transformation Events by Combined Use of Antibiotic Selection and Vital Detection of Green Fluorescent Protein (GFP) in Carrot (Daucus carota L.) Callus

Genetic transformation is a useful technique to complement conventional breeding in crop improvement. Although carrot has been a model organism for in vitro embryogenesis study, genetic transformation of carrot is still lengthy and labor intensive. An efficient transformation and detection system is desirable. Direct infection of Agrobacterium to carrot calli has provided an easy way for carrot genetic transformation. To improve the efficiency of antibiotic selection in this method, we report the combined use of an improved green-fluorescent protein, referred to as smGFP, to establish a versatile selection method for carrot callus transformation system. By combining antibiotic selection with the bright fluorescence observed in the callus tissue, we were able to easily identify stable transformants in early stage of the transformation process. In addition to the GFP expression of the callus cells, the transgenic nature of callus cells was confirmed with Southern and Western analysis. We found we can link the simplicity of carrot-callus-cell transformation, early detection of stable transformants with antibiotic selection, visualization of GFP fluorescence, and molecular analysis （Southern and Western） of callus tissue （non-photosynthetic tissue） to provide a more efficient way in identifying stable transformants at early stage of carrot transformation.

1例类鼻疽脓毒症患者的全程个体化药学监护

目的为类鼻疽脓毒症(MS)抗菌药物治疗方案的调整、不良反应的识别和个体化药学监护提供参考。方法临床药师利用血药浓度和基因检测全程参与1例MS患者强化期和根除期治疗过程。通过测定β-内酰胺类和复方磺胺甲噁唑(TMP/SMZ)血药浓度并计算其药代动力学与药效学(PK/PD)参数,结合文献对MS抗菌药物治疗方案进行调整;同时通过高通量测序检测药物相关基因多态性,对药物不良反应的发生原因进行分析并进行处理。结果临床药师利用血药浓度和基因检测手段,提出了亚胺培南西司他丁钠(IMP)给药剂量调整建议,分析了多种药物不良反应的发生原因;通过测定β-内酰胺类药物和TMP/SMZ血药浓度计算PK/PD靶标,通过查询指南和文献为临床医生解释类鼻疽患者脓毒症期和非脓毒症期状态下的达标情况;利用血药浓度和基因检测分析MS患者神经毒性与IMP cmin的相关性,并发现肾毒性与TMP/SMZ的cmax无关,而与患者饮水量相关。经全程抗菌药物治疗后,患者病情好转出院,不良反应得到有效处理。结论临床药师基于抗菌药物血药浓度和基因检测结果解读情况协助临床医生制定MS治疗方案,并为患者提供全程用药监护,提高了临床药物治疗的安全性和有效性。

北京市售生食果蔬中耐药基因赋存特征及迁移风险

目的调研抗生素耐药基因(antibiotic resistance genes,ARGs)的赋存特征,探讨其在食品安全领域的潜在风险。方法采用高通量定量聚合酶链式反应(high-throughput quantitative polymerase chain reaction,HT-qPCR)技术,对北京市售生食果蔬中ARGs及可移动遗传元件(mobile genetic elements,MGEs)的多样性和存在丰度进行描述,并通过高风险筛查、相关性分析、冗余分析、方差分解分析,探讨ARGs的迁移风险。结果共检出9大类188个ARGs和9个MGEs,丰度范围分别为6.18×10^(3)~1.24×10^(8) copies/g、5.86×10^(3)~3.34×10^(8) copies/g;四环素类、氨基糖苷类、β-内酰胺类、大环内酯-林可霉素-链阳霉素类(macrolide-lincosamide-streptogramin B,MLSB)ARGs分布最广;多重耐药类ARGs丰度最高;涉及的主要耐药机制贡献大小为抗生素灭活>外排泵>细胞保护。其中,苦菊的ARGs检出率最高,青椒的ARGs丰度最高;茄果类、叶菜类ARGs丰度普遍高于根茎类蔬菜;水果类样品中ARGs的检出率和丰度最低。高风险ARGs普遍存在,丰度最高可达7.85×10^(7) copies/g,且氨基糖苷类、磺胺类、四环素类、多重耐药类ARGs具有高迁移风险,整合酶和转座酶两类转移机制共同构成主要驱动因素(46.44%)。结论生食果蔬中ARGs赋存情况严重,具有较高的迁移风险,很可能导致耐药现象的大量产生及扩散,危害人类健康,应引起高度重视。

