Summary
Recognition of the role that biofilms play in the persistence of chronic
wounds and lack of response to therapy in horses is increasing.
Prevention of biofilm development in early stages of wound care involves
three primary strategies: wound debridement and cleansing to reduce
bacterial counts in the wound bed, appropriate use of advanced wound
dressings, and implementation of topical antimicrobial agents. Once
formed, eradication of biofilms requires elimination to improve the
wound environment for contraction and epithelialization while not
further harming the native cells integral to the healing process, which
is achieved predominantly through repeated lavage and debridement
combined with topical antimicrobial therapy. This review will establish
why and how biofilms form, how to recognize clinical indications that
biofilms have formed in equine wounds, and to review current diagnostic
options and biofilm-based wound care (BBWC) strategies to eradicate
biofilms. Clinical scenarios for cases in which biofilms developed and
were successfully treated will be presented. This review will advance
practitioners’ understanding of the presence and role of biofilms in
chronic wounds and provide an updated summary of recommended treatment
strategies.
Introduction
Bacterial biofilms are organized communities of bacteria attached to a
surface and enveloped in a three-dimensional extracellular matrix. A
recent systematic review and meta-analysis of wound care literature in
humans reported the prevalence of biofilms in chronic wounds to be
78.2% (Malone et al., 2017). Consensus guidelines for the
identification and treatment of biofilms have further stated that
biofilms should be assumed to be involved in most, if not all, chronic
non-healing wounds (Schulz et al., 2017). Furthermore, multiple
studies to date have documented evidence of biofilms in chronic wounds
of horses specifically (Freeman et al., 2009; Westgate et
al., 2011). The high prevalence of biofilms in non-healing wounds, the
frequency with which equine practitioners treat wounds in daily
practice, and the increasing reported incidence of multi-drug resistant
bacterial strains in equine practice in general (Herdan et al.,2012; Loncarac et al., 2014; Theelin et al., 2014; van den
Eede et al., 2012), highlight the need for implementation of more
advanced training in wound care strategies to address these clinical
scenarios.
The purpose of this review is to summarize the current literature
describing problems caused by bacterial biofilms in wounds, clinical
indications that biofilms are involved, laboratory testing to improve
biofilm detection, and biofilm-based wound-care (BBWC) strategies to
provide clinicians with practical guidelines for case management where
biofilms are suspected. Recommendations for antimicrobial duration in
veterinary practice further support administration for the shortest
effective duration to reduce risk of development of resistant pathogens
(Hansen et al., 2014; Gandini et al., 2022); therefore,
local surgical and topical techniques to address biofilm formation will
be emphasized to minimize unnecessary systemic antimicrobial
administration. Early recognition of the presence of biofilms in
non-healing wounds and targeted treatments are key to the successful
management of biofilms in equine practice (Pezzanite et al.,2021).
Understanding the role of biofilms in wounds
Biofilm formation is divided into three main stages: bacterial
attachment, growth, and detachment (Lappin-Scott and Bass 2001). In
stage one, planktonic (free-floating) bacteria adhere to surfaces within
several minutes (Parsek et al., 2005). In stage two, individual
attached bacteria (i.e., ‘sessile’) secrete a three-dimensional
extracellular matrix (also known as extracellular polymeric substance
(EPS)) that includes water, proteins, glycolipids, polysaccharides,
bacterial DNA, and potentially other microbes benefiting from the
protected environment which makes up 90% of the biomass of the biofilm
itself (Clutterbuck et al., 2007; Jacques et al., 2010;
Wolcott et al., 2008a; Percival, McCarty, Lipsky 2015; Flemming
and Wingender 2010). This occurs within 6 to 12 hours of attachment and
the biofilm continues to grow based on coordinated cell-to-cell
signaling known as ‘quorum-sensing.’ (Parsek et al., 2005; Prada
& Săndulescu, 2019; McCarty et al., 2012). In stage three,
biofilms reach maturity within 2 to 4 days and shed free-floating
planktonic cells which disperse and attach to other areas of the wound
bed (Kostakioti, Hadjifrangiskou, & Hultgren 2013). This cell
distribution activates the host immune response, which further
stimulates production of exudates that provide nutrients and promote
survival of the biofilm (Orsini et al., 2017; Dart et al.,2017a; Stewart and Richardson, 2019), and may lead to additional
complications for the host animal, including bacteremia or bacterial
colonization of distant anatomical sites (Bjarnsholt et. al.,2013).
