Bacterial aggregate size determines phagocytosis efficiency of polymorphonuclear leukocytes

AbstractThe ability of bacteria to aggregate and form biofilms impairs phagocytosis by polymorphonuclear leukocytes (PMNs). The aim of this study was to examine if the size of aggregates is critical for successful phagocytosis and how bacterial biofilms evade phagocytosis. We investigated the live interaction between PMNs andPseudomonas aeruginosa,Staphylococcus aureus,Escherichia coli andStaphylococcus epidermidis using confocal scanning laser microscopy. Aggregate size significantly affected phagocytosis outcome and larger aggregates were less likely to be phagocytized. Aggregates ofS. epidermidis were also less likely to be phagocytized than equally-sized aggregates of the other three species. We found that only aggregates of approx. 5  μm diameter or smaller were consistently phagocytosed. We demonstrate that planktonic and aggregated cells of all four species significantly reduced the viability of PMNs after 4 h of incubation. Our results indicate that larger bacterial aggregates are less likely to be phagocytosed by PMNs and we propose that, if the aggregates become too large, circulating PMNs may not be able to phagocytose them quickly enough, which may lead to chronic infection.
Source: Medical Microbiology and Immunology - Category: Microbiology Source Type: research