2021年西安市食源性腹泻患者致泻大肠埃希菌耐药性及分子分型

目的 了解2021年西安市食源性腹泻患者致泻大肠埃希菌（DEC）的感染状况、致病型分布、耐药性及分子分型特征。方法 收集西安市5家哨点医院腹泻患者粪便标本,进行DEC分离和PCR毒力基因分型鉴定,采用微量肉汤稀释法和脉冲场凝胶电泳（PFGE）对分离株进行药敏试验和分子分型,结果采用SPSS 19.0软件进行统计学分析。结果 389份粪便标本检出DEC阳性40份,阳性检出率为10.28%（40/389）。共分离到41株DEC,以肠产毒性大肠埃希菌（ETEC）和肠集聚性大肠埃希菌（EAEC）为主,分别占41.46%（17/41）和39.02%（16/41）。ETEC以estIa/estIb基因型为主（70.59%,12/17）,EAEC以astA/pic基因型为主（87.50%,14/16）。40株菌（97.56%,40/41）对至少1种抗生素耐药,对氨苄西林、四环素、头孢噻肟和萘啶酸耐药率均超过50%,多重耐药率为56.10%（23/41）。41株DEC聚类分析得到40种带型,相似度为62.0%~100.0%。结论 2021年西安市食源性腹泻患者中DEC检出率较高,主要致病型为ETEC和EAEC,PFGE带型较为分散,菌株耐药及多重耐药现象比较严重。     

2019—2021年武汉市致泻大肠埃希菌分子分型与耐药性研究

目的 了解2019—2021年湖北省武汉市腹泻患者来源致泻大肠埃希菌的毒力基因分布、耐药情况以及种群多样性。方法 定期收集来自武汉市5家医疗机构的致泻大肠埃希菌菌株并通过生化反应和飞行时间质谱进行确认。对经确认的菌株进行药敏试验以及多重PCR检测毒力基因。采用脉冲场凝胶电泳技术和多位点序列分型技术对收集的菌株进行分子分型。通过聚类比对和构建最小生成树进行同源性分析。结果 收集到59株致泻大肠埃希菌，共检出3种基因型别。其中检出产肠毒素大肠埃希菌（ETEC）29株，占比最高为49.15%；肠集聚性大肠埃希菌（EAEC）、肠致病性大肠埃希菌（EPEC）各检出15株，占比均为25.42%。59株致泻性大肠埃希菌对除多黏菌素E外的11种抗生素表现出不同程度的耐药，对氨苄西林（67.80%）、萘啶酸（61.02%）、四环素（45.76%）、复方新诺明（37.29%）、头孢噻肟（30.51%）、氯霉素（13.56%）表现出较高的耐药性。EAEC和EPEC均存在14种不同的脉冲场凝胶电泳带型，均可被分为11种不同的ST型别。ETEC存在28种不同的脉冲场凝胶电泳带型，可被分为10种不同的ST型别，且超过50%的ETEC属于同一种优势克隆复合体CC-10。结论 武汉市食源性致泻大肠埃希菌的污染长期存在且耐药情况严重，其中EAEC和EPEC型别多样，ETEC的优势克隆复合体CC-10被广泛检出。     

温州市食品中小肠结肠炎耶尔森氏菌分布及分子分型研究

目的 了解温州市食品中小肠结肠炎耶尔森氏菌的分子分型及分布特征。方法 4 ℃增菌后用选择性培养基对食品中的小肠结肠炎耶尔森氏菌进行分离鉴定,分析阳性菌株的生物型、血清型、毒力基因型、耐药性和脉冲场凝胶电泳（PFGE）分子型别。结果 采集6类食品,共676份样品,其中68份样品检出69株小肠结肠炎耶尔森氏菌,检出率为10.1%（68/676）。调理肉制品检出率最高（20.5%,9/44）,其次为速冻食品（17.2%,11/64）。95.7%（66/69）的分离株为生物1A型,生物血清型以1A/O∶5（29.0%）为主,其次为1A/O∶8（14.5%）;88.4%（61/69）的菌株仅携带ystB基因,检出1株4/O∶3型菌株携带毒力基因ail、ystA、yadA、virF。分离株对14种抗菌药物的敏感率达到94%以上。32株血清已分型菌株,分为29种PFGE带型。结论 温州市食品中存在一定程度的小肠结肠炎耶尔森氏菌污染,且检出致病性小肠结肠炎耶尔森菌,菌株耐药率处于较低水平,分子分型提示菌株呈高度遗传多态性。     

