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Journal of Orthopaedic Surgery 2008;16(2):175-8
The use of qualitative cultures for detecting
infection in open tibial fractures
A D’Souza, N Rajagopalan, RS Amaravati
Department of Orthopaedics, St John’s Medical College Hospital, Bangalore, India
ABSTRACT
Purpose. To determine the role of qualitative
cultures for detecting infection in open tibial
fractures.
Methods. From January 2003 to December 2004, 95
men and 13 women (mean age, 34 years) with open
tibial fractures in one or both limbs and without any
other sites of infection were prospectively studied.
Patients who had been treated with intravenous
or oral antibiotics before presentation and/or had
undergone debridement or other surgery were
excluded.
Results. Infection was not correlated with age,
sex, interval from injury to debridement, and
cause of fracture. The association of infection
with predebridement cultures was stronger (odds
ratio=12.5) than that with postdebridement cultures
(odds ratio=4.7).
Conclusion. Pre- and post-debridement cultures have
a role in detecting infection in open tibial fractures.
For detecting infection, predebridement cultures have
better sensitivity, while postdebridement cultures
have better specificity.
Key words: debridement; fractures, open; infection; tibial
fractures
INTRODUCTION
Treatment for open fractures is a challenge. It involves
early wound debridement with copious irrigation,
prompt initiation of intravenous antibiotics, good
coverage for the bone and soft tissue, as well as
adequate, rigid stabilisation.1–10
We aimed to determine the role of qualitative
cultures (both pre- and post-debridement) in detecting
infections in open tibial fractures, and to highlight any
correlation between infections and other variables
(age, sex, interval to debridement, cause of fracture,
and the Gustilo classification).
Address correspondence and reprint requests to: Dr Rajkumar S Amaravati, Department of Orthopaedics, St John’s Medical
College Hospital, Bangalore, 560 034, India. E-mail: [email protected]
Journal of Orthopaedic Surgery
176 A D’Souza et al.
MATERIALS AND METHODS
From January 2003 to December 2004, 95 men and
13 women (mean age, 34 years) with open tibial
fractures in one or both limbs and without any
other sites of infection were prospectively studied.
Patients who had been treated with intravenous
or oral antibiotics before presentation and/or had
undergone debridement or other surgery were
excluded.
All patients were clinically examined and
their medical history recorded. Their open
fractures were classified based on the Gustilo
classification.10 Under strict aseptic precautions,
the wound was cleaned with saline soaked gauze.
Swabs were taken before and after a standard
debridement procedure, and necessary stabilisation
performed. Intravenous cefazolin, gentamicin,
and metronidazole were prescribed for gradeI and -II open fractures. For grade-III fractures,
the cefoperazone/sulbactam combination as well
as amikacin and metronidazole were prescribed.
The wound was inspected for signs of infection.
If infected, a repeat culture was obtained and
appropriate antibiotics started. If there was
no evidence of infection, the antibiotics were
discontinued after the third day. 6
Data were tabulated and analysed using Chi
squared and Fisher’s exact tests to determine any
correlation between infection and other parameters.
Diagnostic statistics were used to derive predictive
values for pre- and post-debridement cultures
showing infection.
RESULTS
Infection did not yield a significant correlation with
age (p>0.05), sex (p=0.48), and interval from injury
to debridement (p=0.756) by Chi squared test. Nor
was there a significant correlation with the cause
of fracture (p=0.851, Chi squared test), because of
small numbers and unequal distribution of cases
in different categories, although ‘assault’ and ‘fall
from height’ showed a positive trend (Table 1).
The association of infection with predebridement
cultures was stronger (odds ratio=12.5) than that
with postdebridement cultures (odds ratio=4.7)
[Table 2]. The grade of fracture correlated with
infection (p=0.39, Chi squared test, Table 3). The most
common organisms cultured were non-fermenting
Gram-negative bacilli, followed by pseudomonas
and mixed growths. Their antibiotic sensitivities are
shown in Table 4.
