CTX-M-producing Escherichia coli strains: resistance to temocillin, fosfomycin, nitrofurantoin and biofilm formation

Aim: ESBL-producing and bacterial biofilms-forming Escherichia coli are associated with antimicrobial treatment failure. This study aimed to investigate the phenotypic resistance mechanisms of CTX-M E. coli against old antibiotics - cell wall synthesis inhibitors temocillin, nitrofurantoin and fosfomycin. Materials & Methods: Susceptibility to old antibiotics testing was performed using disk diffusion method, biofilm formation was evaluated spectrophotometrically, and PCR was used for the determination of CTX-M type. Results & conclusion: Temocillin was active against nearly 93%, nitrofurantoin and fosfomycin, respectively, 91.7% and 98.6% of tested E. coli. Thus, it demonstrated to be a good alternative therapeutic option against ESBL infections. Bacteria resistant to old antibiotics had CTX-M-15 or CTX-M-15, TEM-1 and OXA-1 combinations. No significant association was found between CTX-M E. coli resistance to temocillin, nitrofurantoin and fosfomycin; however, the level of biofilm formation was found as not affected by the type of CTX-M beta-lactamases.

Automated summary

The study revealed that temocillin, nitrofurantoin, and fosfomycin showed high activity against the majority of tested CTX-M Escherichia coli. Bacteria resistant to old antibiotics typically carried combinations of CTX-M-15, TEM-1, and OXA-1. Additionally, there was no significant association found between the level of biofilm formation and the type of CTX-M beta-lactamases.