Predisposing factors to biofilm formation include the presence of
foreign bodies, sequestra and surgical implants, reduced vascular
perfusion to the anatomical region, inappropriate antimicrobial
sensitivity, and the immune status of the patient (age, sepsis,
malnutrition, antibody deficiency, chronic stress, corticosteroid
administration, or underlying diseases including pituitary pars
intermedia dysfunction [PPID] or Cushing’s disease) (Seth et
al., 2012, Orsini et al., 2017). Strategies to prevent biofilm
development in acute wounds include wound debridement and cleansing to
reduce bacterial counts and appropriate use of advanced dressings and
topical antimicrobial agents. Addressing systemic conditions
(e.g., Cushing’s disease in horses) may promote more rapid
bacterial clearance and healing in immune-incompetent patients as well.
Furthermore, the ability of the host’s immune response to effectively
control microbes decreases as the biofilm matures. As a consequence,
infections involving biofilms frequently recur following discontinuation
of antimicrobials (Dart et al., 2017b), emphasizing that early
recognition of treatment of both the wound and the animal’s systemic
health status are key to successful management.
Wounds with biofilms may not necessarily exhibit signs typically
associated with infection besides prolonged and impaired healing (Dartet al., 2017a). The presence of biofilms has been demonstrated to
delay epithelialization and induce a chronic non-healing inflammatory
state (Wolcott et al., 2008; Schierle et al., 2009).
However, it is important to note that polymicrobial biofilms, which are
considered more pathogenic than monobacterial colonies, have been
reported in multiple types of equine wounds, not limited to those
considered chronic (e.g., acute or chronic, surgical or traumatic
in origin) (Westgate et al., 2001; Freeman et al., 2009;
Pastar et al., 2013). Metabolically active, nondividing persister
cells, which are tolerant to antimicrobials, are integral to
reestablishing biofilms following topical treatments (Kostakioti,
Hadifrangiskou and Hultgen, 2003). Specific bacterial species may
integrate chromosomal β-lactamase, efflux pumps, and mutations in target
antibiotic molecules to evade host defenses. Finally, extracellular DNA
(eDNA) present in bacterial biofilms promotes acid-base interactions
between bacterial cells and surfaces, therefore playing an essential
structural role in both establishing biofilms and protecting cells
within the biofilm from environmental challenges (Lewenza et al.,2013; Thomann et. al., 2016).
Locally, polymicrobial infections delay wound closure through alteration
of cytokine levels and receptors (Pastar et al., 2013). For
example, S. aureus and P. aeruginosa are known to
downregulate keratinocyte growth factor 1 expression of fibroblasts,
resulting in delayed re-epithelialization through reduction of
keratinocyte migration and proliferation (Pastar et. al., 2013).
Bacteria in biofilms secrete enzymes (e.g., proteases, elastase,
phospholipase) to degrade local host tissues to provide nutrients and to
protect bacteria within the biofilm from host immune cells
(Michalkiewicz et al., 1999; Flemming and Wingender, 2010;
McCarty et al., 2017). For example, the proteases secreted byPseudomonas aeruginosa degrades and inactivates interferon gamma
which suppresses innate immune recruitment and reduces elimination of
biofilm bacteria (Michalkiewicz et al., 1999). Continuous
production of exudate is detrimental to wound healing as the
inflammatory process continuously breaks down the ECM (McCarty et.
al., 2012) and may degrade growth factors associated with normal wound
healing processes (Percival et al., 2015). Various cell types
including keratinocytes, fibroblasts, endothelial cells, and
inflammatory cells (e.g., monocytes, lymphocytes, and
macrophages) express matrix metalloproteinases (MMPs) involved in
epithelial repair, wound contraction, and degradation of damaged ECM
within the skin (Caley et al., 2015) which is upregulated in
wound edge keratinocytes to allow epidermal cell migration across wound
beds (McCarty et al. 2012). However, in wounds associated with
biofilms, the presence of devitalized tissue and abnormal immune cell
activity results in excessive production of MMPs which perpetuates ECM
destruction propogating the inflammatory response and wound chronicity
(Caley et al., 2015; Parnham and Bousfield 2018; Kandhwalet al., 2022). Approaches to restore normal wound healing involve
techniques directed towards inhibition of these biofilm virulence
factors through effective, sustained debridement of devitalized tissues
(Schierle et al. , 2009; Parnharm and Bousfield 2018).
