94 research outputs found
Multidrug-resistant Streptococcus pneumoniae in Poland: identification of emerging clones
Penicillin resistance among Streptococcus pneumoniae isolates has rapidly
emerged in Poland during the last decade and has reached prevalence levels
of up to 14.4% in 1997. In order to investigate the nature of this
increase, a molecular epidemiological analysis of
non-penicillin-susceptible multidrug-resistant pneumococci isolated in
1995 and 1996 was conducted. Thirty-seven patients who suffered mainly
from upper respiratory tract infections and pneumococcal pneumonia were
enrolled in this study. The medical centers to which the patients were
admitted were located in 16 Polish towns across the country. Eight
distinct BOX PCR types were observed, representing 14 subtypes.
Restriction fragment end labeling (RFEL) analysis divided the pneumococcal
strains into 16 distinct types. By combining the BOX PCR and RFEL data,
four genetically distinct clusters of strains were identified. Two
clusters represented the genetic clones 23F and 9V, which have recently
emerged all over the world. The two other genetic clusters, which
represented serotypes 23F and 6B, clearly predominated in the analyzed
collection of Polish non-penicillin-susceptible pneumococcal strains.
Since the latter clusters did not match any of the 133 RFEL types of
non-penicillin-susceptible pneumococci collected in 15 other countries,
their Polish clonal origin is most likely
Excited states in bilayer graphene quantum dots
We report on ground- and excited state transport through an electrostatically
defined few-hole quantum dot in bilayer graphene in both parallel and
perpendicular applied magnetic fields. A remarkably clear level scheme for the
two-particle spectra is found by analyzing finite bias spectroscopy data within
a two-particle model including spin and valley degrees of freedom. We identify
the two-hole ground-state to be a spin-triplet and valley-singlet state. This
spin alignment can be seen as Hund's rule for a valley-degenerate system, which
is fundamentally different to quantum dots in carbon nano tubes and GaAs-based
quantum dots. The spin-singlet excited states are found to be valley-triplet
states by tilting the magnetic field with respect to the sample plane. We
quantify the exchange energy to be 0.35meV and measure a valley and spin
g-factor of 36 and 2, respectively
The putative proteinase maturation protein A of Streptococcus pneumoniae is a conserved surface protein with potential to elicit protective immune responses
Surface-exposed proteins often play an important role in the interaction
between pathogenic bacteria and their host. We isolated a pool of
hydrophobic, surface-associated proteins of Streptococcus pneumoniae. The
opsonophagocytic activity of hyperimmune serum raised against this protein
fraction was high and species specific. Moreover, the opsonophagocytic
activity was independent of the capsular type and chromosomal genotype of
the pneumococcus. Since the opsonophagocytic activity is presumed to
correlate with in vivo protection, these data indicate that the protein
fraction has the potential to elicit species-specific immune protection
with cross-protection against various pneumococcal strains. Individual
proteins in the extract were purified by two-dimensional gel
electrophoresis. Antibodies raised against three distinct proteins
contributed to the opsonophagocytic activity of the serum. The proteins
were identified by mass spectrometry and N-terminal amino acid sequencing.
Two proteins were the previously characterized pneumococcal surface
protein A and oligopeptide-binding lipoprotein AmiA. The third protein was
the recently identified putative proteinase maturation protein A (PpmA),
which showed homology to members of the family of peptidyl-prolyl
cis/trans isomerases. Immunoelectron microscopy demonstrated that PpmA was
associated with the pneumococcal surface. In addition, PpmA was shown to
elicit species-specific opsonophagocytic antibodies that were
cross-reactive with various pneumococcal strains. This antibody
cross-reactivity was in line with the limited sequence variation of ppmA.
The importance of PpmA in pneumococcal pathogenesis was demonstrated in a
mouse pneumonia model. Pneumococcal ppmA-deficient mutants showed reduced
virulence. The properties of PpmA reported here indicate its potential for
inclusion in multicomponent protein vaccines
Novel mutations expand the clinical spectrum of DYNC1H1-associated spinal muscular atrophy
OBJECTIVE
To expand the clinical phenotype of autosomal dominant congenital spinal muscular atrophy with lower extremity predominance (SMA-LED) due to mutations in the dynein, cytoplasmic 1, heavy chain 1 (DYNC1H1) gene.
METHODS
Patients with a phenotype suggestive of a motor, non-length-dependent neuronopathy predominantly affecting the lower limbs were identified at participating neuromuscular centers and referred for targeted sequencing of DYNC1H1.
RESULTS
We report a cohort of 30 cases of SMA-LED from 16 families, carrying mutations in the tail and motor domains of DYNC1H1, including 10 novel mutations. These patients are characterized by congenital or childhood-onset lower limb wasting and weakness frequently associated with cognitive impairment. The clinical severity is variable, ranging from generalized arthrogryposis and inability to ambulate to exclusive and mild lower limb weakness. In many individuals with cognitive impairment (9/30 had cognitive impairment) who underwent brain MRI, there was an underlying structural malformation resulting in polymicrogyric appearance. The lower limb muscle MRI shows a distinctive pattern suggestive of denervation characterized by sparing and relative hypertrophy of the adductor longus and semitendinosus muscles at the thigh level, and diffuse involvement with relative sparing of the anterior-medial muscles at the calf level. Proximal muscle histopathology did not always show classic neurogenic features.
CONCLUSION
Our report expands the clinical spectrum of DYNC1H1-related SMA-LED to include generalized arthrogryposis. In addition, we report that the neurogenic peripheral pathology and the CNS neuronal migration defects are often associated, reinforcing the importance of DYNC1H1 in both central and peripheral neuronal functions
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