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Objective: Knowledge of wound bioburden can guide selection of
therapies, for example, the use of negative pressure wound therapy
(NPWT) devices with instillation in a heavily contaminated wound.
Wound and periwound bacteria can be visualised in real-time using a
novel, non-contact, handheld fluorescence imaging device that emits
a safe violet light. This device was used to monitor bacterial burden
in patients undergoing NPWT.
Methods: Diverse wounds undergoing NPWT were imaged for
bacterial (red or cyan) fluorescence as part of routine
wound assessments.
Results: We assessed 11 wounds undergoing NPWT. Bacterial
fluorescence was detected under sealed, optically-transparent
(routine) adhesive before dressing changes, on foam dressings, within
the wound bed, and on periwound tissues. Bacterial visualisation in
real-time helped to guide: (1) bioburden-based, personalised treatment
regimens, (2) clinician selection of NPWT, with or without instillation of
wound cleansers, and (3) the extent and location of wound cleaning
during dressing changes. The ability to visualise bacteria before
removal of dressings led to expedited dressing changes when heavy
bioburden was detected and postponement of dressing changes for
24 hours when red fluorescence was not observed, avoiding
unnecessary disturbance of the wound bed.
Conclusion: Fluorescence imaging of bacteria prompted and helped
guide the timing of dressing changes, the extent of wound cleaning,
and selection of the appropriate and most cost-effective NPWT
(standard versus instillation). These results highlight the capability of
bacterial fluorescence imaging to provide invaluable real-time
information on a wound’s bioburden, contributing to clinician
treatment decisions in cases where bacterial contamination could
impede wound healing.
Declaration of interest: The author has no conflict of interest
to declare.
A
n optimal wound care treatment plan
requires initial patient and wound
assessment and comprehensive
monitoring to re-evaluate wound status,
bioburden and effectiveness of the chosen
wound therapies. Negative pressure wound therapy
(NPWT) has been established as an advanced therapy
which improves wound closure rates by increasing local
blood flow and formulation of granulation tissue.1–3
Evidence to date suggests that bioburden control is
not a clear benefit of standard NPWT.4–7 Some studies
report NPWT suppression of non-fermentative Gramnegative
bacilli, for example, Pseudomonas spp., but this
is associated with enhanced growth of Gram-positive
bacterial species.8 NPWT with instillation (NPWTi) can
be used on challenging wounds which would benefit
from a combination of vacuum-assisted closure and
constant irrigation with topical wound solutions, such
as wound cleansers, antiseptics or saline. Most studies
show that this therapy removes bioburden and other
contaminants without manual intervention
or disruption.4,7,8
bacterial fluorescence imaging  ● MolecuLight ●  negative pressure wound therapy  ●  wound infection  ●  wounds
The diverse wounds on which experts suggest beneficial
use of NPWTi includes chronically infected or
contaminated wounds, wounds in patients with diabetes,
traumatic wounds, those with exposed bone or underlying
osteomyelitis and painful wounds.9 Management of
bioburden in these wounds is critical and underscores
why NPWTi of wound cleansers could be successful, when
used appropriately.1,10 However, treatment with standard
NPWT, a lower cost treatment option,11 is common
practice for many of these wound types, often once
bioburden has been controlled. Ultimately, treatment
selection must be customised on a wound-by-wound basis
by the treating clinician after thorough assessment.12
Knowledge of when to select NPWTi over standard
NPWT, how long to use NPWTi, the ideal length of time
between dressing changes and how to optimise these
resources has been hampered for several reasons:
●● NPWTi is the more novel therapy, therefore evidence
is continuously evolving as large clinical studies and
retrospective reviews enter the literature1,9,13
●● Monitoring of bioburden status via sampling or via
clinical signs and symptoms requires removal of the
adhesive and NPWT foam, i.e a complete dressing
change, which is costly in terms of both materials and
clinician time14,15
●● Wound sampling is further associated with delays
while awaiting microbiological results.
Fluorescence imaging guided dressing
change frequency during negative
pressure wound therapy: a case series
*Rose Raizman,1 RN-EC, NSWOC, MSc, Adjunct Lecturer*
*Corresponding author email: rraizman@shn.ca
1  Lawrence S. Bloomberg Faculty of Nursing, University of Toronto and Department of
Professional Practice, Scarborough Health Network.
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To address the latter concerns, wounds undergoing
NPWT were assessed using a handheld bacterial
fluorescence imaging device (MolecuLight Inc, Toronto,
Canada) that visualises bacterial fluorescence in
real-time.
