|Post operative surgical site infections; Bacteria; Antibiotic
susceptibility patterns; Gondar; Ethiopia
|Surgical wound infections are those infections which are confined
to the incisions and involving structures adjacent to the wounds that
were exposed during operation . Hospital acquired surgical site infection
(SSI) is one of the major health problems throughout the world
and is a serious complication affecting hospitalized patients [1-4].
Among hospital acquired infections, SSI accounts for 14-16% of the inpatient
infections . SSI is dangerous condition with a heavy burden
on the patient has been associated with an increased morbidity, mortality
and health care cost that have huge economic impact .
|The risk of acquiring hospital infection on hospitalized patients in
relation to surgery is high, since about 77% of death of patients with
nosocomial infections was reported to be related with post operative
infections [3,4]. The number of surgical patients in developing countries
is also increasing but surgical care given to the patients is poor.
Surgical cases are responsible for approximately 6-12% of all paediatric
admissions. But due to poor surgical care, there is a significant number
of death and disability associated to post operative complications .
|Microorganisms can get access into a wound either by direct contact
of air borne dispersal or by contamination . Although there is no
definitive evidence, direct contact and poor hand washing techniques
of health care practitioners during pre and post operative phases of patient
care are considered to be major factors . The risk of developing
a surgical wound infection is largely determined by three factors: the
load, type of microbial contamination of the wound and host susceptibility
. Certain transient organisms such as S. aureus, hospital acquired
methicillin resistant S. aureus (MRSA) and coliform occur on
the skin with other commensals  could easily contaminate the surgical
wounds from poor hygiene.
|Antimicrobial resistance has been a problem in the field of surgery,
as advances in control of infections have not completely eradicated this
problem [9,10]. The widespread uses of antibiotics, together with the
length of time over which they have been available have led to major
problems of resistant pathogens contributing to morbidity and mortality.
The antibiotics resistant pathogens are acquired either from hospital
environment or from the skins of infected patients . Hospital acquired
infections are further complicated by an increasing prevalence
of multidrug resistant organisms like MRSA, methicillin resistant coagulase
negative Staphylococci (MRCoNS) and vancomycin resistant
Entrococci (VRE) spp .
|In most developing countries like Ethiopia, it is a common practice
that antibiotics can be purchased without prescription. This leads to
misuse of antibiotics by the public thus contributing to the emergence
and spread of antimicrobial resistance [13-15]. However, studies assessing
the etiological agents of surgical site infections in Ethiopia are very
scarce. Thus, it is necessary to identify bacterial agents and determine
their antibiotic susceptibility pattern from wounds for empirical treat- ment in reference to the inadequate culture and sensitively service in
Ethiopia . Therefore, this study was aimed to determine the distribution
of bacterial pathogens isolated from post-operative wounds and
their antimicrobial susceptibility patterns.
|Materials and Methods
|Study area and study population
|A cross-sectional study was carried out between January 2010 and
June 2010 at University of Gondar Teaching Hospital, Northwest Ethiopia
by involving consecutive in patients with post operative surgical site
infections seen at surgery, and gynaecology and obstetrics wards. The
hospital is a tertiary level teaching and referral hospital catering more
than 450 beds for inpatients and rendering referral health services for
over 5 million inhabitants in the North-west Ethiopia.
|Sample selection criteria
|During patient selection, a standard definition for post operative
surgical site infection was used .
|A standardized pretested questionnaire was used to obtain data
from the patients. Pus swabs were aseptically obtained using sterile cotton
wool swabs from surgical sites before the wound was cleaned by
antiseptic solution. Environmental sampling was also conducted in two
different wards and operating rooms. Furthermore, we evaluated bacterial
contamination of personnel nasal swabs and some medical equipment
too. All surface samples were taken after decontamination. The
swab specimens were transported to the Microbiology Laboratory of
Gondar Teaching Hospital, within 1-2 hours of collection.
|Sample/rinse method was used for sampling in the present study.
Cotton tipped sterile swabs that were moistened in sterile brain-heart
infusion broth (BHI) (Merck, Germany) were used to take samples
from different surfaces. In each sampling, approximately 25cm2 was
covered by moistened swab. The samples were categorized to clinical
(patients area) and non-clinical surfaces (common area). The main target
of sampling was hand contact surfaces .
|Culture of specimens
|The specimens were inoculated on nutrient agar, MacConkey agar,
mannitol salt agar, blood agar and chocolate agar (Oxoid, Basingstoke,
and Hampshire, UK, England). Plates were thereafter incubated at
37ºC for 24-48 hours. Primary cultures were sub cultured following the
standard procedures .
