Investigation On Antibacterial Drug Resistance Of Three Swine Source Pathogens And Influences Factors In Guangdong Province

Antimicrobials not only prevent and treat infectious diseases of livestock,but also promote animal growth and increase feed efficiency.Antibacterial drugs have been widely used in veterinary clinics.Staphylococci,Enterococci and Escherichia coli are common zoonotic pathogens,which are widely present in all aspects of aquaculture production and may cause many diseases in both humans and animals.This study investigated the application of antibacterial drugs on pig farms across Guangdong Province.Furthermore this study also investigated the drug resistance of Staphylococci and Enterococci,and provided data support for the rational use of antibiotics on pig farms.Follow-up monitoring of a farm to study the drug resistance of pathogens in pigs at different growth stages and the change in the detection rate of colistin-resistant Escherichia coli after colistin were banned from feed additives is in progress.It provides a theoretical basis to risk assessment for colistin.The prosperity of farms is closely related to the widespread use of antimicrobials.However,the abuse and unreasonable use of antimicrobials in livestock production is very common.We investigated the use of veterinary drugs on 48 farms in different areas of Guangdong Province.The results showed that there were 37 kinds of veterinary drugs used on the farms and the most used category was antibacterial drugs.The most frequently used antibacterial drugs were Florfenicol,Doxycycline and Amoxicillin.At the same time,there were certain problems in the use of veterinary drugs on the farms.Therefore,the government should strengthen supervision,and the breeding staff should also improve their professional quality.In this study,446 Staphylococcus strains isolated from 10 typical farms and two hog markets were used as experimental subjects between 2015 and 2016.The sensitivity of these tested strains against 14 antimicrobial agents was determined by agar dilution method.The resistance rates of clindamycin,erythromycin,florfenicol,tetracycline and tiamulin were all over 80%,and no vancomycin-resistant strains were detected.There are differences in the drug resistance status of Staphylococci isolated from different sources and farms at different growth stages.The resistance of Staphylococci on farms is more serious,and the piglets and nursery pigs on the farm are at a more serious stage of drug resistance.The detection rates of multidrug resistance cfr and optr A genes were 12.3% and 7.0%,respectively,while the detection rate of methicillin-resistant Staphylococi was 51.8%.The frequent use of florfenicol in pig breeding may be the main reason for the widespread spread of cfr and optr A genes in staphylococci.The sensitivity of 362 Enterococci to 13 antimicrobial agents was determined.The results showed that they were sensitive to vancomycin,linezolid and tigecycline,and the sensitivity to penicillin and ampicillin was over 90%.The resistance rate of Enterococci to rifampicin was 19.3%,and the resistance rate to amikacin,erythromycin,tetracycline and clindamycin was over 90%,followed by florfenicol and chloramphenicol.The resistance rate of ciprofloxacin reached 80.4%,58.4% and 43.4%.Four strains(1.1%)and 270 strains(74.6%)of Enterococcus faecalis carried cfr gene and optr A gene,respectively,indicating that the cfr gene was not widely transmitted in Enterococcus faecalis,and the optr A gene has been widely distributed in Enterococcus faecalis.There was no significant difference in the resistance rates of Staphylococci,Enterococci and Escherichia coli carried by the same batch of pigs at different growth stages to most antimicrobial agents;florfenicol and doxycycline were commonly used drugs in pig breeding.Staphylococci,Enterococci and E.coli obtained were also having a high level of resistance to florfenicol and tetracycline.In order to find whether colistin-resistant Escherichia coli can be effectively contained on the farm before and after the ban of colistin,a two-year follow-up survey was conducted on a farm lacated in Guangdong Province.It was found that colistin sulfate was banned from feed additives,and its resistance rate continued to decrease,from 71.1% to 7.0%.Prohibiting antibacterial drugs for feed additives to promote growth is effective in reducing the high prevalence of drug-resistant bacteria in farms.In summary,the resistance of Staphylococcus aureus,Enterococcus and Escherichia coli in China is serious.Staphylococci and Enterococci are more sensitive to vancomycin.No vancomycin-resistant strains,Escherichia coli to carbapenem are found.Drugs are more effective after colistin was banned as feed additive,the detection rate of colistin-resistant E.coli on pig farms gradually decreased.It was significant to prevent and control the generation and spread of bacterial antibiotics resistance.by strengthening rational antibiotics use and detecting antibiotics-resistant pathogens on pig farms.