Table 1
Association between infection and the cause of injury*
Cause of injury
Assault
Blast
Fall from height
Industrial
Road traffic accident
Total
No. (%) of infection
Yes
No
1 (50)
1 (50)
4 (67)
6 (55)
39 (45)
51 (47)
1 (50)
1 (50)
2 (33)
5 (45)
48 (55)
57 (53)
* p=0.851, Chi squared test
Table 2
Pre- and post-debridement cultures for diagnosing infection
Diagnostic statistics
Sensitivity (%)
Specificity (%)
Odds ratio
Accuracy (%)
Kappa co-efficient
p Value
Debridement
Pre
Post
83
71
12.5
74
0.42
<0.00
42
87
4.7
77
0.29
0.002
Table 3
Association between infection and the grade of fracture*
Gustilo classification
Grade I
Grade II
Grade IIIA
Grade IIIB
Grade IIIC
Total
No. (%) of infection
Yes
No
3 (17)
17 (49)
4 (40)
18 (62)
9 (56)
51 (47)
15 (83)
18 (51)
6 (60)
11 (38)
7 (44)
57 (53)
* p=0.39, Chi squared test
DISCUSSION
Infection is the main complications following open
fractures, and may result in limb loss, sepsis, and
death. Despite improvements in open fracture
management, late infection continues to occur in 2 to
25% of all open fractures.4,9,11,12
Emergency wound debridement, copious
irrigation, and intravenous antibiotics use are
mandatory for avoiding infection.1–3,5–7,9,10,13 The
use of qualitative culture swabs to detect infection
Vol. 16 No. 2, August 2008
Qualitative cultures in detecting infection in open tibial fractures 177
Table 4
Infective organisms and corresponding antibiotic sensitivity
Organism
No. of
infections
Debridement
Pre
Post
Antibiotic sensitivity
Non-fermenting Gramnegative bacteria
Pseudomonas
Enterococcus
Enterobacter
Escherichia coli
15
18
6
14
3
4
13
8
4
4
4
3
3
5
Methicillin-resistant
Staphylococcus aureus
Klebsiella
Staphylococcus aureus
Mixed growth
1
-
-
Cefoperazone sulbactam>gentamicin/ciprofloxacin>amikacin>
ceftazidime
Amikacin>ceftazidime>ciprofloxacin>cefoperazone> gentamicin
Gentamicin>vancomycin>penicillin
Amikacin>gentamicin>ciprofloxacin>ceftazidime/cefotaxime
Amikacin>gentamicin/ciprofloxacin/ceftazidime>cefotaxime/
cefuroxime
Vancomycin>chloramphenicol>teicoplanin>ciprofloxacin
1
13
2
3
9
3
3
Cefoperazone sulbactam>amikacin>gentamicin & netilimycin
Cloxacillin/methicillin
-
remains controversial.4,14–19 Some authors consider
predictability of infection from pre- and postdebridement wound cultures to be poor; if used at
all, postdebridement samples are regarded as having
better prognostic value.15 Others consider both
quantitative smears and cultures are of predictive
value in the management of traumatic wounds when
taken immediately,16 or when the bacterial load
exceeds 105 colonies/gram in skin tissue, or when
any level of bacterial load is present in muscle.17
Some authors found no correlation between the
interval elapsing from fracture to debridement and
quantitative bacterial count levels.19 Others suggested
that postdebridement quantitative bacterial counts are
more predictive of infection.18 35% of initial cultures do
not yield any bacterial growth; if a culture is positive
and the wound is infected, then the organism isolated
has the highest probability of being the cause.20
However, another study found little correlation
between initial quantitative bacterial counts and
subsequent sepsis.4 In our series, predebridement
cultures were found to have high sensitivity in
detecting infection; if infection was present, then
the chance of detecting the offending organism was
almost 84%. Invasive procedures such as repeated
debridement and multiple antibiotic therapy were
performed, based mainly on the clinical status of the
wound and patient’s condition (not positive culture).
Postdebridement cultures yielded good specificity; if
an open fracture wound did not display any evidence
of infection, then no organism was isolated in almost
87% of cases. Thus, our findings are contrary to other
studies that have suggested that culture swabs do not
have a role in detecting infections.4,15,19
Infection rates correlate with the extent of soft
tissue damage and the classification of the open
wound.10,21 The infection rate for grade-I open fractures
is reportedly 0 to 2%. For grade-II fractures it is 2 to 7%.
For grade-III fractures the overall rate is 10 to 25%,10
being 7% in grade-IIIA, 10 to 50% in grade-IIIB, and
25 to 50% in grade-IIIC fractures.4,9–11,20 The beneficial
effects of antibiotics for patients with open fractures
have been well documented.12,15,16 Infections occur
in 13.9% of open fractures in which management is
exclusively surgical (without antibiotics),22 compared
to 2.3% in open fractures treated with cephalothin
and surgical debridement. The chosen antimicrobial
should provide Gram-positive and -negative
cover.9,13,21 The duration of antibiotic cover in open
fracture management remains controversial and
varies from one to 10 days.6,10
The microbial flora of open fractures has been
changing since the late 70s. Coagulase-positive
Staphylococcus aureus was predominant in the 70s and
early 80s.13,22 Infections were also caused by penicillinresistant coagulase-positive bacteria,8,10,22 Gramnegative bacteria and mixed growths (for which use
of combined antibiotic therapy was needed).4,9,10
We recommend that all antibiotic usage be
tailored according to the type of fracture, level
of contamination, soft tissue status, and most
importantly the prevailing infection and culture
sensitivity patterns in the hospital.
CONCLUSION
Pre- and post-debridement cultures have a role in
detecting infection in open fractures. Predebridement
cultures have better sensitivity, while postdebridement
178 A D’Souza et al.
cultures have better specificity for detecting infection.
There is no correlation between the development of
infection in open fractures with age, sex, and the
interval between injury and debridement.
Journal of Orthopaedic Surgery
ACKNOWLEDGEMENT
We thank Ms BS Rathna for her technical assistance in
writing this manuscript.
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