Center for Biofilm Engineering
Abstract:
"Compromised Host Defense on Pseudomonas aeruginosa Biofilms:
Characterization of Neutrophil and Biofilm Interactions"
03-031 Pseudomonas aeruginosa is an opportunistic pathogen that
forms biofilms on tissues and other surfaces. We characterized the interaction
of purified human neutrophils with P. aeruginosa, growing in biofilms, with
regard to morphology, oxygen consumption, phagocytosis, and degranulation.
Scanning electron and confocal laser microscopy indicated that the neutrophils
retained a round, unpolarized, unstimulated morphology when exposed to P. aeruginosa PAO1 biofilms. However, transmission electron microscopy demonstrated
that neutrophils, although rounded on their dorsal side, were phagocytically
active with moderate membrane rearrangement on their bacteria-adjacent surfaces.
The settled neutrophils lacked pseudopodia, were impaired in motility, and were
enveloped by a cloud of planktonic bacteria released from the biofilms. The
oxygen consumption of the biofilm/neutrophil system increased 6- and 8-fold over
that of the biofilm alone or unstimulated neutrophils in suspension,
respectively. H(2)O(2) accumulation was transient, reaching a maximal measured
value of 1 micro M. Following contact, stimulated degranulation was 20-40% (myeloperoxidase,
beta-glucuronidase) and 40-80% (lactoferrin) of maximal when compared with
formylmethionylleucylphenylalanine plus cytochalasin B stimulation. In summary,
after neutrophils settle on P. aeruginosa biofilms, they become phagocytically
engorged, partially degranulated, immobilized, and rounded. The settling also
causes an increase in oxygen consumption of the system, apparently resulting
from a combination of a bacterial respiration and escape response and the
neutrophil respiratory burst but with little increase in the soluble
concentration of H(2)O(2). Thus, host defense becomes compromised as biofilm
bacteria escape while neutrophils remain immobilized with a diminished oxidative
potential.
Jesaitis, A.J., M.J. Franklin, D. Berglund, M. Sasaki, C.I. Lord, J.B. Bleazard, J.E.
Duffy, H. Beyenal and Z. Lewandowski, "Compromised Host Defense on Pseudomonas
aeruginosa Biofilms: Characterization of Neutrophil and Biofilm Interactions,"
J. Immunol., 171:4329-4339
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