Supplement bij veertiende jaargang, april 2006 - NVMM

stress resistance and virulence. Hfq mediates basepairing
between sRNAs and complementary sequences present
in target mRNAs and thus controls gene expression at the
posttranscriptional level.
A hfq homolog is present in the available sequenced
genomes of Neisseria meningitidis, but its riboregulated
network is unknown. The aim of our study is to unravel
this network to identify novel, Hfq dependent, meningococcal
virulence factors, being potentially new targets for
intervention and diagnostics.
A hfq knock-out of N. meningitidis strain H44/76 was
constructed. This knock-out strain is highly sensitive to
exposure to UV light compared to the wild type strain. In
addition, the mutant is severely hampered in growth in
rich media, and does not grow at all under conditions of
iron limitation. Expression of hfq in trans in the knock-out
strain restored growth. Preliminary analysis of proteins
subjected to Hfq regulation, assessed by the comparison
of protein profiles of the knock-out strain and the wild
type strain and peptide mass finger prints, resulted in the
identification of meningococcal components involved in i)
iron-acquisition (major ferric iron binding protein, fbpA), ii)
nitrogen sensing (glnD), iii) protection of the cells against
damage by free radicals (putative oxido-reductases such
as sucA and NMB1796), and components involved in the
assembly of pili and a variety of outer membrane proteins
with unknown functions.
The reduced growth rate and tolerance for stress conditions
of the hfq knock-out strain and the identification of Hfq
regulated genes that encode for components involved in
adaptation to the environment and adherence, strongly
indicates that meningococcal Hfq is involved in the
regulation of the response to environmental stress and
thereby contributes to the virulence of the bacteria.
05.14
Identification of putative surface exposed proteins specific for
hospital adapted vancomycin-resistant Enterococcus faecium
A.P.A. Hendrickx, W. van Wamel, M.J.M. Bonten, R.J.L.
Willems
UMC Utrecht, Eijkman-Winkler Institute for Microbiology,
Department of Internal Medicine, Utrecht
Introduction: The incidence of infections caused by
vancomycin-resistant Enterococcus faecium (Efm) has
dramatically increased in hospitals world wide. The majority
of clinical relevant Efm cluster together by multilocus
sequence typing (MLST) in a hospital-adapted genogroup,
designated clonal complex-17 (CC17). Due to their multiresistant
nature, infections with CC17 Efm are difficult to
treat. The objective of the current study was to identify cell
surface proteins (CSP) that are found enriched in CC17 Efm
Ned Tijdschr Med Microbiol 2006; 4:Supplement
S27
and that may serve as targets for immunotherapy to prevent
and treat infections with these bacteria.
Methods: Two approaches were followed to identify CC17
enriched surface proteins; (1) CSP of multiple Efm strains
from CC17 and non-CC17 were covalently labelled with
biotin to detect differences in CSP expression, (2) the
genome of Efm DO (which belongs to CC17), was searched
for genes encoding CSP containing the LPXTG cellwall
anchor motif. Using PCR a set of 100 Efm isolates
belonging to CC17 and other complexes was screened for
the presence of these CSP genes.
Results: Biotin labelling of CSP of CC17 and non-CC17
isolates revealed at least one CSP unique for CC17. The
genome search revealed 16 putative CSP genes and PCR
screening of 100 CC17 and non-CC17 isolates identified
5 CSP genes, which were predominantly found in CC17.
Negative PCRs were confirmed with Southern hybridization.
Clustering based on the presence and absence of
the CSP genes showed a comparable grouping as MLST
suggesting that the clinical relevant strains of CC17 have
an unique profile of putative CSP.
Conclusions: (1) Using biotin labelling one CSP was
identified, which is unique for and highly expressed in
CC17. (2) PCR screening identified 5 putative CSP genes
enriched in CC17 and highly homologous to microbial
surface components recognizing adhesive macromolecules.
These putative CSP could be potential targets for
new treatments to combat the emergence of CC17 Efm.
(3) The distinct CSP profile of CC17 Efm may enhance its
pathogenic potential thus contribute to its success in the
hospital environment.
05.15
Infections of complement resistant and complement
sensitive Borrelia burgdorferi sl in Wildtype and C3 deficient
mice.
N.D. van Burgel1 , N. Balmus 2 , A.P. van Dam 1
1 2 LUMC, Medical Microbiology, Leiden, LUMC, Pathology,
Leiden
Of the different species within Borrelia burgdorferi sensu
lato, B. burgdorferi sensu stricto, Borrelia afzelii and a
subgroup of Borrelia garninii strains show resistance to
complement, whereas other B. garinii strains and Borrelia
valaisiana strains are sensitive. This resistance is due to
binding host factor H through CRASPs (Complement
Regulatory Aquired Surface Proteins). We evaluated in
a murine model whether absence of complement would
influence infectivity and pathogenicity of complementsensitive
and -resistant Borreliae.
Five groups of 3 mice deficient in complement component
C3 (C3KO) and syngeneic C57Bl/6 control mice were
challenged with a pathogenic B. burgdorferi ss. strain