Development of infection involving biofilms has important implications
in management of wounds in horses, as they present unique challenges in
diagnosis and are more resistant to typical treatment methods (Dartet al., 2017a). Bacteria that produce biofilms are able to
survive and grow at slower metabolic rates in environments depleted of
nutrients and oxygen, termed phenotypic heterogeneity (Donlan et
al., 2001; Clutterbuck et al., 2007). Mature biofilms secrete
protective enzymes, shielding themselves from host defenses and exterior
physiologic changes that may be detrimental to bacterial health
(Percival et al., 2015). Once formed, bacteria in biofilms
differentiate into complex communities with enhanced resistance to
environmental challenges (e.g., cells of the innate immune
system, desiccation, etc.), biocides, and antibiotics (Costertonet al., 1999; Fux et al., 2005) and variable morphology
depending on nutrient availability (Klausen et al., 2003,
Flemming and Wingender, 2010). As a result, bacteria within biofilms are
more tolerant to the host immune response, antimicrobial therapy
administered systemically (antibiotics) or topically (antiseptics)
including hydrogen peroxide, alcohols, bleach, oxygen radical generators
and acids (unless administered at concentrations toxic to the animal’s
cells) (Clutterbuck et al., 2007). For example,Staphylococcus aureus has been shown to be up to 100 times more
resistant to antimicrobials when in biofilm versus planktonic form (Leidet al., 2002). These challenges in addressing bacteria in
biofilms may only be overcome if antimicrobials to which the bacteria
are sensitive can be delivered at adequate concentrations for a
sufficient time to achieve bactericidal activity (Stewart and
Richardson, 2019).
Diagnosing biofilms – laboratory testing and clinical
indications
Traditional bacterial culturing techniques are generally considered
inadequate to comprehensively identify bacterial species associated with
biofilms (Kirketerp-Moller et al., 2008). Diagnosis of biofilms
in wounds can only be definitively made using scanning electron or
confocal microscopy imaging or molecular techniques to identify
bacterial components, which are not readily available modalities to
clinicians (Wolcott and Rhoads 2008; Percival et al., 2015; Dartet al., 2017; Schulz et al., 2017; Hurlow et al.,2015). Recent studies have demonstrated that biofilms associated with
wounds are most commonly polymicrobial communities, with an average
number of 3.02 +/- 1.65 species identified (range, 0-8) (Westgateet al., 2001; Freeman et al. 2009). Genera identified were
similar to those found in human infections, with Pseudomonas,
Enterococcus , and Staphylococcus species being most common
(Wolcott and Rhoads 2008; James et al., 2008; Dowd et al.,2008; Darvishi et. al., 2021). However, molecular analyses of
chronic wound samples have revealed far more diverse polymicrobial
communities with up to 17 genera per wound, including anaerobic species
not identified by routine culturing, and further highlighting the
challenges faced by clinicians in accurately identifying and treating
bacterial species contained within biofilms (James et al., 2008;
Han et al., 2011).
Standard methods to assess bacterial burden in wounds include
qualitative and quantitative techniques (Hendrickson 2019a). Qualitative
assessment determines the genera of bacteria found in wounds and is
coupled with sensitivity testing to provide clinicians basis for
antibiotic choices in treatment. Quantitative bacteriology methods are
less commonly performed in veterinary medicine but should be considered
in cases when wound healing is not progressing as anticipated or
following skin graft failure. Active infection has typically been
considered to be the case in situations where bacterial counts are found
to be greater than 105 per gram tissue or mL exudate
(Robson and Heggers, 1969). However, the number of bacteria required to
establish an infection is reduced in situations where the patient’s
bacterial resistance or immunocompetence is decreased, foreign material
is present including implants, sutures, foreign bodies or necrotic
debris, or bacterial virulence is high (Bowler 2003). In polymicrobial
infections, as is most typical of those involving biofilms, multiple
microorganisms act synergistically to result in greater virulence
compared to an infection caused by either species alone (Serra et
al., 2015). In cases involving multidrug resistant isolates, as few as
100 bacteria per gram tissue or mL exudate may be sufficient to incite
infection (Rodeheaver et al., 1974).