Bacterial fluorescence imaging is a method to quickly
visualise and monitor bacterial presence in and around
wounds at the bedside.16,17 This is a safe, non-contact
and contrast agent-free method to visualise bacteria in
real-time using a portable handheld device. The device
emits a violet light (405nm), which excites the tissue
and bacteria within and around a wound. This causes
tissues to fluoresce green while bacteria fluoresce either
red (most bacteria species) or cyan (Pseudomonas
aeruginosa), enabling immediate bacterial
localisation.16,17 A clinical trial demonstrated that
bacterial (red) fluorescence positively predicted the
presence of bacteria at loads of clinical concern, ≥104
colony forming units (CFU)/g or moderate/heavy
growth, in 100% of the 60 studied wounds.17 This and
other clinical trials have demonstrated the bacterial
fluorescence imaging device’s ability to detect the most
common wound pathogens, including Staphylococcus
aureus, Escherichia coli, Klebsiella pneumonia and
Pseudomonas aeruginosa.16–19 The clinical use of the
bacterial fluorescence imaging device has previously
been established for chronic wounds,16,18,20,21 burn and
trauma wounds22,23 and surgical wounds.24,25 However,
its specific usage in conjunction with NPWT has not
been described. This case series reports the use of
bacterial fluorescence imaging in conjunction with
routine wound assessments for clinical signs and
symptoms of infection. Real-time information on
bioburden was obtained from fluorescence images,
including the presence or absence of bacterial
fluorescence, its location and observed changes over
time. This information significantly impacted treatment
decisions and was used to improve resource use.
Methods
Patients
This case series includes both chronic and surgical
wounds, diverse wound locations and a variety of
negative pressure systems. Informed written consent
was obtained from each patient for publication of their
wound images and anonymous case information in a
scientific publication format. Over a three-month
period, all Scarborough Rouge Hospital inpatients and
wound care clinic outpatients receiving NPWT from the
wound care specialist (author) performing this study
were eligible for inclusion.
Wound care patients not undergoing NPWT and any
patients unable or unwilling to provide consent were
ineligible for this study. All wounds were assessed by
the wound care clinician as per standard of care for
clinical signs and symptoms of infection.26 The
standard of care was based on severity and location of
wound and included cleansing with appropriate
antiseptic solution, either povidone iodine or
chlorhexidine, and irrigation with antiseptic (solutions
such as hypochlorus acid compound from the
pharmacy or commercially available) during
installation when appropriate and dressing changes
between 2–4 days. If dressing changes were less
frequent than every two days, imaging was performed
daily. Wound assessments by this clinician also
routinely included bacterial fluorescence imaging to
provide information on bacterial presence and
location. Hospital inpatients also received wound care
from additional attending wound care clinicians who
do not incorporate fluorescence imaging into their
wound assessments.
Imaging procedure
Fluorescence images, obtained in real-time, were used
to determine if and where significant bacterial loads
(≥104CFU/g)17 were present in wounds. Images were
taken during routine wound assessments, most often at
scheduled NPWT dressing changes or immediately
before initiation of NPWT. Images were acquired using
the MolecuLight i:X Imaging Device (MolecuLight Inc,
Toronto, Canada), as previously described in detail.17
Standard images of the wound were acquired under
traditional room lighting conditions, after which the
room was made dark, the violet excitation light from
the device was turned on and fluorescence images were
acquired. When excited by the imaging device’s 405nm
violet light, tissues fluoresce green while the majority
of bacterial pathogens fluoresce red (for example,
Staphylococcus aureus, Escherichia coli, Enterobacter spp.,
Klebsiella spp., Proteus spp.). Pseudomonas aeruginosa
uniquely fluoresce cyan in colour. Specialised optical
filters reveal these red, green and cyan signals in realtime
on the device’s display screen.16–18 A range finder
on the device was used to ensure all images were taken
at the optimal imaging distance (8–12cm) and a light
sensor on the device indicated when the room was dark
enough for fluorescence images to be acquired. If
sufficient darkness could not be achieved by turning off
room lighting, for example in rooms with windows, a
disposable dark drape attachment (MolecuLight Inc)
was used to provide the required darkness. The dark
drape attaches onto the device and blocks all light,
establishing an area of complete darkness over the
wound for image acquisition in fluorescence mode.
This imaging device was used per its intended use for
visualising bacteria within and around wounds. Images
acquired before NPWT dressing changes were taken
through the sealed, optically transparent adhesives
routinely used with NPWT. If a dressing change
occurred, additional images were acquired after removal
of all adhesives. Wounds exhibiting red fluorescence
were considered to have clinically concerning bacterial
loads. Any changes to wound management as a result
of bacterial fluorescence images were noted.
