Avaliação e caracterização de bacteriófagos líticos e suas endolisinas recombinantes para controle de Staphylococcus aureus na cadeia produtiva do leite

Abstract

Bovine mastitis is an infection that affects dairy herds. This disease is often associated with Staphylococcus aureus, resulting in economic losses for the milk production chain. Furthermore, these bacteria can produce enterotoxins and cause food poisoning in humans. The indiscriminate use of antibiotics to control pathogens in livestock and humans carries with it risks, such as the selection of resistant bacteria, which can reduce the effectiveness of these drugs. In addition, such practices have raised concerns about food safety and environmental impact. Therefore, an increasing number of scientific studies have been dedicated to investigating new therapeutic options that can be used as alternatives to conventional treatment. A promising alternative for biological control of S. aureus is the use of lytic bacteriophages and their endolysins, which have the ability to lyse bacteria. Thus, the objective of this work was to evaluate and characterize lytic bacteriophages and their recombinant endolysins regarding their antimicrobial activity against S. aureus. The phages were submitted to morphological and biochemical characterization, as well as tested against different bacterial strains of S. aureus and other species. Furthermore, endolysins from Phage 2 and 4 were expressed, purified and evaluated for lytic spectrum. They were also characterized in silico in relation to morphological, biochemical and allergenicity aspects. By analyzing the morphology of Phages 2 and 4, it was possible to conclude that both belong to the Siphoviridae family. Among the strains tested, Phage 2 lysed 62.22% of them, while Phage 4 lysed 51.11%. Phage 2 maintained its stability in a temperature range between 4°C and 37°C, as well as in NaCl concentrations between 50 mM and 250 mM. Furthermore, in the present study, it was identified that the two endolysins, EndF2 and EndF4, have a CHAP domain, an Amidase2 domain and an SH3 cell wall binding domain, and both did not show critical aspects of allergenicity. It was demonstrated that recombinant endolysins exhibit high lytic activity against staphylococcal strains, in which EndF2 lysed 71.43% and EndF4 76.20% of the S. aureus strains tested. It is concluded that Phages 2 and 4 and their respective recombinant endolysins EndF2 and EndF4 proved to be active on S. aureus strains and that they may constitute an alternative to control this pathogen. To prove the results, in vivo tests are necessary.