hns基因对大肠埃希菌生物膜形成能力的影响

目的 建立大肠埃希菌Red重组系统无痕敲除方法,探讨hns基因对大肠埃希菌生物膜形成能力的影响.方法 以大肠埃希菌MG1655为研究对象,将pKD46质粒转化入MG1655感受态细胞.以质粒pKD3为模板扩增氯霉素抗性基因片段,并将其转化入MG1655/pKD46,氯霉素抗性平板筛选阳性克隆.利用pCP20质粒删除氯霉素抗性基因,构建MG1655 hns基因缺失菌株.96孔板结晶紫染色法分析MG1655 hns基因缺失株生物膜形成能力的变化.苯酚-硫酸法检测细菌胞外多糖含量.结果 氯霉素抗性基因消除后的hns基因缺失株PCR产物长度为434 bp,测序鉴定正确,成功构建MG1655 △hns基因缺失株.MG1655△hns菌株生物膜形成能力和胞外多糖产生显著低于MG1655(P＜0.01).结论 利用Red重组技术成功构建出MG1655△hns菌株,hns基因对细菌生物膜的形成具有重要的调控作用.     

临床大肠埃希菌感染分布与药物敏感分析研究

目的 研究大肠埃希菌临床分布及其耐药情况,为临床医生提供帮助.方法 采用VITEK 2 Compact鉴定系统,对临床感染患者的标本进行病原菌分离培养鉴定和体外药敏试验.结果 在694株大肠埃希菌中,尿液标本分离率最高(47.6%);超广谱β-内酰胺酶(ESBLs)阳性率为60.8%,其中阳性菌株对氨苄西林、氨苄西林/舒巴坦、头孢替坦、头孢他啶、头孢曲松、头孢吡肟、环丙沙星和复方新诺明等有较高的耐药率,阴性菌株对大部分抗菌药物有较低耐药率.结论 产ESBLs大肠埃希菌比阴性菌株具有较高的耐药率,临床要重视对大肠埃希菌ESBLs的检测.     

No difference in the occurrence of mismatch repair defects and APC and CTNNB1 genes mutation in a multi-racial colorectal carcinoma patient cohort

BACKGROUND AND AIMS: Colorectal cancers of different subtypes involve different pathogenic pathways like the Wnt and the mutator pathways. In this study, we screened 73 colorectal cancer cases from a multi-racial group for genetic and expression profile defects with the aim of correlating these with patients' clinicopathological characteristics. METHODS: Mutation screening of the entire coding region of APC and exon 3 of CTNNB1, loss of heterozygosity (LOH) of APC, and microsatellite instability (MSI) status were assessed for 44 patients with available paired frozen normal and tumour tissues. In addition, 29 cases with available paraffin embedded tumour blocks were screened for mutation in exon 3 of CTNNB1, the APC mutation cluster region (codon 1286-1513), and hMLH1, hMSH2, hMSH6 protein expressions by immunohistochemistry method. RESULTS: In our study, 15/73 cases showed APC mutations (20.5%), 1/73 cases had CTNNB1 mutation (1.4%), 5/32 cases had APC LOH (15.6%), and 16/70 (22.9%) cases revealed at least some form of mismatch repair (MMR) defect. Tumour grade (poor differentiation) was found to correlate significantly with right-sided tumour and mucinous histology (p = 0.01879 and 0.00320, respectively). Patients of younger age (below 45 years) more often had tumours of mucinous histology (p = 0.00014), while patients of older age (above 75 years) more often had tumours on the right side of the colon (p = 0.02448). Tumours of the mucinous histology subtype often had MMR defects (p = 0.02686). There was no difference in the occurrence of APC and CTNNB1 mutations and MMR defects found within our multi-racial colorectal cancer patient cohort. CONCLUSION: Our findings support the notion that racial factor may not be related to the occurrence of MMR defects and APC and CTNNB1 mutations in our multi-racial patient cohort.     