Results
Patients ranged in age from 18 to 87 years. We assessed
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11 wounds undergoing NPWT (10 patients in total)
were imaged for bacterial fluorescence as part of this
study. A beneficial effect of bacterial fluorescence images
on wound management was noted for all 11 wounds;
these benefits are described in Table 1 along with
information on wound type and any available
microbiological findings. Of the 11 wounds, eight were
positive for bacterial fluorescence and three were
negative for bacterial fluorescence. Wound swabs were
taken in six of the 11 wounds and in all six cases culture
results confirmed the bacterial positive or bacterial
negative imaging findings. Culture results from
fluorescence-positive wounds confirmed the presence of
moderate or heavy growth of numerous common
wound pathogens (Escherichia coli, Enterococcus faecalis,
Staphylococcus aureus, Diptheroid bacillis, Klebsiella
pneumoniae, Bacteroides fragilis, Morganella morganii,
Streptococcus agalactiae, mixed anaerobes).
Images in this study visualised bacteria that had been
drawn out from the wound bed and tissues and brought
Table 1. Summary of cases in which bacterial fluorescence imaging was beneficially used in combination with NPWT
Patient Wound type Time of
imaging
Bacterial
fluorescence?
Microbiological swab
confirmation?
FL-guided treatment change Effect on short
term wound
care cost
1 Pressure ulcer
(sacral)
At numerous
dressing
changes
Positive Heavy growth of
Escherichia coli,
Enterococcus faecalis,
Staphylococcus aureus;
light growth Proteus
vulgaris
(1) Prompted early dressing
changes
(2) Prompted switch to NPWTi
(3) Demonstrated effectiveness of
instillation
(4) Guided targeted cleaning at
dressing changes
Increase
2 Necrotising
fasciitis
(pectoral)
After 2, 4 and 6
weeks of NPWT
+ instillation
Negative Negative for bacteria Negative images led to a 24-hour
postponement of dressing change,
leaving wound bed undisturbed
Decrease
3 Surgical wound
(abdominal)
Before initiating
NPWT
Positive N/A Images confirming bacterial
burden prompted selection of
NPWT + instillation, rather than
standard NPWT
Increase
4 Necrotising
fasciitis
(scrotum)
At scheduled
dressing
changes
Positive Heavy growth mixed
anaerobes; light growth
coagulase negative
Staphylococci
(1) Confirmed continued presence
of bacterial burden, (2) Facilitated
education on necessity of dressing
change in patient refusing dressing
change due to fear of pain
No change
5 Surgical wound
(appendectomy
abscess)
At scheduled
dressing
change
Positive Moderate growth
Escherichia coli, light
growth Propionibacterium
acnes, very light growth
Staphylococcus aureus
Guided additional, targeted
cleaning during dressing change
Increase
6 Two pressure
ulcers
(sacral)
At scheduled
dressing
change
Wound 1:
positive
Wound 2:
negative
N/A (1) Wound positive for bacterial
fluorescence had scheduled
dressing change, (2) wound
negative for bacterial fluorescence
was left undisturbed for another 24
hours
Decrease
7 Breast abscess At scheduled
dressing
change
Positive Heavy growth Diptheroid
bacillis, moderate growth
Klebsiella pneumoniae
(1) Led to maintenance on NPWTi
(2) Guided additional cleaning
during dressing change
Increase
8 Surgical wound
(pilonidal sinus)
At scheduled
dressing
change
Positive Heavy growth
Bacteroides fragilis,
Morganella morganii,
Streptococcus agalactiae
(1) Guided additional, targeted
cleaning during dressing change
and (2) Facilitated patient
education
Increase
9 Venous leg ulcer
(calf)
At scheduled
dressing
change
Negative N/A Clinician confidence to discontinue
use of antimicrobials and continue
NPWT with regular gauze
Decrease
10 Surgical wound
(abdominoplasty)
At scheduled
dressing
change
Positive N/A Guided additional (1) targeted
cleaning, (2) prompted earlier
dressing changes, (3) prompted
use of silver product in
combination with NPWT
Increase
FL—fluorescence; NPWT—negative pressure wound therapy; NPWTi—NPWT with instillation
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into the foam and/or tubing through negative pressure
application to the wound. The compelling images of
this process demonstrated that NPWT is effective in
removing bacterial burden from the wound bed, at least
to some extent (Fig 1). In the absence of this drawing
out, the bacteria presumably would have remained
within the wound tissues, likely delaying healing.
