Research Article (Open access) |
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ABSTRACT- Two hundred fifty samples were collected from Khartoum teaching hospital (KTH) by swabs from units'
surfaces including walls, seats, tables, floor, medical devices, doors and windows. Air samples were also investigated by
using settle plate method. The samples were cultured on blood agar for primary isolation. Identification of MRSA was
carried out according to standard method. Resistance to methicillin and vancomycin was done for each isolate. The disc
diffusion method and In-Use test were used to evaluate the effectiveness of the four disinfectants (Clorox (sodium
hypochlorite) + Water, Phenol + liquid soap + Chloroxylenol "Dettol", Formalin + Water, and Dettol (Chloroxylenol
solution) + Liquid soap + Water) against MRSA. Data were analyzed by the statistical analysis program Statistical Package
for the Social Science (SPSS) using One-Way Analysis of Variance (ANOVA) and Least Significant Difference
(L.S.D) test.
The results revealed that the prevalence of MRSA was 66 (25%). Among these 11(16%) were vancomycin resistant.
Moreover, the study on the role of disinfectants in controlling infection showed that two of these disinfectants (Formalin +
Water, Dettol (Chloroxylenol solution) + Liquid soap + Water) were significantly effective on MRSA (P<0.05), while the
other two disinfectants (Clorox (sodium hypochlorite) + Water, Phenol + liquid soap + Chloroxylenol "Dettol", Formalin
+ Water) were insignificantly effective (P>0.05) on the same organisms.
It is concluded that the prevalence of MRSA in KTH was high and the rate of Vancomycin resistant S. aureus (VRSA) is
increasing. The disinfectants used routinely in KTH were not equal in their efficiency and there was failure in the actions
of two of them.
Key words: MRSA, Hospital, Disinfectants, Infection Control, Sudan.
INTRODUCTION
Microorganisms on hospital surfaces can be transmitted to
the hands of healthcare workers, patients, co-patients and
visitors, resulting in cross-infections.
Despite the performance of routine cleaning and
precautionary measures in most hospitals, effective
environmental decontamination methods are still in demand
[1]. Disinfectants are commonly used to minimize the risk
of Methicillin-resistant Staphylococcus aureus (MRSA) [2].
This organism first reported from England in 1961 as a
leading pathogen of nosocomial infections [3]. The later in
hospital due to MRSA is increasing.
Recently, emergence of resistance strains of S. aureus to
vancomycin has made MRSA more difficult to treat than
before. Patients who infected with hospital strain have
increased mortality risk and expanded hospital stay,
resulting in increased treatment costs, compared with
patients who do not have hospital strain infections [3].
Moreover, the increased risk of a new patient with
antibiotic resistant bacterium when admitted to a room
previously occupied by another patient with the same
bacterium has also been reported. Disinfection of the hightouch
areas reduces the load of antibiotic resistant bacteria
in the hospital environment [4].
Treatment of Multi-Drug Resistant (MDR) strains is very
difficult due to limited alternative to select effective
antibiotics. The MDR strains exist in the hospital environment
can infect patients through health care devices.
Therefore, it is very important to eliminate MDR strains
from health care devices by using highly efficient
disinfectant [5].
Thus, hospital surfaces disinfection rates remain a true
problem, despite a growing body of research [6].
The objectives of this study were to determine the prevalence
of MRSA in Khartoum Teaching Hospital (KTH),
evaluate the efficiency of disinfectants currently in use, and
provide data on the level of bacterial contamination.
MATERIALS AND METHODS
This study was carried out in Khartoum Teaching Hospital
(KTH), Sudan during the period October 2007 - August
2008. This hospital is a leading hospital in Sudan. The
experimental work was carried out in the Research
Laboratory, College of Medical Laboratories Science,
Sudan University of Science and Technology.
The samples were collected from KTH sections and units
including (emergency, surgery, blood bank, pediatrics and
obstetrics-gynecology). A total of two-hundred fifty swab
samples were collected and eighteen air samples were
investigated.
The data were collected primarily from emergency unit 80
samples, general surgery 80, pediatric 40, obstetricsgynecology
30 and blood bank 20.
Air samples were collected from emergency unit 6 samples,
general surgery 3, pediatric 3, obstetrics-gynecology 3 and
blood bank 3.
The samples were collected from the sections and unit's
environments by using sterile swabs to cover the surfaces
of floor, tables, windows, doors, walls, seats and medical
devices. Air samples were examined by using settle plates
technique [7].
Disinfectants:
In KTH several types of disinfectants have been used, some
of which in a daily basis to clean floors and surfaces in the
units and rooms and others were use to disinfect surgical
theatres. Four disinfectants from KTH were used in this
study including Clorox (sodium hypochlorite) + Water,
Phenol + liquid soap + Chloroxylenol "Dettol", Formalin +
Water, and Dettol (Chloroxylenol solution) + Liquid soap +
Water.
