Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections pose significant health risks, potentially leading to severe conditions such as bacteremia. Developing effective treatments to eliminate resistant bacteria from the bloodstream, simultaneously mitigate infection-related complications, and reduce mortality remains challenging. Herein, microspheres are synthesized with bacterial elimination and inflammation prevention by crosslinked sulfonium poly(amino acids). As-synthesized microsphere, PM10.6B MS, exhibits an ultrafast adsorption efficiency of 0.41 × 108 CFU mg?1 min?1 for MRSA, which positions the highest index among the reported resin and inorganic adsorptions. This bacterial-specific and efficient capture of PM10.6B MS is attributed to its strong interactions with teichoic acids in MRSA (Ka: 1.8 × 105 M?1) rather than acting with phospholipids of mammalian cells. Unlike the present resin-based adsorbent, for example, heparin-modified polyethylene in the only commercial Seraph® 100, PM10.6B MS kills adsorbed bacteria within 1 h and can be reused by simple treatment. Meanwhile, PM10.6B MS also shows good hemocompatibility and longer thrombin activation time to reduce the risk of thrombosis and hemolysis. In vivo experiments further confirm the abilities of PM10.6B MS to prevent inflammation by removing bacteria. This adsorbent is a promising candidate for early treating life-threatening bloodstream infections, potentially preventing bacteremia and subsequent organ damage.