Effects of the natural antimicrobial peptide aureocin A53 on cells of Staphylococcus aureus and Streptococcus agalactiae involved in bovine mastitis in the excised teat model.

Aureocin A53 is an N-formylated antimicrobial peptide (AMP) produced by Staphylococcus aureus. Aureocin A53 has a broad spectrum of antimicrobial activity against human and animal pathogens. In the present study, its antagonistic activity was investigated towards 30 strains of S. aureus and 30 strains of Streptococcus spp. isolated from bovine mastitis cases in Brazil. Bovine mastitis is a disease that causes a major economic impact worldwide. Aureocin A53 inhibited the growth of all 60 strains tested, including multidrug-resistant streptococcal isolates and strains of S. aureus belonging to different pulsotypes. This AMP proved to be bactericidal against the six target strains randomly selected among staphylococci and streptococci, also exhibiting a lytic mode of action against the staphylococcal cells. Furthermore, it was determined that 2,048 AU/mL of the AMP were required to inhibit 99.99% of the cell growth of the strain less sensitive to aureocin A53. Aureocin A53 was not toxic to bovine mammary gland epithelial cells after a 24-h exposure and maintained its antimicrobial activity when tested in the excised-teat model against strains of S. aureus and Streptococcus agalactiae, the species responsible for most intramammary infections, not only in Brazil but in other countries as well. Therefore, the use of aureocin A53 in the development of new pharmacological products for the prophylaxis and/or treatment of bovine mastitis was considered promising.

Draft genome sequence of the producer strain of aureocin 4181, an antimicrobial peptide with antagonistic activity against multidrug-resistant staphylococci.

OBJECTIVES: The present study reports the draft genome sequence of Staphylococcus aureus 4181, a strain involved in bovine mastitis that produces aureocin 4181, a broad-spectrum antimicrobial peptide (AMP). Inhibition of multidrug-resistant (MDR) staphylococci involved in human infections by S. aureus 4181 was also investigated. METHODS: A sequencing library was constructed using a Nextera XT DNA Library Preparation Kit (Illumina). Whole-genome shotgun sequencing was performed using an Illumina MiSeq System. The A5-miseq pipeline was employed for de novo genome assembly. Genome annotation was performed by the RAST server. The online automated tools BAGEL4 and antiSMASH v.5.0 were used for mining gene clusters encoding AMP production. The virulence potential of the strain was investigated employing online tools. Its inhibitory activity toward MDR staphylococcal isolates associated with human infections was tested by the deferred antagonism assay on brain-heart infusion agar medium. RESULTS: The total scaffold size was determined to be 2 719 949 bp, with a G + C content of 32.7%. Genome analyses revealed 2504 protein-coding sequences and 74 RNA-coding sequences as well as several genes encoding drug resistance and a single AMP gene cluster coding for aureocin 4181. Staphylococcus aureus 4181 exhibited a pathogenic potential and inhibited all MDR staphylococcal isolates tested as a target. CONCLUSIONS: This study describes the main features of the draft genome of S. aureus 4181, a strain that produces the third four-component bacteriocin described in the literature, namely aureocin 4181. This bacteriocin is a potential alternative drug to control MDR staphylococcal isolates involved in human infections.