Occurrence of K1 and K2 serotypes and genotypic characteristics of extended spectrumβ-lactamases-producing Klebsiella pneumoniae isolated from selected hospitals in Malaysia

Objective:To determine the distribution,phenotypic and genetic background of extended spectrumβ-lactamases(ESBL)-producing Klebsiella(K.)pneumoniae clinical isolates associated with K1 and K2 serotypes in two selected hospitals in Malaysia.Methods:A total of 192 K.pneumoniae isolates were collected and subjected to antibiotic susceptibility,hypermucoviscosity test and multiplex PCR to detect the presence of K1-and K2-serotype associated genes.Multilocus sequence typing(MLST)was performed on ESBL-producing K.pneumoniae isolates presented with K1 and K2 serotypes,followed by phylogenetic analysis.Results:A total of 87 out of 192(45.3%)of the K.pneumoniae isolates collected were ESBL producers.However,only 8.3%(16/192)and 10.9%(21/192)of the total isolates were detected to carry K1-and K2-serotype associated genes,respectively.Statistical analysis showed that K1 and K2 capsular serotypes were not significantly associated with ESBL phenotype(P=0.196).However,they were significantly associated with hypervirulent,as demonstrated by the positive string test(P<0.001).MLST analysis revealed that ST23 as the predominant sequence type(ST)in the K1 serotype,while the ST in the K2 serotype is more diverse.Conclusions:Although the occurrence of ESBL-producing isolates among the hypervirulent strains was low,their coexistence warrants the need for continuous surveillance.MLST showed that these isolates were genetically heterogeneous.

Characteristics of β-Lactamase Synthesis in E. coli and K. pneumanie Strains in Nosocomial Infections

Background: Recently micro-organisms that synthesize extended-spectrum β-lactamase (ESBLs) were increased. The peculiarities of ESBL synthesis of Escherichia coli and Klebsiella pneumoniae strains that cause nosocomial urinary tract infections, surgical site infections and pneumonia in surgical clinic were studied. ESBL synthesis were observed 38.9% of E. coli strains obtained from urine, 92.3% of strains obtained from surgical site infections, and 50% of strains obtained from sputum. ESBL synthesis were observed 37.5% of K. pneumoniae strains obtained from urine, 85.7% of strains obtained from surgical site infections, and 60% of strains obtained from sputum. Different levels of ESBL synthesize of E. coli and K. pneumoniae strains isolated from different pattern is discussed. Conclusion. ESBL synthesis is common in E. coli and K. pneumoniae strains, which cause nosocomial infections. The frequency of occurrence of ESBL s synthesis among of these strains depends on clinical forms of nosocomial infections.

一种新型可移动TEM喇叭辐射波模拟器的模拟优化

为改善基于TEM喇叭的辐射波模拟器的低频辐射特性从而展宽其辐射近场半高宽,首次提出了在指数型TEM喇叭上/下两个极板的端口加上2个金属直板、并通过倾斜金属板和并联电阻相连的新型可移动模拟器的设计方案。基于FDTD方法模拟分析了该新型模拟器的特性参数对其近场辐射性能的影响,并给出了优化后的模拟器及其阵列的辐射特性。计算结果表明:尺寸为6 m×6 m×6.24 m的优化后的新型模拟器在距离口面3 m的中心位置的辐射近场脉宽能达到18.95 ns,而达到相同低频辐射性能的常规模拟器尺寸为9 m×12 m×6.8 m。且与常规模拟器相比,优化后的模拟器的场峰值更大。与前人的研究相比,优化后的模拟器场在保持高峰值的同时,时域波形后延震荡的幅度与主峰的比值明显减小。优化后的模拟器2×2阵列模型的测试平面中心点场峰值最大,且在测试平面上满足6 dB均匀性要求的有效测试区最大;有效测试区在横向上范围最大的是2×2阵列模型,其次是2×1阵列模型;在纵向上范围最大的是2×2阵列模型及1×2阵列模型。

L1 β-Lactamase催化反应机理研究

用混合量子力学和分子力学(QM/MM)方法和密度泛函理论讨论了L1β-Lactamase催化Nitrocefin水解的过程,研究结果表明,反应为多步反应:第一步亲核进攻反应为反应的决速步骤,并且伴随着酰胺键的断裂,第二步反应为质子迁移反应.同时讨论了金属锌在反应中的作用.