|Identification of bacterial pathogens
|Pure cultures on secondary plates were characterized using physical
appearances on selective and differential media. Biochemical tests such
as catalase, coagulase, oxidase, Voges-Prauskauer, hydrogen sulphide
test, urease, methyl red, indole, citrate and sugar utilization tests were
done for each pathogen following the standard procedures .
|Antibiotics used and concentrations
|A total of fifteen antibiotics which represent the most commonly
prescribed antibiotics in the study area were used in this study: amoxicillin
(30μg), ampicillin (10μg), ceftriaxone (30μg), chloramphenicol
(30μg), erythromycin (15μg), gentamicin (10μg), methicillin (5μg),
trimethoprim sulphamethoxazole (TMP-SMX) (25μg), vancomycin
(30μg), doxycycline (30μg), amikacin (30μg), clindamycin (2μg), ciprofloxacin
(5μg), kanamycin (30μg), tetracycline (30μg). The criteria used to select the antimicrobial agents tested were based on their availability
and frequent prescriptions for the management of wound infections.
|Antibiotic susceptibility testing
|Susceptibility testing was performed by Kirby-Bauer technique
 according to the criteria of the National Committee for Clinical
Laboratory Standards by disc diffusion method . From a pure culture
3-5 pure colonies of bacteria were taken and transferred in to a
tube containing 5 ml sterile nutrient broth (Oxoid) and mixed gently
until the turbidity of the suspension become adjusted to a McFarland
0.5 standard. Using sterile cotton swab, the bacteria were seeded evenly
over the entire surface of Mueller-Hinton agar (pH 7.2-7.4) (Oxoid).
The plates were left at room temperature to dry for 3-5 minutes and a
set of 15 antibiotic discs (Oxoid) with the recommended concentrations
were placed on the surface of a Muller-Hinton plate. Finally, the
plates were incubated at 37ºC for 24 hours. Diameters of growth inhibition
around the discs were measured and interpreted as sensitive,
intermediate or resistant as per the standard protocol . Reference
strains E. coli ATCC 25922 and S. aureus ATCC 25923 were tested as
controls according to the National Committee for Clinical Laboratory
Standards (NCCLS) .
|The data were entered and analyzed using SPSS soft ware version 16
package. Simple descriptive statistics were used to present the findings.
|Patients were enrolled after obtaining informed consent. The consents
of children were obtained through their parents and guardians.
Ethical clearance was obtained from the Research and Publication Office
of the University of Gondar. Patients with positive isolate were managed
following the routine patients’ management system of the hospital.
|A total of 1627 surgical procedures were undertaken from surgery
and gynaecology and obstetrics wards during the study period and
among this a total of 57 (3.5%) patients developed post operative surgical
wound infections. Among these 57 patients, 36 (63.2%) were females
and 21 (36.8%) were males. The ages of the study groups ranged from
7 to 75 years. Forty-three (38.7%) of bacterial pathogens were identified
from study participants below the age of 21 years old. Emergency
type of surgery represented 83 (74.8%) of the bacterial pathogens. Most
(64.9%) of the bacterial pathogens were recovered within 10 days after
operation. One hundred and one (91%) of the bacterial pathogens were
isolated from patients who had already a prophylaxis before surgery
was undertaken (Table 1).
|One hundred eleven bacteria were isolated and among these 70
(63.1%) and 41 (36.9) were from surgical and gynecology & obstetrics
wards, respectively. Gram negative and Gram positive bacteria represented
62 (55.9%) and 49 (44.1%), respectively. The most common isolates
was Escherichia coli (27/111, 24.3%) followed by S.aureus (26/111,
23.4%), coagulase negative Staphylocci (CoNS) (22/111, 19.8%) and
Enterobacter spp. (11/111, 9.9%) (Table 2).
|Overall bacterial isolates were seen at the surgical ward 70(63.1%)
were higher than gynaecology and obstetrics wards 41(36.9%) (X2=
15.2, P<0.001). The same was true for Enterobacter spp. 10 (90.9%)
(P=0.05) but S. aureus 15(57.7%) was significantly higher in gynaecology
and obstetrics ward (X2= 6.28, P< 0.012) (Table 2). Although higher
distribution of S. aureus 21 (80.8%), CoNS 14(63.6%), E. coli 17(63.0),
and Enterobacter spp. 10 (90.9%) were isolated from patients who undergo
emergency type of surgery, the difference was statistically non significant (Table 3). However, the over all bacterial isolates distribution
showed that majority of were from patients who undergone emergency
surgery 83 (74.8%) (X2= 54.5, P< 0.001) (Table 3).
|From all 111 pathogenic bacteria isolated; 44 (39.6%) were detected
from patients operated by residents in the Department of surgery and
35 (31.5%) were from patients operated by general practitioners in the
Department of Gynecology and Obstetrics (Table 4).