Antibiotic discs included methicillin (M), 10µg, vancomycin
(Va), 30 µg. Standard strain S. aureus ATCC
25923.Obtained from National Health Laboratory in
Khartoum. Sterile filter paper was obtained from Micro
Master Lab. Pvt. Ltd., India. All media were obtained from
Hi Media Lab. Pvt. Ltd. Mumbai, India.
Under aseptic conditions the swabs were inoculated on
blood agar and incubated at 37°C overnight.
Only the growth that showed characteristic colonial
morphology of golden, yellow and white colonies of 1-2
mm, like staphylococci were selected. For further investigations,
the colonies isolated were sub-cultured on Nutrient
agar and incubated at 37°C overnight.
S. aureus isolates were identified by their colonial
morphology, Gram’s stain, and biochemical tests including
catalase, coagulase, mannitol fermentation, DNase.
Examination of air (Settle plates):
Examination of air using settle plates technique, uncovered
blood agar plates were exposed to air 1 meter above the
ground for 30 minute, and the plates were incubated at
37°C for 48 hours.
Only plates showing colonies count between "30-300" were
considered.
Antimicrobial susceptibility tests:
Sensitivity test was performed using Kirby-Bauer disc
diffusion method [8]. Briefly, 1-3 isolated colonies were
emulsified in 5 ml of sterile physiological saline, and then
the turbidity of suspension was adjusted to McFarland
standard by adding normal saline or more bacterial
colonies. A swab was dipped into the suspension and the
excess fluids was removed by pressing and rotating the
swab against the inner side of wall tube, and then streaked
the swab over the surface of Muller-Hinton agar three
times, rotated the plate through an angle of 60° each time to
ensure the distribution of inoculums over the surface of the
agar plate. The discs were placed on the surface of the
inoculated plate. Each disc was pressed down gently to
ensure its contact with the agar. The plates were incubated
at 37°C for 24hr. inverted aerobically for overnight. The
diameter of zone, of inhibition was measured in mm. the
diameter of inhibition zone were compared to the standard
inhibition zone in the chart (Chart given with the
antibiotic).
Disinfectant efficacy:
This test was used to determine the potency of disinfectants
used in KTH. The same steps in Kirby-Bauer diffusion disc
were followed in this test. Sterile filter paper discs were
soaked in the disinfectant solution and left to dry for few
minutes. The impregnated discs were placed on the Muller-
Hinton agar plates and incubated overnight at 37°C.
After incubation, the clear zone surrounding the disc was
measured the effects of disinfectants were used against the
MRSA organisms. The zone inhibitions were measured by
a ruler. The last was carried out in replicated. The
efficiency of these chemicals was judged by the diameter of
the inhibition zone.
In-use test:
The test was done according [9]. Briefly, by using this test
we can test the disinfectants were used in hospital. In this
test the disinfectants were tested twice one in the normal
conditions and in the real environment and could see the
ability of disinfectants against normal organisms which
already exist normally in the environment. In the second
part of test were. The disinfectant is tested in a small place
and in stable temperature and stable conditions, so we can
see the results according to the test rules. With a sterile
pipette, transfer 1 ml of the used disinfectant into 9 ml of
nutrient broth in sterile tubes. 0.02 ml drops of this mixture
placed onto ten different areas of each of two well dried
nutrient agar plates. One of the plates was incubated for 3
days at 37°C and the other for 7 days at room temperature.
Presence of growth in more than five drops on either plate
indicates failure of disinfectant.
Statistical analysis:
The statistical analysis was done using SPSS program. The
data obtained from the zone diameter of the disinfectant
activity against MRSA were analyzed using One-Way
ANOVA (Analysis of Variances) and Post Hoc Test (L.S.D
test) to know the variances between the results. For each
dependent variable the descriptive output gives the sample
size, mean, standard deviation, minimum, maximum,
standard error, and confidence interval for each level of the
(quasi) independent variable. The ANOVA output gives us
the analysis of variance summary table. There are six
columns in the output:
The hypothesis in this test is:
H0: d1=d2=d3=d4 (the means are equal)
H1:d1?d2?d3?d4 (the means is not equal)
Where (d) = the means of disinfectant activity
The table show the mean of reading between and within
groups, also show the test of linearity and the deviation
from linearity "linear trend" (this describe if the mean of
data for all disinfectants being on right line or if they are
equal).
In this test we calculate the F-value, the difference between
F-calculated and F-tabulated (sig.); if the F-calculated is
bigger than F-tabulated (sig.) we refuse the first hypothesis.
That means there's variance between the means.
In this table we see the F-value > sig. so we refused the
hypothesis of equality between means, so we go to use the
Post Hoc Test (L.S.D) to know the value of variances
between the means.
The variances in the means between disinfectants shown in
the second column and it's appear that disinfectant number
3 is more effective than the other disinfectants, also show
that disinfectant number 1 is the most weak based on the
mean of diameter zone. Hence the disinfectants used in
KTH were not equal in efficiency while some were not
effective.
