الفهرس 
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Abstract
Antimicrobial resistance poses a serious threat to human health on a global scale,
prompting researchers to look at unconventional antibacterial medicines in order to assist
quick interventions and stop the emergence and spread of bacteria that are resistant to
common antibiotics. There is an urgent need for fresh approaches to the treatment of bacterial
infections because of the changing patterns of infectious disease and the emergence of
bacterial strains resistant to current antibiotics
At the intersection of physics, nanotechnology, and microbiology, numerous novel
antibiotic-free strategies are being created while the conventional ones are being updated.
Different physical methods are used to kill the bacteria. The use of ultrasound, light
sources and electric fields alone or in combination with antibiotics could represent an aid for
modern medicine in the continuous battle against pathogenic microorganisms.
The aim of this study was to determine the effect of DC electric field on different Gram
positive and Gram-negative bacterial strains with different antibiotic sensitivity and to
determine the most effective electrical factor of the possible DC effect on bacteria.
Two DC protocols of volts and time of exposures were applied. One protocol to
examine the effect of different electrical energies at constant exposure time and the other
protocol is to examine different exposure times with the same electrical energy. These
protocols will indicate the most effective parameter in bioelectric effect.
Four bacterial reference strains representing Gram positive and Gram-negative bacteria
were used including:
Gram- negative types: Pseudomonas aeruginosa (ATCC27853) and E. coli
(ATCC25922).
Gram-positiveve types: Staphylococcus aureus (ATCC25923), and Enterococcus
faecalis (ATCC29212).
The results of the present study revealed that the cell viability reduction is dosedependent.
10 V (240 J) causes 100% cell death for all the tested bacteria except small traces
in Enterococcus faecalis, while less than 10 V is a sub-lethal dose and more than that is not
needed at all.
The results showed that 100 % cell death for all the tested bacterial types despite the used
condition. These results confirms that 240 J is the lethal dose for all the tested bacteria.
The obtained results clarified that temperature increases in all groups cannot be the main
reason of bacterial death as the bacteria can still be viable and active for such temperature
elevation while there is very obvious galvanic reaction in the used electrodes indicating the
release of the electrode ions which in turn leads to a high increase in ROS production and a
change in the nature of the bacterial media which is not suitable for the bacterial survival, the
change in the media color increases by increasing the applied energy.
The obtained results revealed that A strong significant reduction of the vital cells due to
the application of DC electric field could be observed. Increasing the electrical energy
resulted in a more significant potency of antibacterial activity. The results indicate that there
is no significant change between the two 60 J groups or between the two 140 J groups. Based
on this test, the inhibition percentage was calculated which revealed the high impact of DC on
bacterial growth compared with the control group for all the bacterial strains, and this
inhibition is energy dependent, that there is a significant reduction in the viability in 140 J
groups compared to 60 J groups. The inhibition results indicate also, that there is no
significant change within the same energy groups.
The results indicated that there is high significant reduction in the total protein amount
of 60 J groups compared to control, there is a significant decrease in 140 J groups compared
with 60 J groups. There is not a significant change between 60 J groups or within 140 J
groups. These results are for all the examined bacterial strains. On the other hand, the
extracellular protein concentration reflects the amount of dead bacteria. The extracellular
protein concentration significantly increases in energy dose behaviour, while there is no
significant change within the same energy groups which confirms the potency of DC exposure
on all the examined bacterial strains.
The obtained results clarified that that as the electrical energy increases, there is a
significant increase in lactate dehydrogenase activity compared to control, while there is no
significant change within the same energy groups.
With various exposure settings, there was a noticeable decomposability and decline in
the DNA band intensity, which is related to their quantity.
The presence of plasmic was indicated by double bands around 3000 bp; however, upon
electric field exposure, there was fragmentation and breaking down refereed by the presence
of an additional band at 500 bp and also the disappearance of the plasmid, reflecting the
shearing effect of electricity as in the case of Pseudomonas aeruginosa. The presence of
plasmic was indicated by double bands ranged from 3500 to 4000 bp; however, upon
exposure there was fragmentation and breaking down and also the disappearance of the
plasmid, reflecting the shearing effect of electricity as in E. coli. Also, the presence of plasmic
was indicated by double bands around 2000 bp in case of Staphylococcus aureus. Some
shearing is observed in Enterococcus faecalis.
The results showed that exposure to DC significantly decreases the DNA concentration.
As the electrical energy increases, the DNA concentration decreases compared to control in
all the bacterial strains. There is no significant change within 60 J groups, or within 140 J
groups.
The results indicated that very high significant increase in the produced ROS in 60 J
groups compared to control, also very high significant elevation occurred in 140 J groups
compared to 60 J groups. There is no significant change within 60 J groups or within 140 J
groups.
The electricity influenced adversely on Gram negative bacteria in this study in a higher
rate than Gram-positive; indicated by their cells morphology in most cells as indicated by
SEM. Generally, the cell wall of gram-positive bacteria, which is composed of thick
peptidoglycan layer, participated mainly in their tolerance and resistance to electricity.
The results indicated that antibiotic antibiotic-resistant bacteria can be converted into
antibiotic sensitive to the same antibiotic after exposure to DC.