The best diagnostic method currently available to clinicians in equine
practice when biofilms are suspected is submission of a deep tissue
biopsy or swab of the deepest tissues available (or both) for bacterial
culture and sensitivity to guide future treatment practices (Dartet al., 2017). In general, tissue samples, while being more
invasive to collect, are more likely to yield reliable culture results
compared to swabs (Westgate et al., 2001; Freeman et al.,2009). Ideally, submission of tissue samples should be performed prior
to beginning or altering antimicrobial protocols; however, if considered
necessary to collect samples while horses are currently receiving
antimicrobial, it is recommended to notify the receiving laboratory of
the horse’s current regimen and when the most recent dose was received
in relation to sample collection (Orsini et al., 2017). Following
superficial wound debridement, tissue samples should be collected from
within the deepest regions of the wound (e.g., fissures or
pockets in the wound bed) and from multiple sites if possible to avoid
false positive results (Sen et al., 2012; Rhoads et al.,2012). If tissue swabs are collected, the swab should be drawn across
the wound surface with sufficient pressure to collect the biofilm itself
while avoiding drawing blood which contains antimicrobial elements that
may affect culture results. Positive culture results should be
interpreted with the assumption that the full microbial spectrum is
likely underrepresented with currently available techniques.
In lieu of obtaining a positive culture result or if submission is not
an option due to financial or other case-related considerations,
diagnosis of biofilms in wounds may be based on clinical indications
(Table 1 ). Clinical findings consistent with biofilm presence
include indicators of inflammation (heat, swelling, pain, redness),
persistent or recurrent infection despite administration of
antimicrobial therapy or recurrence following antibiotic
discontinuation, excessive wound moisture/exudate, poor quality
granulation tissue, history of negative culture findings despite
clinical suspicion of infection, or in general a wound that remains in a
chronic and recalcitrant inflammatory state despite standard treatment
and evaluation of the patient for comorbidities (e.g.,immunosuppression). In summary, culture findings to diagnose biofilms
are unreliable and observation of clinical indications that biofilms are
present in the wound bed should prompt practitioners to implement wound
care strategies directed specifically at addressing and reducing biofilm
formation in wounds.
Biofilm-based wound-care treatment strategies
4.1. Biofilm-based wound-care guidelines - Recent
consensus documents in human wound care have described biofilm-based
wound-care (BBWC) strategies to provide practical guidelines for case
management in which biofilms are suspected (Wolcott and Rhoads, 2008b;
Schultz et al., 2017; Metcalf et al., 2014; Bianchiet al., 2016) (Table 2 ). Biofilm treatment is
recommended in three stages: 1) physical debridement of the biofilm, 2)
topical treatment to delay or prevent reformation, and 3) repeated
therapy until full resolution is achieved (Orsini et al., 2017).
These strategies emphasize that repeated debridement to physically
disturb the biofilm structure is necessary to disrupt the matrix and
remove devitalized tissues that serve as nutrients to the microbes
involved and allow increased susceptibility to antimicrobial therapies
for a period of time to prevent bacterial reattachment as immature
biofilms are more susceptible to antimicrobials (Dart et al.,2017). Implementation of a multimodal therapeutic strategy to address
biofilms has a reportedly higher success rate compared to antimicrobials
alone (Wu et al., 2015).
4.2. Debridement principles - The overall objective of
debridement is to remove as much devitalized tissue, biofilm and
associated extracellular matrix as possible to expose the remaining
bacteria to antimicrobial agents. The organization and complex
physiology of mature biofilms increases their resistance to antibiotics
resulting in colonized bacteria being up to 1000-fold times more
resistant to antimicrobials than planktonic cells (Hoiby et al.,2010). Debridement removes ECM and eDNA to prevent recurrence of
biofilms in the wound by removing the basis for nutrition and protection
of the bacterial component of the biofilm (Hajska et. al, 2014).
The immature biofilms that begin to reform following debridement are
subsequently more susceptible to topical therapies. General principles
described by Wolcott et al. in addressing wounds infected with
biofilms include debridement with the goal to alter the wound bed
anatomy by removing any devitalized or discolored tissue and all tissue
surfaces that touch one another until normal bleeding tissue is
encountered (Wolcott et al., 2010). Application of topical
treatments is then recommended within four hours following debridement
prior to biofilm reformation (Roche et al., 2012; Hajska et
al., 2014). An example of how biofilms may be successfully treated and
how rapidly they reform in the absence of consistent treatment is daily
removal of dental enamel plaque by regular tooth brushing (i.e.,
debridement) performed in combination with topical antiseptic
mouthwashes, which are of minimal benefit without prior flossing and
tooth brushing (Orsini et al., 2017).
Biofilm debridement may be performed sharply (e.g., scalpel
blade), mechanically with gauze across the wound bed, or using water-jet
irrigation or low-frequency ultrasonic debridement. It is recommended
that horses be sedated, and the wound desensitized with local or
regional anesthesia to facilitate procedures and reduce discomfort to
the patient. In some cases, the initial debridement may be performed
under general anesthesia if the wound is extensive or inaccessible or if
dictated by the patient’s temperament. When working with multi-drug
resistant organisms or particularly when using pulsed water-jet
irrigation, face protection or use of surgical masks during the
debridement stage is recommended to protect again aerosolized organisms.
