Biofilm
Describe dispersal (5th and final stage of biofilm formation)
Fully mature biofilms continuously she's planktonic bacteria, micro-colonies and fragments of biofilm that can attach to other sites within the wound bed and form new biofilms
What are the aims of the biofilm wound management?
Prevent biofilm formation Where present or sustoexted disrupt biofilm Prevent biofilm reformation
What types of broad spectrum antimicrobial topical antimicrobrial are there?
Silver, honey, iodine, and polyhexamethylene biguanide. There is no clear guidance which one is the preferred first line treatment So a dressing that is suitable for the woudns condition must be selected from what is available on the local formulary. If there is a lack of progress with the selected antimicrobial over a 2 week period, than a different product should be used. Some wounds respond well to microbial treatment but when the antimicrobial is discontinued symptoms may return. In such cases the use of the same dressing is not recommended as prolonged use of the same antimicrobial should be avoided. If treatment with a differing anti-microbial is not successful the patient may require referal for aggressive debridement of the kind (Dowsett, 2013).
How quickly do biofilms form?
Studies have shown that planktonic bacteria commonly found in wounds e.g. pseudomonas aeroginosa and escherichia colo, can: Attach to a surface within minutes Form attached micro-colonies within 2-4 hours Develop initial extracellular polymeric substance and tolerance to biocides within 6-12 hours Evolve into mature biofilm colonies withinn2-4 days Rapidly recover from mechanical disruption and reform mature biofilm within 24 hours (Phillips et al, 2010) This suggests there is a period of less than 24 hours following wound debridement/ biofilm disruption in which antimicrobial treatments are more effective in reducing both planktonic and biofilm micro- organisms in wounds (Phillips et al, 2010).
What is the Matrix made up of and how does it work?
Sugars, proteins and DNA It attaches to the biofilm to an inert or living surface It gives the microorganisms within it protection from threats such as the immune system or antimicrobial agents such as antibiotics and antiseptics making them difficult to eradicate (Phillips et al 2010).
Where have they been known to form?
Medical devices- catheters, orthopaedics implants, and contact lenses
Describe the initial attachment (1st stage of biofilm development)?
Micro organisms that are free floating and solitary are known as free living or planktonic. These micro-organisms are capable of spreading infection and are vulnerable to treatment with antibiotics. Usually the growth of planktonic microorganisms is often limited by several factors including the availability of nutrients. Planktonic micro organisms may infiltrate a wound but a healthy immune system will destroy them or keep numbers in check. In vulnerable tissue planktonic microorganisms will attach to the tissues and form a small community or micro colony. This attachment is initially reversible but as the micro-organisms multiply they begin to communicate a step which is key to the formation of a mature biofilm (cooper, 2010).
What does necrotic sloughy tissue act as?
Necrotic and sloughy tissue in the wound can act as a physical barrier to healing and provides the ideal environment for bacteria growth.
Can all debridement or cleansing remove all of a biofilm?
No, a mature biofilm (2-4 days) can recover from mechanical debridement within 24 hours (costerston, 1984). If the wound is not progressing following regular use of one method then a more aggressive debridement approach and/ or referral to a specialist may be needed (Phillips et al, 2010)
How do biofilms form in wounds?
They form in 5 stages 1. Initial attachment 2.irreversible attachment 3. Maturation 1 4. Maturation 2 5. Dispersal (ditch and Davies, 2003)
Why would you use a topical antimicrobial to get rid of a biofilm?
Topical antimicrobial dressings should be used in conjunction with regular debridement to protect the wound from infection with new microorganisms and to kill any microorganisms remaining in the wound as a result of the biofilm disruption (Galloway et al 2012).
Why would you use a broad spectrum antimicrobial that kills?
Because biofilms are usually polymicrobial
What is a biofilm?
Biofilms are communities of micro- organisms that grow in clumps and live together under the protection of a blanket of slime which is also known as a polymeric matrix.
What is the relationship between chronic wounds and biofilms?
Biofilms are estimated to occur in 60-90% of chronic wounds (Shultz, 2015) and are thought to result in delayed healing (Dowsett, 2013). The presence of a biofilm triggers a chronic inflammatory response that results in neutrophils and macrophages surrounding it. The neutrophils and macrophages secrete large volumes of reactive oxygen species (ROS) that adversely affect biofilm and surrounding tissue. Inflammatory cells attracted to the area can also secrete high levels of proteases (matrix metalloproteases and elastase) that can help to break down the attachments between biofilms and tissues to dislodge them. However the ROS and proteases also damage normal surrounding tissues and degrade proteins that are essential for wound healing, impairing the healing process (Holloway et al, 2012).
How do you do a wound assessment for a biofilm?
Biofilms are microscopic structures that cannot be seen with the naked eye. Routine wound swabs if the wound surface also frail to identify biofilms as cultivation methods only support the growth of planktonic bacteria, which does not reveal if they originated from biofilm (Holloway et al 2012; cooper 2010). The only way to see a biofilm is using specialised microscopy that is not routinely available.
