Ability of M0 and M1 Macrophages to Engulf Bacteria Attached to a Surface

Authors: Bharti Sharma, Karin Sauer, Cláudia N. H. Marques

Field of Study: Biological Sciences

Faculty Mentors: Cláudia N.H. Marques

Easel: 4

Timeslot: Midday

Abstract: Implantable medical devices have transformed personalized medicine, yet their surgical placement carries a significant risk of infection. Device-associated infections often involve opportunistic pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus, which can resist antibiotics through biofilm formation. Understanding how macrophages respond to these biofilm infections is vital for developing effective treatments. This study aimed to determine whether bacteria are engulfed by macrophages or invade them, and to compare the engulfment abilities of naïve (M0) and inflammatory (M1) macrophages. After a 2-hour attachment period, various bacterial inocula were tested in a 2-hour engulfment assay. Results showed that bacteria entered cells through engulfment rather than invasion. Engulfment rates varied with inoculum size, with M1 and M0 macrophages performing similarly, except at high concentrations of P. aeruginosa, where M1 macrophages exhibited a greater effectiveness. These findings indicate that macrophage activation does not always enhance the clearance of surface-associated bacteria.