|The susceptibility patterns of bacteria isolated from surgical site
infection against 15 antimicrobial agents are presented in Table 5. Clindamycin,
doxycycline, erythromycin, methicillin and vancomycin were
tested only for Gram positive bacteria. High level of resistance was
observed against amoxicillin (95.5%), ampicillin (89.2%), TMP-SMX
(80.2%) and chloramphenicol (74.8%) (Table 5).
|Out of 27 isolates of E. coli, (100%), (96.3%), (92.6%), (88.9%),
(77.8%), (70.4%), (70.4%), (59.2%), (55.6%), and (29.6%) were resist ant to amoxicillin, ampicillin, chloramphenicol, TMP-SMX, tetracycline,
kanamycin, amikacin, gentamicin, ceftriaxone, and ciprofloxacin,
respectively. Among 11 isolates of Enterobacter spp., 11 (100%), 11
(90.9%) and 9 (81.8%) were resistant to amoxicillin, ampicillin and
TMP-SMX, respectively but 11 (100%) of them were sensitive to ciprofloxacin
|From 26 isolates of S. aureus, 9 (34.6%) were methicillin-resistant
but 26 (100%) and 23 (88.5%) of them were sensitive to vancomycin
and clindamycin, respectively. Among the 22 isolate of CoNS, 17
(77.3%) were methicillin-resistant and 20 (90.9%) were resistant for
doxycycline and chloramphenicol, while 1 (4.5%) of them were resistant
to vancomycin (Table 5).
|Distribution and frequency of bacterial isolates from hospital environment
are presented in Table 6. Bacterial pathogens were assessed
from 75 environmental sites showing an isolation rate of 41 (54.7%).
Coagulase negative Staphylococcus 41 (41.8%), S. aureus 19 (19.4%),
Pseudomonas. aeruginosa 16 (16.3%) and E.coli 10 (10.2%) were the
major isolates. Majority of bacteria 60 (61.2%) were isolated from operating
room from which gram positive bacteria accounts 44 (73.3%)
(Table 6). The resistance pattern of bacterial isolates from the environment
is indicted in Table 7. E. coli was resistant to ampicillin (90.0%),
amoxicillin (100.0%), tetracycline (70.0%), TMP-SMX (70.0%), and
kanamycin (60.0%). K. pneumonia was resistant to amikacin (80.0%),
gentamicin (80.0%), chloramphenicol (60.0%), and ceftriaxone (60.0%)
(Table 7). Citrobacter spp. and Serriata spp. were resistant to most antimicrobial
agents tested. Two (2.0%) MRSA isolates were obtained from
operating room samples which were culture positive.
|Successful management of patients with bacterial infection depends
on the identification of bacterial pathogens and on the selection
of an antibiotic effective against the organism in question. Antibiotics
are one of the pillars of modern medical care and play a major role
both as the prophylaxis and treatment of infectious diseases. The issue
of their availability, selection and proper use are of critical importance
to the global community .
|The result of this study showed that E. coli, S. aureus, CoNS and Enterobacter
spp. were highly associated with surgical wound infections.
Over all, more bacterial pathogens were more commonly isolated from
surgery ward. However, S. aureus was a major pathogen from patients
in Gynecology and Obstetrics wards and most commonly isolated bacteria
from patients who undergone emergency type of surgery which
may be due to surface contamination by this bacterium on the skin and
environment causing nosocomial infections. E. coli was most commonly
isolated from patients who undergone elective type of surgery which
can be due to contamination of wounds with patient’s endogenous flora
since E. coli and Coliforms is normal flora of gastro-intestinal tract
. According to CDC , S. aureus, CoNS and E. coli was the most
prevalent organism associated with surgical wound infections . The
current findings showed 55.9% and 44.1% of Gram negative and Gram
positive bacteria, respectively which is comparable with a study done
by Kollef  on surgical nosocomial infections which reported 50.3%
Gram-negative bacteria followed by Gram-positive bacteria 31.1%.
|From the total isolated bacteria, 91% were isolated from patients
who received antibiotic prophylaxis before surgery which is in agreement
with similar study reported from Addis Ababa [22,26,27]. The
present study showed relatively frequent isolation among patients who
received antibiotic prophylaxis and the most commonly prescribed
drug for prophylaxis was ampicillin alone or in combination with other antibiotics such as gentamicin and chloramphenicol. This shows some
antibiotics alone or in combination, requires periodic evaluation and
the establishment of antibiotics policy for prophylaxis and treatment
guidelines in the Ethiopian setting.
