مجال
التميز
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تميز دراسي و بحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Altered Competitive Fitness,
Antimicrobial Susceptibility, and Cellular Morphology in a Triclosan-Induced
Small-Colony Variant of Staphylococcus aureus
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رابط إلى البحث:
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تاريخ النشر:
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21/06/2015
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موجز عن البحث:
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Staphylococcus aureus can produce
small-colony variants (SCVs) that express various phenotypes. While their
significance is unclear, SCV propagation may be influenced by relative
fitness, antimicrobial susceptibility, and the underlying mechanism. We have investigated
triclosan-induced generation of SCVs in six S. aureus strains, including
methicillin-resistant S. aureus (MRSA). Parent strains (P0) were repeatedly
passaged on concentration gradients of triclosan using a solid-state exposure
system to generate P10. P10 was subsequently passaged without triclosan to
generate X10. Susceptibility to triclosan and 7 antibiotics was assessed at
all stages. For S. aureus ATCC 6538, SCVs were further characterized by
determining microbicide susceptibility and competitive fitness. Cellular
morphology was examined using electron microscopy, and protein expression was
evaluated through proteomics. Triclosan susceptibility in all SCVs (which
could be generated from 4/6 strains) was markedly decreased, while antibiotic
susceptibility was significantly increased in the majority of cases. An SCV
of S. aureus ATCC 6538 exhibited significantly increased susceptibility to
all tested microbicides. Cross-wall formation was impaired in this bacterium,
while expression of FabI, a target of triclosan, and IsaA, a lytic
transglycosylase involved in cell division, was increased. The P10 SCV was
49% less fit than P0. In summary, triclosan exposure of S. aureus produced
SCVs in 4/6 test bacteria, with decreased triclosan susceptibility but with
generally increased antibiotic susceptibility. An SCV derived from S. aureus
ATCC 6538 showed reduced competitive fitness, potentially due to impaired
cell division. In this SCV, increased FabI expression could account for
reduced triclosan susceptibility, while IsaA may be upregulated in response
to cell division defects.
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البحث (2): |
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عنوان البحث:
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Fatty Acid Supplementation Reverses the Small
Colony Variant Phenotype in Triclosan-Adapted Staphylococcus aureus: Genetic,
Proteomic and Phenotypic Analyses
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رابط إلى البحث: |
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تاريخ النشر:
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01/03/2018
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موجز عن البحث: |
Staphylococcus aureus can
develop a small colony variant (SCV) phenotype in response to sub-lethal
exposure to the biocide triclosan. In the current study, whole genome
sequencing was performed and changes in virulence were investigated in
five Staphylococcus aureusstrains following repeated exposure to
triclosan. Following exposure, 4/5 formed SCV and exhibited point mutations in
the triclosan target gene fabI with 2/4 SCVs showing mutations
in both fabI and fabD. The SCV phenotype was in
all cases immediately reversed by nutritional supplementation with fatty acids
or by repeated growth in the absence of triclosan, although fabI mutations
persisted in 3/4 reverted SCVs. Virulence, determined using keratinocyte invasion
and Galleria mellonella pathogenicity assays was significantly
(p < 0.05) attenuated in 3/4 SCVs and in the non-SCV triclosan-adapted
bacterium. Proteomic analysis revealed elevated FabI in 2/3 SCV and
down-regulation in a protein associated with virulence in 1/3 SCV. In summary,
attenuated keratinocyte invasion and larval virulence in triclosan-induced SCVs
was associated with decreases in growth rate and virulence factor expression.