Debridement and efforts to reduce biofilm reconstitution should be
repeated daily to at least every other day for as long as necessary to
resolve infection. Mature biofilms reform as rapidly as every 24 to 72
hours after debridement, resulting in a window of opportunity to impede
regrowth in which topical therapies and bactericidal drugs can exert an
enhanced effect. If improvement is not observed within three to four
days of initiation of the multimodal therapeutic approach outlined or if
response to therapy is less than anticipated, review of all aspects of
the case is indicated. These may include repeated physical examination,
bloodwork, evaluation of antibiotic suitability with repeated bacterial
culture and sensitivity, and further debridement and exploration of the
wound and potentially additional diagnostic imaging to evaluate for
alternate reasons for delayed healing (e.g., foreign material).
4.3. Topical therapies to prevent biofilm reformation -
Reduction or prevention of biofilm reformation following debridement may
be achieved in multiple ways. Topical antiseptic agents do not penetrate
necrotic debris and have minimal effect to reduce bacterial populations
deep in the wound bed or without debridement; therefore, they should
generally be reserved for use on intact skin and in wound beds (Alveset al., 2021). Examples of antiseptic agents contraindicated for
use in biofilm associated wounds include alcohols, hydrogen peroxide,
iodine, povidine-iodine, chlorhexidine, aluminum salts, boric acid,
formaldehyde, hexachlorophene, hypoclorite, merthiolate, or
permanganate. However, unlike antiseptics, topical antimicrobial agents
can have minimal negative side effects on wound healing depending on the
vehicle and dose used and provide efficacy against bacteria in the wound
bed when administered following debridement and based on results of
culture and sensitivity.
Surfactant dressings such as polyhexamethylene biguanide (PHMB) or
polyhexanide can be used as adjunctive therapies in the early
post-debridement period, as they reduce biofilm surface tension to
facilitate degradation and removal (Palumbo et. al., 2016;
Percival et al., 2019). Other topical dressings such as silver
sulfadiazine (1%) or other silver impregnated wound dressings may be
used in the early post-debridement stage to reduce biofilm reformation,
particularly if bacterial culture and sensitivities to guide topical
antimicrobial treatments are not available (Morones et al., 2005;
Fey et al., 2010; Gunaskaran et al., 2012). Silver works
through interacting with ribosomes to suppress enzymatic expression and
protein formation essential for ATP production (Yamanaka et al.,2005). The methods by which silver interacts with bacteria reduces
formation of resistance and results in broad-spectrum antibacterial
properties (Gunaskaran et al., 2012). In addition, silver
enhances re-epithelialization, angiogenesis, deposition of collagen
fibers, and myofibroblast distinction from fibroblasts prompting wound
contraction (Toczek et. al., 2022). Manuka honey also exhibits
antimicrobial properties due to high methylglyoxal and leptosperin
content and may be used as an adjunctive topical antimicrobial therapy
against a variety of bacterial species with minimal host cytotoxicity
(Molan and Rhodes, 2015; Liu et al., 2017). Finally, topical
application of plasma (autologous natural plasma or hyperimmune plasma
to target specific organisms) may provide additional benefit as a
topical therapy as plasma inhibits bacterial adhesion and growth (Feltset al., 2000; Bauer et al., 2004; Lopez et al.,2014).
4.4. Antimicrobial guidelines – In general,
contaminated wounds including those with suspected biofilm involvement
are more appropriately treated with bactericidal versus bacteriostatic
antimicrobial agents. Although ideally dictated by culture and
sensitivity findings, broad-spectrum antimicrobial therapy is generally
instituted initially with commonly administered agents include
penicillins, cephalosporins, aminoglycosides, quinolones, metronidazole
and rifampin (Orsini et al., 2017). Commonly used initial
combinations include pencillin G (crystalline or procaine penicillin) or
a cephalosporin (cefazolin or ceftiofur) and an aminoglycoside such as
gentamicin. Collection of a separate sample to perform in-house
point-of-care Gram staining may help to guide interim antimicrobial
therapy in lieu of culture and sensitivity findings. In treatment of
distal limb wounds, antimicrobials can also be delivered via regional
limb perfusion. Antimicrobial concentrations delivered locally are
greatest immediately following biofilm degradation so timing of
perfusion to directly follow debridement may improve outcomes although
further investigation is indicated. Finally, repeated culture and
sensitivity is also generally considered indicated in cases where
response is less than anticipated, signs of infection recur following
discontinuation of antimicrobials, if the infection is polymicrobial or
multidrug resistant, or during periods of prolonged antimicrobial
administration.