What factors delay healing of Patients with chronic wounds?
Co- mornidities Poor nutrition Poor diagnosis/ mismanagement Non- concordance These factors should be eliminated as contributing factors to delayed healing before a biofilm is considered.
What is debridement?
Debridement physically removes devitalised tissue from the wound bed so that healing can occur.
What are they thought to be responsible for?
Delayed wound healing 60% of chronic wounds contain biofilm compared to 6% Of Acute wounds (James et al 2008).
What do biofilms play a role in?
Development of persistent infections they contribute to disease progression and the development of complications in vulnerable patients. They play a role in many chronic inflammatory conditions in healthcare, including cystic fibrosis, periodontal disease and osteomyelitis
In the absence of an accessible way of detecting the presence of biofilm in clinical practice how does the clinician look for clinical signs that indicate a biofilm may be present when carrying out wound assessment?
Failure of the wound to heal it becomes static despite best management Excess exudate or unexpected sudden increase in volume Malodour Shinny slimy gelatinous material in the surface of wound that is removed easily and reforms quickly Persistent necrotic tissue Persistent slough that reforms despite debridement Poor quality granulation tissue either fragile or hypergranulated. Signs of local infection (as biofilms is a precursor to infection) e.g. heat redness swelling, pain, malodour Persistent or reoccurring infection Slow or no response to antiseptic dressings such as silver iodine and PHMB Polymicrobial microbiology (more than one species picked up on wound swabs biofilm releasing planktonic to spread infection) (Phillips 2010; perceivable et al, 2012). The presence of slimy material within a wound should not be assumed to be related to biofilm since the arrangement of cells within the slime can only be seen using a high powered magnification. However there is a link between biofilms and slough. As biofilms stimulate inflammation, vascular permeability increases promoting an increase in wound exudate and the build up of fibrin slough. Therefore slough may indicate the presence of biofilm in the wound (holloway et al. 2012).
What do biofilms consist of?
It's a single species of bacteria or fungi but they are usually polymicrobial meaning they are made up of many different species that are continuously changing (Hall-stupidly and stoodley, 2009)
Describe the maturation 1 (stage 3 of the biofilm development)
The cells continue to grow and form an uneven mass with bulbous projections or micro colonies.
Describe the maturation 2 (stage 4 of the biofilm formation)
The cells within mature biofilms have different characteristics to planktonic cells. This is because quorum- sensing molecules initiate differentiation in then biofilm cells so that they have increased virulence, slower growth and are less susceptible to antimicrobial agents and the immune response (cooper, 2010).
Describe the irreversible attachment (stage 2 of the biofilm formation)
The production and recognition of chemical signals (quorum sensing molecules) allows one micro-organisms to communicate with another of the same species are nearby. It also allows communication between different species. When the number of cells of the same species reaches a critical level (also known as quorum) biofilm formation is triggered and cells start to produce the slimy matrix that will hold all the cells together.
What is the role of biofilm
The role of biofilm in inflammatory diseases has long been recognised with their presence in chronic wounds now being thought of as a reason for delayed healing.
What benefit does a monofilament debridement method have?
Using the monofilaments debridement pads to mechanically debride wounds containing biofilm may have additional benefits for biofilm disruption and bacterial management as well as being more clinically and cost effective than then the use of autolytic dressings
What are the clinical indicators that biofilm has been removed from the wound?
When healing begins to progress, the volume of exudate produced by the wound is reduced and less slough is present on the wound bed. Clinical judgement is needed on when to reduce debridement frequency and the discontinuation of antimicrobial dressifn use (Phillips, 2010).
What is Biofilm based wound care?
With all wound management a holistic approach should be taken to the management of wounds with suspected biofilm. This encompasses optimising nutrition, optimising management of any co-morbidities which may delay healing (see the wound healing module to learn more about these factors), wound bed preparation and best practice wound management. Biofilm based wound care is a strategic approach to managing biofilm (Walcott et al 2008). Biofilms can be difficult to eradicate as the biofilm blocks most antibiotics and antiseptics from reaching the micro organisms within. The reduced metabolism by the bacteria to have an efficacy , since they need to be metabolised by the bacteria to have an effect. Phagacytic immune cells which can eradicate planktonic bacteria easily cannot engulf destroy the biofilm as to to large (cooper 2010).
why would you disrupt the biofilm and prevent reformation?
Wound bed preparation is key to the disruption of existing biofilms and the prevention of new ones forming. Biofilm disruption and prevention of reformation is achieved using: Debridement Topical antimicrobials
How do you prevent biofilm formation?
Wound biofilms can be prevented by identifying patients at risk such as those who are immunocompromised or who have multiple co-morbidities and optimising wound management in these patients. This includes frequent wound cleansing and/ or debriding and the use of antimicrobial dressings to kill bacteria INR eh wound bed and block the entry of new bacteria respectively (Holloway et al, 2012).