|The prevalence of bacterial contamination among all wards that
was done in line to isolation of pathogens from patients has not been
determined accurately yet and the current study was the first one in
our hospital. The fact that most Gram-positive bacteria, such as MRSA
contaminate the inanimate environment has been well established in
colonized or infected patients, personnel in the hospitals and the major
mechanism is done via the unwashed hands of health care workers
. Presence of bacteria was different from ward to ward based
on activities. For example S. aureus and CoNS were the predominant
isolate in operating rooms; whereas P. aeruginosa was the main isolate
in surgical ward and gynecology and obstetrics wards. Most of isolates
were from operating rooms, and many studies suggested that excellent
surgical technique is widely believed to reduce the risk of surgical site
|The susceptibility testing of S. aureus showed 9(34.6%) were resistant
to methicilin which is slightly lower than (38.56%) from Delhi 
and higher than (21.7%) from Chennai . All isolates of S. aureus
were sensitive to vancomycin which seems to be the only antimicrobial
agent which shows 100% sensitivity but 88.5% were sensitive to clindamycin.
Vancomycin remains the first choice of treatment for MRSA
and to preserve its value, vancomycin use should be limited to those
cases where there are clearly needed. Methicilin resistant CoNS have
become the predominant pathogen and increasing dramatically in hospitalized
patients [35,36]. According to the current study, methicilin
resistant CoNS were 77.3% which is in line with the study that reported
72.5% resistant strains . The present study also showed a single isolate
of CoNS resistant to vancomycin which is less from the isolates
found India . The emergence of vancomycin resistance in CoNS in
our teaching hospital may pose therapeutic problems, and therefore the
empirical antibiotic treatment of suspected infections caused by CoNS
should be prescribed according to antimicrobial susceptibility testing.
|The susceptibility testing of the gram-negative organisms; E. coli, P.
aeruginosa and P. mirabilis showed that higher resistant to amoxycillin,
ampicillin and ceftriaxone (β-lactam antibiotics). This high resistance
of organisms to β-lactam is not surprising, as these antibiotics are the
most commonly used antibiotics and resistant pattern were reported
from many studies [14,22,28,36,38] in Northwest Ethiopia. Similarly, a
study  in Europe reported the high resistance of E. coli and P. aeruginosa
isolated from surgical wounds.
|Majority of gram negative bacteria showed very high resistant to
chloramphenicol, tetracycline and TMP-SMX. The high rate of bacterial
resistance against chloramphenicol and TMP-SMX is likely due to
indiscriminate use of antibiotics both within hospital and outside as it
was described two decade ago in the study area .
|P. aeruginosa were resistant to kanamycin (100%) and gentamycin
(100%), while 33.3% were resistant to amikacin. This result is consistent
with the data obtained by Clark in USA . The isolation of aminoglycosides
resistant P. aeruginosa might be plasmid mediated type of
resistance leading to membrane impermeability. Regarding to E. coli
isolate, more than 70.4% were resistant to kanamycin and amikacin
while 59.2% were resistant to gentamycin. As many of the isolates were
susceptible to gentamycin, the continued use of the drug in surgical
conditions is thus indicated.
|From the quinolones, ciprofloxacin was highly active against all gram-negative organisms examined. From this investigation, ciprofloxacin
stands out to be the most effective antibiotic against pathogens
associated with surgical wound infections. However, the level
of resistance to ciprofloxacin is increasing from zero in the year 2000
 and 16.0% in the year of 2004  to 27% in the present study
(2010). Thus the frequency of single as well as multiple drug resistance
was alarmingly high. This might be a reflection of inappropriate use of
antimicrobials, lack of diagnostic laboratory services or unavailability
of guideline regarding the selection of drugs that enforce to empirical
|The higher counts of bacteria obtained from the patients in the
wards and from the hospital environment and are of great concern,
highlighting the quality of wards and operating rooms, and the need
for the attention of the hospital authorities to take necessary preventive
measures to maintain a sound and healthy atmosphere for the patients,
as well as the hospital personnel. There is a need to reinforce rational
antimicrobial use to limit emergence and spread of resistant and /or
continuing surveillance of bacterial antimicrobial sensitivity tests at local
level to guide empirical drug choice. The practice of aseptic technique
during and after surgery rather than overreliance on antibiotics
is necessary to reduce emergence and spread of resistant pathogens.
Future studies should be extended to include cultures under anaerobic
conditions to establish presence of other organisms that require such
environment for growth. It is also recommended that gentamicin, ciprofloxacin,
vancomycin and clindamycin be used in preference to ampicillin
and amoxycillin for treatment of post operative surgical site infections.
In this study, anaerobic bacterial, fungal and viral agents were not
investigated due to limited laboratory facilities and expertise.
|This research was funded by a grant from University of Gondar Research
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