北京市通州区食源性疾病监测病例中副溶血弧菌的病原特征分析

目的 了解通州区2015—2021年食源性疾病监测病例中副溶血弧菌的脉冲场凝胶电泳（PFGE）优势带型、耐药情况和毒力基因携带情况,为副溶血弧菌感染防控和治疗提供参考数据。方法 对2015—2021年通州区定点监测医院门诊腹泻病例的粪便样本进行副溶血弧菌分离培养,对其进行血清分型、毒力基因检测、PFGE聚类分析及药敏试验。结果 2 828份粪便标本中检出副溶血弧菌100株,检出率为3.54%,每年7~9月是检出高峰月份。不同年份副溶血弧菌检出率差异具有统计学意义（χ²=53.94,P<0.001）。100株副溶血弧菌中有一株未携带tlh基因,89.00%的菌株携带致病性毒力基因tdh。副溶血弧菌优势血清型为O3∶K6（66/100）,其次是O4∶K8（9/100）。98株菌副溶血弧菌（2株降解）PFGE分型结果显示副溶血性弧菌有39个PFGE带型,命名为V1-V39,条带相似度在79.6%~100%之间,基因分布呈高度多态性,V22和V25是通州区副溶血弧菌的优势带型。菌株对头孢唑林的耐药率最高（32.00%）,其次是氨苄西林（14.00%）和多黏菌素E（13.00%）,对四环素类、氯霉素类、氨基糖苷类、碳青霉烯类四类药物100%敏感。结论 通州区2015—2021年食源性疾病监测病例中检出的副溶血弧菌主要是O3∶K6型tdh⁺- trh^-菌株,对头孢唑林,氨苄西林和多黏菌素E耐药。PFGE图谱主要流行菌株带型相似度在93.1%以上,存在暴发风险,食品安全相关部门需做好副溶血弧菌监测及暴发预警工作,预防食源性疾病暴发。     

多黏菌素类抗生素耐药性编码基因检测用质粒标准样品研制

目的 研制适合多黏菌素类抗生素耐药性编码基因检测用质粒DNA标准样品。方法 由National Center for Biotechnology Information（NCBI）数据库检索得到mcr-1、mcr-3、mcr-5基因参考序列,构建重组质粒和重组菌株;将重组菌传代至15代检测目标基因的遗传稳定性。提取重组质粒,真空干燥,制得标准样品。将标准样品水化、连续10倍梯度稀释,测定聚合酶链式反应（PCR）和实时荧光PCR（RT-qPCR）扩增目标基因的检出限。随机抽取质粒DNA标准样品,采用PCR法和紫外分光光度计法检验样品的均匀性及其在4 ℃、37 ℃、-20 ℃的贮存稳定性。结果 成功获得多黏菌素类抗生素耐药机制编码基因mcr-1、mcr-3、mcr-5基因片段,重组菌15代传代中目的基因遗传稳定。mcr-1、mcr-3、mcr-5标准样品PCR和RT-qPCR最低检出限分别为1.67×10⁴ 拷贝数/μL和1.67 拷贝数/μL、1.31×10⁶ 拷贝数/μL和13.1 拷贝数/μL、1.55×10⁵ 拷贝数/μL和1.55 拷贝数/μL。T检验表明,各基因随机抽取的12管标准样品质量间的F值均小于F_临界值,且PCR均可检出,均匀性符合要求。标准样品在4 ℃贮存90 d、37 ℃贮存14 d、-20 ℃贮存360 d,定性、定量检验结果稳定、无极显著性差异。结论 本实验制备的mcr-1、mcr-3、mcr-5质粒DNA标准样品目的基因遗传稳定,均匀性和贮存稳定性良好。本研究结果可用于多黏菌素类抗生素耐药机制的快速预测和相关基因检测的质控样品。     

