ABSTRACT
Copper activation has been a standard diagnostic for measuring 14.1-MeV neutron yields in deuterium-tritium fusion experiments, which is essential to evaluate their performance for potential ignition in the future. Copper-activation equipment, especially data-acquisition systems, is updated constantly thanks to the rapid developments in electronics. Here, a multi-function digital coincidence spectrometer for neutron copper-activation diagnostics was developed. The digital pulse processing includes pulse shaping, multichannel pulse analysis, coincidence event picks, and coincidence multichannel time analysis were implemented on a single field-programmable gate array (FPGA) chip. The results demonstrate that the coincidence background is 0.013 counts per second. By using the multi-function digital coincidence spectrometer, the copper-activation diagnostics could be performed at the SG-III Laser facility when the neutron yield is ≥ 1.0 × 1010/hit.
ABSTRACT
The aim of this study was to analyze the molecular epidemiologic characteristics of Acinetobacter baumannii. A total of 398 isolates were collected in 7 regions of South China from January to June of 2012. Drug sensitivity was tested toward 15 commonly used antibiotics; thus, 146 multi-drug-resistant strains (resistant to more than 7 drugs) were identified, representing 36.7% of all isolates. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used for molecular subtyping. According to the PFGE results (with a cutoff of 70% similarity for the DNA electrophoretic bands), 146 strains were subdivided into 15 clusters, with cluster A being the largest (33.6%, distributed in all districts except Jiaxing). Cluster B was also widespread and included 14.4% of all strains. In addition, MLST results revealed 11 sequence types (ST), with ST208 being the most prevalent, followed by ST191 and ST729. Furthermore, 4 novel alleles and 6 novel STs were identified. Our results showed that multi-drug-resistant A. baumannii in South China shares the origin with other widespread strains in other countries. The nosocomial infections caused by A. baumannii have been severe in South China. Continuous monitoring and judicious antibiotic use are required.
Subject(s)
Acinetobacter Infections/epidemiology , Acinetobacter baumannii/genetics , Cross Infection/epidemiology , Drug Resistance, Multiple, Bacterial/genetics , Genotype , Phylogeny , Acinetobacter Infections/diagnosis , Acinetobacter Infections/drug therapy , Acinetobacter Infections/microbiology , Acinetobacter baumannii/classification , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/isolation & purification , Alleles , Anti-Bacterial Agents/pharmacology , Bacterial Typing Techniques , China/epidemiology , Cross Infection/diagnosis , Cross Infection/drug therapy , Cross Infection/microbiology , Electrophoresis, Gel, Pulsed-Field , Humans , Molecular Epidemiology , Multigene Family , Multilocus Sequence TypingABSTRACT
In order to get insights into plasmid evolution and the dissemination of multidrug resistance, we performed extensive comparative genomics analyses of the Klebsiella pneumoniae plasmid pKF3-94 and some of its related plasmids. pKF3-94 is one of three plasmids isolated from the K. pneumoniae strain KF3. Of the 144 putative genes it harbors, 69 can be functionally assigned to be involved in transfer conjugation, transfer leading, antimicrobial resistance, transposon function, and plasmid replication. Comparison of plasmid replicon sequence types revealed that pKF3-94 carries two replicons that are distinct from those carried on the two sibling K. pneumonia plasmids pKF3-70 and pKF3-140, thereby allowing pKF3-94 to coexist with these latter plasmids in the same host cell. Comparative genomics analyses further showed that pKF3-94 is more similar to plasmids pK1HV and pC15-k, which were isolated from different K. pneumonia strains, than to pKF3-70 and pKF3-140. Interestingly, pK1HV contains a unique 49 kb region rich in mobile genetic elements and drug resistance genes, while pKF3-94 and pC15-k share a 15 kb homology region partitioned into a region rich in drug resistance genes and one containing a replicon. It is conceivable, therefore, that pK1HV and pC15-k have both arisen from a common pKF3-94-like plasmid. The comparisons lend further support for the role horizontal gene transfer plays in genome evolution and in the dissemination of genetic elements including drug resistance genes.