A urokinase-type plasminogen activator deficiency diminishes the frequency of intestinal adenomas in ApcMin/+ mice

The interaction of urokinase-type plasminogen activator (uPA) and its receptor, uPAR, on cell surfaces facilitates the generation of cell-bound plasmin, thus allowing cells to establish a proteolytic front that enables their migration through protein barriers. This complex also activates cell signalling pathways that influence cell functions. Clinical studies have identified uPA as an indicator of poor overall survival in patients with colorectal cancer. In the current study, a mouse model of colon cancer, Apc(Min/+), with an additional deficiency of uPA (Apc(Min/+)/Plau-/-) was used to determine the effects of uPA on tumour initiation and growth. Utilizing this model, it was found that the number of tumours was diminished in these mice relative to Apc(Min/+) mice, which correlated with the decreased leukocyte infiltration in the tumours. However, tumour growth was not impeded in Apc(Min/+)/Plau-/- mice, and proliferation and tumour vascularization were, in fact, enhanced in Apc(Min/+)/Plau-/- mice. These latter effects are consistent with a mechanism involving up-regulation of COX-2 expression and Akt pathway activation in Apc(Min/+)/Plau-/- mice. The results from this study suggest that uPA plays dual and opposing roles in regulating lesion development: one early, during the transition from normal epithelia to dysplastic lesions, and another later during tumour growth.     

Impact of total body weight on acute kidney injury in patients with gram-negative bacteremia

Background: The impact of total body weight (TBW) on the development of acute kidney injury (AKI) associated with gram-negative bacteremia has not been previously evaluated.

Methods: The cohort included 323 patients >/ = 18 years old with gram-negative bacteremia (1/1/2008–8/31/2011) who received >/ = 48 hours of antibiotics. We compared the incidence of AKI in patients with a TBW </ = 80kg vs. >80kg with a multivariable stepwise logistic regression adjusting for age >/ = 70 years, baseline serum creatinine of > 2.0 mg/dl, and receipt of a vasopressor. AKI was defined as an increase of 0.5 mg/dL or a > 50% increase from baseline for at least two consecutive days.

Results: The cohort was 62% TBW </ = 80kg and 38% TBW >80kg. TBW >80kg patients had higher risk of AKI (24% vs. 9%, p < 0.001), which was significant in the multivariable analysis (OR 3.41, 95% CI 1.73–6.73). A baseline serum creatinine of > 2.0 mg/dl and vasopressor use were also independently associated with AKI.

Conclusions: TBW >80kg was associated with the development of AKI. However, the mechanism for this association is not clear.     

2株不同序列分型耐黏菌素大肠埃希菌耐药机制分析

目的探讨2株黏菌素耐药大肠埃希菌的耐药机制。方法采用Vitek 2 Compact全自动微生物鉴定药敏系统鉴定细菌及检测常见抗菌药物敏感性,并检测菌株是否产超广谱β-内酰胺酶(ESBLs);用三维试验检测菌株是否产AmpC酶;用微量肉汤稀释法测定菌株对黏菌素的最低抑菌浓度(MIC);用PCR及测序检测耐药基因;多位点序列分型(MLST)和脉冲场凝胶电泳(PFGE)分析菌株的分子分型和同源性;接合试验和S1酶切脉冲场凝胶电泳(S1-PFGE)对菌株的质粒特征进行分析。结果2株菌均对碳青霉烯类药物敏感,对黏菌素耐药,其中N408对头孢类药物耐药;PCR扩增和测序分析显示2株菌均携带mcr-1基因,且N408和N433分别携带blaCIT和blaTEM-1基因;2株菌质粒接合试验均成功,接合子均检测到mcr-1基因;MLST分析显示N408为ST453型,N433为ST8900型,PFGE显示为不同条带。S1-PFGE显示N408有2个质粒,N433有1个质粒。结论本地区已出现携带mcr-1基因黏菌素耐药大肠埃希菌,且可通过质粒在不同菌株间水平播散,应引起临床的重视,加强此类菌株的检测。     

