Detecting The Biofilm Formation Ability Of E.coli And Drug Susceptibility

E. coli is one of the common bacteria cause nosocomial infection, both inside and outside of intestinal. The ability of bacteria to persist and grow in a biofilm seems to represent a major factor for pathogenesis, especially in many insert devices related infections. Routine dose of drugs often cannot penetrate biofilm, and lead to recurrent infection. How to effectively break through the protective of bacterial biofilm to kill bacteria, is very important to treat infections. So, discovering variety of the drug resistance in the case of biofilm formation, can provide the basis for clinical rational drug use. Objective Establish E.coli biofilm formation in vitro model to detect the biofilm forming ability of strains. Comparison of five kinds of antibiotics on E.coli minimum inhibitory concentration(MIC) and biofilm inhibitory concentration(BIC). Methods This study collected 82 Escherichia coli strains isolated from acute diarrhea patients’ faeces and acute urinary tract infection patients’ urine in a hospital. This study collected 82 strains of E.coli a hospital clinical specimens, and use microdilution to detect MIC of drugs(ampicillin, cefotaxime, levofloxacin, gentamycin, ciprofloxacin, imipenem). Using crystal violet staining to detect biofilm-forming ability of strains. Selected strains biofilm formation positive from this 82 E.coli as the research object. Established of bacterial biofilms in vitro model by plate culture method to detect BIC. Then, comparison of five kinds of antibiotics on E.coli MIC and BIC. Results1. Study on E.coli biofilm formation abilityQuantitative analysis of the 62 E. coli strains isolated from acute diarrhea patients’ faeces and the 20 E. coli strains isolated from acute urinary tract infection patients’ urine by crystal violet staining. To control the quality in ATCC25922 strains, take the blank hole without strain as negative control. Strain biofilm formation ability judgment standard: Negative(-): no biofilm formation,OD≤ODC; Weakly positive(+): ODC<OD ≤ 2 × ODC; Moderately positive(++): 2×ODC<OD ≤ 4 × ODC; Strongly positive(+++): OD>4×ODC. ODC is defined as 3 times of standard deviation after the average absorbance of the three negative control. OD is defined as the mean value of absorbance of every strains’ three holes. Based on this standard, according to the results of all strains, 11 strains of biofilm formation ability is weak positive, and one of eleven was isolated from urine, ten were isolated from faeces; 67 strains is moderately positive, and sixteen of these were isolated from urine, fifty-one were isolated from faeces; 4 strains is strongly positive, and three of these were isolated from urine, one was isolated from faeces. Above results show, among the 82 E.coli, moderately positive biofilm formation ability taken the most proportion.2. Antimicrobial drugs of E.coli MICMicrodilution method is used to detect biofilm formation ability of the 82 strains of e. coli. Above criteria results show, in this 82 strains that biofilm formation ability were positive, the resistant rates to ampicillin were 80.5%(66/82), to cefotaxime were 45.1%(37/82), to levofloxacin were 26.8%(22/82), to gentamycin were 35.4%(29/82), to ciprofloxacin were 43.9%(36/82), to imipenem were 6.1%(5/82). Therefore, the results show the 82 strains of E. coli had the lowest resistance to imipenem, and some with multiple drug resistance.3. Antimicrobial drugs of E.coli BICEstablished of bacterial biofilms in vitro model by plate culture method to detect BIC. According the CLSI2014 standards to the analysis, the results show the resistant rates to ampicillin were 100%(82/82), to cefotaxime were 81.7%(67/82), to levofloxacin were 90.2%(74/82), to gentamycin were 87.8%(72/82), to ciprofloxacin were 67.1%(55/82), to imipenem were 25.6%(21/82).Conclusion: Can be concluded from this study, the ability of biofilm formation is no statistically significant difference between the E.coli strains isolated from acute diarrhea patients’ urine and acute urinary tract infection patients’ fecal. The rate of Escherichia bacteria resistance and multiple drug resistance are high. The 82 clinical isolated strains of E.coli had the ability of biofilm formation, and the bacterial resistance increased after biofilm formation.