1.Effect of antimicrobial reduction on the diversity of antibiotic resistance genes in large scale dairy farms
Yujie WEI ; Chuncai LIANG ; Xudan WANG ; Yingjie LI ; Juxiang LIU
Chinese Journal of Veterinary Science 2024;44(9):2031-2039
In order to study the effect of antimicrobial drug reduction on the resistance of E.coli and diversity of antibiotic resistance genes(ARGs)and mobile genetic elements(MGEs)in the intes-tinal microbiota of dairy cows in dairy farms in Hebei Province,and to evaluate the implementation effect of antimicrobial drug reduction actions,anal swab samples and fecal samples were collected from three qualified dairy farms and two non-standard dairy farms in different regions of Hebei Province,and E.coli was isolated from the anal swab samples and tested for their resistance to 16 antimicrobial drugs,and the differences in the drug resistance rate of E.coli in the two types of dairy farms were analyzed.SYBR fluorescent dye method was used to detect ARGs and MGEs in dairy feces,their relative abundance was calculated,the differences and correlation between the two types of dairy farms were analyzed.The results showed that a total of 192 ARGs and 7 MGEs were detected in 15 samples,and the relative abundance of ARGs was the highest in β-lactam resistance genes,followed by tetracycline resistance genes.The detection of ARGs and MGEs in some stand-ard dairy farms was lower than that in non-standard farms,suggesting that the large use of antimi-crobial drugs may be related to the production and transmission of ARGs,and the number of MG-Es detected was correlated with the number of ARGs detected,and ARGs may be transmitted through horizontal gene transfer.The results showed that there was little difference in the drug re-sistance rate of E.coli from the two types of dairy farms,and multi-drug resistant strains were more likely to occur in non-standard farms.The implementation of antimicrobial reduction had a certain effect on the diversity of antibiotic resistance genes,but had no significant effect on the prevalence of E.coli drug resistance and the diversity of ARGs in dairy farms in the short term,and there was little difference between different regions,which also revealed the prevalence of anti-biotic resistance in dairy farms.