埋地钢质管线非开挖检测TEM技术新进展

主要介绍了埋地钢质管道非开挖检测TEM技术在实际应用中的最新进展情况,并根据最新国内外发表的文章、专利和论文,归纳了现阶段埋地管道TEM检测过程中出现主要问题及现在最新的应对手段,并对影响埋地管道TEM检测的技术原因进行了总结分析,提出了相应的建议和措施。

基于框架语义学的TEM8汉译英试题讲解策略新探

专业八级考试(简称TEM8)是本科英语专业高年级阶段最重要的等级考试之一,其汉译英部分既是考试的难点也是考生成绩的主要堵点。基于框架思想的TEM8真题讲解策略包括:教师借助通用概念框架引导学生建构原文认知图像;通过引入免费线上语料资源FrameNet中的框架信息指导学生在目标语中重构认知图像;引导学生利用FrameNet中的真实语料,特别是框架元素的句法构型,打磨并评估译文。

Prevalence and characteristics of extended spectrum β-lactamase-producing Escherichia coli from bovine mastitis cases in China

The aim of the study was to investigate the prevalence and characterization of extended-spectrum β-lactamase （ESBL）- producing Escherichia coli isolated from bovine mastitis cases in China. ChromID ESBL agar was used to confirm ESBL-producing E. coli. PCR and DNA sequencing were employed to characterize the genotype of ESBL-producers. Antimicrobial susceptibility was measured by disc diffusion. Overall, 73 of 318 E. coli isolates （22.96％） were identified as ESBL-producers. Of these ESBL-producing E. coli, the prevalence of blaCTX-M and blaTEM-1 was 97.26 and 71.23％, respectively. The predominant CTX-M-type ESBL was CTX-M-15 （65.75％）, followed by CTX-M-14 （10.96％）, CTX-M-55 （9.59％）, CTX-M-64 （5.48％）, CTX-M-65 （4.11％） and CTX-M-3 （1.37％）. This study is the first report of CTX-M-64 and CTX-M-65 in E. coli isolated from bovine mastitis. Furthermore, 72 ESBL-producing E. coli isolates （98.63％） were found to be multidrug-resistance. This study noted high prevalence and rates of antimicrobial resistance of ESBL-producing E. coli isolates from bovine mastitis cases in China.

Analysis of AmpC β-lactamase Gene in Pseudomonas aeruginosa

The gene and the amino acid sequence of the structural and regulatory region of the Pseudomonas aeruginosa with different resistance patterns were analyzed. Six strains with different resistance patterns were selected and the AmpC β-lactamase was identified. The objective gene fragment was amplified by colonies PCR. The sequences of the PCR-products were analyzed. The DNA sequence of the structural gene ampC and the regulatory genes ampR, ampD and ampE was detected. The 6 strains and the wild-type Pseudomonas aeruginosa are highly homogeneous in structural and regulatory region. Some new mutant points were found.

Antimicrobial Resistance and Genotype Analysis of Extended-Spectrum-β-Lactamase-Producing Proteus Mirabilis

To analyse the genotypes of clinical isolates of Extended-Spectrum-β-Lactamase-Producing (ESBL-producing) Proteus mirabilis (P. mirabilis) and the mechanisms of antimicrobial resistance, to guide reasonable use of antibiotics and to avoid nosocomial outbreak infections by ESBL-producing P. mirabilis. 125 clinical isolates of P. mirabilis were collected from the Drug-Resistant Bacteria Surveillance Center of Anhui Province (from Jan 2009 to May 2010). Searching for the genotypes of ESBLs was perfomed by PCR amplification and DNA sequencing, and performed conjugation test simultaneously. Among ESBL-producing strains, CTX-M was the major genotype (3 CTX-M-13 and 1 CTX-M-3). TEM-1b spectrum β-lactamase was also prevalence in P. mirabilis. The diversity of β-lactamases in P. mirabilis and the emergency of multi-drug-resistance clinical strains will present serious threat to clinical therapy and even will lead to outbreak of nosocomial infections. Our study emphasizes the need for enhanced supervision of ESBL-producing P. mirabilis. Timely and reasonable drug-resistance data are indispensable to clinical therapy.