大肠埃希菌和肺炎克雷伯菌中质粒介导的喹喏酮类耐药研究

目的:研究国内11家医院分离大肠埃希菌(ECO)和肺炎克雷伯菌(KPN)中质粒介导的喹喏酮类耐药。方法:收集北京大学第三医院无重复临床分离产超广谱β-内酰胺酶(ESBL s)的ECO和KPN共84株,另10家医院相应菌株共155株,北京协和医院对头孢西丁不敏感的ECO和KPN共25株。采用琼脂稀释法测定抗生素最低抑菌浓度M IC;接合实验判断该基因位置和移动性;聚和酶链反应(PCR)及其产物测序确定基因型。结果:北医三院84株菌中1株KPN(编号24)阳性,ECO的发生率是0;余10家医院155株产ESBL s菌株中没有阳性结果;协和医院25个临床株中3株KPN(编号P 3、P 6、P 10)阳性。这4株菌只有P 6接合试验阳性,相应接合子qnr-PCR阳性。环丙沙星C IP对该菌的M IC是0.5μg/m l,对该接合子的M IC是1μg/m l,而对受体菌EC 600的M IC是0.125μg/m l。对24号标本和P 6标本及其接合子进行测序证实:二者的qnr↑序列和AY 878718(qnrA)100%同源,并且qnr基因的上游都有ORF 513存在。结论:北医三院和北京协和医院分类株中存在质粒介导的喹喏酮类耐药基因qnr,其他医院分离株本次研究中未发现该基因。     

足菌清杀灭微生物效果及刺激性的试验观察

足菌清消毒原液含苯甲酸、水杨酸、间苯二酚、硼酸分别为20.06、24.88、25．00、25.06mg/L,pH2.0~3.0.为了解对微生物杀灭效果、稳定性及对皮肤刺激性,进行了载体定量杀菌试验、稳定性与刺激性试验。结果,以其原液作用40min,对布片上大肠杆菌．金黄色葡萄球菌、白色念珠菌的杀灭率均达100%;小牛血清对其杀菌效果无明显影响:其原液对家兔皮肤刺激反应积分为0;置37℃存放90d,各成分下降率均＜10%。表明该消毒剂杀菌效果受有机物影响较小,稳定性较好,属于无刺激性物质。     

有机物对优氯净杀菌效果影响的实验研究

以最低有效浓度及最短有效时间为试验剂量,采用悬液定量杀菌试验,对两种有机物影响二氯异氰尿酸钠杀菌效果进行比较观察。结果,含体积分数50%小牛血清与1.5%小牛血清白蛋白对二氯异氰尿酸钠杀菌效果的影响无明显差别。与不含有机干扰物组比较,50%小牛血清和1.5%白蛋白对二氯异氰尿酸钠杀菌效果均有轻度影响。结论,所试验的两种有机物对二氯异氰尿酸钠杀菌效果的影响无明显差别。     

尿液分离产ESBLs大肠埃希菌对磷霉素耐药的分子流行病学及耐药机制研究

目的 探究尿液分离产超广谱β-内酰胺酶（ESBLs）大肠埃希菌对磷霉素耐药的分子流行病学及其耐药机制。方法 收集南京大学医学院附属鼓楼医院2016年1-12月尿液分离大肠埃希菌308株，通过药敏试验筛选产ESBLs及磷霉素耐药菌株；PCR扩增ESBLs基因及磷霉素相关耐药基因；采用多序列位点分型（MLST）对菌株进行遗传相关性分析，采用接合试验验证耐药基因的转移性。结果 308株尿液分离大肠埃希菌中产ESBLs的菌株168株（54.54％）；产ESBLs菌株中检出磷霉素耐药菌株18株（10.71%）。其中，ESBLs耐药基因携带率为blaSHV 88.9%（16/18）、blaCTX-M 77.8%（14/18）、blaTEM-208，5.6%（1/18）；blaTEM-1b 61.1%（11/18）；fosA3基因的携带率为83.3％（15株）。 MLST分型主要为ST131（27.78%），接合试验表明，fosA3阳性菌株的耐药性均具有可转移性。结论 产ESBLs的大肠埃希菌对磷霉素的耐药率仍处于较低的水平，fosA3基因是这些菌株磷霉素耐药的主要机制，该基因位于可接合的质粒上，易于水平传播，需要高度重视。 关键词：大肠埃希菌； 产超光谱β内酰胺酶； 磷霉素； 耐药机制