Single-walled carbon nanotubes (SWNTs) have shown promise as in vivo contrast nanoagents for medical theranostics, in particular photoacoustic and photothermal imaging and therapy, as well as targeted drug delivery systems. However, SWNTs have not proved able to evade biological obstacles, such as opsonization and phagocytosis by macrophage and nonspecific attachments to cells and other biological components in the bloodstream, before reaching target tissues and cells in vivo. Here, we demonstrate the stealth character of dextran sulfate (DS) coated SWNTs (DS-SWNTs) towards human macrophages and other biological barriers using Staphylococcus aureus, a bacterial pathogen, as a model. DS-SWNTs were compared to PEGylated SWNTs, a commonly accepted standard for rendering nanoparticles immune to opsonization. Also a new site-specific conjugation strategy was developed to functionalize antibody (Ab) on DS-SWNT in an upright way, enhancing their targeting efficiency. DS coating was proved to be resistant to opsonins and bacterial cells, demonstrating its potential to provide considerable stealth.character to SWNTs with excellent immunity versus macrophages and other biological barriers, and achieve prolonged blood circulation times. Moreover, the hybrid nanoagents could not only selectively bind to target pathogenic cells upon the controlled Ab attachment but also effectively eradicate pathogens after near-infrared laser irradiation.