BackgroundESBLs hydrolyze the beta-lactam ring of antibiotics and are not affected by 1st, 2nd, 3rd, and 4th generation antibiotics. There are over 400 ESBL enzymes that have already been investigated globally are present in Enterobacteriaceae species such as Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca strains. Prevalence of ESBLs is slowly increased, from 10 to 40% in E. coli and K. pneumonia strains. Microorganisms producing ESBLs are challenging to physicians, clinical microbiologists, and antibiotic researchers.ResultsIn this study, ESBL-producing strains of E. coli were subjected to antibiotic sensitivity screening. The efficacy of myco BR-AgNPs on growth in E. coli ATCC (25922) and clinical isolates of E. coli was determined by well diffusion method. Myco BR-AgNPs reduced the growth as well as inhibited the biofilm formation in ESBL-producing strains of E. coli. MIC and MBC were determined by using serial microdilution and surface drop method. The MICs were 0.078–0.625 µg/ml and MBCs were 0.312–1.25 µg/ml. The biofilm formation was effectively inhibited by myco BR-AgNPs when compared with control. The expression of CTX-M-15 gene was studied in clinical isolates of E. coli treated with antibiotic (positive control), mycosilver nanoparticles (test) and compared with the other positive control (untreated strains). Interestingly, the expression of CTX-M-15 was downregulated in the samples treated with myco BR-AgNPs.ConclusionThe use of myco BR-AgNPs and their growth inhibitory effect on ESBL-positive strains were the main focus of this research. ATCC and ESBL strains used in this study were effectively inhibited by myco BR-AgNPs. The effect of myco BR-AgNPs on the expression of a gene encoding CTX-M-15 was tested on a molecular level, and the observed results showed that the gene expression was reduced when compared with control and antibiotic treatment. According to the current research, myco BR-AgNPs synthesized with the aid of endophytic fungal extract could be used to suppress the growth of ESBL-positive strains of E. coli. Myco BR-AgNPs may be an important alternative to various antibiotics in preventing bacterial resistance if optimized and tested for toxicity.