ISOLATION, IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY OF ELIZABETHKINGIA ANOPHELIS DERIVED FROM TRIONYX SINENSIS

Elizabethkingia anophelis has been recognized as an important opportunistic pathogen in human and animal infection in recent years. The study represents the first successful isolation of this bacterium from Trionyx sinensis. The objective of this study was to isolate and culture a suspected strain of Elizabethkingia anophelis from infected Trionyx sinensis, identified the strain, and analyze its antimicrobial susceptibility characteristics. In our study, liver and spleen tissues were obtained from diseased Trionyx sinensis in aseptic environment. These tissues were ground and cultured in LB medium to obtain the target strain EJX2021. Identification of the strain involved morphological observations, determination of the 16sRNA gene sequence, and physiological and biochemical identification. Subsequently, artificial regression infection, histopathological observation, virulence factor analysis and antibiotic susceptibility test were performed to study the pathogenic ability and antimicrobial susceptibility characteristics. We successfully isolated a dominant strain EJX2021, from the diseased Trionyx sinensis. It was identified as Elizabethkingia anophelis based on phenotypic characteristics, 16sRNA gene sequence, and physiological and biochemical identification. The results of artificial regression infection showed that LD₅₀ of the strain against Trionyx sinensis at 15d was 1.62×10⁸ CFU/mL, with a 95% confidence interval of 0.78—3.37 ×10⁸ CFU/mL. Histopathology analysis revealed different degrees of pathological changes in the intestines, lungs, spleen, liver and other tissues. Virulence factor analysis showed that the strain contained 246 potential virulence genes in 16 categories. In terms of antimicrobial susceptibility, the strain exhibited multi-drug resistance. It was sensitive to doxycycline, minocycline, kanamycin, piperacillin, enrofloxacin and florfenicol, moderately sensitive to ceftriaxone and cefoperazone, and resistant to 15 antibiotics such as neomycin. Our study proved that Elizabethkingia anophelis can cause the disease of Trionyx sinensis, and provided scientific basis for the detection, identification and control of the Trionyx sinensis disease caused by the bacteria.