Beneficial effects of bacterial fluorescence imaging on
treatment plans were observed for management of both
chronic wounds, for example, pressure ulcers (PU),
venous leg ulcers (VLU) and of a variety of surgical
wounds. Instantaneous information on the absence or
presence and location of bacterial (red) fluorescence
within the wound and periwound tissue guided
numerous treatment decisions. For example, dressing
change timing was influenced in five study wounds.
Dressing changes were postponed for 24 hours in two
inpatient wounds negative for bacterial fluorescence,
leaving those wounds to heal without disturbance and
saving clinician time and resources, and were expedited
in cases where bacterial burden was clearly present.
Additional wound management strategies employed as
a result of images positive for bacterial fluorescence
included:
●● Prompted initiation of or maintenance on NPWTi
with wound cleansers (3/10 patients)
●● Prompted use of antimicrobial products (for example,
silver containing products and polyhexamethylene
biguanide gauze) in conjunction with NPWT (1/10
patients)
●● Led to additional, targeted cleaning during dressing
changes (5/10 patients)
●● Facilitated patient education (2/10 patients).
The simple colours on images (green–tissue, red–
bacterial) also facilitated patient education on the
necessity of their dressing changes or on the necessity
of improved patient hygiene. Additional details can be
found in Table 1. Note that treatment decisions were
made after evaluation of fluorescence information as
well as standard assessment for clinical signs and
symptoms, patient condition and history and before
microbiological findings (when applicable). Treatment
decisions were based on clinician’s judgement of this
combined information.
This study demonstrated that 9/10 patients were
likely to have received inappropriately triaged care
without the fluorescence information (Table  1). We
observed that 60% of patients were to be undertreated;
these patients therefore benefited from increased
resources in the short term, while 30% of patients were
being overtreated and fluorescence information
prompted a decrease in resource use. Based on
microbiological confirmation (when available) and
wound progress in these patients, triaging resources
elsewhere did not compromise wound progress.
We will discuss two cases in detail (patients 1 and 2
in Table 1), one PU positive for bacterial fluorescence
and one healing necrotising myelitis wound negative
for bacterial fluorescence. These wounds were imaged at
Fig 1. Detection of bacterial (red) fluorescence in a deep sacral pressure
ulcer that had recently begun NPWT. (a–b) Fluorescence images acquired
in week two, three days after initiation of NPWT with instillation (NPWTi),
detected bacterial (red) fluorescence under sealed, optically-transparent
(routine) adhesive before dressing changes (a), within the wound bed and
on periwound tissues (b). Regions of red fluorescence in and around the
wound bed are highlighted with arrows. The patient was switched to
regular NPWT after 10 days, as per NPWT guidelines and standard
practice. In week 4 (c–e), widespread bacterial fluorescence was
visualised under sealed adhesive (d) just 48 hours after a dressing
change. This prompted an early dressing change during which bacterial
fluorescence was also present on foam dressing (e). Patient was returned
to NPWTi. In week 5, after one week of NPWTi (f–g), bacterial
fluorescence was notably reduced to a small region of the packed wound
(g, red, circled), demonstrating the effectiveness of instillation treatment.
In week 9 (h–k) a small region of red fluorescence (circles) was still
detectable under adhesive (h) and was also observed on comparable
region of foam dressing (k) and on periwound tissue (j); no red
fluorescence was detected on the wound bed. Periwound fluorescence
prompted additional cleaning of periwound region (k), better preparing the
wound bed for NPWT and maintenance of this patient on NPWTi, rather
than the planned return to standard NPWT
Week2
A B
Foam
dressing
C D E
F G
Foam
dressing
Week4Week5
H I J
K
Week9
Week2
A B
Foam
dressing
C D E
F G
Foam
dressing
Week4Week5
H I J
K
Week9
Week2
A B
Foam
dressing
C D E
F G
Foam
dressing
Week4Week5
H I J
K
Week9Week2
A B
Foam
dressing
C D E
F G
Foam
dressing
Week4Week5
H I J
K
Week9Week2
A B
Foam
dressing
C D E
F G
Foam
dressing
Week4Week5
H I J
K
Week9Week2Week4Week5Week9
a
c
f
h i j
k
g
d e
b
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numerous timepoints during NPWT treatment and
swabs confirmed the findings of fluorescence images.
Case 1
An 87-year-old, female patient fell from a chair in her
home while reaching for a ceiling fan chain. She fractured
her right femur from the fall, was immobile, and spent
three days on the floor before discovery. During this time
a deep, unstageable sacral PU developed. The patient was
able to keep hydrated with water. At time of admission the
patient suffered from rhabdomyolysis (CK=966), renal
failure, hypothyroidism (TSH=13.96), and low albumin.
