Biomedical Engineering Reference
In-Depth Information
communities consisting of several species or are they monospecific biofilms? We
became interested in these questions and we assessed implants explanted for mal-
function but not infection. If biofilms could be detected on asymptomatic implants
a comparison with similar implants explanted because they became infected would
teach a lot about infectious biofilm communities. Rhythm management devices such
as pacemakers were chosen for the assessment of bacterial colonization. Tomake sure
that any bacteria present on the implants have not been introduced during implanta-
tion only devices which were implanted for at least 5years were analyzed.
2.1 Biofilm Communities of Asymptomatic Implants
For this purpose, devices changed because of battery depletion were ideal and the
explanted devices were routinely assessed for bacterial DNA. A total of 108 devices
from asymptomatic patients were examined for evidence of bacterial DNA on the
device and in the surrounding tissue using single strand conformation polymorphism
analysis (SSCP) [
12
]. In 47.2% of the patients, bacterial DNA was demonstrated on
the device, which had been in place for 63.7months in average. The SSCP analysis
revealed that also all devices carrying biofilms had multi-species biofilm commu-
nities. This is in accordance from many other environmental studies that bacterial
species seldom live alone but prefer to grow in communities and consortia.
Excision of the main bands of the SSCP-gels and sequence analyses of the
extracted DNA allowed the identification of the main members of the biofilm
communities. From 27.8% at least one bacterial species could be identified by
sequence analysis but some sequences could not be unambiguously identified due
to shortness of the amplicons. Most devices showed several bacterial species, in
which 16% belongs to the genus
Pseudomonas
,11%to
Staphylococcus
,10%to
Stenotrophomonas
,9%to
Rhizobium
, and 7% to
Propionibacterium
[
13
]. However,
some rare species, e.g.
Leptotrichia
sp.,
Sphingobium
sp.,
Rhizobium
sp.,
Halomonas
sp., or
Burkholderia ferrariae
could also be identified. Most of these species have
rarely been reported from humans but are known from human microbiome analy-
ses. One biofilm community harbored a
Lactobacillus
species and one
Klebsiella
oxytoca
. All patients showing
Staphylococcus
species on their devices developed
later on infection of the devices. Therefore, these samples were excluded from the
analysis.
Concerning the species composition of the biofilm communities, a huge diversity
was observed between different patients and no identical biofilm communities could
be detected between two different patients. This highlights again the immense and
complex influence the host has on the species composition of its colonizing bacteria
[
14
]. From the available patient data no correlations between species composition and
the patient could be detected. With the exception of the few cases of
Staphylococcus
species no bacterial species could be found which are known as human pathogens.
However, a number of the detected bacteria are facultative pathogens. The origin of
the bacteria remained unclear. It has been speculated that some of them are derived
