Interactions between Polymorphonuclear Leukocytes and Pseudomonas aeruginosa Biofilms on Silicone ImplantsIn Vivo

Abstract

ABSTRACTChronic infections withPseudomonas aeruginosapersist because the bacterium forms biofilms that are tolerant to antibiotic treatment and the host immune response. Scanning electron microscopy and confocal laser scanning microscopy were used to visualize biofilm developmentin vivofollowing intraperitoneal inoculation of mice with bacteria growing on hollow silicone tubes, as well as to examine the interaction between these bacteria and the host innate immune response. Wild-typeP. aeruginosadeveloped biofilms within 1 day that trapped and caused visible cavities in polymorphonuclear leukocytes (PMNs). In contrast, the number of cells of aP. aeruginosa rhlAmutant that cannot produce rhamnolipids was significantly reduced on the implants by day 1, and the bacteria were actively phagocytosed by infiltrating PMNs. In addition, we identified extracellular wire-like structures around the bacteria and PMNs, which we found to consist of DNA and other polymers. Here we present a novel method to study a pathogen-host interaction in detail. The data presented provide the first direct, high-resolution visualization of the failure of PMNs to protect against bacterial biofilms.