The aim of this study is to identify the cause of death of a South China tiger cub at the Meihuashan breeding institute of Fujian Province.Pathogenic bacteria were isolated and cultured from liver,spleen,lung and other tissue samples of the dead South China tiger aseptically.The iso-lated bacteria were identified through morphological observation,biochemical characterization,sequence analysis of housekeeping gene gyrB,virulence gene detection,animal pathogenicity test and drug sensitivity test.A pathogenic Aeromonas hydrophila strain,designated FJ/Tiger-201809 was successfully isolated from the trachea of dead South China tiger.The nucleotide sequence ho-mology between the isolate and 11 strains of Aeromonas gyrB ranged from 91.2％to 99.1％,with the highest homology of 99.1％observed with Aeromonas hydrophila(AF208251.1).Genetic evo-lution analysis showed that the isolated strain FJ/Tiger-201809 was in the same evolutionary branch as other reference strains of Aeromonas hydrophila and was closely related.The pathoge-nicity test in mice showed artificial infection of mice with the strain resulted in varying degrees of lesions in several organs of the mice,and the median lethal dose(LD50)was 1 × 107.8 CFU/mL.Virulence gene test results showed that the isolate FJ/Tiger-201809 carried two virulence genes,aer and act.The results of drug sensitivity test showed that FJ/Tiger-201809 was highly sensitive to enrofloxacin and ampicillin among 18 commonly used antibiotics,relatively sensitive to penicil-lin G and doxycycline,and resistant to the other 14 antibiotics.In conclusion,this study isolated and identified a strain of Aeromonas hydrophila from a dead South China tiger with multiple drug resistance and strong pathogenicity,which provided an important reference for the prevention and control of bacterial diseases in South China tiger.

The aim of this study is to identify the cause of death of a South China tiger cub at the Meihuashan breeding institute of Fujian Province.Pathogenic bacteria were isolated and cultured from liver,spleen,lung and other tissue samples of the dead South China tiger aseptically.The iso-lated bacteria were identified through morphological observation,biochemical characterization,sequence analysis of housekeeping gene gyrB,virulence gene detection,animal pathogenicity test and drug sensitivity test.A pathogenic Aeromonas hydrophila strain,designated FJ/Tiger-201809 was successfully isolated from the trachea of dead South China tiger.The nucleotide sequence ho-mology between the isolate and 11 strains of Aeromonas gyrB ranged from 91.2％to 99.1％,with the highest homology of 99.1％observed with Aeromonas hydrophila(AF208251.1).Genetic evo-lution analysis showed that the isolated strain FJ/Tiger-201809 was in the same evolutionary branch as other reference strains of Aeromonas hydrophila and was closely related.The pathoge-nicity test in mice showed artificial infection of mice with the strain resulted in varying degrees of lesions in several organs of the mice,and the median lethal dose(LD50)was 1 × 107.8 CFU/mL.Virulence gene test results showed that the isolate FJ/Tiger-201809 carried two virulence genes,aer and act.The results of drug sensitivity test showed that FJ/Tiger-201809 was highly sensitive to enrofloxacin and ampicillin among 18 commonly used antibiotics,relatively sensitive to penicil-lin G and doxycycline,and resistant to the other 14 antibiotics.In conclusion,this study isolated and identified a strain of Aeromonas hydrophila from a dead South China tiger with multiple drug resistance and strong pathogenicity,which provided an important reference for the prevention and control of bacterial diseases in South China tiger.

Objective To prepare a nano drug(PFOB@Lip-MMC)with liposome as the carrier,liquid perfluorooc-tyl bromide(PFOB)as core and mitomycin C(MMC)loading on the liposome shell and study its inhibitory effect on the proliferation of human pterygium fibroblasts(HPFs).Methods The thin film dispersion-hydration ultrasonic method was used to prepare PFOB@Lip-MMC and detect its physical and chemical properties.Cell Counting Kit-8,Cam-PI cell viability staining and flow cytometry were employed to detect the impact of different concentrations of PFOB@Lip-MMC on the via-bility of HPFs.DiI fluorescence labeled PFOB@Lip-MMC was used to observe the permeability of the nano drug to HPFs under a laser confocal microscope.After establishing HPF inflammatory cell models,they were divided into the control group(with sterile phosphate-buffered saline solution added),PFOB@Lip group(with PFOB@Lip added),MMC group(with MMC added),PFOB@Lip-MMC group(with PFOB@Lip-MMC added)and normal group(with fresh culture medi-um added)according to the experimental requirements.After co-incubation for 24 h,flow cytometer was used to detect the apoptosis rate of inflammatory cells,and the gene expression levels of interleukin(IL)-1β,prostaglandin E2(PGE2),tumor necrosis factor(TNF)-α and vascular endothelial growth factor(VEGF)in cells were analyzed by PCR.Results The average particle size and Zeta potential of PFOB@Lip-MMC were(103.45±2.17)nm and(27.34±1.03)mV,respec-tively,and its entrapped efficiency and drug loading rate were(72.85±3.28)％and(34.27±2.04)％,respectively.The sustained-release MMC of drug-loaded nanospheres reached(78.34±2.92)％in vitro in a 24-hour ocular surface environ-ment.The biological safety of PFOB@Lip-MMC significantly improved compared to MMC.In terms of the DiI fluorescence labeled PFOB@Lip-MMC,after co-incubation with inflammatory HPFs for 2 h,DiI fluorescence labeling was diffusely dis-tributed in the cytoplasm of inflammatory HPFs.The apoptosis rate of inflammatory HPFs in the PFOB@Lip-MMC group[(77.23±4.93)％]was significantly higher than that in the MMC group[(51.62±3.28)％].The PCR examination results showed that the gene transcription levels of IL-1 β,PGE2,TNF-α and VEGF in other groups were significantly reduced com-pared to the control group and PFOB@Lip group,with the most significant decrease in the PFOB@Lip-MMC group(all P＜0.05).Conclusion In this study,a novel nano drug(PFOB@LIP-MMC)that inhibited the proliferation of HPFs was successfully synthesized,and its cytotoxicity was significantly reduced compared to the original drugs.It has good bio-compatibility and anti-inflammatory effects,providing a new treatment approach for reducing the recurrence rate after pte-rygium surgery.