4.5. Other considerations - Limitations of current
laboratory testing and definitive clinical signs indicating biofilm
presence make it impossible to objectively determine whether biofilms
have been eradicated from a wound. Further investigation of stall-side
testing techniques to identify biofilm presence may enhance monitoring
techniques in the future; however, currently, monitoring of clinical
progression with reduced exudate and slough remains the most effective
method to determine response to treatment and biofilm resolution (Leaperet al., 2012). However, despite appropriate treatment, biofilms
associated with orthopedic implants or other foreign devices frequently
necessitate removal for resolution (Richardson and Stewart 2019). In
some cases, infection can be controlled temporarily through a
combination of systemic and local antimicrobial therapy until fracture
or arthrodesis consolidation has occurred (Wu et al., 2014 ). If
cases with both infection and instability, implants may be removed and
replaced, or cleaned, sonicated, and reimplanted using new orthopedic
screws when financially feasible. Alternatively, internal implants may
be removed, and cases managed with a transfixation pin cast or other
external fixator. The fracture site and surrounding tissues should be
debrided and lavaged, and previous screw holes and the surrounding
region may be treated locally with antibiotic eluting materials. In
general, when communicating with clients about the cost of care in
biofilm-associated wounds, it is recommended to emphasize that the
greater expense incurred in the earlier stages of wound management
typically reduces duration of therapy and costs overall in treatment
long-term (Orsini et al., 2017). Clinical case examples where
wounds with biofilms were successfully treated are provided and
summarized in Figures 1 and 2 .
Future directions in diagnostic techniques and treatment
strategies for biofilms
Novel techniques to reduce infection burden associated with biofilms are
currently being investigated and further developed. Methods described
include further investigation of surfactant-based agents, cellular
therapeutic options (e.g., platelet rich plasma lysates,
mesenchymal stromal cells), quorum-sensing inhibitors (RNAIII inhibiting
peptide), hydrophobic polycationic or sol gel coatings, bacteriophage
therapies (antibacterial viruses), antimicrobial peptides, ultraviolet
light, low-voltage pulsed electrical fields, acetylsalicylic acid,
xylitol, dispersin B, gallium, or antimicrobial tethering (Tilleret al., 2001; Levy et al., 2004; Nablo et al.,2005; Balaban et al., 2005; Williams and Hare 2011; Stewartet al., 2012; Schaer et al., 2012; Barsotti et al.,2013; Spaas et al., 2013; Bussche et al., 2015; Mohammedet al., 2016; Grassi et al., 2017; Orsini et al.,2017; Hans et al., 2019; Gilbertie et al., 2021; Gordonet al., 2021). In addition, future diagnostic tests may be more
effective at definitively identifying the presence and location of
biofilms within a wound bed to guide more patient-specific treatment
strategies. For example, a stall-side or patient-side test to quantify
wound bed protease activity could be one method to indirectly quantify
and longitudinally evaluate the amount of residual biofilm in a wound,
as protease activity correlates generally to the amount of viable or
active biofilm (Leid et al., 2002). Further evaluation of methods
to improve detection of biofilms, monitoring of treatment efficacy, and
overall management of biofilms in case-controlled studies and randomized
controlled clinical trials in warranted.
Conclusions
The recognition that most chronic wounds in equine practice involve
pathogenic bacterial biofilms is
key to successful treatment. Clinical indications that biofilms are
present in the wound bed include wounds that remain in a chronic
inflammatory state recalcitrant to standard therapies, excessive
exudate/moisture, poor quality local granulation tissue, other common
indications of infection (heat, swelling, pain), and/or negative
bacterial culture results despite clinical suspicion of infection.
Biofilm-based wound care strategies emphasize repeated debridement and
lavage combined with topical surfactants or antimicrobials applied
within four hours of debridement that have minimal local cytotoxicity to
host tissues. Finally, improved diagnostic tools to detect biofilms and
monitor response to treatment as well as adjunctive treatments may
facilitate improved outcomes in the future.
Authors’ declaration of interests: No conflicts of interest
have been declared.
Ethical animal research: Review of current literature; not
applicable.
Source of funding: None.
Authorship: All authors contributed to conception and design,
acquisition of data, drafting and final approval of the manuscript.