Magnetic Field Effect on Growth and Antibiotic Susceptibility of Staphylococcus aureus

Abstract

It is aimed to investigate the effect of exposure of different magnetic fields (400, 800.1200 and 1600 Gauss for 2 to 24 hours) on the growth rate and antibiotic sensitivity of Staphylococcus aureus. The experiments were done in Hawler Medical Research Centre Erbil, Iraq. The bacteria were isolated from medical case in Rizgary hospital and identified using API STAPH system. The antibiotic susceptibility of Staphylococcus aureus measured according to Kirby-Bauer disc diffusion technique. Results showed a significant decrease in the logarithm in the number of Staph. aureus (41.4 to 27 X 10 6) treated with high frequency magnetic field. Sensitivity of Staph.aureus to antibiotic increase during a short period (4-6 hours) and increase its resistance to same antibiotic at log term of exposure (18-24 hours). Some results of biochemical tests also showed positive effects of magnetic fields on the biochemical properties according to API STAPH results. The bacterial enzymes MAL (Maltose), LAC (Lactose), TRE (D-Trehalose), MAN (D-Mannitol), SAC (Sucrose) and NAG (N-acetyl-glucosamine) were affected by magnetic field at 24 hours of incubation. It is concluded that the cellular membrane of the microorganism had been affected by the magnetic field, also the response increased when the field intensity increased. So the magnetic field effects on bacteria are considered bactericidal, and hence, a change in the number of the cells per ml or the measured change in the membrane sensitivity to antibiotic demonstrated also the change in the internal structure of the cells.

Full text

Journal of Al-Nahrain University Vol.17 (3), September, 2014, pp.138-143 Science

Magnetic Field Effect on Growth and Antibiotic Susceptibility of
Staphylococcus aureus
Fouad Houssein Kamel*1, Chiman Hameed Saeed** and Saleem Saaed Qader**
* Erbil Medical Technical Institute, Hawler Polytechnic University, Erbil-Iraq.
** Medical Research Centre, Hawler Medical University, Erbil-Iraq.
1E-mail: fhkamel2013@yahoo.com.
Abstract
It is aimed to investigate the effect of exposure of different magnetic fields (400, 800.1200 and
1600 Gauss for 2 to 24 hours) on the growth rate and antibiotic sensitivity of Staphylococcus
aureus. The experiments were done in Hawler Medical Research Centre Erbil, Iraq. The bacteria
were isolated from medical case in Rizgary hospital and identified using API STAPH system. The
antibiotic susceptibility of Staphylococcus aureus measured according to Kirby-Bauer disc
diffusion technique. Results showed a significant decrease in the logarithm in the number of Staph.
aureus (41.4 to 27 X 106) treated with high frequency magnetic field. Sensitivity of Staph.aureus to
antibiotic increase during a short period (4-6 hours) and increase its resistance to same antibiotic at
log term of exposure (18-24 hours). Some results of biochemical tests also showed positive effects
of magnetic fields on the biochemical properties according to API STAPH results. The bacterial
enzymes MAL (Maltose), LAC (Lactose), TRE (D-Trehalose), MAN (D-Mannitol), SAC (Sucrose)
and NAG (N-acetyl-glucosamine) were affected by magnetic field at 24 hours of incubation.
It is concluded that the cellular membrane of the microorganism had been affected by the
magnetic field, also the response increased when the field intensity increased. So the magnetic field
effects on bacteria are considered bactericidal, and hence, a change in the number of the cells per
ml or the measured change in the membrane sensitivity to antibiotic demonstrated also the change
in the internal structure of the cells.
Keywords: Magnetic field, Staphylococcus aureus, Antibiotics susceptibility test, API Staph.
Introduction
For the first time, in 1976, the biological
effects of electromagnetic fields usage were
considered. With the growing development of
technology in various fields and waves,
greater use of technologies leads to increasing
exposure to electromagnetic fields (EMFs),
such as power lines and ordinary devices used
inside house and work places. As
consequence, organisms and especially the
human who has affected today [1].
Ma et al. [2] studied the effect of pulsed
magnetic field intensity and pulse number
(PMF) on bactericidal property of PMF in
sterilization of fresh watermelon juice.
Their results showed that the overall
bactericidal effect was strengthened as the
magnetic field intensity and pulse number
increased with the best effect observed when
the magnetic field intensity was 2.53 T and
pulse number was 20.
The study of effects of ELF-EMF on
bacteria is essential not only for investigation
of environmental stress influences on
biological systems, but also to explore the
possibility of controlling the sensitivity of
bacteria toward antibiotics in the environment
or in clinical laboratories [3].Investigations
sponsored by Bio-Magnetics Systems, Inc.
have shown that unidirectional magnetic fields
inhibited or increased the growth of cancer
cells, depending on the field polarity, as
disclosed by Trappier [4].
So the effects of magnetic fields were
studied in different areas such as drug
delivery, cancer therapy, sterilization, and
water treatment [5].
Magnetic field affects DNA synthesis and
transcription [6] as well as ion transcription
through all membrane [7]. Piatti et al.[8]
found that the exposure of the bacteria
Serratia marcescens to a static magnetic field
80 +20 Gauss resulted in inhibition of growth.
The effect of magnetic field was variable
depending on the type of the microorganism
and field. Novak et al. [9] clarify that

