DISCOVERIES REPORTS (ISSN 2393249X), 2026, volume 9
ORIGINAL ARTICLE
CITATION: Gaur L, Suhaib M, Kakru DK. Experimental Induction of Resistance in Escherichia coli to different antibiotic groups through repeated fixed drug exposure. Discoveries Reports 2026; 9(1): e46. DOI: 10.15190/drep.2026.1
Experimental Induction of Resistance in Escherichia coli to different antibiotic groups through repeated fixed drug exposure
Lipika Gaur 1, Mohammad Suhaib 1,*, Dalip K Kakru 1
1 Department of Microbiology, School of Medical Science Research, Sharda University, Greater Noida, India.
* Corresponding author: Prof. Dr. Mohammad Suhaib, Department of Microbiology, School of Medical Science Research, Sharda University, Greater Noida, India. Email: 2011sohaib@gmail.com.
Abstract
The overuse of antibiotics in healthcare has accelerated the emergence of antimicrobial resistance (AMR) and the development of multi drug-resistant “superbugs” worldwide. The study aimed to induce resistance in standard ATCC Escherichia coli strain by fixed concentration of different antimicrobial groups through repeated exposure in our institutional laboratory.
E. coli, ATCC 25922 strain which was initially susceptible to antibiotics was serially exposed to five groups of antibiotics (ampicillin, co-trimoxazole, tetracycline, gentamicin, and amoxicillin–clavulanate) over 60 daily passages. Antibiotic susceptibility testing (AST) was performed by Kirby–Bauer disk diffusion method on Müller-Hinton agar with a standardised inoculum (~10^6 CFU). On day 0, a Muller Hinton Agar (MHA) plate was inoculated with the broth and mentioned antibiotic disks were placed for zone diameter estimation. Thereafter, for each next passage, colonies from the edge of the inhibition zone for each drug were picked and inoculated on fresh MHA plates and were further rechallenged with the same antibiotic discs. Inhibition zone diameters were measured after overnight incubation at 37°C. On day 0, E. coli was fully susceptible to all five antibiotics. After 60 serial passages, the E. coli population exposed to ampicillin developed resistance, with the inhibition zone decreasing from 19 mm initially to resistant zone of 6 mm. This work provides insights into the mechanisms by which E. coli adapts to sustained antibiotic pressure and offers a basis for developing strategies to prevent the rise of multi drug-resistant bacteria.
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