Colistin is an antibiotic commonly used to treat diseases caused by the Escherichia coli (E. coli) bacterium, such as colibacillosis in piglets. This disease, which frequently develops after weaning, causes diarrhoea. The problem is that using high levels of colistin can result in the development of resistant bacteria. One of the solutions that is being explored to use less colistin is to combine it with nanoparticles of alginate, a polysaccharide. The antibiotic is incorporated into these nano-sized particles.
As part of the Sincolistin project (Strategic alternatives to reduce the use of colistin in pig farming), funded by the French National Research Agency, the efficacy of these nanoparticles was tested in batches of eight piglets infected with E. coli that were experiencing diarrhoea or hyperthermia. After the start of treatment, none of the 96 faecal samples collected from piglets treated with the nanoparticles showed any signs of diarrhoea. In comparison, symptoms of diarrhoea were observed in three of the samples collected from piglets treated with colistin administered conventionally; this figure was nine for the untreated group. It can therefore be concluded that the colistin-alginate nanoparticle formulation is at least as effective as conventional treatment while using a smaller amount of colistin. Moreover, a few days after treatment, most of the faecal E. coli population was not resistant to colistin.
“Since colistin formulated with alginate nanoparticles requires less colistin than conventional treatment, a smaller amount of antibiotic is released into the environment after treatment, which means that bacteria are less likely to develop resistance” concludes Isabelle Kempf, Head of the Mycoplasmology, Bacteriology and Antimicrobial Resistance Unit at ANSES's Ploufragan-Plouzané-Niort Laboratory. Her unit conducted the study on piglets in collaboration with the laboratory's Department for Production of Specific-pathogen-free Pigs and Experimentation. The study was published in Veterinary Microbiology in March 2022. Further studies now need to be carried out to confirm, in various experimental and field conditions, the therapeutic efficacy and safety of colistin-loaded alginate nanoparticles used to treat post-weaning diarrhoea in piglets.