Detection of Resistance and Resistance Genes of Swine Escherichia coli in Guizhou to Tetracyclines
In order to investigate the resistance to tetracycline and the prevalence of resistant genes of E.coli in Guizhou province,the sensitivity of 783 E.coli isolated from swine of 8 farms in Guizhou province to 6 kinds of tetracyclines was determined by broth microdilution method,and tetracycline resistance gene was detected by PCR method.The results showed that the resistance rates of isolates to oxytetracycline,tetracycline,chlortetracycline,doxycycline,minocycline and tigecycline were 97.3%,97.6%,96.6%,89.3%,48.0% and 34.2%,respectively.The resistance levels of oxytetracycline and tetracycline were the highest,their MIC50were 256 and 128 μg/mL, respectively,while the MIC90were both 512 μg/mL,and the drug resistance times of tetracycline were higher than that of oxytetracycline.The drug resistance level of minocycline and tigecycline were the lowest,and their MIC90were 32 and 4 μg/mL,respectively,the drug resistance times of minocycline and tigecycline were the same.The detection rates of tetracycline resistance genes tetA,tetB,tetC and tetD were 92.60%,41.50%,58.75%,58.62% and 70.10%,respectively.The tetA gene was mainly type in resistance strains,and most of them carried complex resistance genes.The resistance rates of E.coli to oxytetracycline,tetracycline,chlortetracycline,doxycycline and minocycline were extremely significantly correlated with the detection rates of tetB and tetM genes(P<0.01).The detection of tetD gene was positively with tigecycline and minocycline re-sistance(P<0.01)respectively.The drug resistance of E.coli from swine in Guizhou province was widespread,especially to tetracycline and oxytetracycline;The drug resistance trend of chlor-tetracycline and doxycycline were highly;The mechanism of efflux pump was the main drug re-sistance mechanism of tetracyclines;It had a great relationship between the prevalence of resist-ance genes and grow th of antimicrobial resistance in veterinary clinical practice.
drug sensitivity testtetracyclinesdrug resistance genesdrug-resistant phenotype