Fouad Houssein Kamel

magnetic field has significant effect on
bacterial cell as well as on its life and they
added that the effect of magnetic field was
enclosed in cell membrane.
The aim of our objectives were to study
the effects of different exposure periods (400,
800, 1200 and 1600 G locally prepared static
magnetic field) on the cell activity. The effects
of such magnetic fields on the growth rate and
antibiotic sensitivity were explored, too.
Material and Methods
The bacterium Staphy. aureus was isolated
and identified on culture medium of patient
samples in Rizgary hospital and suspend into
10 ml of nutrient broth, incubated at 37 ºC for
24 hours as a stock culture.
Dipolar magnetic field was prepared
locally with different forces including 400,
800, 1200, 1600 Gausses and measured by
Teslometer in Physical Department, College
of Science, University of Salahddin, Erbil,
Iraq. Later 0.1 ml of stock bacterial suspension
was inoculated into five groups of tubes
contained 5ml of nutrient broth. Four groups
of tubes were subjected to magnetic field (400,
800, 1200, 1600 Gauss) respectively. While
the fifth group was subjected to magnetic field
as a negative control, later all tubes were
incubate at 37 ºC for 2 to 24 hours.
The effects of different forces of magnetic
fields on growth rate were evaluated by
measurement of the optical density using
McFarland Turbidity Standards (0.5). The API
STAPH kits were prepared by BioMerieux
Company and used due to BioMerieux
Company instrctions. Inoculation of API
Staph kit with bacteria from
each group done separately. Antibiotic
susceptibility test was carried out using
Muller-Hinton Agar medium depending
Kirby-Bauer Disk Diffusion technique.
Gentamycin (30 mcg), Tetracycline (10mcg),
Chloramphenicol (30μg), Rifampcin (5mcg),
Ceftazidium 30mcg), Ceftriaxone (30mcg),
Metronidazol (5 μg) disks were placed over
the medium. The antibiotics used in this study
were chosen to be with different modes of
action. The diameters of the inhibition zone
were measured after 24 hours from the
exposure process.
Results and Discussion
Results indicated that magnetic fields
(400, 800, 1200, and 1600 G.) increased the
logarithmic phase of Staphyl. aureus growth
(within 4 hrs of treatment, but decreased
growth curve after a period of 8 hrs (Fig.(1)).
A considerable change in the growth rate of
Staphy. aureus (Table (1)). A decrease in the
colony forming units (CFU) started
immediately after the magnetic field was
switched on and that magnetic field effect on
bacteria could be considered as bactericidal.
These results are in agreed with others [5,
10-12] who reported the exposure of E. coli,
Staph. aureus and Salmonella typhi
to the magnetic field has similar effects.
Fojt et al. [13] found that E. coli, bacteria
decarboxylation and Staphy. aureus viability
was affected with the magnetic field (10 mT,
50 Hz). Nasher and Hussein [11] concluded
that magnetic field effect on bacteria could be
considered as bactericidal. Babushkina et al.
[14-17] demonstrated that ELF-EMF
positively affect functional parameters (cell
growth and viability) and bacteria antibiotic
sensitivity depending on physical parameters
of the electromagnetic field (frequency and
magnetic flux density) applied, the time of the
exposure, and/or the type of bacteria cells
used.