强还原处理对土壤中常见抗生素及其抗性基因的影响研究

土壤中抗生素长期累积所引发的抗性致病菌富集以及抗性基因(Antibiotic resistance genes,ARGs)的传播扩散,已成为当前备受关注的环境问题。为研究强还原处理(Reductive soil disinfestation,RSD)对土壤中抗生素及其ARGs的影响,以常用且难降解的抗生素四环素、土霉素、磺胺嘧啶和磺胺甲恶唑所构建的质量分数为20 mg·kg^(-1)的抗生素混合污染土壤为研究对象,分别设置以玉米秸秆(2%,RCS)、甘蔗渣(2%,RSR)为有机物料的RSD处理,同时设置不处理对照,于处理第7、14、28天进行破坏性采样,利用高效液相色谱和荧光定量PCR技术分析RSD处理过程中抗生素质量分数及ARGs和可移动遗传元件(Mobile genetic elements,MGEs)丰度的变化。结果表明,RSD处理可有效降解土壤中的四环素类和磺胺类抗生素,处理28 d后磺胺类抗生素的降解率为45.2%-100%,优于四环素类的33.5%-57.2%;RSR处理对四环素和磺胺嘧啶的降解效果优于RCS处理,其降解率可达57.2%-64.8%,而RCS处理对土霉素的降解率可达44.7%;两种RSD处理对磺胺甲恶唑的降解率在14 d时即可达100%。RSD处理后土壤中ARGs绝对丰度显著增加,RCS处理的增加作用强于RSR处理;随处理时间延长,tetM、qacH等基因相对丰度在RSD处理中呈下降趋势,一定程度上表明ARGs增加带来的生态负面效应得到缓解。RSD处理可显著降低IS26基因的相对丰度,表明其能通过消减特定MGEs削弱ARGs水平转移能力。综上,RSD处理可有效降解土壤中四环素类和磺胺类抗生素,具有消减土壤中ARGs并降低其传播风险的潜力。研究结果可为解决土壤抗生素污染问题、降低ARGs扩散风险提供一定的理论与技术支持。

冬季天津临港复合型人工湿地对抗生素抗性基因的去除效果

环境中耐药菌和抗生素抗性基因(ARGs)因抗生素的大量应用而广泛存在,影响抗生素对疾病的治疗效果,对人体健康和生态安全构成威胁。研究表明人工湿地(CWs)能够有效去除ARGs,但目前对于北方冬季复合型CWs对ARGs的去除效果尚不明确。以天津临港复合型的CWs(调节塘+水平潜流湿地+表流湿地工艺)为研究对象,开展冬季其对ARGs去除效果的研究;针对不同功能区采集水体样本,采用高通量荧光定量PCR对水体中16S rRNA基因、ARGs、可移动遗传元件(MGEs)及细菌种群组成进行检测,综合分析CWs对ARGs的去除效果,探讨冬季运行期间影响去除效果的关键因素。结果表明:冬季水体中表征细菌数量的16S rRNA基因绝对丰度为2.70×10^(4)~1.41×10^(5)拷贝/mL;ARGs总检出率为72.5%,其中floR和sul2并非源于进水。各ARGs在不同功能区的丰度差异明显,不同功能区对ARGs的去除效果也存在明显差异。整体来看,CWs对氨基糖苷类抗性基因和多重耐药基因的去除效果最好,总绝对丰度去除率分别为85.59%、47.78%,总相对丰度去除率分别为97.09%、89.44%;对β-内酰胺类抗性基因去除效果最差,总绝对丰度和相对丰度去除率分别为−404.40%、−2.01%。调节塘、水平潜流湿地、表流湿地对ARGs总绝对丰度去除率分别为38.05%、−7.78%和−2.41%;总相对丰度去除率分别为75.02%、−45.60%和−7.75%,不同功能区的去除效果表现为调节塘>表流湿地>水平潜流湿地,其中调节塘对除四环素类抗性基因外的其他ARGs的绝对丰度均有较好的去除效果,水平潜流湿地对磺胺类抗性基因去除效果较好,表流湿地对大环内酯类抗性基因有一定的去除效果。冬季低温、MGEs、不同工艺类型功能区及其运行时间是ARGs去除效果的关键影响因素,ARGs对细菌宿主的非选择性促进了其在天津临港CWs系统中各种细菌类群间的迅速传播。建议今后加强CWs对新污染物ARGs去除效果的优化技术研究。

