Antibacterial activity of extracellular biosynthesized iron oxide nanoparticles against locally isolated β-lactamase-producing Escherichia coli from Egypt

Nowadays, extended spectrum β-lactamase (ESBL) producing Escherichia coli has been recognized and recorded worldwide as one of the main causing agents and a major contributor to nosocomial infections. The current study aimed to isolate and detect β-lactamase-producing E. coli and use it in the extracellular biosynthesis of iron oxide nanoparticles (Fe 2 O 3 NPs). Fifteen Gram-negative (G-ve), lactose-fermenting, negative citrate and non-spore-forming coliform bacteria were isolated from the total bacterial isolates from water samples. Different tests were performed to detect β-lactamase-producing E. coli isolates including the chromogenic methods as acidimetric and iodometric techniques and the phenotypic methods as cloverleaf test and Masuda double-disc test. ESBL-producing E. coli was detected and confirmed by a modified double disc synergy test using ceftazidime, cefotaxime, ceftriaxone, amoxicillin combined with clavulanic acid, imipenem, cefepime, and cefoxitin. The quantitative assay of β-lactamase was done using a micro-iodometric assay. Among E. coli bacterial isolates, S1B1 isolate (the highest isolate of β-lactamase activity) was selected and tested for the extracellular biosynthesis of Fe 2 O 3 NPs. The produced nanoparticles (NPs) were characterized by UV–visible spectroscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope and Zeta analysis. Results confirmed the successful biosynthesis of Fe 2 O 3 NPs which displayed an absorption peak at 346 nm and a Fe 2 O 3 crystallographic lattice plane at (104). Fe 2 O 3 NPs were negatively charged spherical-shaped NPs with an average size of ≈ 24 ± 2 nm. The FTIR spectrum refers to the presence of NPs-associated proteins which act as stabilizing and capping agents. Antibacterial activity of Fe 2 O 3 NPs was tested against Staphylococcus aureus ATCC25923, Bacillus cereus ATCC6633 (G+ve bacterium), Pseudomonas aeruginosa ATCC27853 (G-ve bacterium), as well as the β-lactamase-producing E. coli S1B1 strain. Fe 2 O 3 NPs revealed moderate to strong antibacterial action against the tested strains with a minimum inhibition concentration (MIC) ranging from 25 to 40 µg/ml. Article Highlights Isolation, identification, and detection of β-lactamase-producing E. coli using chromogenic methods (acidimetric and iodometric techniques) and phenotypic methods (cloverleaf test and Masuda double-disc test). A green, cheap, and facile approach was used to biosynt