2016—2020年上海市市售即食食品微生物污染状况分析及评价

目的 了解上海市市售即食食品中微生物污染情况,及时发现食品安全隐患,为即食食品风险评估、管理和标准制定提供科学依据。方法 2016-2020 年共采集上海市即食食品20类共10 521份食品样品,对菌落总数、大肠埃希氏菌计数2种卫生指示菌和副溶血性弧菌、金黄色葡萄球菌、致泻大肠埃希氏菌、沙门氏菌、蜡样芽孢杆菌、单核细胞增生李斯特氏菌（以下简称单增李斯特菌）6种食源性致病菌进行定量或定性检验,并分析卫生指示菌和食源性致病菌污染水平及关联性。结果 凉拌米面制品、沙拉、中式凉拌菜的指示菌污染水平较高,菌落总数均值分别为（5.13±1.43）lgCFU/g、（4.56±1.13）lgCFU/g、（4.26±1.75）lgCFU/g;大肠埃希氏菌计数分别为（1.20±1.00）lgCFU/g、（1.47±1.41）lgCFU/g、（1.18±1.06）lgCFU/g。冷锅串串、沙拉、中式凉拌菜、熟肉制品中单增李斯特菌检出率较高,分别为6.27%、3.36%、2.71%、2.69%;副溶血性弧菌仅在生食动物性水产品（3.65%）、中式凉拌菜（2.58%）、熟肉制品（0.42%）中检出;米面制品中蜡样芽孢杆菌（7.51%）显著高于寿司（0.53%）（P<0.05）。菌落总数均值与大肠埃希氏菌计数均值呈极显著正相关（P<0.001）;菌落总数均值与致病菌样品阳性率呈显著正相关（P<0.05）。结论 上海市生食食物、凉拌、夹心等最后一步加工工艺非加热的即食食品,卫生指示菌和致病菌污染水平较高,食源性致病风险较高,应重点防范。固体即食食品菌落总数计数水平与食源性致病菌污染状况存在相关性。     

荧光PCR法检测原料乳中大肠埃希氏菌喹诺酮类的耐药基因

目的 建立喹诺酮类抗生素主要耐药基因的TaqMan荧光PCR检测方法,为原料乳中耐药大肠埃希氏菌的监测提供技术方案。方法 利用Chelex 100法快速获取细菌基因组DNA,通过对aac(6’)-Ib-cr和qepA基因的序列分析,利用Primer Express 3.0软件设计特异性引物和探针,建立单重和双重TaqMan荧光PCR方法。通过耐药基因阳性菌株和原料乳中分离大肠埃希氏菌菌株,对方法进行评估。结果 以Chelex 100法快速提取耐药基因阳性菌株细菌基因组DNA为模板,建立的aac(6’)-Ib-cr和qepA基因的单重和双重荧光PCR反应均有特异性曲线扩增,方法灵敏度为菌液浓度10_^-4 CFU/mL。北京地区52份原料乳中共分离出32株大肠埃希氏菌,利用建立的双重荧光PCR方法检测aac(6’)-Ib-cr和qepA基因结果为阴性,和环丙沙星肉汤稀释法药敏结果一致。结论 本方法的建立为原料乳中大肠埃希氏菌常见喹诺酮类耐药基因的快速检测提供了新的技术手段。     

