Antibiotic-resistant mechanisms of plasmid pA1137 carrying aminoglycoside resistance gene aacC2 / 军事医学

Objective To achieve detailed genomic characterization and investigate the antibiotic-resistant mechanisms of plasmid pA1137 carrying the aminoglycoside resistance gene aacC2.Methods Antibiotic-resistant genes were deter-mined by PCR.Conjugation experiments were performed to verify the transferability of plasmid pA 1137.The minimum in-hibitory concentration(MIC)values of bacterial strains were tested with microdilution method.The genetic background, mobile elements and antibiotic resistance mechanisms of pA 1137 were determined using a whole genome sequencing meth-od.Results Both carbapenem-resistant gene blaIMP-8and aminoglycoside-resistant genes aacC2 and aacA4 were carried by A1137 isolated from Enterobacter cloacae(ECL).aacC2 was located in plasmid pA1137 while the other two resistant genes were observed in chromosomes.Plasmid pA1137 was an IncFⅡplasmid,whose total length was 68.97 kb,and GenBank accession number was MF190369.Plasmid pA1137 contained multiple replicons and intact conjugative transfer regions,so it could be transferred into ECL through conjugation experiments and confer corresponding antibiotic resistance to the transconjugant A1137-EC600.Conclusion IncFⅡ plasmid pA1137 has a single accessory region, the first reported Tn5403-based aacC2-tmrB-related region,which can cause stable inheritance and mediate the resistance to aminoglycoside antibiotics in ECL A1137.

Application of locomotor activity test to evaluate functional injury after global cerebral ischemia in C57BL/6 mice / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To evaluate the application of locomotor activity test in functional injury after global cerebral ischemia (GCI) in C57BL/6 mice.</p><p><b>METHODS</b>GCI was induced by bilateral carotid arteries occlusion for 30 min in C57BL/6 mice. Mice were divided into sham group, GCI group and minocycline group. Saline or minocycline (45 mg/kg) was i.p. injected once daily for 6 d after ischemia. At Day 6 after ischemia, locomotor activity was recorded for 1 h in open field test. Total distance, central distance, central distance ratio, periphery distance, periphery distance ratio, central time and periphery time were used to evaluate the behavior characteristics of locomotor activity in C57BL/6 mice after ischemia. The survival neuron density was detected by Nissl staining in hippocampus, cortex and striatum.</p><p><b>RESULTS</b>Compared with sham group, total distance, central distance and central time increased and periphery time decreased in C57BL/6 mice after GCI (Ps<0.05). However, minocycline significantly reduced the central distance and central time and increased the periphery time (Ps<0.05). Neurons were damaged in hippocampus, cortex and striatum after GCI, which manifested by decreased neurons and the most serious damage in hippocampal CA1 region. Minocycline significantly improved the neuron appearance and increased the neuron number in hippocampus and striatum (P<0.001 or P<0.05).</p><p><b>CONCLUSION</b>Locomotor activity in open field test can objectively evaluate the behavior injury after GCI in mice. Central distance and central time can be used as indexes of quantitative assessment.</p>