Characteristics of Escherichia coli biofilm production, genetic typing, drug resistance pattern and gene expression under aminoglycoside pressures.

In our studies, qualitative (scanning electron microscope) and semi-quantitative (modified crystal violet staining method) methods had been used to evaluate Escherichia coli biofilm-forming ability. Broth microdilution method and enterobacterial repetitive intergenic consensus-based PCR (ERIC-PCR) were performed to study E. coli drug resistance pattern and genetic typing. Based on the results above, we studied the correlation between biofilm-forming ability phenotype, drug resistance pattern and genetic typing in E. coli. Real-time qPCR (qRT-PCR) was used to reveal mRNA expression level of E. coli biofilm related multiple antibiotics resistance genes (acrA, agn43, csgA, csgD, ompF and pgaA) under different concentrations of four aminoglycoside pressures. Our results showed that: (i) forty-nine out of 64 strains of E. coli (76.56%) showed significant production of biofilm and most of them performed weak biofilm-forming ability; (ii) ERIC-PCR showed that there was significant correlation between biofilm-forming ability and genotype; while there was weak correlation between biofilm-forming ability and drug resistance patterns based upon the results of semi-quantitative method and antibiotics susceptibility test; (iii) qRT-PCR revealed mRNA expression of acrA, agn43, csgA, csgD, ompF and pgaA genes changed accordingly by stimulation of different concentrations of four aminoglycosides.