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Asian Jr. of Microbiol. Biotech. Env. Sc. Vol. 11, No. (3) : 2009 : 501-505
© Global Science Publications
* Corresponding author
PATTERN OF BACTERIAL CONTAMINATION OF WOUNDS
AT THE FEDERAL MEDICAL CENTRE, YENAGOA;
BAYELSA STATE, NIGERIA
*N. FRANK–PETERSIDE AND T. SAMPSON
Department of Microbiology, Faculty of Science, University of Port Harcourt, P.M.B. 5323,
Port Harcourt, Nigeria
Key words: Bacteria, Wound Contamination, Yenagoa
Abstract–Bacteria associated with wound infection in Yenagoa, Nigeria and their antimicrobial
susceptibility profile was investigated using standard microbiological techniques. Of the 100 patients
investigated, 58 were men and 42 were women. Burn injuries, diabetic wounds, Post Operative Wound
Injuries and traumatic wounds were the categories of wound studied. One hundred and one isolates were
characterized and identified from the 100 patients. In the overall analysis, S. aureus had the highest
frequency (35.6%) E. coli – 26.7%, P. aureginosa – 21.8% and Proteus; 15.8%. The sensitivity result obtained
showed that 69.3% of the isolates were sensitive to colostrin sulphae (polymyxin E) and the highest level
of resistance was to Ampicillin – 26.7%. There was a high level of resistance. This study highlights the
predominant bacterial pathogens among the infected wounds in our locality.
INTRODUCTION
A wound is any breach of the skin surface whether
accidental or surgical, that provides an open door for
bacterial infection (Duerden et al, 1987). Wounds are
defined as endogenous or exogenous depending on
the sources of the contaminating/infecting organism.
The former is caused by organisms that have been
leading a commensal existence elsewhere in the patient’s
body while the later is caused by organisms from outside
the patient’s body (Mackie and McCarteny, 1989).
Initially, these wounds are free of infection. Infected
wound is defined as wounds harbouring bacteria that
exceed 105 colony forming units per gram
(Adegbehinge et al. 2007). A wound is also considered
infected if purulent material is observed without the
confirmation of a positive culture.
The severity of the complications depend on the
infecting pathogen and on the site of infection
(Shittu el al. 2002). There are four major categories of
wound, they are burns, diabetic and traumatic
including post operation wound injuries (POWI).
Burn injury is a major problem in many areas of the
world. Thermal injury destroys the physical skin
barrier that normally prevents the invasion of
microorganisms thus providing novel sites of
bacterial colonization, infection and clinical sepsis in
burn patients (Ahmed et al, 2006). A population of
those affected, survive the initial trauma and shock
but succumb to infection (Topley and Wilson, 1990).
Worldwide, diabetic lesions are a major medical,
social, and economic problem and are the leading
cause of hospitalization for patients with diabetics
(Gadepalli et al. 2006). Diabetic wounds in some cases
emerge as consequences of patient’s underlying
disease. Diabetic mellitus, especially in older patients
seem to predispose sufferers to several infectious
diseases. Tissue necrosis may result due to
inadequate peripheral circulation and peripheral
neuropathy. Surgical or postoperative sepsis is
described as an intentional trauma of the skin or other
tissues (Mackie and McCartney, 1989). This is
different from traumatized wounds in that the later
arises as a result of accidental damage of the skin or
other tissues, creating noble sites/opportunities for
microbial invasion (Mackie and McCarthey, 1989).
The widespread resistance of microorganisms to
antibiotics has greatly affected the management of
wounds. Knowledge of associated organisms will
help in the management of these wounds. The aim
of this study therefore is to analyze and elucidate the
pattern of microorganisms (bacterial) associated
with wound infections and to determine the
antibiotic sensitivity of the isolates.
502 PETERSIDE AND SAMPSON
MATERIALS AND METHODS
Study Centre – This study was carried out at the
Federal Medical Centre, (FMC) Yenagoa, Bayelsa
State, Nigeria between April and June, 2007.
Patient Selection – One hundred patients, (42
females and 58 males) participated in this study.