猪肠道非致病性且无耐药性大肠杆菌的分离鉴定、生长特性和基因组进化分析

【目的】从猪肠道中分离出无毒力基因且无抗生素耐药性的大肠杆菌,并分析其生长性能和遗传进化规律,以期为开发猪用微生态制剂或口服疫苗奠定基础。【方法】采集广东省2个地区养猪场的11头和15头健康成年猪的粪便样本。首先,采用培养方法从麦康凯培养基中分离出疑似大肠杆菌的菌株,通过16S rRNA序列分析鉴定其是否为大肠杆菌菌株;然后,采用PCR方法验证所选大肠杆菌是否含有13种常见的猪致病性大肠杆菌毒力基因,并以7类(14种)抗生素进行药敏试验;最后,对筛选出的优质大肠杆菌菌株进行生长动力学分析,并提取其全基因组DNA,构建全基因组系统进化树。【结果】在260株疑似为大肠杆菌菌株中,经16S rRNA序列分析确认后有206株属于大肠杆菌。其中,107株大肠杆菌不含13种常见毒力基因,25株大肠杆菌对7类(14种)抗生素敏感。在这25株菌株中,有23株非致病性且无抗生素耐药性大肠杆菌(编号为2-9、3-2、3-4、5-1、6-1、6-2、6-9、6-10、8-2、8-9、10-5、B-4、B-6、B-7、B-10、D-10、E-2、E-10、J-1、J-4、K-6、L-6和O-9)的生长性能与大肠杆菌Nissle1917、MG1655相似,其他2株大肠杆菌(编号为6-4和5-2)的生长速度高于Nissle 1917和MG1655。此外,有10株菌株(编号为E-10、E-2、6-4、6-9、8-2、O-9、3-2、6-2、J-1、K-6)耐酸性能较好,可能适合长期定殖于猪胃肠道内。基于SNP核心基因组系统进化树分析,发现这25株菌株中有9株菌株(编号为3-2、6-10、10-5、6-1、8-9、5-2、L-6、O-9、K-6)在系统进化树开端处属于同一大类群,表明它们极可能为猪原生大肠杆菌的祖先群。【结论】综合上述大肠杆菌的抗生素敏感性、生长性能和全基因组进化树和胃液环境耐受性能分析,菌株O-9在这4个方面均具备优势,该菌株与大肠杆菌Nissle 1917、MG1655的生长动力学相似甚至更优,意味着O-9菌株可能是优质的猪肠道原生大肠杆菌,具有极大研究潜力。

海南省39株幽门螺杆菌的耐药性及毒力基因特征

目的了解海南省幽门螺杆菌(Hp)耐药性及其毒力基因vacA、cagA和iceA基因型特征。方法对146例上消化道症状疾病患者进行胃镜检查,取胃黏膜组织进行Hp的分离和培养,对Hp进行药敏检测;通过聚合酶链式反应(PCR)对毒力基因cagA、vacA和iceA进行检测和分型,cagA测序进行聚类分析、并构建系统进化树;使用Fisher确切概率法分析各型毒力基因和患者疾病发生的相关性。结果共培养出39株Hp,对阿莫西林和克拉霉素的耐药率分别为2.6%和48.7%;39株均为vacA^(+)菌株,iceA 1型26株、2型13株;33株为cagA^(+)菌株,其中5株为西方型(EPIYA-ABC型),28株为东亚型(EPIYA-ABD型);cagA^(+)和vacA^(+)菌株与胃和十二指肠疾病有显著的相关性(P<0.05),iceA则无显著性差异(P>0.05)。结论海南省胃和十二指肠Hp患者中Hp毒力基因多样化,vacA s1am2/cagA^(+)基因型在消化性溃疡患者中占优势,不同毒力基因型对胃和十二指肠疾病的发生具有明显的差别,阿莫西林可作为该地区根除Hp首选抗生素。

沈阳典型粳稻种植区稻田土壤ARGs和MGEs污染分布特征分析

农田土壤中抗生素抗性基因(ARGs)与可移动遗传元件(MGEs)的污染问题,在学术界已引发广泛关注。为研究沈阳市粳稻种植区稻田土壤中ARGs与MGEs的存在和相关性,并探讨其对土壤-植物系统的潜在影响,通过采集沈阳市辽中区、新民市、沈北新区和苏家屯区的粳稻种植区域土壤样品,利用高通量qPCR技术,对285个ARGs、10个MG-Es和一个16S rRNA基因进行检测和定量分析。结果表明:在不同地区的稻田土壤中共检测到273种ARGs和MGEs,且种类和丰度存在显著差异。进一步的相关性分析发现,ARGs与MGEs之间存在一定相关性,并且这种相关性在不同地区间有所差异。多种ARGs与MGEs之间存在显著正相关(p<0.05),其中部分ARGs[tet(32)等]与MGEs(tnpA-01等)存在及极显著正相关(p<0.01),这表明在土壤中MGEs对ARGs迁移和扩散起到促进作用。4个采样区根际土中ARGs和MGEs的总相对丰度均高于非根际土壤,这进一步凸显根际环境在ARGs和MGEs分布中的重要性。此外,还发现在不同地区的稻田土壤中,抗生素失活机制在ARGs中占据主导地位。综上所述,试验结果为深入了解东北水稻种植区稻田土壤中ARGs的污染现状及其潜在影响提供了数据支持和理论基础。这些发现不仅有助于认识农田土壤中ARGs和MGEs的分布与迁移规律,还为制定针对性的土壤污染防控措施提供了科学依据。

