Antimicrobial Susceptibility Of Clostridium Perfringens And Escherichia Coli From Food Animals In Guangdong And Guangxi Province

With the wide use of antimicrobial agents,the increase in antimicrobial resistance has become a major worldwide public health problem.Clostridium perfringens and Escherichia coli have serious harms to animal husbandry production,and there is relatively little research on the resistance of Clostridium perfringens in domestic and foreign countries.The objective of this study was to investigate the antimicrobial susceptibility of Clostridium perfringens and Escherichia coli isolated from farms and trading markets of Guangdong and Guangxi Province so as to provide evidences on reasonable usage of antibacterial drugs in veterinary clinic,and reference for the government to make policy.1230 samples of Clostridium perfringens were collected from farms,livestock and poultry trading markets and vegetable markets in Guangdong and Guangxi Province from April to December 2018,including 540 samples from chickens and 690 samples from pigs.147 and 134 Clostridium perfringens were isolated from chicken and pigs,respectively.169and 590 strains,obtained from 920 Escherichia coli samples,were isolated from chicken and pigs,respectively,which include 200 samples from chickens and 720 samples from pigs.Antimicrobial susceptibility test was performed with the agar dilution method and microdilution method to determine the MICs of Escherichia coli and Clostridium perfringens,and the drug sensitivity results were statistically analyzed.210 Clostridium perfringens strains showed different degrees of sensitivity to various antibiotics,and lowest sensitivity to sulfa drugs.The MIC₅₀ and MIC₉₀ of sulfamethoxazole and sulfisoxazole were higher than the highest tested concentrations,>16/304 mg/L and>512mg/L,respectively.The sensitivity of aminoglycosides,lincomycin,phospho-containing polysaccharides and tetracycline drugs was low,and MIC₅₀ was between 2mg/L and 128mg/L.Most strains were sensitive to?-lactams,peptides,and glycopeptides,and MIC₅₀ was?4mg/L.MIC values>8 mg/L were observed in little strains.759 Escherichia coli strains demonstrated high resistance to tetracycline,ampicillin,doxycycline,fluorbenicol and sulfamethoxazole/trimethoprim.The resistance rates were 96.97%,93.28%,73.39%,85.11% and 88.27%,respectively.The drug resistance rate of carbapenems was the lowest,only 0.13%,and the resistance rate of colistin was 3.29%.The multi-drug resistance of Escherichia coli of animal origin was serious,and strains resistant to more than five drugs accounted for 68.37%.Among different animal species isolates,the anitimicrobial resistance of swine origin was more serious than that of chickens.The?-lactams MIC₅₀ and MIC₉₀ of Clostridium perfringens from pigs were higher than those from chickens,which were generally higher than three concentration gradients.In addition to streptomycin,the drug resistance rate of Escherichia coli of swine origin was higher than that of chicken,and the difference of drug resistance between gentamicin and neomycin was the largest.The gentamicin resistance rate of pigs and chickens was 43.73% and 9.47%,respectively;the drug resistance rate of neomycin was 60.17%and 31.95%,respectively.In the different growth stages of pigs,Escherichia coli from sows and piglets had the most serious drug resistance.Sows had the most serious drug resistance to the?-lactam drugs,and the cefoxitin drug resistance rate was 21.43%,which was much higher than other growth stages.Escherichia coli strains from breeding chickens were more resistant to cefoquime,doxycycline and myxomycin than those from broilers.Broilers had more severe drug resistance to cefoxitin,amikacin and gentamicin,but the Escherichia coli from breeding chickens was relatively more resistant than broilers.The results of this study showed that the Escherichia coli from pigs and chickens in Guangdong and Guangxi regions had severe drug resistance,with the drug resistance rates of most drugs over 50%,and multiple drug resistance is serious.Clostridium perfringens was relatively sensitive,with MIC₅₀?4 mg/L for most drugs.It reminds us that rational drug usage should be used to reduce the development of bacterial resistance.