Streptococcus spp.: Integrating Advances in Molecular Biology, Pathogenicity, and Strategies Against Antimicrobial Resistance

The genus Streptococcus comprises Gram-positive pathogens with a high impact on public and animal health, including Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus mutans, and Streptococcus suis. The rise of multidrug resistance to classic antibiotics, such as beta-lactams and macrolides, drives the need for novel therapeutic approaches. This narrative review aimed to discuss virulence and antimicrobial resistance in streptococci, as well as molecular advances in the development of new therapeutic and anti-virulence strategies. The pathogenicity of Streptococcus species is primarily influenced by critical mechanisms such as surface proteins, biofilm formation, and the production of toxins (e.g., pneumolysin and SpeB) that facilitate immune evasion and bacterial persistence. Antimicrobial resistance in Streptococcus represents a global health emergency, evidenced by the reduced efficacy of beta-lactams and macrolides via mechanisms such as structural alterations and biofilm formation. This scenario is further exacerbated by severe multidrug resistance in species like S. suis, S. pneumoniae, and S. pyogenes, which challenge conventional therapeutic lines. Innovative strategies based on molecular biology are discussed, including the development of vaccines based on conserved proteins (such as PspA) and anti-virulence approaches that aim to "disarm" the bacteria by inhibiting adhesion and toxicity rather than focusing exclusively on cell lysis. Additionally, emerging technologies such as the use of nanocarriers, antimicrobial peptides, and combination therapies (the "Trojan Horse" strategy) are explored. It is concluded that the integration of nanotechnology and the molecular characterization of pathogenic mechanisms is crucial to overcoming the antimicrobial resistance crisis and enhancing immunoprophylaxis strategies against severe streptococcal infections.