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181.
《Saudi Journal of Biological Sciences》2020,27(3):788-796
Escherichia coli is zoonotic bacteria and the emergence of antimicrobial-resistant strains becomes a critical issue in both human and animal health globally. This study was therefore aimed to investigate the plasmid-mediated resistance in E. coli strains isolated from healthy and diarrheic sheep and goats. A total of 234 fecal samples were obtained from 157 sheep (99 healthy and 58 diarrheic) and 77 goats (32 healthy and 45 diarrheic) for the isolation and identification of E. coli. Plasmid DNA was extracted using the alkaline lysis method. Phenotypic antibiotic susceptibility profiles were determined against the three classes of antimicrobials, which resistance is mediated by plasmids (Cephalosporins, Fluoroquinolone, and Aminoglycosides) using the disc-diffusion method. The frequency of plasmid-mediated resistance genes was investigated by PCR. A total of 159 E. coli strains harbored plasmids. The isolates antibiogram showed different patterns of resistance in both healthy and diarrheic animals. A total of (82; 51.5%) E. coli strains were multidrug-resistant. rmtB gene was detected in all Aminoglycoside-resistant E. coli, and the ESBL-producing E. coli possessed different CTX-M genes. Similarly, fluoroquinolone-resistant E. coli possessed different qnr genes. On the analysis of the gyrB gene sequence of fluoroquinolone-resistant E. coli, multiple point mutations were revealed. In conclusion, a high prevalence of E. coli with high resistance patterns to antimicrobials was revealed in the current study, in addition to a wide distribution of their resistance determinants. These findings highlight the importance of sheep and goats as reservoirs for the dissemination of MDR E. coli and resistance gene horizontal transfer. 相似文献
182.
Tn5 was introduced into Alcaligenes eutrophus strain H1 by a suicide vector pSUP1011. Physical characterization of mutants obtained after Tn5 mutagenesis revealed a relatively high frequency of plasmid curing, or deletion of a 50 kb plasmid DNA segment. Results of Southern hybridization and chromosomal walking indicate that the same continuous stretch of plasmid DNA (designated as D region of plasmid) is deleted in four independent isolates. Moreover, the same deletion of plasmid DNA is also observed in a mitomycin C-generated mutant strain H1-4.Journal Paper No. J-12095 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2607, supported in part by a grant from the Iowa High Technology Council 相似文献
183.
Amir Majlesi Reza Kamali Kakhki Amir Sasan Mozaffari Nejad Rasoul Yousefi Mashouf Amir Roointan Malek Abazari Mohammad Yousef Alikhani 《Saudi Journal of Biological Sciences》2018,25(3):426-430
Plasmid mediated quinolone resistance (PMQR) determinants have arisen as a significant concern in recent years. The aim of this study was screening of resistant-clinical isolates to fluoroquinolone antibiotics and detection of qnr and aac(6′)-Ib-cr genes.For this purpose we collected 100 fluoroquinolone-resistant Enterobacteriaceae which were from 3 hospitals in Hamadan, west provinces of Iran, between October 2012 and June 2013. The all samples were identified by biochemical tests and confirmed by PCR method. Antimicrobial susceptibility to 14 antimicrobial agents including levofloxacin and ciprofloxacin were determined by disk diffusion methods and ciprofloxacin MIC was obtained by broth microdilution method as Clinical Laboratory Standards Institute (CLSI) recommendations. The isolates were screened for the presence of qnrA, qnrB, qnrS and aac(6′)-Ib-cr genes using PCR assay. Among the screened isolates, 64 strains (64%) of Escherichia coli, 23 strains (23%) of Klebsiella pneumoniae, 13 strains (13%) of Proteus mirabilis were collected as quinolone-resistant isolates. out of 100 isolates, two (2%) were positive for qnrS, seventeen (17%) isolates were positive for qnrB and we did not find qnrA gene in any of the isolates. There were also 32 positive isolates for aac(6′)-Ib-cr determinant. We described the prevalence of qnr and aac(6′)-Ib-cr genes in fluoroquinolone-resistant Enterobacteriaceae in Hamadan city. The carriage rate of multidrug-resistant Enterobacteriaceae in healthy people in Hamadan City is extremely high. Moreover, genes encoding transferable quinolones, in particular aac(6′)-Ib-cr, are highly prevalent in these strains. 相似文献
184.
利用常压室温等离子体诱变技术(ARTP)处理磷脂酶A1重组质粒p ET28a-pla B,经琼脂糖凝胶电泳检测发现随着处理时间的延长,质粒超螺旋结构逐渐转变为开环及线性结构。对处理后的质粒转化到BL21宿主菌中,在特定选择培养基中检出突变株转化子,结果表明,质粒处理时间与转化率成反比,与突变率成正比,在60 S达到最优诱变值。挑选圈径比较大的转化子测定其酶活,结果显示突变株(12)最高酶活为12.8 U/ml,与原始菌株(CK)4.8 U/ml相比,提高了2.67倍。对两菌株测序比对,发现碱基突变率为0.74%,且大都集中在A→G和C→T。ARTP对离体质粒具有较好的诱变效应。 相似文献
185.