She had a history of right nephrectomy and renal cell
carcinoma, chronic obstructive pulmonary disease,
dyslipidemia, hypertension, and chronic kidney disease.
During her 18-week inpatient stay the patient developed
pruritis, and anxiety also became a significant issue.
The patient was given a course of systemic antibiotics
and her unstageable PU was cleansed with hypochlorous
acid (1:20) alternated with betadine-soaked gauze. This
therapy was deemed ineffective at debridement and,
therefore, after 1.5 weeks the patient was switched to
NPWTi of hypochlorous acid (1:20) (wound size:
15x9cm, depth not recorded), with good results seen
one week later (wound size: 12x8x3.5cm). NPWTi and
subsequent dressing changes were extremely painful for
this patient; administration of analgesics was required.
Three days after initiation of NPWTi treatment
(week 2), fluorescence images acquired at a scheduled
dressing change detected bacterial (red) fluorescence.
These were detected:
●● Before the dressing change under sealed, opticallytransparent
(routine) adhesive (Fig 1a)
●● Within the wound bed (Fig 1b)
●● On periwound tissues (Fig 1b).
After 10 days of NPWTi treatment the wound was
presumed clean and the patient was switched to
standard NPWT. The study clinician was not present at
that wound assessment, therefore real-time information
on the wound’s bioburden via fluorescence imaging was
not obtained and evaluated as part of this treatment
decision. Rather, this change in treatment plan was
made based on standard institutional practice/resource
conservation1,13 and clinical signs and symptoms
during wound assessment.
When next imaged (week 4, Fig 1c), one day before
the patient’s next scheduled dressing change, red
bacterial fluorescence was apparent under the clear
adhesive (Fig 1d) and throughout the NPWT foam
(Fig 1e). This prompted an immediate dressing change
and switch back to NPWTi of hypochlorous acid (1:20).
Wound swabs taken at this time confirmed heavy
growth of Escherichia coli, Staphylococcus aureus and
Enterococcus faecalis, and light growth of Proteus vulgaris.
Wound size was 11x7.5x2.5cm. After one week (week 5,
Fig 1f), the patient was imaged for bacterial fluorescence
again 24 hours before a scheduled dressing change.
Bacterial fluorescence was notably reduced; however, a
small area of red fluorescence was still evident on
images taken through the sealed, optically-transparent
adhesive (Fig 1g). The dressing change was therefore
expedited and the patient was maintained on
NPWTi therapy.
In week 6, after 14 days of NPWTi, the patient’s
wound size was 8x6x4.5cm (100% granulation) and red
fluorescence was present only in periwound tissue
(wound bed was negative for fluorescence, images not
shown). Periwound tissue received additional cleaning
under fluorescence guidance and the patient was
switched to standard NPWT. In week 9, a small region
of red fluorescence could still be seen under adhesive,
on foam and in periwound tissue (Fig 1h–k). Patient was
Fig 2. Fluorescence images confirm the absence of significant bioburden
in a pectoral necrotizing fasciitis wound undergoing NPWT. (a–b) Images
taken in week two of NPWT with instillation (NPWTi) were negative for
bacterial fluorescence (b), as were fluorescence images acquired in week
3 (confirmed via wound culture) (d) and again in week 6 (g). Based on
images, clinician delayed several dressing changes by 24 hours, leaving
the wound bed undisturbed for better healing and saving clinician time
and resources. (h–j) Images taken of the wound bed and foam dressing
during a week 6 dressing change also were negative for red fluorescence
Week2
A B
C D
F G
Week3Week6
H I J
Standard Imaging Fluorescence Imaging
Week2
A B
C D
F G
Week3Week6
H I J
Standard Imaging Fluorescence Imaging
Week2
A B
C D
F G
Week3Week6
H I J
Standard Imaging Fluorescence Imaging
Week2
A B
C D
F G
Week3Week6
H I J
Standard Imaging Fluorescence Imaging
Week2
Standard imaging Fluorescence imaging
Week3Week6
a
c
f
h i j
g
b
d
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maintained on standard NPWT and additional,
fluorescence-guided cleaning was performed until
periwound red fluorescence was no longer observed
(Fig 1k). Wound size was 7x4x1.5cm.
After 14 weeks, the patient was discharged to an
alternate level of care and NPWT therapy was ceased
due to patient mobility concerns. The wound (5.5x3cm)
was treated with methylene blue dressings, and
promogram and adjunctive hyperbaric oxygen therapy
(HBOT) over the next month. At time of discharge from
hospital, after 18 weeks of care, wound size was
6x3x0.3cm. The wound healed fully two months later.
