Bacterial aggregate size determines phagocytosis efficiency of polymorphonuclear leukocytes

Maria Alhede, Melanie Lorenz, Blaine Gabriel Fritz, Peter Østrup Jensen, Hans Christian Ring, Lene Bay, Thomas Bjarnsholt*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

40 Citations (Scopus)
85 Downloads (Pure)

Abstract

The 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 and Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Staphylococcus epidermidis using confocal scanning laser microscopy. Aggregate size significantly affected phagocytosis outcome and larger aggregates were less likely to be phagocytized. Aggregates of S. 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.

Original languageEnglish
JournalMedical Microbiology and Immunology
Volume209
Pages (from-to)669–680
ISSN0300-8584
DOIs
Publication statusPublished - 2020

Keywords

  • Chronic bacterial infection
  • E. coli
  • P. aeruginosa
  • Phagocytosis
  • Polymorphonuclear leukocytes (PMNs)
  • S. aureus
  • S. epidermidis

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