Development of Nucleic Acid Sequence-Based Amplification Assay for Detection of Macrobrachium rosenbergii Nodavirus

A nucleic acid sequence-based amplification(NASBA)assay was established for the detection of Macrobrachium rosenbergii Nodavirus(MrNV).The specific primers were designed according to the high conserved region of RNA2 sequence of MrNV.The 224 bp specific amplification product was obtained in positive sample determined with 3%agarose gel electrophoresis,while no product was generated from shrimp infected with other viruses including DNA viruses(IHHNV,WSSV)and RNA viruses(TSV,IMNV,YHV).The detecting limit of the assay was 8pg nucleic acid,which is more sensitive than that of PCR method.

Research progress and prospects of nucleic acid isothermal amplification technology

Nucleic acid(DNA and RNA)detection and quantification methods play vital roles in molecular biology.With the development of molecular biology,isothermal amplification of DNA/RNA,as a new molecular biology technology,can be amplified under isothermal condition,it has the advantages of high sensitivity,high specificity,and high efficiency,and has been applied in various fields of biotechnology,including disease diagnosis,pathogen detection,food hygiene and safety detection and so on.This paper introduces the progress of isothermal amplification technology,including rolling circle amplification(RCA),nucleic acid sequence-dependent amplification(NASBA),strand displacement amplification(SDA),loop-mediated isothermal amplification(LAMP),helicase-dependent amplification(HDA),recombinase polymerase amplification(RPA),cross-priming amplification(CPA),and its principle,advantages and disadvantages,and application development are briefly summarized.

一种基于SBL和APIT的混合定位算法

由于子区域分割粒度的限制,基于阶次序列的定位算法(Sequence-based localization,SBL)存在边缘区域节点定位误差较大和不能保证平均定位误差性能的问题。针对这些问题,提出了一种基于SBL和APIT的混合定位算法,利用APIT信标三角形切割SBL算法子区域,减小子区域面积,实现了分割粒度的细化。通过预先进行系统训练,优化了混合算法的加权系数,进一步提升了算法的定位精度。仿真结果表明,相比于原算法,所提出的混合算法有效地提升了边界区域节点的定位精度,其平均定位误差降低了17.9%,使基于阶次序列的定位算法的定位精度得到了有效改善。

Molecular detection of oxacillinase genes and typing of clinical isolates of Acinetobacter baumannii in Tehran, Iran

Objective:To determine patterns of antimicrobial resistance,analyze the prevalence of oxacillinase and molecular typing of strains of Acinetobacter baumannii(A.baumannii).Methods:A total of 121 strains of A.baumannii were obtained from patients admitted to Imam Hossein and Imam Khomeini Hospitals,Tehran,Iran,from January 2016 to November 2018.Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion method according to the Clinical and Laboratory Standards Institute recommendations.The presence of oxacillinase genes was assessed by polymerase chain reaction(PCR).To determine clonal relatedness,all isolates were subjected to repetitive sequence-based PCR(REP-PCR).Results:The isolates were obtained from 56(46.3%)males and 65(53.7%)females with the mean age of 39.5 years.Colistin with 100.0%sensitivity rate had the highest effect,while ceftriaxone with 16.5%sensitivity rate had the least effect on A.baumannii isolates.In addition,96(79.3%)and 99(81.8%)isolates were resistant to imipenem and meropenem,respectively.A total of 109 isolates(90.0%)exhibited multiple drug resistance with 10 different resistotypes.In total,75(75.7%)of carbapenem resistant isolates were positive for blaOXA-23-like,and 14(14.1%)for blaOXA-24-like gene.The five main clones A,B,C,D,and E were detected in 25(25.2%),36(36.4%),10(10.1%),8(8.0%),and 6(6.1%)of isolates,respectively.Conclusions:Carbapenem-resistant A.baumannii strains are high in the current study.To control the spread of carbapenem-resistant A.baumannii strains,regular monitoring programs are needed.

Obligate aerobic, gram-positive, weak acid-fast, nonmotile bacilli, Tsukamurella tyrosinosolvens: Minireview of a rare opportunistic pathogen

Tsukamurella species are obligate aerobic,gram-positive,weak acid-fast,nonmotile bacilli.They are found in various environments,such as soil,water,sludge,and petroleum reservoir wastewater,and belong to the order Actinomycetales.In 2016,there was a reclassification of species within the genus Tsukamurella,merging the species Tsukamurella tyrosinosolvens(T.tyrosinosolvens)and Tsukamurella carboxydivorans.Tsukamurella species are clinically considered to be a rare opportunistic pathogen,because most reported cases have been related to bacteremia and intravascular prosthetic devices and immunosuppression.To date,it has been isolated only from human specimens,and has always been associated with clinical disease;human infections are very rare.Reported infections have included pneumonia,brain abscesses,catheter-related bloodstream infections,ocular infections,bacteremia,and sepsis presenting with septic pulmonary emboli in patients who are immunocompromised.To date,there is no commercially available test for identification.On the other hand,sequence-based identification,including matrix-assisted laser desorption ionization time-of-flight mass spectrometry,is an alternative method for identifying clinical isolates that are either slow growers or difficult to identify through biochemical profiling.The golden standards for diagnosis and optimal management still remain to be determined.However,newer molecular biological techniques can provide accurate identification,and contribute to the appropriate selection of definitive therapy for infections caused by this organism.Combinations of several antimicrobial agents have been proposed for treatment,though the length of treatment for infections has yet to be determined,and should be individualized according to clinical response.Immunocompromised patients often experience severe cases due to infection,and life-threatening T.tyrosinosolvens events associated with dissemination and/or failure of source control have occurred.Favorable prognoses can be achieved through earlier identification of the cause of infection,as well as successful management,including appropriate antibiotic therapy together with source control.Further analyses of similar cases are required to establish the most adequate diagnostic methods and treatment regimens for infections.