Recombinant expression and antimicrobial activity of Aureocin A53 against Staphylococcus aureus isolated from bovine intramammary infections

Bovine mastitis causes major economic losses in dairy production. Staphylococcus aureus, the most prevalent causative pathogen of mastitis, is often resistant to antibiotics. Bacteriocins, like Aureocin A53 (A53), are antimicrobial peptides that can provide an alternative treatment.

The present study aimed to express a recombinant peptide (A53) in Escherichia coli and evaluate its antimicrobial activity against S. aureus isolated from bovine mastitis.

The A53 gene was cloned into pET24a and expressed in E. coli strains BL21(DE3), Tuner (DE3), and Rosetta (DE3), in different induction conditions.

Among all the evaluated conditions, A53-pET24a in E. coli Rosetta (DE3) induced with IPTG 0.2 mM overnight appeared to yield slightly higher expression levels than the other conditions tested. Cell lysates supernatants containing recombinant A53 showed inhibitory activity against two S. aureus indicator strains in agar diffusion assays. Microtiter plate assays conducted with S. aureus isolated from bovine mastitis showed that purified recombinant A53 significantly reduced bacterial growth after 24 h of incubation, in comparison with non-treated cultures.

Our results underscore the feasibility of producing active recombinant A53. Further studies are needed to evaluate its effectiveness against additional S. aureus isolates and to optimize expression and recovery processes. Improving production scalability will be essential to evaluate the stability and efficacy of peptide in in vivo models, such as the bovine mammary gland, thereby supporting its potential therapeutic application.