我国食品中大肠埃希菌O157耐药及PFGE分子分型特征分析

了解我国食品中分离的110株大肠埃希菌O157的耐药及脉冲场凝胶电泳(PFGE)分子分型特征,完善我国食品中大肠埃希菌O157菌株特征的基础信息,为该菌的风险评估提供依据。方法 使用琼脂稀释法对确认的110株大肠埃希菌O157进行药敏试验,完成耐药特征的分析。参照美国疾病预防控制中心PulseNet试验方法,对110株大肠埃希菌O157,运用XbaⅠ酶进行酶切并完成PFGE分析,利用BioNumerics软件对分离株的指纹图谱进行聚类分析。结果 ①110株菌中,43株菌至少对一种抗生素有抗性。耐药率最多的前三种抗生素依次是四环素(30.0%,33/110),磺胺甲恶唑(29.1%,32/110),萘啶酸(26.4%,29/110);②一共有24个耐药谱,耐两种以上抗生素的菌株有34株,耐3种以上抗生素的多重耐药菌株有32株。最常见的三种耐药谱依次是SMX(6),AMP-NAL-SMX-SXT-TET(6),AMP-CHL-NAL-SMX-SXT-TET(4)/AMP-SMX-SXT-TET(4)/TET(4);③大肠埃希菌O157非H7 (O157∶hund)对所测试的抗生素的耐药率明显高于大肠埃希菌O157∶H7(χ²=72.010 P<0.05)。其中37株携带了志贺毒素基因的大肠埃希菌O157∶H7仅对磺胺甲恶唑(2.7%,1/37)、萘碇酸(2.7%,1/37)有耐药,没有多重耐药菌株;④通过不同种类食品中大肠埃希菌O157菌株耐药率比较发现,从生猪肉、生禽肉中分离的菌株耐药率相对高于其他食品种类;⑤PFGE分子分型研究显示菌株具有基因多态性,且可以很好将大肠埃希菌O157非H7和大肠埃希菌O157∶H7菌株区分开。结论 我国食品中分离的大肠埃希菌O157耐药现象严重。我们应加强养殖环节和零售环节食源性致病菌,特别是大肠埃希菌O157(包括产志贺毒素大肠埃希菌O157)菌株药敏特征的监测,探明食品与养殖环节菌株耐药的传播关系,并为国家制定科学的养殖业抗生素用药提供依据。     

2016—2021年无锡市副溶血性弧菌毒力基因和耐药性分析及分子分型研究

目的 分析2016—2021年无锡市不同来源副溶血性弧菌的毒力基因、耐药性和分子分型结果。方法 采用多重荧光PCR、微量肉汤稀释法、脉冲场凝胶电泳（PFGE）分别对204株分离自无锡市各类监测样本中的副溶血性弧菌进行tlh/tdh/trh毒力基因检测、耐药试验和分子分型。数据比较采用χ²检验。结果 204株菌tlh基因携带率为100%（204/204），tdh基因携带率为82.35%（168/204），trh基因携带率为2.45%（5/204），食品及环境分离株与病患分离株tdh基因携带率差异具有统计学意义（P<0.001）。菌株对头孢唑啉耐药率最高达96.08%（196/204），对3种及以上抗菌药物的耐药率为2.94%（6/204），食品及环境分离株与病患分离株对氨苄西林、四环素、磺胺甲??唑/甲氧苄啶、环丙沙星耐药率差异具统计学意义（P<0.05）；204株副溶血性弧菌经过聚类分析，分为123个PFGE带型，相似度49.1%~100.0%，按85%的相似度聚类可分为18个带型簇。结论 无锡市副溶血性弧菌病患分离株大部分携带tdh基因；菌株对头孢唑啉耐药率最高；PFGE型别呈多态性，优势带型不明显。     

北京市售鸡肉和猪肉中大肠杆菌污染情况及耐药特征分析

目的 分析北京市售生鸡肉和生猪肉中大肠杆菌的污染情况以及耐药表型及耐药基因型。方法 从北京市辖6个区的大型超市和农贸市场随机采集259份生鲜肉类样品（鸡肉168份、猪肉91份）,增菌后分离大肠杆菌,并使用基质辅助激光解吸电离-飞行时间质谱和16 s rRNA测序对分离菌株进行鉴定。对分离菌株进行药物敏感性测定和全基因组测序,对耐药基因和耐药表型进行比较分析。结果 从259份样品中分离出169株大肠杆菌,检出率为65.25%,其中鸡肉和猪肉中大肠杆菌的检出率分别为77.38%和42.86%。药敏试验结果表明大肠杆菌对甲氧苄氨嘧啶-磺胺甲恶唑（鸡肉83.33%,猪肉91.67%）高度耐药,其次是多西环素（鸡肉32.35%,猪肉38.89%）,同时,它们对庆大霉素、妥布霉素、头孢噻肟、黏菌素等药物都呈现出了不同程度的耐药性。耐药基因分析发现β-内酰胺类基因ampC1与ampC2携带水平最高,检出率分别为93.10%、98.28%,另外也检测到ESBL、NDM-1、mcr-1等重要耐药基因,其中bla_TEM-1D和blaCTX-M_-9是主要存在的ESBL耐药基因。结论 目前北京市售鸡肉存在较为严重的大肠杆菌污染,分离菌株呈现复杂的耐药表型并携带多样的耐药基因,应加强对生鲜肉类样品的微生物污染和细菌耐药性控制,尤其是产ESBL耐药大肠杆菌,为预防控制由其引起的食源性疾病提供科学依据。     