Case 2
A 45-year-old female patient presented at the emergency
room with severe right breast pain, worsening over the
previous three days. The patient had a past medical
history of type II diabetes (uncontrolled and medicated),
hypertension, cardiac stenosis and acid reflux. Discomfort
rapidly progressed while in emergency care and she
became hypotensive and tachycardic. The patient was
diagnosed with Group A Streptococcus pectoral necrotising
fasciitis (blood culture). A CT scan showed extensive
oedema and infiltration of the right breast and interior
wall. Patient was treated with ampicillin (2g IV q 6 hours)
and fluconazole. Exploratory surgery on the chest wall
soft tissue and fascia was performed during which time
NPWTi was initiated. Patient became palliative after
suffering cardiac arrest and anoxic brain injury. The
patient was maintained on ampicillin and fluconazole
with NPWTi (1:20 hypochlorous acid) dressing changes
2–3 times per week.
Fluorescence images were first acquired two weeks
after patient admission and the initiation of NPWT
therapy. The wound was scheduled for a dressing
change. However, upon seeing that images were
negative for bacterial fluorescence (Fig 2b), the clinician
decided to delay the dressing change by 24 hours,
leaving the wound bed undisturbed. Assessment of
clinical signs and symptoms supported this decision.
The decision to delay a dressing change was made again
in week three when images of the wound acquired
through the optically-transparent adhesive were again
negative for bacterial fluorescence. A wound swab taken
later in the week confirmed the absence of bacteria;
only Candida tropicalis was present. Wound size was
18x6.5x4.5cm.
In week 6 the wound was healing well (wound size
14x5x1.5cm); images acquired through the adhesive were
negative for bacterial fluorescence (Fig 2g), as were images
of the wound bed (Fig 2i) and the packing foam (Fig 2j).
The wound continued to decrease in size until all
treatments were stopped in week 10, for palliative reasons.
Discussion
This case series reports a novel use of a fluorescence
imaging device, to facilitate real-time, evidenced-based
decision-making around selection of optimal NPWTs
and timing of NPWT dressing changes. There is
currently a reliance on manufacturer guidelines,
clinician experience and/or institutional practice
standards, rather than real-time evidence, for NPWT
treatment decisions, for example, time between dressing
changes, length of total NPWT treatment. This forces
generalisation across patient care practice when, in fact,
the World Union of Wound Healing Societies (WUWHS)
has stated that a patient-specific treatment plan is
required for each wound.12 Yet, real-time, woundspecific
evidence has been unavailable for such
decisions, as a clinician cannot assess a wound being
treated with NPWT without first removing the vacuum
and dressings. This study demonstrates the power of
bacterial fluorescence imaging to provide valuable
information on bioburden before NPWT dressing
removal. The potential benefits of this real-time
information on improved decision making, resource
management and cost savings are discussed below. This
case series also reproduces the findings of other studies
on bacterial fluorescence, namely that these images can
be used to guide wound cleaning,20 debridement,20,22
and patient education.20,27
Case 1 demonstrates the pitfall of guideline-based
treatment decisions, rather than real-time evidence.
This bioburdened wound was presumed clean after
10 days of NPWTi. Yet, recent studies with NPWTi have
demonstrated a bioburden reduction of only 50% in
infected wounds after a week of treatment.7 Furthermore,
because bacterial fluorescence imaging was not standard
practice for other members of the wound care team,
images were not acquired at the day 10 dressing change
to confirm at the bedside that bioburden had been
eliminated. The still-contaminated wound was switched
to standard NPWT. This decision was likely made to
conserve resources: Gupta et al.1 reported a daily
therapy cost for NPWTi as $194 versus $106 USD for
standard NPWT). However, emerging studies have
repeatedly shown that standard NPWT (without
instillation) leads to an increase in bioburden over one
week of treatment in contaminated wounds.4,6,7 Indeed,
one week later, images acquired through sealed dressing
adhesive clearly demonstrate widespread red (bacterial)
fluorescence, suggesting a reversal of some initial
benefits of NPWTi. Therefore, if images had been taken
earlier, instillation treatment could have been
continued, increasing short-term costs of instillation
therapy but likely saving costs overall.11 After this
patient was returned to NPWTi, bacterial fluorescence
images were used to monitor treatment effectiveness.
When red fluorescence was observed after a further
10  days of instillation treatment this bioburdenchallenged
patient was maintained on NPWTi, a patient
specific treatment plan based on real-time observation
of the wound’s bacterial burden.
