| Pathogenic Escherichia coli, a kind of important bacteria of zoonotic disease, which causes acute or deadly infectious diseases to people, chickens, pigs, cows or other animals. Presently, the usage of antimicrobial agents is a main measure to prevent and control the bacterial diseases. Because of the increasing usage of the drugs and the spread of drug-resistant genes, antimicrobial resistance of E. coli have been becoming more and more serious. The way of transmission in the bacterial resistance includes horizontal and mutation transfer of the resistance genes. Integron and plasmid, two mobile genetic factors, play an important role in the spread of E. coli resistance genes. This study has carried out a resistance testing of 18 kinds of antimicrobial agents to the E. coli, which were isolated from chickens, pigs and cows. We researched the E. coli resistant phenotype and its correlation with class 1 integron and 18 plasmids, in order to provide important reference and theoretical basis for the next study of resistance mechanism and effective control to E. coli disease.1. Drug susceptibility testing of E. coliWe used disk diffusion method of K-B recommend by the WHO and pressed the criteria of CLSI (2012) to test 818 pathogenic E. coli (644 from chicken,113 from pigs,61 from cows) which were isolated from Jiangsu Province with 18 kinds of antibiotics susceptibility. And then analyze the resistance rate and multi-drug resistance. The results show that the probability of chicken and pig multiple resistance of E. coli was 88.2%(568/644) and 82.3%(93/113), which were significantly higher than cows of 21.3%(13/61) (P<0.016). E. coli isolated from chickens and pigs were highest resistance to 16 kinds of antibiotics, which was higher the resistance to 11 kinds of antibiotics in cows. E. coli isolated from chickens and pigs have exceeded 50% resistance rates of antibacterial drug which were commonly used in clinic, such as ampicillin, streptomycin, tetracycline, nalidixic acid, trimethoprim/sulfamethoxazole, and sulfisoxazole. However, E. coli isolated from cows were more sensitive to antimicrobial drugs, which only two antimicrobial agents, ampicillin and nalidixic acid, were more than 20% in the resistance rates. The ceftazidime, ertapenem, aztreonam and amikacin do not show resistance. E. coli isolated from chickens and pigs performed most serious resistance in tetracycline, nalidixic acid and sulfisoxazole. The resistance rates of E. coli isolated from chicken were 93.5%,81.2% and 78.9%, respectively; the resistance rates of E. coli isolated from pigs were 90.2%,84.1% and 69.9%, respectively; but the resistance rates of E. coli isolated from cows were 19.7%,21.3% and 18.0%, respectively.2. The correlation of E. coli resistance and class 1 integronThe results of PCR assay showed that 80.9% of E. coli (662/818) carried class 1 integron. Among them, the positive rate of class 1 integron in cow strains is 21.3%(13/61), which lower than chicken strains 87.0%(560/644) and pig strains76.1%(86/113) (P<0.014) significantly. In the chickens, pigs and cows multi-resistant strains, the positive rate of class 1 integron were 93.0%,92.5% and 84.6%, respectively. However, the positive rate of class 1 integron in the multiple non-resistant strains were 39.5%,0 and 4.2%(P<104), respectively. The correlation analysis between E. coli resistance phenotype and the result of its class 1 integron showed that E. coli resistance to five kinds of antibiotics (ampicillin, nalidixic acid, sulfisoxazole, enrofloxacin, trimethoprim/sulfamethoxazole) and class 1 integron have a significant positive correlation (P<0.023).3. The correlation off. coli resistance and plasmidThis study has established a triple PCR method and selected 255 E. coli (161 from chicken, 67 from pigs,27 from cows) to test the plasmids. The result showed that 5 plasmids were positive, which were 4.7%(IncHI2),15.3%(IncI1),15.7%(IncN),1.6%(IncA/C),13.7%(IncY). However, other 13 plasmids (IncB/O, IncFIC, IncP, IncT, IncK/B, IncW, IncFIIA, IncFIA, IncFIB, IncFreP, IncX, IncHI1 and IncL/M) were negative. The results showed that four kinds of plasmids (IncHI2, IncI1, IncN, IncA/C) and E. coli resistance have a significant positive correlation (P<0.049), but IncY and E. coli resistance have a significant negative correlation (P<0.037). The IncHI2 positive E. coli (n=12) have higher resistance rates to chloramphenicol, ceftriaxone and cefotaxime which were 83.3%,66.7% and 66.7%, respectively, but the resistance rates of IncHI2 negative E. coli (n=243) were 41.2%,12.8% and 16.5%. The IncI1 positive E. coli (n=49) have higher resistance rates to sulfisoxazole, trimethoprim/ sulfamethoxazole, and tetracycline which were 97.9%,97.9% and 95.9%, respectively, but the resistance rates of IncI1 negative E. coli (n=206) were 77.7%,78.6% and 82.5%. The IncN positive E. coli (n=40) have higher resistance rates to sulfisoxazole, trimethoprim/sulfamethoxazole, and tetracycline which were all 97.5%, but the resistance rates of IncN negative E. coli (n=215) were 80.0%,79.5% and 87.0%. The IncA/C positive E. coli (n=4) have higher resistance rates to gentamicin, ceftriaxone and ceftazidime which were all 75%, but the resistance rates of IncA/C negative E. coli (n=251) were 26.3%,14.3% and 8.4%. Opposite, The IncY positive E. coli (n=35) have lower resistance rates to nalidixic acid, ciprofloxacin and enrofloxacin which were 45.7%,42.8% and 45.7%, respectively, but the resistance rates of IncY negative E. coli (n=220) were 78.2%,52.3% and 49.1%.In summary, we have tested antimicrobial agents of the E. coli which isolated from chickens, pigs and cows and explore these E. coli resistant phenotype and its correlation of class 1 integron and 18 plasmids. Strains which were isolated from chickens and swines expressed higher rates of resistance and multi-drug resistant than cows. The positive rate of multi-druj| resistant strains of class 1 integron is two times larger than positive rate of non-multi-drug resistant strains. Carrying plasmids (IncHI2, IncI1, IncA, IncA/C) one or more, E. coli resistance increase obviously and have a significant positive correlation. This study tested E. coli resistant, and to explore the factors that E. coli resistance formed from molecular level. It provides important information for rational drug use prevention and treatment of bacterial disease and scientific medicine, and provides a theoretical basis for the study of mechanism of drug-resistant... |
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