30845 Suppl Giot.pdf - Giornale Italiano di Ortopedia e Traumatologia

As the implant provides an especially attractive surface for the
attachment of bacteria, and hence promotes biofilm formation,
it is possible that the biofilms form
faster than the neutrophils can infiltrate
and destroy the biofilm.
With regard to the second question,
a possible explanation is that this
persistent biofilm infection elicits an
ongoing neutrophil infiltration and
activation. These neutrophils could
then during the presumed phagocytosis
– the main defence mechanism
of neutrophils against invading pathogens
– release cytotoxic entities,
which in turn could attack the host
cells and tissues, a process also known
as “frustrated phagocytosis” 18 19 . The
“frustrated PMN”, but also dead and
dying cells or the degraded tissue,
would attract even more PMN, and
also other cells of the immune system
as reinforcement. In that situation two
outcomes are possible: either the PMN
together with the other cells of the
immune response are now sufficiently
activated to fight the biofilm resulting
in a self-limitation of the local
inflammatory response, or the host
defence fails to clear the infection. In
that case, the inflammatory reaction
would progress, and tissue damage
and loosening of the implant, would
be the consequence. Of note, the
proinflammatory environment might
also attract monocytes as precursors
of bone-degrading osteoclasts. There
is evidence in the literature that proinflammatory
mediators might promote
the generation of osteoclasts 20-25 . In
that, the persistent biofilm infection
could finally be linked to bone resorption,
as it occurs in patients with
implant-associated osteomyelitis.
So far, the therapeutic options are
rather limited. Attempts are made to
select antibiotics or biocides that alone
or in combination with other means,
can detach, solubilise and eliminate
established biofilms. Another major
objective in research is the prevention
of biofilm infection, e.g. by modifying
the implanted materials or by impregnating
them with antibiotics in order
to inhibit attachment of bacteria and
hence biofilm formation. Impregnated
bone cement or silver-coated osteo-
E. Meyle, G. M. Hänsch
synthesis materials are now available; their efficacy in clinical
settings is now being tested.
Fig. 1. Biofilms grown on metal implants: Shown is a Kirschner wire (A) where a Staphylococcus aureus biofilm (stained in red) is formed at a site of
minor damage of the wire (arrow). The lower panel shows an enlargement of this area. In (B) a plate decorated with a biofilm is shown. (C) In the
course of implant-associated osteomyelitis neutrophils are activated as seen by up-regulation of surface receptors, for example of the LPS-receptor CD14.
Here, the results of cytofluorometric analysis of an individual patient is shown with IgG representing the isotype (“negative”) control, and the other two
histograms the expression of CD14 on the neutrophils isolated out of the peripheral blood and of cells recovered from the infected site (“lavage”). In
(D) data of 10 patients are summarised. Each line represents one patient, with line connecting the mean fluorescence values obtained for the peripheral
blood cells with that of the cells from the lavage. One the very left, the normal values (mean of 20 healthy donors) is shown.
(E) When neutrophils (large green dots with red rims) were placed on a biofilm (grown in vitro; stained green) areas depleted of biofilm (black areas)
became apparent within 30 to 60 min, especially in the vicinity of the PMN (arrows). (F) The enlargement of selected cells shows binding of bacteria (small
green dots) to the cells followed by uptake of those bacteria, shown in (G), which eventually results in a yellow staining of the cell (H). In parallel to the
uptake, the neutrophils degranulate and release, among other components, lactoferrin (I), apparent as green “patches” around the cell (arrowhead).
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