基于自适应差分优化算法的SQUID TEM数据电阻率-极化率多参数提取研究

超导时域电磁探测方法(Superconducting Quantum Interference Devices Time Domain Electromagnetic Method,SQUID TEM)是多金属矿探测的有效手段之一.在实际探测中超导传感器虽然可以观测到极其微弱的极化效应,但还无法同时提取电阻率和极化率信息.本文提出了基于种群个体自适应进化筛选策略的差分优化算法,分析了传统差分优化算法中突变和交叉因子均为定值时,对电阻率和极化率提取精度的影响,设计优化了突变因子随柯西分布、交叉因子随高斯分布的自适应控制方式,重构了同时包含极化率和电阻率信息的目标函数,从而实现了极化率和电阻率参数的同时提取.通过典型层状模型,对比了自适应差分优化与差分进化、线性权重粒子群算法进行电阻率和极化率参数提取的效果,自适应差分优化算法的提取结果更接近真实模型.将该新方法应用于黑龙江大兴安岭地区的SQUID TEM野外数据,实现了地下不同深度电阻率、极化率信息的提取,结果与钻孔资料一致,验证了新方法双参数提取的有效性.

集成X射线、TEM和STM的晶体学教学尝试

以Si晶体为例,介绍了一种结合X-射线、电子显微学和扫描隧道显微技术进行晶体学教学的尝试。主要是从基本原理、实验技术、实验结果等方面建立不同方法之间的联系,也说明其区别。目的是使学生能依据基本的晶体学原理、概念和数据,理解不同的晶体结构分析和表征方法提供的晶体学信息之间的区别和联系,达到融会贯通的效果。

EXTRACELLULAR RELEASE OF β-LACTAMASE BY OSMOTIC SHOCK IN SYNECHOCOCCUS TRANSFORMANT

A unicellular cyanobacterium Synechococcus sp. strain PCC 7002 was transformedwith plasmid pQL1, on which β-lactamase gene (bla) and β-galactosidase gene (lacZ) were encoded.The transformant cells released β-lactamase into medium by an abrupt drop of osmotic pressure. This re-sult indicates that this cyanobacterium recognizes and processes the signal sequence of β-lactamase, andaccumulates the enzyme in periplasm. Repeated release of β-lactamase was possible by repeated osmoticshocks without impairing cell viability. On the other hand, most of the β-galactosidase remained in cyto-plasm under the osmotic shock.

Metallo-β-lactamase producing nonfermentative gram-negative bacteria:An increasing clinical threat among hospitalized patients

Objective:To detect and evaluate the various methods for metallo-β-lactamases(MBL) production in Pseudomonas aeruginosa(P.aeruginosa) and Acinetobacter species.Methods:A total of 109 P.aeruginosa and 85 Acinetobacter species were screened for imipenem resistance by Kirby- Bauer disc diffusion methods.Detection of MBL production was(lone by imipenem-EDTA combined disc test,double disc synerygy test(DDST) and imipenem-EDTA MBL E test.Results: A total of 63(57.8%) strains of P.aeruginosa and 46(54.1%) strains of Acinetobacter spp.were found to be resistant to imipenem.Of the 63 imipenem resistant P.aeruginosa tested for MBL production.44(69.89;) were found to be positive and among 46 imipenem resistant Acinetobacter. 19(41.3%) were shown to be the MBL producers.Conclusions:Imipenem-EDTA combined disc test and MBL E test are equally effective for MBL detection in both P.aeruginosa and Acinetobacter spp.,but given the cost-constraints,combined disc can be used as a convenient screening method in the clinical microbiology laboratory.

Multidrug resistance extended spectrum β-lactamase and AmpC producing Escherichia coli isolated from the environment of Bogor Slaughterhouse,Indonesia

To determine the multidrug resistance extended spectrum β-lactamase and AmpC (ESBL/AmpC producing) Escherichia coli (E. coli) isolated from the environment of Bogor slaughterhouse, Indonesia.MethodsA total of 35 samples from 7 locations in slaughterhouse i.e., source of water, slaughtering floor, swab of carcass area floor, swab of evisceration area floor, untreated waste water, treated waste water, drinking water for cattle were collected from March to April 2016. Presence of ESBL/AmpC producing E. coli and susceptibility testing against 8 antimicrobial agents (penicillin G, streptomycin, gentamycin, ciprofloxacin, enrofloxacin, tetracycline, trimethoprim-sulfamethoxazole, and polymyxin B) were detected by disk diffusion test according to Clinical and Laboratory Standards Institute.ResultsESBL/AmpC producing E. coli were identified in 14.3% (5/35) of the collected samples from the environment of Bogor slaughterhouse. ESBL/AmpC-producing E. coli isolates were detected in untreated waste water (n = 3), slaughtering floor (n = 1), and carcass area floor (n = 1). Most of ESBL/AmpC-producing E. coli isolates (80%) showed multidrug resistance phenotypes against at least three classes of antibiotics. The highest incidence of antibiotics resistance was against penicillin G (100.0%) and streptomycin (100.0%), followed by gentamicin (60.0%), trimethoprim-sulfamethoxazole (60.0%), tetracycline (40.0%), ciprofloxacin (40.0%), enrofloxacin (20.0%), and polymyxin B (0.0%).ConclusionsThe transmission of antimicrobial resistant bacteria into the environment may be a potential risk for human health.

