| Assessing the contamination risk of antibiotic resistance genes(ARGs)is one of the current research hotspots.Livestock manure is an important repository of veterinary antibiotics and ARGs.It is particularly important to clarify the residual characteristics of ARGs in livestock manure after using veterinary antibiotics to assess the ecotoxicological effects and pollution risks after entering the environment.Therefore,this thesis takes Fluoroquinolones Resistance Genes(FRGs)as the object to study the changes in the abundance of FRGs in pig feces after the injection of Enrofloxacin(ENR)at a therapeutic dose,and analyze the key influencing factors.Provide reference for scientific evaluation of FRGs contamination risk after ENR administration.Twenty-seven D×Y×L boars weighing 57.11 ± 5.88 kg were selected and randomly divided into 3 groups with 9 pigs in each group;the pigs in the CK group were intramuscularly injected with the same dose of normal saline as the test group,and the H and L groups were based on the pig weight and exceeded the standard The dose of 5 mg/kg and the prescribed dose of 2.5 mg/kg in the Veterinary Pharmacopoeia of the People’s Republic of China(2015 edition)are respectively injected with ENR intramuscularly;the test period is 13 days,including the medication period of 3 days,the drug withdrawal period of 10 days,and the medication period of 8 per day Swine manure samples will be collected every day at0:00 and 20:00 and at 20:00 during the drug withdrawal period to determine the concentration of ENR and its main active metabolite Ciprofloxacin(CIP),FRGs,multiple ARGs,and mobile genetic elements(Mobile Genetic Elements,MGEs),microbial community structure diversity and physical and chemical indicators.The main results obtained in this paper are as follows:1.After intramuscular injection of ENR,on the 2.5th day,the concentration of ENR and CIP in pig manure reached the highest value.At this time,the concentrations of ENR in group H and L were 219.75 ± 88.05 mg/kg DM and 88.67 ± 45.46mg/kg DM,CIP The concentrations of DM were 38.99 ± 24.15 mg/kg DM and 17.22± 8.37 mg/kg DM;ENR and CIP could not be detected in pig manure at the end of the drug withdrawal period;the concentration of ENR in pig manure between the test groups was from the 2nd to the 4th day There were significant differences(P<0.05),and there were significant differences in the concentration of pig manure CIP between the test groups from 1.5 to 4 days(P<0.05),both showed that the concentration of H group was greater than that of L group.2.After intramuscular injection of ENR,the metagenomics annotated that there are 17 ARGs and 4 MGEs in the pig manure of each group in the experiment,and the relative abundance of FRGs ranks 15 th.Compared with the CK group,on the 13 th day,the relative abundance of total FRGs in the L group was 0.0009 ± 0.001copies/16 S r RNA,which was significantly higher than that in the CK group(P<0.05),while the total MGEs had no significant change(P>0.05).The absolute abundances of qnr S,tol C,int1,and tnp A in groups H and L have a decreasing trend.The absolute abundance of qnr S in pig manure on the 3rd day was reduced by 10.69% and 9%,respectively,compared with that on the 0th day.The difference is not significant(P>0.05).3.Intramuscular ENR significantly reduced the microbial diversity of pig feces in H and L groups on the 3rd day(P<0.05),and there was a decreasing trend in the total number of bacteria in H and L groups.Thermovenabulum,Aeromonas(Aeromonas),Citrobacter,Cronobacter,Enterorhabdus,Shigella and Succinomonas(Succinimonas)is a potential host for qnr S;Citrobacter,Kronohella,Escherichia,Shigella,and Yersinia are potential hosts for tol C bacteria.4.Microbes,MGEs and physical and chemical indexes are significantly correlated with FRGs(P<0.05).Among them,Bacteroides,Proteobacteria,int1,int2,tnp A,water content,total organic carbon and p H are significantly positively correlated with qnr S and tol C(P<0.05);ENR and CIP are significantly negatively correlated with qnr S and tol C(P <0.05).In summary,the use of ENR in accordance with the regulations will not increase the risk of FRGs in pig manure.Pig manure microorganisms and tnp A are key factors affecting FRGs. |
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