Distribution Characteristics of Antibiotic Resistant Bacteria and Antimicrobial Resistant Genes in the Intestine of Cultured Sea Cucumber (Apostichopus japonicus) Seedlings in Shandong Province

Abstract:

In order to understand the current status of drug-resistant bacteria and drug-resistant genes in the sea cucumber, seedlings were collected from 6 aquaculture farms in Shandong Province. The number, proportion and species of antibiotic-resistant bacteria in the intestinal were tested. Meanwhile, the distribution of seven drug-resistant genes of four classes of antibiotics was analyzed by quantitive real-time PCR (qRT-PCR). The results were listed as follows: All of the six kinds of antibiotic-resistant bacteria are detected at all six sampling sites. According to the proportion of drug-resistant bacteria to total cultured bacteria, the top three highest proportions are mequindox, nalidixic acid and tetracycline-resistant bacteria, with the proportions are 0.05%~40.06%, 2.16%~39.94% and 0.06%~23.15%, respectively. The proportion of florfenicol, gentamicin and streptomycin-resistant bacteria range from 0.01% to 4.15%. The 98 antibiotic-resistant bacteria strains are identified as 4 phyla, 5 classes and 30 genera based on 16S rDNA sequence. The top 3 genera are Vibrio, Bacillus and Psychrobacter with the detection rates of 15.30%, 13.27% and 12.25%, respectively. The components of drug-resistant bacteria species varied at different sampling sites, and there are compound antibiotic-resistant strains in Vibrio, Bacillus and Psychrobacter genera. The abundances of seven antibiotic resistance genes in six samples show that the contents of different antibiotic resistance genes against the same antibiotic are significantly different. There is significant correlation between the relative copy number ratio of aminoglycoside resistance gene (aadA) and the proportion of streptomycin and gentamicin-resistant bacteria. The correlation between the abundance of the other six genes and the proportion of drug-resistant bacteria is not significant. The results indicate that there is a certain risk of drug-resistant bacteria and drug-resistant genes in the seedling stage of sea cumber.