Molecular Characterization of Extended Spectrum <i>β</i>-Lactamase Genes in Clinical <i>E. coli</i>Isolates

Extended Spectrum Beta-Lactamases (ESBLs) encoding genes (TEM, SHV and OXA) were amplified from multidrug resistance E. coli. The multidrug resistance E. coli isolates from different clinical sources were documented to be plasmid encoded and resistance against β-lactam and cephalosporin. Conventional laboratory analysis showed that seventy percent (70%) of the selected multidrug resistant clinical isolates were ESBLs positive, showing a ≥5 mm increase in zone diameter for either antibiotics compared to its zone when tested alone. The antibiotic susceptibility result showed that 100% of the isolates were resistant to amoxicillin-clavulanic acid, amoxicillin, cefuroxime and ampicillin-sulbactam while 90% of the isolates were resistant to ceftazidine and tetracycline, 80% to ofloxacin, 70% to ceftriazon, nalidixic acid, cefalexin, 60% to ciprofloxacin, 50% to nitrofurantoin, 40% to chloramphenicol and 20% to gentamicine. The multiplex PCR with primers TEM (931bp), SHV (868), OXA-2 (478), aac(3)-IIa (900) and rmtA (634), which are genes responsible for extended spectrum β-lactamase and aminoglycoside resistance in E. coli shows that: isolate W15 comprises of three (3) resistant gene, which corresponds with TEM resolving as a 931 base pair, SHV 868 base pair, and a 478 bp indicating OXA-2 that is faint probably indicating a low concentration of the gene. Isolate B2 comprises single resistant gene, which is interpreted as OXA-2 with 478 base pair while isolate URO2, U64 and S45 comprises of two resistance genes which resolve as 868 and 478 base pair indicating SHV and OXA-2 respectively. However, isolates S57, U58 and B7 showed no gene amplification despite the various degree of resistance in MIC and antibiotic susceptibility profile test obtained with conventional detection analysis. We assume that their resistant genes are not coded for by the primers used in this study as these isolates are likely to contain other resistant genes, which are also expressed at a molecular level. This study stands to show that molecular characterization has a great correlation with analytical methods.

Unravelling Antimicrobial Resistance Phenotypes and Carriage of Extended-Spectrum β-Lactamase Genes in Escherichia coli Isolated from Dairy Farms in Kiambu County, Kenya

The use of antibiotics for prophylaxis and growth enhancement in livestock farming is on the increase globally. This practice has led to the emergence and spread of antimicrobial-resistant bacteria in livestock. Only limited research has been done to establish the role of cattle farming in antimicrobial resistance. The current study sought to establish the carriage of multi-drug resistance and extended-spectrum beta-lactamase genes in Escherichia coli from farmers, their cattle, and cattle slurry within Kiambu County. A total of 286 (81%) E. coli isolates were recovered from 352 samples analysed. Antibiotic resistance profiles showed 114 (40%) isolates were resistant to ≥3 antimicrobial classes and were considered multidrug-resistant. Among multidrug-resistant (MDR) E. coli strains, 40 (14%) were resistant to 3 different antimicrobial classes, while 71 (25%) were resistant to between 4 and 7 antibiotic classes. Extended-spectrum β-lactamase resistance was found in 18 isolates: human (n = 14), cattle (n = 2), and environmental (n = 2). Both the blaCTX-M and blaTEM genes were detected in 10 and 15 strains, respectively. Sequence analysis showed that the isolates carried the blaTEM-116 (n = 7), blaTEM-1 (n = 5), and blaCTX-M-15 (n = 8) genes. Genotyping MDR isolates using (GTG) 5 PCR demonstrated that the isolates were not clonal. This data shows antimicrobial resistance profiles and different types of resistance genes in the E. coli population on dairy farms. As a result, more effective, targeted public health policies and measures need to be put in place to control and prevent the emergence and spread of resistant bacteria.

