Identification and Characterization of a Two-Peptide Class IIb Bacteriocin in Streptococcus pluranimalium Isolated from the Nasal Cavity of a Healthy Pig

In addition to be an important zoonotic agent, Streptococcus suis serotype 2 causes severe infections in pigs. In this study, we characterized a new bacteriocin produced by Streptococcus pluranimalium 2N12 isolated from a pig nasal sample. The bacteriocin, termed pluranimalicin 2N12, was a two-peptide class IIb bacteriocin active against S. suis. The gene cluster responsible for the biosynthesis of pluranimalicin 2N12 by S. pluranimalium contained seven open reading frames, including putative genes for peptides (plu alpha, plu beta), export (pluA, pluB), and regulation (pluC, pluD, pluE). The deduced amino acid sequences of the peptides Plu alpha (33 amino acids) and Plu beta (29 amino acids) showed 73% and 69% identity in amino acid residues, respectively, with the peptides SthA and SthB of the streptocin produced by Streptococcus gordonii. The antibacterial activity of pluranimalicin 2N12 against S. suis was dependent on the presence of the two peptides Plu alpha and Plu beta that exhibited a membrane permeabilization effect. No activity was found against the other swine pathogens tested. Depending on the concentrations used, Plu alpha and Plu beta displayed no or low toxicity towards swine tracheal epithelial cells. The pluranimalicin peptides Plu alpha and Plu beta, either individually or in combination, exhibited anti-inflammatory activity since they attenuated IL-6 and TNF-alpha production by macrophages challenged with lipopolysaccharide. Given its dual action (antibacterial and anti-inflammatory), pluranimalicin 2N12 holds promise as a potential therapeutic agent for controlling S. suis infections.