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Objective:To investigate the prevalence and characteristics of mcr genes in clinical isolates of Aeromonas spp. in our hospital, and provide reference for clinical analysis of the prevalence and expression of colistin resistance genes. Methods:Polymerase chain reaction (PCR) was used to detect mcr genes in 183 Aeromonas spp. strains. The minimum inhibitory concentrations (MICs) of colistin and polymyxin against mcr-positive Aeromonas spp. were detected by micro broth dilution method. Broth conjugation and filter mating conjugation were performed. Whole genome sequencing was used to analyze the genetic environment of mcr-3 gene in Aeromonas spp.. A recombinant Escherichia coli ( E. coli) DH5α-pGEM-T: : p mcr-3 strain was constructed to verify the expression of mcr-3 gene. Results:The positive rate of mcr-3 gene in 183 strains of Aeromonas spp. was 2.19% (4/183). No mcr-1 or mcr-2 gene was detected among these isolates. Antimicrobial susceptibility test showed that four mcr-3-carrying Aeromonas hydrophilia ( A. hydrophilia) strains were sensitive to colistin and polymyxin (MIC<2 μg/ml). Conjugation experiments indicated that mcr-3 gene could not be transferred between strains. Whole-genome sequencing analysis suggested that the mcr-3 genes carried by the A. hydrophilia isolates belonged to mcr-3.2 and mcr-3-like variants, and no adjacent transfer element was detected upstream and downstream. The recombinant E. coli DH5α-pGEM-T: : p mcr-3 strain was sensitive to colistin (MIC=2 μg/ml). Conclusions:The clinical isolates of A. hydrophilia in our hospital carried mcr-3 gene, but does not exhibit colistin resistance, and no evidence supported the transfer of mcr-3 gene for the time being.
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Sixteen dogs were allocated to 4 groups in equal number and were fed with Rad ix Rhod od end ri Mollis 0.170, 0.345 and 1.420 g/kg for three months respectively, with one group as control. The results showed that Rad ix Rhod od end ri Mollis can cause focal necrosis, edema, ballooning degeneration and fatty degeneration of liver cells. It can also increase the permeability of glomerulus, and cause edema and even ballooning degeneration of renal tubular epithelial cells. Biochemical analysis showed that GPT and BUN apparently increased. Urine analysis showed that qualitative examination of protein, epithelial cells, white and red blood cells were all positive. It is considered that long-term administration of Rad ix Rhod od end ri Mollis can cause functional and structural damage of liver and kidney, and timely suspension of the drug and treatment may render the damage.