Animal Physiology

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Browsing Animal Physiology by Subject "E. coli"

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    Evaluation of short- and long-term antibiotic treatment regimens on emergence of antimicrobial resistance in mice infected with E. coli
    (Addis Ababa University, 2024) Timotiwos Wogaso; Takele Beyene
    Antimicrobial resistance (AMR) is a global issue impacting human and animal health. E. coli commonly found in gut serve as an indicator organism to monitor AMR and multidrug resistance (MDR) in commensal bacteria. This research investigates the impact of oxytetracycline and penstrep (a fixed combination of penicillin and dihydrostreptomycin) misuse on AMR emergence in mice infected with drug-susceptible E. coli, analyzing the effects of short-term and long-term ( low, optimum and high) antibiotic dosing on the AMR profiles of susceptible E. coli strains. The research was carried out on 40 two-month-old female mice at the AAU-CVMA mice rearing facility and microbiology laboratory from November 2023 to April 2024. The study involved infecting the mice with E.coli, treating them with one of those two antibiotics, sampling every seven days start from day zero, isolating E. coli from the samples, testing for phenotypic resistance to seven antibiotics using agar dilution test, and identifying resistance genes through PCR and lateral flow assays with anti-CTX-M and CARBA 5 monoclonal antibodies. The study revealed higher AMR in penstrep and oxytetracycline groups, with 31.4% and 24.7% resistance, respectively. Infected and naïve control groups had 1.9% and 0.5% resistance, indicating selection pressure effects. Low-dose long-term treatments showed more antibiotic resistance than optimum and higher doses for both oxytetracycline and penstrep. The low-dose penstrep group had the highest MDR at 100% on day 28, followed by the low-dose oxytetracycline group with 86%. Significant variation in AMR emergence was observed at different time points post-treatment, peak on day 28. PCR results showed blaTEM gene growth and detection of the E. coli gene, while the lateral flow assay indicated negative results for CARB-5 and CTX-M genes. The study suggests long-term low-dose antibiotic use increases AMR risk, especially fixed combination therapy (penstrep). It is recommended to use antibiotic alternatives in food animals to reduce AMR impact. If antibiotics are necessary, use an optimum dose within the nontoxic range for the shortest recommended duration.