Cases 2 and 6 (Table 1) demonstrate how incorporation
of bedside bacterial fluorescence imaging can lead to
cost savings and resource optimisation. NPWT’s
effectiveness in wound healing is evident from a wealth
of studies over many years.28–30 However it is still
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practice
S 3 5J OURNAL OF WOUND CARE  NOR TH AMERICAN SUPPLE M E N T V OL 28, N O 9, S E P TE M BE R 2019
©2019MAHealthcareltd
perceived as a costly therapy in terms of supplies and
clinician time. A NPWT dressing change requires skilled
personnel31 to remove the previous dressing and foam,
assess the wound, prepare the wound bed, cut then place
foam, apply adhesive, cut and prepare drainage tubing,
establish a vacuum seal, program the NPWT device (in
some cases) and then test the vacuum seal. In a study of
42 wounds, average time for this dressing change was 31
minutes,14 at a total labour cost of $20/dressing change.14
In contrast, in the current study it took less than one
minute to image the wound through the adhesive
dressing to determine if a dressing change should be
expedited or delayed. The average cost of NPWT supplies
per dressing change was reported as $69 USD in a 2017
retrospective review of >35,000 total days of NPWT
occurring over 15 years,15 for a total cost of $89 USD per
dressing change. NPWT dressing changes were
performed every 2–3 days in these studies, as per
manufacturer guidelines. However, the ideal interval
between dressing changes will vary from wound to
wound, with contaminated wounds requiring much
more frequent changes. A 72-patient study of noninfected
trauma wounds, comparing NPWT dressing
changes every three days versus seven days, found no
difference in rate of complications, including
infections.32 This suggests that wounds free of heavy
bioburden, such as the wounds in cases 2 and 6, can
receive less frequent changes, so long as they are
carefully and objectively monitored by skilled personnel,
monitoring that is facilitated by fluorescence imaging
information. For example, over the eight weeks of
bacteria-free NPWT care in case 2, delaying all dressing
changes by 48 hours, in conjunction with daily bacterial
fluorescence monitoring, would have decreased the
number of dressing changes required from 19 to 11. This
treatment plan adjustment would have decreased NPWT
care costs by $1552 USD (eight fewer dressing changes x
$194 USD) in this patient alone. This would free up
resources to focus on patients struggling with wounds
containing excessive bacterial burden, for example, case
1, and triage treatment resources across all NPWT
patients, allocating more appropriate care. Note that
while the cost of therapies is an important factor in the
total wound care cost, the dominant driver of cost is
duration of the wound.35 Wounds harbouring high
bacterial burden are associated with longer wound
duration.12,36 Therefore, facilitating appropriately
triaged care for wounds, even with a short-term cost
increase, is likely to yield cost savings in the long-term.
Larger studies to validate dressing change
postponement based on fluorescence information are
required. Due to the novel nature of this study, we were
not comfortable delaying dressing changes by more
than 24 hours based on negative fluorescence image
information alone. Based on the results of this case
series, in future we would consider delaying dressing
changes by more than 24 hours. This decision would be
made on a case by case basis and would take into
consideration that leaving the foam too long can
increase growth of the granulation tissue into the foam
and thus increase pain at dressing changes.
This case series also demonstrates how incorporation
of bedside bacterial fluorescence can facilitate patient
education and increase patient comfort. NPWT can be
extremely painful and analgesics are often administered
before a dressing change in patients with significant
pain.13 Patients 1 and 4 in this case series experienced
pain so severe that they were refusing much needed
dressing changes, even with administration of
analgesics. Fluorescence images were acquired at
bedside and were immediately used to educate these
patients about the bacteria that was present. The simple
colours were easy for them to understand. After seeing
the images of bacterial fluorescence, both patients
agreed to have dressing changes, thereby increasing
their adherence to the recommended treatment plan.
In cases 2 and 6, images consistently free of bacterial
fluorescence led to less frequent dressing changes,
thereby sparing these patients unnecessary pain.
Although the ability to visualise bacterial fluorescence
within NPWT foam through optically transparent
sealant has not previously been described, the presence
of bacteria within NPWT foam does not come as a
surprise. Microbiological analysis of NPWT foams
(68 foams from 17 patients, including both polyurethane
and polyvinyl alcohol based foams) revealed high
bacterial loads, 106CFU/ml or higher in 69% of foams
studied.33 In the current study, polyurethane foams
were exclusively used, and can be seen in both Fig 1
and 2. Interestingly, bacterial loads have been reported
to be higher in polyvinyl alcohol foam relative to
polyurethane,33 yet polyurethane foam has been
speculated to facilitate better removal of bacteria due to
higher blood flow increases.34 Regardless, the high
prevalence of bacteria, confirmed via microbiological
methods in foams from diverse wound types and
locations, suggests that real-time bacterial visualisation
in NPWT foam could have widespread use.
