鸡、猪粪便源大肠杆菌对4种抗生素耐药性的比较

以琼脂稀释法对67株鸡源大肠杆菌及61株猪源大肠杆菌进行最低抑菌浓度(MIC)测定,并以SPSS分别进行卡方检验和Probit模型估算,分析不同来源大肠杆菌耐药差异显著性及不同抗生素的半数抑菌浓度(MIC50),以期对不同畜禽粪便来源的大肠杆菌耐药差异进行详细准确的探讨。结果显示,鸡源大肠杆菌对头孢噻肟、诺氟沙星、环丙沙星和四环素耐药率分别为98.51%、68.66%、56.72%和100%,猪源大肠杆菌对头孢噻肟耐药率为88.52%,对诺氟沙星、环丙沙星和四环素则100%耐药。除四环素,鸡源、猪源大肠杆菌对诺氟沙星、环丙沙星、头孢噻肟的耐受差异显著(P0.05),51%的鸡源大肠杆菌和89%的猪源大肠杆菌均呈4重耐药。SPSS分析结果表明,Probit模型估算结果优于当前MIC50常规计算方法,头孢噻肟、诺氟沙星、环丙沙星和四环素对鸡源大肠杆菌MIC50分别为40.031μg·m L~(-1)、40.020μg·m L~(-1)、2.683μg·m L~(-1)和101.418μg·m L~(-1),对猪源大肠杆菌MIC50分别为8.724μg·m L~(-1)、56.044μg·m L~(-1)、31.214μg·m L~(-1)和130.915μg·m L~(-1)。回归方程显示环丙沙星对鸡源大肠杆菌抑制作用最强;高于40.031μg·m L~(-1)时,诺氟沙星抗菌作用弱于头孢噻肟,低于120.23μg·m L~(-1)时,诺氟沙星抗菌作用强于四环素;头孢噻肟、环丙沙星、诺氟沙星和四环素对猪源大肠杆菌的抑菌作用则呈递减趋势。同时验证了诺氟沙星和环丙沙星属同种作用机制,基于Probit模型计算更简单、快速、直观。研究结果可为畜禽养殖中大肠杆菌的耐药差异监控提供一定的数据基础。

Drug Resistance to Four Antibiotics of Escherichia coli in Chicken and Pig Feces

We determined minimum inhibitory concentration (MIC) of four antibiotics to 67 Escherichia coli in chicken feces and 61 Escherichia coli in pig feces by agar dilution method,and then established Chi-square test and Probit model with Statistical Product and Service Solutions (SPSS) to analyze the significance of antibiotic resistance difference and MIC50.Results indicated that resistance rate of cefotaxime,norfloxacine,ciprofloxacin and tetracycline was 98.51％,68.66％,56.72％ and 100％ for Escherichia coli in chicken feces respectively.However,for Escherichia coli in pig feces,resistance rate of cefotaxime was 88.52％,and resistance rate of the other three antibiotics reached 100％.Except for tetracycline,the resistance difference between Escherichia coli in chicken feces and Escherichia coli in pig feces was significant (P＜0.05).The phenomenon was supposed to correlate with the wide use of tetracycline in livestock farms.89％ of Escherichia coli in pig feces was quadruple drug resistance while 51％ of Escherichia coli in chicken feces was quadruple drug resistance.Escherichia coli which were sensitive to the four antibiotics were not found in our study.SPSS analysis suggested that the results calculated with Probit model were better than the normal method.MIC50 of cefotaxime,norfloxacine,ciprofloxacin and tetracycline of Escherichia coliin chicken feces was 40.031 μg·mL-1,40.020 μg·mL-1,2.683 μg·mL-1 and 101.418 μg·mL-1 while that in pig feces was 8.724 μg·mL-1,56.044 μg·mL-1,31.214 μg·mL-1 and 130.915 μg·mL-1.Regression equation showed that ciprofloxacin could inhibit Escherichia coli in chicken feces significantly.When the concentration was above 40.031 μg·mL-1,antibacterial function of norfloxacine was weaker than cefotaxime.Below 120.23 μg· mL-1,antibacterial function of norfloxacine was stronger than tetracycline.The order of antibacterial function to Escherichia coli in pig feces was followed by cefotaxime ＞ ciprofloxacin ＞ norfloxacine ＞ tetracycline.At the same time,it verified the same inherent mechanism for antibacterial function of norfloxacine and ciprofloxacin.Calculation of MIC50 based on Probit model was more simple,faster and more direct.Results provided essential information for monitoring the resistance difference of Escherichia coli in livestock farms.