| Enterococci are normal flora in the intestinal tract of humans and animals, and also opportunistic pathogen.They can cause not only urinary tract infections, skin and soft tissue and wound infections in humans and animals, but also lead to the serious infections, such as bacteremia, endocarditis, meningitis. In recent years, due to the extensive use of antibiotics, the enterococci become resistant to multiple antimicrobial agents, and become an important pathogen in the hospital infection. In the United States, about 12% of nosocomial infections were caused by enterococci. U.S. nosocomial infection surveillance system (NISS) has listed it as the second largest hospital pathogen after S. aureus infection. Therefore, the study of enterococci resistance mechanism is of great significance to the guidance of antibacterial use in the medical and veterinary clinical and public health.In this study,71 enterococci strains were isolated and identified using the bacterial morphology identification,Gram staining,16S rRNA amplification in Henan Province. Of them,30,21 and 20 strains were isolated from Human, pig and food source, respectively. Antimicrobial susceptibility testing, detection and sequencing of resistance mutations and resistance gene, plasmid conjugation, were performed to study the resistant mechanism of enterococci to fluoroquinolones and macrolides.The results show that the resistant rates of enterococci from human, pig and food source to ciprofloxacin were 60.0%(18/30),52.3%(11/21) and 15.0%(3/20), respectively. Sequencing of gyrA and parC gene PCR products in fluoroquinolones resistance determining regions revealed that single or mutiple mutations occurred in position 83,87 in GyrA and in postion 80 in ParC. That is, Ser83→Ile, Arg, Tyr, Glu87→Gly in GyrA and Ser80→Ile in ParC.The resistance rates of enterococci from Human, pig and food source to erythromycin were 60.0%(18/30),100%(21/21) and 30.0%(6/20)., respectively. PCR detection for macrolide resistance genes (ermA, emrB, ermC, mefA/E, msrC) in Enterococci showed that ermB gene were detected positive in all erythromycin-resistant enterococci, and mefA/E gene were only detected in one strain. Plasmid conjugation experiment showed that ermB gene can transfer, Both conjugation transposon Tn1545 and conjugation plasmid play an important role in the horizontal dissemination of ermB gene. In addition, the presence of integrase tndX were also detected, but not related to the reported Tn5397 and Tn1116, suggesting there may lie a new conjugation transposon, which will be confirmed by further studies.In summary,71 enterococci strains were isolated and identified from hospitals, farms and retail markets in Henan province in this study. The resistance rates of these strains to ciprofloxacin and erythromycin were 45.1% and 63.4%, respectively. Single or mutiple mutations in positions 83 and 87 in GyrA and in postion 80 in ParC. That is, Ser83→Ile, Arg, Tyr, Glu87→Gly in GyrA and Ser80→Ile in ParC were the important reasons for the resistance of enterococci strains from different sources to ciprofloxacin. ermB gene are the main reason for resistance of enterococci strains from different sources to erythromycin, which can transfer by conjugation plasmids or conjugation transposon Tn1545. Further studies to clarify the role of existing or new conjugation transposons in the horizontal dissemination of enterococci macrolide resistance gene ermB has important clinical significance. |
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