Limitations
Several limitations of this imaging device warrant
discussion. Visualisation of bacteria in and around a
wound does not necessarily mean infection is present,
therefore this device does not replace the need for
clinician judgement and assessment for infection-related
signs and symptoms.26 The device also does not indicate
which bacterial species are present nor does it provide
bacterial antibiotic sensitivities; microbiological culture
is still required if the clinician desires that information.
However, bacterial fluorescence can identify an ideal
location for the clinician to sample. A prospective clinical
trial of 60 patients found that regions of red fluorescence
predicted the presence of concerning levels of bacteria in
100% of red-fluorescing wounds.17
Acquisition of fluorescent and standard images in our
windowless clinic rooms generally takes less than
20 seconds, unless the wound is in a challenging position
to image. However, the required darkness for capturing
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practice
S 3 6 JOURNAL OF WOUND CAR E  N OR TH A M E RI C A N S UP P L E M E N T V OL 28, N O 9, S E P TE M BER 2019
©2019MAHealthcareltd
fluorescent images is a challenge in inpatient rooms with
large windows. To overcome this challenge, a disposable
dark drape attachment was used at every inpatient
imaging session (six patients, more than 20 imaging
sessions in total). The drape attachment was completely
effective in achieving the required darkness. Resulting
images had no ambient light-induced artifacts and were
simple to interpret (all fluorescent images shown in Fig 1
and 2 were taken with drape attachment). Attachment of
the drape before imaging did lengthen the total time
spent on imaging, by approximately a minute.
Additional studies on the use of this device in
conjunction with NPWT systems are warranted. In this
small, 10-patient case series we were able to visualise
bacteria through the optically transparent seals used
with many NPWT systems and within the NPWT
packing foam. However, we did not attempt to
determine the depth to which bacteria could be imaged
through these seals and foams. Furthermore, NPWT
systems available on the market with opaque seals and
bandages would presumably hinder penetration of the
device’s violet illumination, therefore the bandage
would need to be removed before imaging. These
10 cases cannot be used to generalise findings, but they
do serve to demonstrate the clinical usefulness of
handheld fluorescence imaging in wound care,
supporting previous studies.16–18,20–25 These cases also
demonstrate, for the first time, how fluorescence
imaging of wounds can be used in conjunction with
NPWT to guide treatment decisions including timing of
dressing changes, treatment selection, and wound
cleaning specifically targeted to regions of bioburden.
Conclusions
Bacterial fluorescence images acquired in this series of
10 patients provided real-time information on bacterial
contamination in wounds. Having access to this
information facilitated immediate, evidence-based and
patient-specific changes in treatment plans. Images
prompted and otherwise helped guide timing of
dressing changes, guided the extent of wound cleaning,
and guided selection of NPWT therapies that were most
appropriate for patient needs. Larger studies are required
to assess whether fluorescence imaging during NPWTtreated
wound assessments can improve healing rates
and lower total wound care costs.  JWC
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Reflective questions
●● What is the current triage process when it comes to wound clinicians and
negative pressure resources in your facility?
●● What information do you currently use to assess wounds undergoing NPWT?
How could information on wound and dressing bioburden improve
your assessment?
●● Fluorescence information on bacterial burden helped to adjust treatment plan
in 90% of studied wounds. How do you currently determine whether a wound’s
bioburden is being treated appropriately?
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The monthly, international
wound care journal
Journal of Wound Care (JWC) is the world’s leading peer-reviewed
publication for tissue viability specialists. An official partner of both
the World Union of Wound Management Societies (WUWHS) and the
European Wound Management Association (EWMA), JWC provides a
trusted evidence base to inform advanced clinical knowledge and skills.
What’s included?
l Clinical expertise and best practice worldwide
l Original research covering all aspects of wound care
l Comprehensive studies of new products and treatments
Official journal of the World Union of Wound Healing Societies
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Multidisciplinary teams in the management
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Health economic burden of wounds on an average clinical commissioning group
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Surgical wound dehiscence: a conceptual
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Photograph-based telemedicine assessment in surgical site infection
Using a modified Delphi methodology to gain consensus on dressing use
Delayed referral of patients with diabetic foot ulcers across Europe
The Japanese registry for surgery of ischial pressure ulcers: STANDARDS-I
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