RESULTS
In this study, 250 samples were collected from different
units: Emergency unit including the units of I.C.U,
Refreshment Surgery unit, internal unit and X ray unit,
General Surgery unit, Blood bank, Pediatrics unit and
Obstetrics-Gynecology unit in Khartoum Teaching Hospital
(KTH). The samples were collected by means of cotton
swabs from floor, walls, tables, doors, seats, windows and
medical devices. Air samples were collected directly on
an agar plate using settle plate technique.
Distribution of samples:
The distribution of samples according to units is shown in
Table (1). Samples were collected from the Emergency
unit, General surgery, Obstetrics-Gynecology, Blood bank
and Pediatrics are shown in Table (2). These samples were
distributed and covered seven different sites in this unit
with an exception of four sites in blood bank. The numbers
of samples was collected from the KTH sites (Doors,
Windows, Seats, Floor, Medical Devices, Walls and
Tables).
Settle plate technique:
This was done to examine the unit's air and to know the
number of the Colony Forming Unit (CFU). Three Plates
were exposed to the air in every unit were covered in this
study, and after incubation the CFU was counted for three
plates and was used to calculate the mean of CFU in every
unit Table (3).
Isolation and identification of S. aureus and MRSA:
Of 250 samples and 18 air samples, 265 (99%) showed
significant growth on blood agar. Sixty-one 250 of swab
samples collected in this study were identified as S. aureus
and distributed on the units as: Emergency unit (22), General
surgery unit (21), Pediatrics unit (9), Blood Bank (3)
and Obstetrics-Gynecology unit (6).
After the sensitivity test to methicillin antibiotic fifty-seven
of 61 were identified as MRSA. Emergency unit (20),
General surgery unit (21), Pediatrics unit (8), Blood Bank
(3) and Obstetrics-Gynecology unit (5), Table (4).
From (18) plates were exposure to air in the units and after
incubation in Emergency unit (3), General Surgery unit (2),
Pediatrics unit (1), Blood Bank (1) and Obstetrics-
Gynecology unit (2) colonies identified as S. aureus all of
these organisms identified as MRSA Table (4).
Of the isolated S. aureus 3 (4%) were sensitive to methicillin,
1 (1%) with intermediate activity and 66 (94%) were
resistant to methicillin Table (5).
Vancomycin sensitivity was done to all S. aureus isolated
and showed that 59 (84%) were vancomycin sensitive S.
aureus (VSSA), and 11 (16%) were vancomycin resistant S.
aureus (VRSA) Table (5).
Efficiency of disinfectants:
All 66 MRSA isolated were tested for susceptibility to the disinfectants used in KTH by using the Kirby-Bauer method
(disc diffusion), The Petri dish was streaked by the organisms and by using sterile filter paper soaked by the disinfectant
was placed on the agar and after incubation the diameter zone inhibition was measured, this test repeated three times to
every MRSA isolated. The SPSS statistical analysis was done to analysis the out put data and by using One-Way ANOVA
test and L.S.D test shows that the four disinfectants were not equal in strength of efficiency
against MRSA organisms isolated and there is significant variance among them.
In-Use test was done to judge on the disinfectants used in KTH and as the results the test show us if the disinfectants were
tested in this study were passed or failure Table (6).
Table 1. Distribution of swabs samples (n=250) according to units
S. No. | Unit | No. of samples (%) |
---|---|---|
Hospital Unit | Site of Collection | ||||||
---|---|---|---|---|---|---|---|
Door
No. of Samples (%) |
Seat
No. of Samples (%) |
Wall
No. of Samples (%) |
Table
No. of Samples (%) |
Med. Device No. of Samples (%) |
Floor
No. of Samples (%) |
Window
No. of Samples (%) | |
Emergency | 7 (9) | 11 (14) | 15 (19) | 16 (20) | 14 (18) | 10 (13) | 7 (9) |
General Surgery | 10 (13) | 10 (13) | 10 (13) | 12 (15) | 15 (19) | 15 (19) | 8 (10) |
Pediatrics | 6 (15) | 7 (18) | 6 (15) | 6 (15) | 4 (10) | 6 (15) | 5 (13) |
Blood bank | - | - | 4 (20) | 4 (20) | 8 (40) | 4 (20) | - |
Obstetrics- Gynecology | 4 (13) | 5 (17) | 4 (13) | 4 (13) | 5 (17) | 4 (13) | 4 (13) |
Unit | Number of plates | CFU/plate |
---|---|---|
Sample Type | Swab | Air | ||
---|---|---|---|---|
Unit | S. aureus | MRSA | S. aureus | MRSA |
Emergency | 22 (28) | 20 (91) | 3 (50) | 3 (100) |
General Surgery | 21 (27) | 21 (100) | 2 (67) | 2 (100) |
Pediatrics | 9 (23) | 8 (89) | 1 (33) | 1 (100) |
Blood bank | 3 (15) | 3 (100) | 1 (33) | 1 (100) |
Obstetrics-Gynecology | 6 (20) | 5 (83) | 2 (67) | 2 (100) |
Total | 61 | 57 | 9 (50) | 9 (50) |
Activity of antibiotic | Methicillin | Vancomycin |
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S. No. | Disinfectant | Result |
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