Studies of β-lactamase production in ampicillin resistant Haemophilus influenzae

Objective:To study the molecular mechanisms of β-lactamase production in ampicillin resistant(AmP ) Hae- mophilus influenzae(HI). Methods: Identified the β-lactamases production strain from AmP HI was isolated from clinical cases with K-B method. β-lactamase encoding gene in enzyme production strains were detected by PCR with lactamase gene specific primers, and both plasmid and chromosomal DNA samples. Results: Thirty-two out of 36 (88 .9% ) were found to be β-lactamase production. Twenty-nine out of 32 enzyme production stain were PCR positive (the ratio of PCR positives 90.6% ). There were 25 stains amplified with plasmid DNA positively, and 4 with chromosomal DNA. Conclusion: (l ) Most of the AmPr HI strain produce lactamase is mediated by plasmid. (2) Detection of lactamase encoding gene in HI is a simple and efficient approach to study the molecular basis of ampicillin resistance.

Intestinal carriage of methicillin resistant Staphylococcus aureus and extended-spectrum β-Lactamase-producing Enterobacteriacae in hospitalized and nonhospitalized patients and their clinical implications

Objective:To determine the clinical implication of and intestinal carriage with methicillin resistant Staphylococcus aureus(MRSA) and extended spectrumβ-lactamase(ESBL)-producing Enterobacteriacae.Methods: A total of 180 stool specimens were screened for MRSA and ESBL-producing enterobacteria.Identification of ESBL- producing Enterobacteriacae was done by MicroScan Walk Away 96 system(Dade Behring Inc.,West Sacramento,CA 95691,USA ) and confirmation by double-disc synergy test.MRSA was identified by disc diffusion using 30μg cefoxitin disc and the MicroScan.Results:The rate of fecal MRSA carriage was 7.8% (14/180),35.7%(5 /14) were recovered from surgical wards.Three patients(21,4%) had MRSA recovered from other body sites,and 2(14.2%) had in addition ESBL -producing Escherichia coli(E.coli) and Klebsiella pneumoniae(K.pneumoniae) respectively.Four(28.5%) patients with MRSA fical carriage died. MRSA fecal carriage was recovered from both inpatients and outpatients.Four(2.2%) cases carried ESBL-producing Enterobacteriacae in feces.Three(75%) were from intensive care unit(ICU).One patient had both ESBL-producing E.coli and K.pneumoniae from stool as well as E.coli from tracheal aspirate.Two ICU patients with fecal ESBL died.Conclusion:Fecal screening for MRSA and ESBL of all patients at high risk admitted to different hospital wards and ICUs and implementing infection control measures were recommended.

Metallo-β-Lactamases:A Major Threat to Human Health

Antibiotic resistance is one of the most significant challenges facing global healthcare. Since the 1940s, antibiotics have been used to fight infections, initially with penicillin and subsequently with various derivatives including cephalosporins, carbapenams and monobactams. A common characteristic of these antibiotics is the four-memberedβ-lactam ring. Alarmingly, in recent years an increasing number of bacteria have become resistant to these antibiotics. A major strategy employed by these pathogens is to use Zn(II)-dependent enzymes, the metallo-β-lactamases (MBLs), which hydrolyse theβ-lactam ring. Clinically useful MBL inhibitors are not yet available. Consequently, MBLs remain a major threat to human health. In this review biochemical properties of MBLs are discussed, focusing in particular on the interactions between the enzymes and the functionally essential metal ions. The precise role(s) of these metal ions is still debated and may differ between different MBLs. However, since they are required for catalysis, their binding site may present an alternative target for inhibitor design.

TSP结合TEM在风险围岩隧道超前地质预报中的应用

为了排查隧道施工过程中潜在的地质风险、指导隧道安全开挖掘进,针对某高速铁路风险围岩隧道浅埋段和可溶岩段,利用TSP和TEM两种方法开展超前地质预报。TSP预报可对掌子面前方围岩状况进行远距离宏观预测,能划定断层、破碎带、地下水等不良地质体的位置和大致规模;TEM预报可在掌子面附近开展多角度、多方位测量,能判定开挖面前方一定空间范围内不良围岩特征,特别是地下水、岩溶的分布及规模。研究表明,TSP震波对应的负反射和低速异常突出反映围岩岩性变化及岩体破碎程度,依据纵、横波速起伏特征可大致判定地下水发育情况;TEM低阻异常直观体现围岩富水状态,并可推测岩溶发育及分布状况,视电阻率阻值变化密集区对应了围岩岩体破碎。研究结果表明,采用两种或多种方法结合开展综合预报,可提升预报结论的准确度和可靠度,TSP结合TEM成功预报的应用实例可为类似风险围岩隧道的超前地质预报提供参考和借鉴。