Prevalence Of Antibiotic Resistance In Escherichia Coli Isolated From Different Pig Farms

In recent years,with the widespread use of antibiotics,gram negative bacteria resistance,especially Escherichia coli,is becoming more and more serious,and it has become a global public health issue.The resistance of E.coli of animal origin is serious due to various factors,particularly irrational use of antibiotics in veterinary medicine.In this study,E.coli isolates collected from a pig farm in Guangdong province were investigated their resistance against tetracyclines,aminoglycosides,?-lactams,fluoroquinolones,phenicols and polymyxins,to compare the impact of different factors such as farm location,seasonal climate and different growth periods on resistance patterns,in order to provide the basis for reasonal usage of antibiotics in pig farm and for reducing the spread of drug-resistant strains.During July 2016 to August 2017,we sampled pig fecal swabs of pigs in different growth periods and different geographic locations in the pig farm,a total of 1556 E.coli isolates were obtained from piglets(n=324),sows(n=222),small fattening pig(n=330),moderate fattening pig(n=293),and big fattening pigs(n=387).E.coli isolates from fattening pigs were collected from four different geographical locations of the farms,including close to the village(n=257),near the road(n=207),near the river(n=319)and in the mountain(227).The susceptibility of 1556 E.coli isolates against 13 antimicrobial agents was determined by agar dilution method.Among them,tetracycline,cotrimoxazole and ampicillin showed high resistance with 98.92%,91.98% and 90.89%,respectively;the resistance rates of doxycycline(88.99%)and streptomycin(80.84%),florfenicol(78.99%),neomycin(76.13%)were more than 70%,and followed by gentamicin(57.10%),ciprofloxacin(43.22%),cefotaxime(33.74%),amikacin(25.40%),colistin(25.39%)and apramycin(25.33%),respectively.Resistance to tetracycline,sulfamethoxazole,ampicillin,and doxycycline were observed in E.coli from all different growth stages.E.coli from piglets and small fattening pigs showed the highest resistance to neomycin,gentamicin,apramycin,cefotaxime and amikacin;while the highest resistance towards florfenicol and ciprofloxacin was observed in small fattening pigs.In addition,pig farms near the villages and road showed the highest resistance against antimicrobial agents,but farms in the mountains showed the lowest resistance rates,except colistin,apramycin and streptomycin.In a year,spring showed the highest resistance.The resistance to colistin decreased from 34.95% to 17.22% with the gradual reduction of usage.To sum up,the resistance rates of swine Escherichia coli at different growth stages were distinct,farms close to village showed higher resistance than farms in the mountain.The season with highest resistance of the year is spring.Thus,we can improve the immunity of piglets and small fattening pigs,keep warm in spring,and reduce the usage of antimicrobial agents,to slow down the increasing drug resistance issue.