植物乳杆菌发酵桑葚酵素工艺优化及质量评价

目的:解决新鲜桑葚难以保存的问题，将新鲜桑葚制成桑葚酵素。方法:以新鲜桑葚汁为原料，植物乳杆菌为生产菌种，总酚含量为评价指标，通过单因素试验结合响应面试验优化了植物乳杆菌桑葚酵素的发酵工艺，并对桑葚酵素的理化、微生物及感官质量指标进行评价。结果:优化后发酵工艺条件为发酵时间40 h、发酵温度32℃、接种量25%,所制得的植物乳杆菌桑葚酵素的总酚含量达(43.48±0.67)μg/mL,是未经发酵的桑葚汁的1.62倍，可溶性固体物含量为5.36%,pH值为4.08±0.01,微生物指标满足国家标准；桑葚酵素呈紫红、色泽均匀，具有浓郁的桑葚果香和发酵的香味、无异味，酸味柔和、风味好，有光泽、无杂质及沉淀。结论:经植物乳杆菌发酵制得桑葚酵素的过程有生物活性物质产生，有利于提高桑葚酵素质量。     

柠檬明串珠菌KM20中D-乳酸脱氢酶的特性

目的：分析柠檬明串珠菌中D-乳酸脱氢酶（D-LDH）的酶学特性。方法：对柠檬明串珠菌KM20中D-乳酸脱氢酶基因进行克隆表达并构建表达质粒,转化至Escherichia coli BL21（DE3）中实现过表达。结果：经Ni-NTA柱亲和层析纯化后,D-LDH-1与D-LDH-2编码的蛋白分子质量分别为40.0,38.5 kDa;比活力分别为2.18,153.10 U/mg;在丙酮酸还原中两种酶的最适pH值与最适温度均为8.0与40 ℃;而乳酸氧化时D-LDH-2的最适pH值与最适温度分别为12.0与30 ℃。D-LDH-1与D-LDH-2对草酰乙酸、苯丙酮酸和2-酮戊二酸具有较强的催化能力,且Ca²⁺、Cu²⁺和Na⁺对其酶活性均具有促进作用,Zn²⁺与SDS对酶活性有极高的抑制作用。此外,两种酶对丙酮酸的K_m值分别为2.98,6.11 mmol/L,对丙酮酸的K_cat/K_m分别为6.04×10²,2.28×10⁴ L/（mol·s）,LDH-2对D-乳酸的K_cat/K_m为65.0 L/（mol·s）。结论：D-LDH-1与D-LDH-2为柠檬酸明串珠菌中催化D-乳酸合成的关键酶。     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

Diversity of lactic acid bacteria in suan-tsai and fu-tsai, traditional fermented mustard products of Taiwan

Fu-tsai and suan-tsai are spontaneously fermented mustard products traditionally prepared by the Hakka tribe of Taiwan. We chose 5 different processing stages of these products for analysis of the microbial community of lactic acid bacteria (LAB) by 16S rRNA gene sequencing. From 500 LAB isolates we identified 119 representative strains belonging to 5 genera and 18 species, including Enterococcus (1 species), Lactobacillus (11 species), Leuconostoc (3 species), Pediococcus (1 species), and Weissella (2 species). The LAB composition of mustard fermented for 3 days, known as the Mu sample, was the most diverse, with 11 different LAB species being isolated. We used sequence analysis of the 16S rRNA gene to identify the LAB strains and analysis of the dnaA, pheS, and rpoA genes to identify 13 LAB strains for which identification by 16S rRNA gene sequences was not possible. These 13 strains were found to belong to 5 validated known species: Lactobacillus farciminis, Leuconostoc mesenteroides, Leuconostoc pseudomesenteroides, Weissella cibaria, and Weissella paramesenteroides, and 5 possibly novel Lactobacillus species. These results revealed that there is a high level of diversity in LAB at the different stages of fermentation in the production of suan-tsai and fu-tsai.     