基于抗生素和除草剂敏感性筛选适宜裂叶地黄遗传转化系统的抗性标记

目的:筛选适宜裂叶地黄遗传转化系统的抗性标记。方法:以裂叶地黄的种子为材料,采用不同浓度抗生素和除草剂对裂叶地黄的种子外植体进行处理,对比不同浓度的卡那霉素、潮霉素和除草剂草铵膦(Basta)的筛选效果,为裂叶地黄遗传转化体系的构建提供基础。结果:裂叶地黄种苗对Basta和潮霉素敏感性的强度强于卡那霉素。Basta浓度为1 mg/L和2 mg/L时,地黄种苗培养30 d存活率为38.03%和5.07%,对裂叶地黄种苗生长有明显的抑制作用;浓度为5 mg/L时,完全抑制裂叶地黄种苗的生长,可作为遗传转化抗性苗筛选的选择压。潮霉素浓度为10 mg/L时,地黄种苗存活率为34.17%,对裂叶地黄种苗生长有明显的抑制作用;浓度为20 mg/L时,将裂叶地黄种苗全部致死,可作为抗性苗筛选的选择压。卡那霉素浓度为50 mg/L时,种苗白化率达到89.17%,种苗生长受到明显抑制。结论:Basta适宜筛选浓度为5 mg/L,潮霉素适宜筛选浓度为20 mg/L,卡那霉素适宜筛选浓度为不低于50 mg/L。

畜禽养殖过程抗生素使用与耐药病原菌及其抗性基因赋存的研究进展

兽用抗生素在提高畜禽生产性能、防治疾病方面发挥着重要作用,目前全球超过一半以上抗生素用于畜禽养殖,畜禽养殖源耐药病原菌、抗性基因及其传播风险愈益得到人们的重视。我国是畜禽养殖和抗生素使用大国,但兽用抗生素使用、病原菌耐药水平及其抗性基因类型等数据却较为缺乏,不利于今后畜禽养殖源耐药病原菌及其传播风险的控制。因此,本文通过文献调研,对我国和主要发达国家的兽用抗生素使用情况、畜禽养殖源耐药病原菌及其携带的抗性基因、基因移动元件以及向环境传播的途径进行分析、总结,以期为规范合理用药、降低耐药病原菌及其抗性基因传播风险,建立从畜禽养殖场至公共环境全过程的抗性污染控制链条提供借鉴。

银白杨遗传转化中抗生素浓度优化的研究

该文探讨了卡那霉素、G418、羧苄青霉素和头孢霉素4种抗生素对银白杨不同培养阶段外植体生长、分化或生根的影响,确立了由农杆菌介导的银白杨遗传转化研究中抗生素种类和转化体的筛选浓度.结果表明:在叶片转化筛选阶段,卡那霉素和G418的适宜浓度分别为15和10mgL,羧苄青霉素和头孢霉素的适宜浓度为200～600mgL和200～400mgL;在抗性芽生根培养时,卡那霉素和G418浓度分别为20～25mgL和15～20mgL,羧苄青霉素和头孢霉素浓度为200～800mgL和200～600mgL.头孢霉素或羧苄青霉素的抑菌效果因农杆菌菌株的不同而存在差异,羧苄青霉素对农杆菌LBA4404抑制效果好,头孢霉素对农杆菌C58抑制效果理想.

沙门氏菌抗生素抗性机理研究进展

沙门氏菌的多重耐药性问题已经成为世界范围内的公共卫生和经济问题。目前沙门氏菌抗生素抗性机理的研究主要集中以下方面:(1)基因突变与抗生素抗性;(2)外排泵与抗生素抗性;(3)耐药基因编码的钝化酶和灭活酶引起的抗生素抗性;(4)可移动的细菌遗传耐药基因元件及其转移与抗生素抗性。本文基于以上几个方面综述了与沙门氏菌抗生素抗性机理研究相关的研究动态和研究进展。

抗生素对台湾青枣茎段和愈伤组织生长的影响

探讨了卡那霉素 (Kan)、羧苄青霉素 (Cb)、头孢霉素 (Cef)和氨苄青霉素 (Amp) 4种抗生素对台湾青枣幼嫩茎段和疏松的愈伤组织生长的影响 ,初步确立了对台湾青枣 (ZiziphusmauritianaLam .)进行农杆菌介导的遗传转化研究中的抑菌和转化体的筛选策略 .Kan 75mg·L-1时 ,5 0d后茎段基本停止生长并开始变成白色 (白化 ) ;Kan2 5mg·L-1时 ,胚性愈伤组织生长受到明显的抑制 ,Kan 5 0mg·L-1时 ,其生长基本停止且开始褐变 ,Kan 75mg·L-1以上时胚性愈伤组织完全变褐 .适当浓度的Cb或Cef对芽的伸长生长有一定的促进作用 ,Cb +Cef却对芽的伸长出现轻微的抑制效应 .