Their ages ranged from 4 to 60 years. The patients
presented at the different wards with the different
wounds. These wards include female surgical, male
surgical, orthopaedic, gynaecological, general/
medical, out patient department and the accident/
emergency ward. These samples were collected
from different categories of wound infections
including burn injuries, diabetic wounds, posto-
perative wounds and traumatic wounds (Table 1).
Sample Collection – Wounds were chosen for this
study by virtue of their purulent nature. The pus
was taken from each wound with a sterile swab and
transported to the laboratory in a sterile container.
Samples were cultured on nutrient, blood, chocolate
and MacConkey agars, aerobically at 370C for 24 hrs.
The organisms isolated were characterized and
identified using standard, bacteriological techniques
(Cheesbrough, 2000).
Susceptibility Testing – Anti-microbial susceptibility
testing was carried out using the multi-disc method.
A loopfull of an overnight broth culture of the test
organism was spread evenly over the nutrient-agar
plate. Antibiotic sensitivity multi-discs code 1788E
(Oxoid) were aseptically placed on the agar plate
and incubated at 370C for 24hrs. Zones of inhibition
were denoted by no growth and this measured the
sensitivity/resistance of the isolated organism to the
antibiotic (Table 2).
RESULTS
Of the 100 wound swabs collected, 20 were from
patients with burn injuries, 26 diabetic wound
infects, 20 post operative wound infection (POWI)
Table 1. The distribution of isolates in different wound infections.
Wound No. of Freq. No. of No. No. with Total no. Freq. of Freq. of Freq. of Freq. of
sample swabs (%) positive without mixed of sample Staph. of Pseudo Proteus E. coli
samples growth growth
Burn 20 20 18 2 - 18 5 (27.8%) 8 (44.4%) 1(5.6%) 4(22.2%)
Diabetic 26 26 25 1 1 26 9 (34.6%) 5 (19.2%) 2(7.7%) 10 (38.5%)
POWI 20 20 18 2 4 22 7 (31.8%) 5 (22.7%) 5 (22.7%) 5 (22.7%)
Trauma 34 34% 30 4 5 35 15 (42.9%) 4 (11.4%) 8 (22.8%) 8 (22.8%)
Total 100 100 91 9 10 101 36(35.7%) 22(21.8%) 16(15.8%) 27(26.7%)
Table 2. Antimicrobial Concentrations
S.N. Antimicrobial Drug Concentration (Ug)
1. Cotrimazole (Cot) 25
2. Gentamycin (Gen) 10
3. Tetracycline (Tet 30
4 Streptomycin (Str) 10
5. Chloramphenical (Chl) 10
6. Ampicillin (Amp) 10
7. Cloxacillin (Cxl) 5
8. Erythromycin (Ery) 5
9. Penicillin (Pen) 1
10. Colistin Sulphate (Col) 10
and 34, traumatic wound injuries (Table 1).
Ninety one (91%) percent of the samples had
growth while nine (9%) had no growth. Ten samples
(10%) had mixed growth (Table 1). Table 3 shows the
types and frequency of isolates from the infected
wounds. S. aureus was the most commonly isolated
pathogens with a total number of 36 out of 101
(35.6%). This was followed by E. coli with a total of
27 (26.7%). Pseudomonas sp had a total of 22 (21.8%)
and Proteus spp 16 (15.8%). The distribution of the
different isolates in the different categories of wound
is also recorded (Fig. 1). It reveals that for all cases of
burn injuries, Pseudomonas sp was the leading
organism with a frequency of 44.4%, S. aureus 27.8%,
E. coli and Proteus spp 22.2% and 5.6% respectively.
Ten (10%) percent of these samples had no growth.
Of the diabetic wounds, E.coli had the highest
frequency with a percentage of 38.5%, S. aureus
34.6%, Pseudomonas and Proteus 19.2% and 7.7%
respectively. POWI bacterial distribution is as
follows: S. auresu 31.8% and Pseudomonas sp Proteins
and E.coli 22.7% each. For traumatic would
infections, Staphylococcus had 42.9%, Proteus and
E.coli had 22.8% each and Pseudomonas had a
frequency of 11.4%. Of the total of 34 traumatic
wound patients four had no growth.