Effect of X-ray treatments on inoculated Escherichia coli O157: H7, Salmonella enterica, Shigella flexneri and Vibrio parahaemolyticus in ready-to-eat shrimp

This study was conducted to evaluate the inactivation effect of X-ray treatments on Escherichia coli O157: H7, Salmonella enteric (S. enterica), Shigella flexneri (S. flexneri) and Vibrio parahaemolyticus (V. parahaemolyticus) artificially inoculated in ready-to-eat (RTE) shrimp. A mixed culture of three strains of each tested pathogen was used to inoculate RTE shrimp. The shrimp samples were inoculated individually with selected pathogenic bacteria then aseptically placed in sterile plastic cups and air-dried at 22 °C for 30 min (to allow bacterial attachment) in the biosafety cabinet prior to X-ray treatments. The inoculated shrimp samples were then placed in sterilized bags and treated with 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 2.0, 3.0 and 4.0 kGy X-ray at ambient temperature (22 °C and 60% relative humidity). Surviving bacterial populations were evaluated using a non-selective medium (TSA) with the appropriate selective medium overlay for each bacterium; CT-SMAC agar for E. coli O157: H7, XLD for S. enterica and S. flexneri and TCBS for V. parahaemolyticus. More than a 6 log CFU reduction of E. coli O157: H7, S. enterica, S. flexneri and V. parahaemolyticus was achieved with 2.0, 4.0, 3.0 and 3.0 kGy X-ray, respectively. Furthermore, treatment with 0.75 kGy X-ray significantly reduced the initial microflora on RTE shrimp samples from 3.8 ± 0.2 log CFU g⁻¹ to less than detectable limit (<1.0 log CFU g⁻¹).     

Effect of a global regulatory gene, afsR2, from Streptomyces lividans on avermectin production in Streptomyces avermitilis

The global regulatory gene, afsR2, from Streptomyces lividans was previously reported to highly stimulate two structurally unrelated antibiotics, actinorhodin and undecylprodigiosin, in both S. lividans and its close relative S. coelicolor. Production of eight avermectin components was also improved in S. avermitilis: the use of wild-type S. avermitilis and its high-producing mutant, transformed by introduction of multiple copies of afsR2, increased the total avermectin productions by 2.3-fold and 1.5-fold, respectively.     

Frequency of DLK1 c.639C>T polymorphism and the analysis of MEG3/DLK1/PEG11 cluster expression in muscle of swine raised in Poland

DLK1 — (Drosophila like element 1) is a paternally expressed gene, associated with the callipyge phenotype in sheep. In a present study we designed a new real-time PCR alleleic discrimination assay for genotyping of a silent C/T mutation (c.639C>T) in DLK1 gene in swine. The DLK1 c.639C>T mutation was highly polymorphic in all breeds analyzed and C allele was predominant in Landrace and Duroc while T allele was more frequent in Pietrain and Pu?awska breed. Moreover, we analyzed mRNA expression of DLK1 and adjacent genes — MEG3 and PEG11 in muscles of swines of different breeds raised in Poland. We did not observe significantly different expression of DLK1, MEG3 or PEG11 mRNA in any of analyzed breeds. We also attempted to assess the effect of DLK1 (c.639C>T) on the expression of genes in callipyge locus but did not find significant differences between animals with alternate genotypes (C/C and T/T homozygotes).     

