Biofilm formation in trimethoprim/sulfamethoxazole-susceptible and trimethoprim/ sulfamethoxazole-resistant uropathogenic Escherichia coli

Abstract Objective To compare biofilm formation in trimethoprim/sulfamethoxazole (SXT)-susceptible Escherichia coli ( E. coli ) (SSEC) and SXT-resistant E. coli (SREC) isolated from patients with urinary tract infections, and study the motile ability and physical characteristics of the isolates. Methods A total of 74 E. coli isolates were tested for antimicrobial susceptibility with the disc diffusion assay. Based on the SXT-susceptibility test, the E. coli isolates were divided into SSEC ( N  = 30) and SREC ( N  = 44) groups. All E. coli isolates were examined for motile ability by using a motility test medium, and for checking biofilm formation a scanning electron microscope was used. Bacterial colony size was measured with a vernier caliper and bacterial cell length was measured under a light microscope. The bacterial growth rate was studied by plotting the cell growth (absorbance) versus the incubation time. Results The frequencies of non-motility and biofilm formation in the SREC group were significantly higher than that in the SSEC group ( P vs . (1.53 ± 0.05) μm, P Conclusions The present study indicated that biofilm formation and phenotypic change of uropathogenic E. coli can be attributed to the mechanism of E. coli SXT resistance.