Journal of Al-Nahrain University Vol.17 (3), September, 2014, pp.138-143 Science

Table (1)
Growth rate of Staph.aureus for each group.
Time of
exposure to
magnetic
field in hour
Optical Density (O.D.) at 600 nm and bacterial cells count(McFarland)
Control
400G
800G
1200G
1600G
O.D.
Bac.
count
x 106
O.D.
Bac.
count
x 106
O.D.
Bac.
count
x1 06
O.D.
Bac.
count
x106
O.D.
Bac.
count
x 106
0
0.034
10.2
0.034
10.2
0.034
10.2
0.034
10.2
0.034
10.2
2
0.139
41.7
0.123
36.9
0.115
34.5
0.113
16.95
0.102
30.6
4
0.138
41.4
0.120
36
0.113
33.9
0.110
33
0.090
27
6
0.110
33
0.108
32.4
0.106
31.8
0.099
29.7
0.075
22.5
8
0.098
29.4
0.085
25.5
0.080
24
0.060
18
0.050
15
20
0.055
16.5
0.040
12
0.036
10.8
0.030
9
0.015
4.5
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0 2 4 6 8 24
Time of exposure (hour)
Absorbance at 600 nm
control
400
800
1200
1600
Fig. (1) Absorbance at 600 nm of Stap.aureus cells with different exposure periods.
Table (2) showed antibiotics susceptibility
test at different periods of exposure (2, 4, 6, 8,
24 hours) which evaluated according to the
mode of action, the results concluded that
Staph.aureus were sensitive for Gentamycin,
Ceftazidium, Tetracycline, Chloramphenicol,
Rifampcin, Ceftriaxone whereas resistant to
Metronidazol. Also the results indicated
that magnetic field alter antibiotic sensitivity
and found that exposing Staphy.aureus to
magnetic field increased antibiotic resistance
absolutely in Chloramphenicol, Rifampcin and
Ceftriaxone. The diameters of the inhibition or
stimulation zone of the different magnetic
forces were measured after 24 hours from the
exposure process compared with unexposed
samples.
These results were in agreement with the
work of Stansell and colleagues [18] who
found that moderate intensity static fields were
able to cause a decrease in the antibiotic
sensitivity and resistance of E. coli. [16] found
that electromagnetic field also induced
transcriptional changes and the acquisition of
resistance to Cephalosporins (Cefuroxime and
Ceftazidime). Therefore, the possibility that
magnetic field could interferes with the surface
charges of the membrane or the charge
distribution on the antibiotic molecule
modifying the rate of antibiotic penetration
may exist.

Fouad Houssein Kamel

Table (2)
Antibiotic test of exposed and unexposed Staph.aureus to magnetic filed.
Antibiotics
Mode of action
Inhibition antibiotics zone diameter in mm
Un
exposed
to M.F
M.F exposure (G) time
2 hour
20 hour
400
800
1200
1600
400
800
1200
1600
Gentamycin
Inhibition of
protein synthesis
(30 S-R)
25
35
25
30
30
22
17
16
16
Tetracycline
Inhibition of
protein synthesis
(30 S-R)
25
36
38
35
30
17
16
16
16
Chloramph-
enicol
Inhibition of
protein synthesis
(50S-R)
18
12
10
10
10
10
10
R
R
Ceftriaxone
Inhibition of
cell wall
25
30
R
R
R
R
R
R
R
Ceftazidium
Inhibition of
cell wall
17
30
25
23
23
16
15
13
10
Rifampin
Inhibition of
nucleic acid
32
18
R
R
R
R
R
R
R
Metronidazole
Inhibition of
nucleic acid
R
R
R
R
R
R
R
R
R
R: Resistance, M.F: Magnetic Field, S- R: Subunit- Ribosome.
According to API STAPH, the bacterial
enzymes MAL, LAC, TRE, MAN, SAC and
ARA affected by magnetic field at 24 hours of
incubation. These results suggest that the
biological effects of magnetic fields may critically
depend on the physical characteristics of the
magnetic signal, in particular the wave forces.
So treating enzyme with different magnetic
fields can inhibit or promote enzyme activity
according to API STAPH. Staphy. Aureus may
be identified by this test (Fig.(2)). Results
agree with results of [16, 19, and 20] which
demonstrated that short-term exposure (20–
120 min.) to an ELF-EMF with a sinusoidal
waveform of amplitude ranging from 0.1 to
1mT and frequency of 50 Hz affected both cell
viability and morphology of cultured E. coli
ATCC 700926. Results also exhibited that
magnetic field can affect membrane functions;
however the magnetic field could interact with
other specific processes that help the
adaptation of bacteria to the new environment.
In this regard, bacteria are able to respond to
environmental stresses by activating suitable
inducible systems, such as the DNA repair
system, and exploit processes which increase
the genetic variability.

Journal of Al-Nahrain University Vol.17 (3), September, 2014, pp.138-143 Science

API STAPH System of Stap. aureus before exposure to magnetic field
API Staph system of Staph.aureus after 24 hours of exposure to magnetic filed
Fig. (2) API Staph System of exposed and unexposed of Staphy. aureus to magnetic field.
Conclusions
It is concluded that the growth rate of
Staph.aureus cells was affected by exposure to
magnetic forces (400, 800, 1200 and 1600).
The magnetic field decreased the logarithmic
phase within 4 -6 hours of treatment compared
with the control. Furthermore, the bacterial
sensitivity to antibiotics increased after
exposure period of 6 hours to certain
antibiotics, but become resistant after 16
hours. The bacterial enzymes MAL (Maltose),
LAC (Lactose), TRE (D-Trehalose), MAN
(D-Mannitol), SAC (Sucrose) and NAG
(N-acetyl-glucosamine) were affected by
magnetic field. Treating of enzymes with
different magnetic fields forces could inhibit
or promote enzyme activity according to API
STAPH tests.
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

API

MAL (Maltose), LAC (Lactose), TRE (D-
Trehalose), MAN (D-Mannitol), SAC
(Sucrose) and NAG (N-acetyl-glucosamine)
     37 


      
       