Mutation occurred in fabI, which encodes the main triclosan target
in all SCVs and the phenotype was reversed by fatty acid supplementation,
demonstrating an association between fatty acid metabolism and
triclosan-induced SCV. |
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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9th Saudi
Students’ Conference
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تاريخ الإنعقاد:
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13/02/2016
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مكان
الإنعقاد:
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Birmingham, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Altered antibiotic
susceptibility and growth rate in Staphylococcus aureus small colony variants
following sublethal exposure to triclosan
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ملخص المشاركة:
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Objectives: Small
Colony Variants (SCV) are a slow growing subpopulation of bacteria that form
in response to environmental stress. There is evidence
that Staphylococcus aureus SCV can emerge in response to
exposure to the microbicide triclosan. These SCV can reportedly exhibit
increased antibiotic susceptibility and reduced relative fitness and
virulence when compared to unexposed isolates. However, the implications of
these alterations remain unclear. This study investigates antibiotic
sensitivity and growth rate in 11 strains of S. aureus following
repeated sublethal exposure to the commonly used
microbicide triclosan.
Methods: Various S.
aureus isolates were obtained from culture collections and clinic
isolates and were repeatedly exposed to triclosan using a
previously validated gradient plating system to
produce triclosan-adapted strains (P10). Subsequently, test bacteria
were then passaged a further ten times in the absence of antimicrobial agent
to generate PX10. Minimum Inhibitory Concentrations (MIC) and Minimum
Bactericidal Concentrations (MBC) to triclosan in addition to
susceptibility to a test panel of antibiotics were determined. Planktonic
growth rate of selected SCVs and non-SCVs was also evaluated before and after
exposure.
Results:
All P10 strains showed reductions in triclosan susceptibility
whilst 7/11 became more susceptible to the majority of tested antibiotics.
5/11 strains formed SCV characteristics including formation of small colonies
and reduced growth rate after
repeated triclosan exposure.
Conclusion:
These results suggest that S. aureus SCVs could emerge following
repeated exposure to triclosan. These SCVs exhibited reductions in
planktonic growth rate and reduced sensitivity to triclosan when
compared to the parent isolates (P0).
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المؤتمر ( 2 ):
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عنوان المؤتمر:
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6th
Annual ECS Research Symposium
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تاريخ الإنعقاد:
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19/04/2017
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مكان
الإنعقاد:
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London,UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Proteomic and
Virulence Analyses of Staphylococcus aureus Small Colony Variants Induced by
Antimicrobial Exposure
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ملخص المشاركة:
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Aims: Staphylococcus
aureus Small Colony Variants (SCVs) are a slow growing subpopulation of
bacteria that form in response to environmental stress, such as exposure to
antimicrobials. Increased antibiotic susceptibility has been previously
reported for SCVs induced by exposure to the antimicrobial compound triclosan
although the implications remain unclear. The current study investigates the
relative pathogenicity in S. aureus SCVs induced by repeated exposure to
triclosan and evaluates underlying mechanisms through proteomic analyses
Methods and results: A selection
of S. aureus isolates were exposed to triclosan ten times to generate P10 and
a further ten times without antimicrobial (PX10). The relative pathogenicity of P10, PX10 and
unexposed bacteria (P0) was assessed using wax worm (Galleria mellonella)
model and using primary human keratinocytes. After triclosan exposure, 4/5
strains formed SCVs. 3/4 SCVs exhibited a significant reduction in relative
pathogenicity, evidenced by reduced virulence against G. mellonella.
Keratinocyte invasion assays showed a reduction in virulence in 2/4 SCVs.
Protein analysis revealed overexpression in triclosan target, FabI, and
down-regulation in cell adhesion proteins (fibrinogen-binding protein and
staphylococcal complement inhibitor) and virulence proteins
(leukocidin/hemolysin toxin and staphylococcal accessory regulator
protein).
Conclusion: Relative pathogenicity and keratinocyte
invasion ability were impaired in SCV induced from a range of S. aureus
isolates. Down regulation in virulence and cell adhesion proteins were
detected in two SCVs
Significance of study: Whilst
it has been suggested that SCVs are associated with increased virulence we
have shown impaired virulence in a section of SCV that were induced by sub-lethal
exposure to triclosan.
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