186.
C. H. Fu W. W. Guo J. H. Liu X. X. Deng 《In vitro cellular & developmental biology. Plant》2003,39(3):360-364
Summary Somatic hybrid plants were regenerated via electrofusion between leaf-derived protoplasts of ‘Chicken heart’ sweet wampee
(Clausena lansium) and embryogenic protoplasts of ‘Newhall’ navel orange (Citrus sinensis Osbeck). Most of the complete plantlets were formed via mini-grafting. Flow cytometry showed that most of the regenerants
were tetraploids as expected, but unexpectedly three plantlets were triploids. Simple sequence repeat (SSR) analysis of seven
randomly selected tetraploids and the three triploids showed that they had specific fragments from both fusion parents, thereby
confirming their hybridity. Analysis of cytoplasmic genomes using universal primers revealed that their chloroplast DNA (cpDNA)
band pattern was identical to the mesophyll parent, while their mitochondrial genomes were of the navel orange type. According
to the SSR results, the triploids obtained in this study were most likely due to chromosome elimination of ‘Chicken heart’
sweet wampee prior to plant regeneration. 相似文献
187.
Despite advances in surgical technology and radiation therapy, the prognosis in the patients with malignant glioma remains
poor. Recent studies show that interleukin-13 receptor {alpha}2 chain (IL-13Ra2), a brain tumor-associated receptor for IL-13,
may play a role in immunotherapy for glioblastoma. We thus amplified human IL-13Ra2 gene from the human glioblastoma cell
line using RT-PCR and cloned the target gene into the pET-28a, a prokaryotic expressing plasmid. After transformation, the
recombinant plasmid expressed a soluble protein induced by IPTG. The purified recombinant protein was shown to be a single
band on the SDS-PAGE with a predicated molecular weight of human IL-13Ra2 gene, suggesting that the recombinant protein of
human IL-13Ra2 was successfully expressed. Recombinant IL-13Ra2 protein can be used as an anti-tumor vaccine, which may provide
a promising new strategy for the treatment of brain malignant gliomas. 相似文献
188.
Fed-batch culture strategy is often used for increasing production of heterologous recombinant proteins in Escherichia coli. This study was initiated to investigate the effects of dissolved oxygen concentration (DOC), complex nitrogen sources and pH control agents on cell growth and intracellular expression of streptokinase (SK) in recombinant E. coli BL21(DE3). Increase in DOC set point from 30% to 50% did not affect SK expression in batch culture where as similar increase in fed-batch cultivation led to a significant improvement in SK expression (from 188 to 720 mg l−1). This increase in SK could be correlated with increase in plasmid segregational stability. Supplementation of production medium with yeast extract and tryptone and replacement of liquid ammonia with NaOH as pH control agent further enhanced SK expression without affecting cell growth. Overall, SK concentration of 1120 mg l−1 representing 14-fold increase in SK production on process scale-up from flask to bioreactor scale fed-batch culture is the highest reported concentration of SK to date. 相似文献
189.
190.
Géraldine A. Van der Auwera Jaroslaw E. Król Haruo Suzuki Brian Foster Rob Van Houdt Celeste J. Brown Max Mergeay Eva M. Top 《Antonie van Leeuwenhoek》2009,96(2):193-204
The self-transmissible, broad-host-range (BHR) plasmid pMOL98 was previously isolated from polluted soil using a triparental
plasmid capture approach and shown to possess a replicon similar to that of the BHR plasmids pSB102 and pIPO2. Here, complete
sequence analysis and comparative genomics reveal that the 55.5 kb nucleotide sequence of pMOL98 shows extensive sequence
similarity and synteny with the BHR plasmid family that now includes pIPO2, pSB102, pTER331, and pMRAD02. They share a plasmid
backbone comprising replication, partitioning and conjugative transfer functions. Comparison of the variable accessory regions
of these plasmids shows that the majority of natural transposons, as well as the mini-transposon used to mark the plasmids,
are inserted in the parA locus. The transposon unique to pMOL98 appears to have inserted from the chromosome of the recipient strain used in the plasmid
capture procedure. This demonstrates the necessity for careful screening of plasmids and host chromosomes to avoid mis-interpretation
of plasmid genome content. The presence of very similar BHR plasmids with different accessory genes in geographically distinct
locations suggests an important role in horizontal gene exchange and bacterial adaptation for this recently defined plasmid
group, which we propose to name “PromA”.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献