The drug sensitivity pattern differed for the
different isolates. Sensitivity or resistance of isolates
Pattern of Bacterial Contamination of Wounds at the Federal Medical Centre, Yenagoa; Bayelsa State, Nigeria 503
was determined by measuring the zone of inhibition
(clearance) as well as their degree of sensitivity
(Table 4).
Table 4. The Frequency, sensitivity and resistance pattern of the isolates to different antibiotics
S.N. Antibiotics Sensitive % sensitivity No. Resistant % Resistance Total
1. Cot 32 31.7% 69 68.3 101
2. Gen 49 48.5% 52 51.5 101
3. Tet 37 36.6 64 63.7 101
4. Str 35 34.7 66 65.3 101
5. Chl 54 53.5 47 46.5 101
6. Amp 27 26.7 74 73.3 101
7. Cxl 43 42.6 58 57.4 101
8. Ery 43 42.6 58 57.4 101
9. Pen 31 30.7 70 69.3 101
10. Col 70 69.3 31 30.7 101
Table 3. Types and frequency of isolates from infected
wounds
Organism No. of times Percentage
isolated isolated (%)
Staphylococcus aureus 36 35.7
Pseudomonas sp 22 21.8
Escherichia coli 27 26.7
Proteus 16 15.8
Total 101 100%
Of the isolates, 69.3% were susceptible to colistin
suphate (polymyxine E) and 30.7% were resistant to
this antimicrobial agent. The highest level of
resistance by the isolates was to ampicillin (73.3%).
The susceptibility of the isolates to the other
antimicrobial agents (antibiotics) was in the
decreasing order as shown below: Chl. (53.5%), Gen
(48.5%), Cxl and Ery (42.6% each), Tel (36.6%) Str
(34.7%), Cot (31. 7%) and Pen (30.7%). (Fig. 2).
KEY
Staphylococcus aureus
Pseudomonas sp
Proteus
E. coli
More than one isolate having the same distribution
Fig. 1.Bar chart showing the distribution of the various
isolates in wound samples
Sensitive (Susceptible)
Resistant
Fig. 2. Bar chart of Sensitivity pattern of isolates.
DISCUSSION/CONCLUSION
Wounds are initially sterile, getting infected with the
introduction of microorganisms: bacteria. These may
be endogenous or exogenous. Bacteria associated
with wounds have been reported severally at
504 PETERSIDE AND SAMPSON
different locations e.g. India, Pakistan, Ile-ife and
Ekpoma (Shittu et al. 2002; Emele, et al 99,
Adegbehingbe et al. 2007, Ahmad, et al 2006,
Gadepalli et al. 2006). The paucity of information on
the subject matter at the FMC. Yenagoa, informed
this study. This study has also become necessary due
to the worldwide problem presented by wound
management. .
This situation is not only a problem to the doctors
but to all who have a stake in the care of wound
patients. The patient is traumatized by the situation
and there is increase in cost of wound management.
In this study, 91% of the total wound samples had
positive growth. These support the study of Braide
1985 where a prevalence rate of 96% was reported in
the study population. The other 9% in this study
showed no growth. This might be as a result of prior
administration of antibiotics or as a result of the
presence of strict anaerobes which would not be
characterized/identified due to the absence of
facilities for anaerobiosis. Onoche and Adedeji, 2004
also reported the absence of facilities for
anaerobiosis, in Nigeria. The overall high frequency
of S. aureus (35.7%) as the commonest pathogen
associated with these wounds confirm the study of
Emele et al. 1999 and Braide, 1987 which reported
39% and 54.2% prevalence, respectively. Shittu et al.
identified nasal carriage of S. aureus as an important
risk factor for the acqiustion of S. aures infection.
They went on to conclude that this may depend on
an array of factors that may be environment related
or patient related. It is postulated that S. aureus
enters through the nose and it is then disseminated
via hand carriage which is then disseminated to
other body sites where infection can occur within
breaks in the skin. This study also showed the
different pathogens that preferentially infected the
different wound types. Burn injuries were most
frequently contaminated by Pseudomonas sp (44.4%).
