屎肠球菌临床分离株的耐药性及 生物膜形成与毒力因子的相关性分析

Objective: To analyze the correlation of drug resistance with biofilm formation and virulence of clinical Enterococcus faecium (E.faecium) in a certain area. Methods:A total of 174 clinical isolates of E.faecium were collected from a tertiary hospital in Xi'an from May to August 2017. Using antimicrobial susceptibility testing to determine the drug-resistant phenotype, we tested the ability of biofilm formation assay by crystal violet staining method and determined its hemolytic property quantitatively. Multinomial logistic regression was used to analyze the association among multi-drug resistance, hemolytic activity and biofilm formation ability of the E.faecium isolates. Results: The resistance of E.faecium to β-lactam antibiotics was higher than 90%; only one strain was resistant to linezolid and no strains were resistant to vancomycin. The rate of isolates resistance to penicillin was higher in females than in males (χ²=4.925, P=0.027). The highest isolation rate of E.faecium was in urine samples (67/38.5%), the resistance of E. faecium isolated from urine samples to quinolones, β-lactams, and erythromycin was significantly higher than that of non-urinary specimens (χ²=6.578, P=0.010; χ²=8.797, P=0.003; χ²=9.533, P=0.002). The positive rate of biofilm formation of the E.faecium isolate was 66.7% (116/174), the hemolytic positive rate was 90.2% (157/174), the strains resistant to β-lactam and quinolones had higher positive rate than negative rate of the biofilm, the lower positive rate than negative rate of the hemolysis. The main multi-drug resistance profiles of the isolates were resistant to levofloxacin, ciprofloxacin, penicillin, ampicillin and erythromycin (72/41.4%), of which 73.6% produced the biofilm, and 86.8% of the strains producing the biofilm were hemolytically positive. The multi-drug resistance profiles of the isolates were resistant to levofloxacin, ciprofloxacin, penicillin, ampicillin, erythromycin and tetracycline (62/35.6%), of which 71.0% produced the biofilm, and 95.5% of the strains producing the biofilm were hemolytically positive. Multi-drug resistance of the isolates was negatively correlated with hemolytic activity (RRR=0.460, P=0.030), but nearly positively correlated with biofilm formation ability (RRR=1.984, P=0.051). Conclusion: It is recommended that infections caused by E.faecium, especially in urinary tract, should avoid the use of β-lactams, quinolones and erythromycin in clinical treatment to reduce biofilm formation and alleviate bacterial resistance development.