Targeting host adaptation in Streptococcus pneumoniae: A narrative review of biological strategies beyond antibiotics

Abstract

Streptococcus pneumoniae remains a leading cause of severe respiratory disease in U.S. adults despite expanded conjugate vaccination and guideline-directed antibiotic therapy. Rising antimicrobial resistance, serotype replacement, and rapid within‑host evolutionary adaptation collectively undermine the long‑term effectiveness of conventional antibiotic‑centric strategies, motivating complementary non‑antibiotic interventions that attenuate pneumococcal virulence rather than directly targeting viability. This review examines emerging host adaptation mechanisms in S. pneumoniae and evaluates biological targets for antivirulence therapy with the potential to reduce pneumococcal pneumonia and invasive disease burden in the United States. Focusing on literature from 2020 onward, the review synthesizes advances in understanding of pneumolysin-mediated immune modulation, complement evasion by capsular and surface proteins, metabolic and regulatory adaptation in the host niche, and small molecule or biologic antivirulence candidates that interfere with these processes. Unresolved questions include the durability of antivirulence-driven selective pressures, optimal combination with vaccines and antibiotics, and host-specific factors that determine therapeutic windows. Addressing these gaps will be essential for integrating antivirulence agents into future pneumonia prevention and treatment frameworks aimed at substantially lowering the pneumococcal disease burden in the United States.