沙门菌、金黄色葡萄球菌、副溶血性弧菌的选择性共增菌培养基的研制

目的 研制一种可同时对沙门菌、金黄色葡萄球菌及副溶血性弧菌进行富集的共增菌培养基SSV,达到同时检测3种食品中常见的食源性致病菌的目的。方法 根据3株菌的营养需求,选择不同的培养基组分进行单因素实验,确定选择性共增菌培养基的配方,通过OD600 nm、受损菌复苏、多重聚合酶链式反应(PCR)、培养基选择性4个方面对SSV培养基进行验证。结果 确定增菌培养基的成分为：蛋白胨10.0 g、KH₂PO₄ 1.5 g、NaCl 15.0 g、LiCl 1.0 g,Na₂S₂O₃ 5.0 g、去氧胆酸钠0.05 g、甘露醇1.0 g、丙酮酸钠5.0 g,蒸馏水1 000 mL。SSV培养基能同时富集以上3株菌,37℃培养16 h后,3株菌的菌体浓度均达到107 CFU/mL及以上;SSV培养基对于受损的目标菌有良好的复苏效果,复苏后OD₆₀₀ nm较于复苏前增长了3倍;同时多重PCR、培养基选择性也得到很好的验证。结论共增菌培养基SSV可用于同时培养沙门菌、金黄色葡...     

Comparison of antimicrobial resistance in Salmonella and Campylobacter isolated from turkeys in the Midwest USA

The current study was carried out to determine the antimicrobial resistance profiles and evaluate some molecular characteristics of a set of Salmonella and Campylobacter isolates recovered from production line turkeys in the Midwest region of the United States. A total of 94 birds identified as being positive for both Salmonella and Campylobacter spp. were selected for study. All Salmonella isolates were examined for antimicrobial resistance using the methods employed in the National Antimicrobial Resistance Monitoring System (NARMS). Campylobacter isolates were subjected to similar analysis using the Etest^®. In addition, polymerase chain reaction (PCR) was carried out to determine the presence of the antimicrobial resistance associated genes, integrase (int1), class 1 integrons (Salmonella and Campylobacter) and a multidrug efflux pump (Campylobacter spp.). Results from the study showed that the Salmonella and Campylobacter isolates examined displayed resistance to a number of antimicrobials, with Salmonella and Campylobacter isolates being resistant to at least three antimicrobials while some isolates showed resistances to 6 or 8 different antimicrobials. In addition, 68.1% of the Salmonella isolates tested were found to be positive for the class I integrase gene (int1), 28.7% possessed a 1000 bp gene cassette and 17% possessed an 800 bp gene cassette. All Campylobacter isolates were negative for int1, but 36.2% tested positive for the Campylobacter multidrug efflux pump (CmeB). A considerable number of Salmonella and Campylobacter isolates tested displayed varying degrees of antimicrobial resistance as well as the presence of some factors associated with the carriage and persistence of antimicrobial resistance. Similarities in the types of antimicrobial resistance observed in Campylobacter and Salmonella strains was evident. The results of this study suggest that prescribing practice at the farm level may be a factor in promoting antimicrobial resistance in more than one species of organism. Such practices may, therefore, contribute to the potential health risk for consumers should micro-organisms carrying multiple antimicrobial resistances enter the food chain. This study may be one of the first to report on the incidence of the multidrug efflux pump (CmeB) in Campylobacters recovered from processed turkeys. The antimicrobial resistance and molecular characteristics of Salmonella and Campylobacter is discussed.     

Feeding deterrent activity of terpenoid lactones with a p-menthane system against stored-product pests

Feeding deterrent activity of eight enantiomeric pairs and one optically inactive terpenoid lactone with a p-menthane system against three storage pests was determined. The lactones were tested on adults of Sitophilus granarius, adults and larvae of Tribolium confusum and larvae of Trogoderma granarium. The isomeric starting natural compounds, (+) and (−) pulegones and (+) and (−) isopulegols, were also tested. The results showed that the introduction of the lactone moiety into the p-menthane system produced antifeedant activity in the lactones obtained. The lactones with a spiro arrangement of lactone and cyclohexane rings were more active than those with condensed rings. The configuration of chiral centres present in the molecule significantly influenced the activity of the compounds studied. In most cases, lactones obtained from R-(+)-pulegone were more active antifeedants than those obtained from S-(−)-pulegone.