Abstract
Antibiotic resistance is one of the biggest health challenges of our time. We are now facing a post-antibiotic era in which microbial infections, currently treatable, could become fatal. In this scenario, antimicrobial peptides such as bacteriocins represent an alternative solution to traditional antibiotics because they are produced by many organisms and can inhibit bacteria, fungi, and/or viruses. Herein, we assessed the antimicrobial activity and biotechnological potential of 54 Streptococcus agalactiae strains isolated from bovine mastitis. Deferred plate antagonism assays revealed an inhibition spectrum focused on species of the genus Streptococcus—namely, S. pyogenes, S. agalactiae, S. porcinus, and S. uberis. Three genomes were successfully sequenced, allowing for their taxonomic confirmation via a multilocus sequence analysis (MLSA). Virulence potential and antibiotic resistance assessments showed that strain LGMAI_St_08 is slightly more pathogenic than the others. Moreover, the mreA gene was identified in the three strains. This gene is associated with resistance against erythromycin, azithromycin, and spiramycin. Assessments for secondary metabolites and antimicrobial peptides detected the bacteriocin zoocin A. Finally, comparative genomics evidenced high similarity among the genomes, with more significant similarity between the LGMAI_St_11 and LGMAI_St_14 strains. Thus, the current study shows promising antimicrobial and biotechnological potential for the Streptococcus agalactiae strains.
Highlights
In the past few decades, antibiotics have played an essential role in treating infectious diseases and in antimicrobial prophylaxis for surgical procedures [1]
Seventy-five strains were used as indicator bacteria in the deferred growth inhibition assays, accounting for Listeria innocua (n = 1), Micrococcus sp. (n = 1), Lactococcus lactis (n = 1), Cellulomonas fimi (n = 2), Klebsiella pneumoniae (n = 2), Staphylococcus aureus (n = 5), Streptococcus uberis (n = 12), Streptococcus porcinus (n = 12), Streptococcus agalactiae (n = 17), and Streptococcus pyogenes (n = 20)
Additional antagonism tests were performed against Streptococcus uberis (n = 12), Streptococcus porcinus (n = 12), Streptococcus pyogenes (n = 19), Streptococcus agalactiae (n = 16), Klebsiella pneumoniae (n = 2), Staphylococcus aureus (n = 4), Cellulomonas fimi, and Micrococcus sp. to test this hypothesis
Summary
In the past few decades, antibiotics have played an essential role in treating infectious diseases and in antimicrobial prophylaxis for surgical procedures [1]. That has not always been the case in history, and microorganisms’ infections used to be partially responsible for a lower global average life expectancy. In 1928, Alexander Fleming discovered the first antibiotic, a compound later named as penicillin, which revolutionized. Microorganisms 2022, 10, 588 treatments of infectious diseases. After its market introduction in the 1940s, mortality rates due to syphilis were drastically reduced. Penicillin’s success created an appeal for the discovery of other similar substances. The collective effort to find new antibiotics resulted in the discovery of several other antimicrobial drugs during the antibiotic golden age, such as sulphonamides and streptomycin for treating scarlet fever and tuberculosis, respectively [2]
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