This is consistent with the findings in other studies
e.g. Ahmed et al. 2006 and Sylvester 1986 who
reported a frequency of 27.3% and 57% respectively.
This might be as a result of the resistance of this
organism to antiseptic agents and many antibiotics.
This therefore makes it difficult to keep bacteria out
of burns and to eradicate them, once they get in.
Ahmad et al 2006 attributed the high level of
Pseudomonas sp in their study to a few reasons (i) the
hospital had no special burn units therefore burn
patients were managed in same wards as others (ii)
beds were shared with general surgery and urology
hence cross-infection was beyond control. The other
microbial agents identified could have been
controlled by antibiotics leaving the less tractable
Pseudomonas aeruginosa as the commonest cause of
serious infections of burn (Duerden et al. 1987).
Diabetic wound infection showed a different
profile. Here, E.col (a lactose fermentor) appeared as
the commonest etiological agent with a prevalence
of 38.5%. Boyd and Bryant 91; reported that insulin
dependent patients with diabetes mellitus suffer
more frequently from severe, Staphylococcus sp
infection than non diabetics. The result in this study
may be due to the excessive amount of glucose
secretions in diabetic wound cases (Duerden et al.
87). Most of the patients in this study are middle
aged and above. Probably, they are cases of type 11
or non-insulin dependent diabetes. This is because
type 1 or insulin dependent diabetes begin before
the age of 20yrs (Berg et al 2002). POWI had S. aureus
as the most frequently isolated pathogen, 31.8%. The
other were uniformly shared by the gram negative
microbes, Pseudomonas, Proteus and E. coli; 22.7%
each. Onche and Adedeji, 04 working on post
operative wound infection in inplants identified S.
aureus as the most commonly isolated
microorganism.
The trauma wound infection is similar to POWI
with S. aureaus having the highest frequency
occurrence of 42.90% followed by Proteus and E. coli
with 22.8% each and Pseudomonas 11.4%. This result
is consistent with what obtained in the studies of
Adegbebingbe, et al 2007. This is slightly different
from a study in a developed country by Gadepalli et
al 06. This study showed a very interesting fact i.e.
wound swabs collected a day after injury was
sustained had no bacterial growth.
The wounding agents included pricks, motor
accidents, gunshots etc. Traumatic wounds could
result in localized or systemic infections. Infective
organisms are either derived from an exogenous
source or endogenous i.e. microflora of patient. It is
therefore important to manage wound cases and
operational procedures carefully to reduce the
incidence of infection.
The antimicrobial susceptibility result of this
work showed that Colistin (Polymyxin E) had the
highest level of inhibitory effect on the wound
isolates. A percentage of the isolates, (69.3) were
susceptible to colistin as against 30.7% level of
resistance. In this study, the isolated organisms
showed the least susceptibility i.e. highest level of
resistance to Ampicillin (26.7% sensitivity and 73.3%
resistance). This high level of resistance by isolates to
Pattern of Bacterial Contamination of Wounds at the Federal Medical Centre, Yenagoa; Bayelsa State, Nigeria 505
Ampicillin, may be traced to the fact that many
organisms quickly form resistance to Ampicillin
(Girdwood 76). In general, a relatively low level of
susceptibility was recorded. A possible reason is that
most of the isolates are gram negative rods with the
ability to produce inactivating enzymes (Beta-
lacternase for example) which render them resistant
to antibiotics. Saureus has been reported by other
studies to have a high level of multi-drug resistance
as well as methicillin resistance. This may also be a
factor responsible for the low level of susceptibility
(Gadepalli et al. 06). Wound management remains a
recurring challenging condition, especially in the
developing countries.
In the period of study it was observed that
traumatic injuries had the highest frequency. This
might not be unconnected to the level of insecurity
during this period in the south south region of
Nigeria. Early diagnosis and treatment are
recommended in the management of wounds.
Asceptic surgical techniques are advised. Antibiotic
sensitivity of the isolates should be ascertained for
more effective management.
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