Effect of ascorbic acid against tetracycline resistant Escherichia coli infection in broiler chicken

Abstract

The emergence of multidrug-resistant organisms due to the indiscriminate use of antibiotics has become a critical health concern for both humans and animals. Efforts to safeguard and extend the efficacy of antibiotics have been increasingly urgent. This study aims to explore the potential of ascorbic acid to enhance both the in vitro and in vivo effectiveness of tetracycline against Avian Pathogenic Escherichia coli (APEC) infections resistant to tetracycline. Isolates of E. coli from broiler chickens affected by colibacillosis were screened for the presence of tetracycline-resistant genes. The in vitro antibacterial properties of ascorbic acid were evaluated through disc diffusion and broth dilution techniques.

In the in vivo experiment, the birds were pre-treated with ascorbic acid beginning on day three, and on day seventeen, they were challenged with tetracycline-resistant APEC. Clinical symptoms of infection were observed two days post-challenge. After five days of tetracycline treatment, blood samples and organ tissues were collected for histopathological, hematological and biochemical analyses.  The study revealed that 60% of the APEC isolates exhibited resistance, with enrofloxacin and tetracycline showing the highest levels of resistance among the eleven antibiotics tested. Birds challenged with E. coli displayed pronounced clinical symptoms, while those treated with ascorbic acid demonstrated a noticeable reduction in disease severity. It was observed that, the combination of ascorbic acid and tetracycline treatment significantly improved levels of total protein, albumin, and ameliorated both macro- and microscopic lesions in the infected birds. Although ascorbic acid did not markedly enhance the antibacterial efficacy of tetracycline in in vitro, its administration in in vivo has notably diminished disease severity.