الفهرس 
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Abstract
Nosocomial infections are substantial risk for the patients admitted to
the hospitals. These infections can transfer by many ways including air,
droplet and contact. Hospital environmental surfaces are considered very
important source of nosocomial associated pathogens by acting a reservoir
for these pathogens as they can survive on these surfaces up to 4 months.
The bacterial biofilm is a surviving mode of growth used by bacteria
against difficult conditions such as chemical biocides. Bacteria attached to
the surface and surrounded itself by extracellular polymeric substance
(EPS) which acting a barrier that kept critical nutrient and molecules ”in”
and keeping dangers to bacteria ”out”, and Protect the resident bacteria
from the therapeutic modalities. This matrix consists of about 97% of
biofilm matrix is water, beside microbial cells and a complex of secretes
polymers, absorbed nutrients and metabolites, cell lysis products,
peptidoglycans, lipids, phospholipids and other cell components, and
macromolecules.
Bacterial biofilm considered as highly due to their high antimicrobial
resistance tendency because of several mechanisms such as low growth
rate, diffusion barrier of extracellular matrix, synergistic participation of
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efflux pumps β-lactams mediated degradation. It is estimated that 65-80%
of all infections is thought to be biofilm-related.
Silver nanoparticles presents a new way to overcome the problems of
multidrug resistance bacteria and biofilm-related infections. This is due to
nanoscale of particles size which enhance their physical, chemical and
biological properties. Silver nanoparticles have many applications in
medicine show anti-inflammatory effect, in medical devices and implants
as silver-impregnated polymers and in water filters for inhibition of biofilm
or additional level of treatment.
Materials and methods:
• Samples collected from frequently touched surfaces in surgical
operating rooms of Suez Canal university hospital.
• Bacterial isolates tested for biofilm production by microtitre plate
method, then the biofilm producers were identified using VITEK
system.
• Silver nanoparticles synthesized using silver nitrate as precursor,
PVP as stabilizer, and isopropanol as scavenger and by using γ-
irradiation at 25-KGy.
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• Determination of minimum inhibitory concentration of silver
nanoparticles using microdilution method and using the turbidity
as an indicator for growth.
• Determination of antibacterial activity of silver nanoparticles and
sodium hypochlorite by microtitre plate method.
• Determination of antibiofilm activity of silver nanoparticles and
sodium hypochlorite on biofilm before and after its formation by
tissue culture plate method and staining with 0.1% crystal violet
aqueous solution for quantification by spectrophotometer.
• Determination of reduction of aerobic colony count in surgical
operating rooms by spraying the silver nanoparticles on semicritical
surfaces and floors and walls by comparing the count
before and after the intervention.
Results:
• One hundred and twelve swab samples collected from five
surgical operating rooms of Suez Canal University Hospital, of
which 71 bacterial samples (63.39%) obtained as growth
positive. The isolated samples were saved in 40% glycerol
nutrient broth for further tests.
• Microtitre plate method showed; Non- or weak biofilm producers
were 27 isolates (38.02 %), 25 isolates (35.21 %) were moderate
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biofilm producers and 19 isolates (26.76 %) were strong biofilm
producers.
• Identification of strong biofilm producer by VITEK system
showed different gram -positive and -negative bacteria. Such as,
staphylococcus spp, Aerococcus spp, and Pseudomonas spp.
• Synthesis of silver nanoparticles Ag NPs synthesis at 25.0 kGy
gamma irradiation dose was recording maximum absorption
(3.123) at the wavelength (433nm).
• The MIC of silver nanoparticles was obtained as 125 ppm.
• The antibiofilm activity of silver nanoparticles, in concentrations
500 ppm, 250 ppm, and 125 ppm, in comparison with sodium
hypochlorite 0.5% was statistically non-significant.
• Silver nanoparticles show significant decrease in Aerobic colony
count on the frequently touched surfaces and non-critical
surfaces (floors and walls) in surgical operating rooms by 95.6%
and 85% reduction, respectively.