Abscess / A collection of pus ( containing live and dead neutrophils and macrophages, bacteria, fibrin and inflammatory mediators, opsonins and complement, and dead cells killed by the infective process) which has accumulated in a cavity formed by surrounding granulationtissue following an infection (usually caused by bacteria, particularly staphylococci or bacteroides, or parasites) or foreign materials (e.g. splinters, bullet wounds, or injecting needles). It is a defensive and localising reaction of the tissue to prevent the spread of infectious materials to other parts of the body.
The organisms or foreign materials kill the local cells, resulting in the release of cytokines. The cytokines trigger an inflammatory response, which draws large numbers of white blood cells to the area and increases the regional blood flow. The tension within the abscess can be high and is the cause of associated pain which is relieved after drainage or spontaneous bursting
The final structure of the abscess is an abscess wall of granulation tissuewhich is formed by the adjacent healthy cells to localise the pus and prevent infection of neighboring structures. However, such encapsulation tends to prevent immune cells or antibacterials fromreaching bacteria in the pus. Abscesses tend to point to the surface and they should be drained surgically. Antimicrobials have a limited role unless there is associated spreading cellulitis or bacteraemia
Antimicrobials / Agents which can inhibit the growth of or kill micro-organisms. These can be antibiotics (active against bacteria and given systemically), anti-fungal agents (active against fungi), antiviral agents (active against viruses) or anti-parasitic agents (active against parasites). There are also other broad spectrum antimicrobial agents such as antiseptics, disinfectants, preservatives and biocides (which are chemically derived but applied topically)
Antiseptics / Chemical, broad-spectrum, antimicrobial agents applied topically to skin or underlying tissues to prevent or control infection or increasing bacterial colonisation by killing or inhibiting pathogens
Argyria / A term that is often misused. This very rare condition produces blue-grey discolouration of the skin and is associated withlong-term systemic exposure to silver salts. Argyria differs from the reversible local discolouration that may be associated with silver dressings; argyria is irreversible and can affect the skin of the entire body and the internal organs. / WICP, page 10
Bacteraemia / The presence of viable bacteria in the blood. MRSA bacteramia is mandatorily reported in the UK
Bactericidal / Antimicrobial agents which destroy (kill) micro-organisms, such as antiseptics, antibiotics and disinfectants / AWCN
Bacteristatic / Antimicrobial agents which inhibit the growth or multiplication of micro-organisms / AWCN
Bioburden / The amount of contaminating micro-organisms presentin tissues or on open ulcers/wounds prior tocleansing. Bioburden ranges from contamination (least) through to colonisation and infection (highest) / AWCN
Biofilms / Alayer of bacteria and/or other microorganisms on a solid or semi-solid surface, tissue or skin ulcer bound together in a bacterially-derived polysaccharide matrix(glycocalyx) shielded against the immune system and antimicrobial agents..
There appears to be a correlation between biofilms and non-healing in chronic wounds.
Cellulitis / A diffuse, spreading, acute infection of the skin and/or subcutaneous tissues characterized most commonly by local heat, redness and pain. There can be systemic signs of tachycardia, tachypnoea, pyrexia and raised white count and sepsis / Mosby’s PDQ for Wound Care (2009). Mosby-Elsevier, St. Louis, MO.
Colonisation / Establishment of a community of microorganisms or ecosystem in a tissue or open ulcer healing by secondary intention, without necessarily resulting in tissue invasion or damage. / WICP, page 1
Contamination / The presence of microorganisms in a tissue or open wound healing by secondary intention, neither increasing in number or causing clinical complications of infection. It is a sequel of colonisation and precedes infection in open wounds / WICP, page 1
Crepitus / A crackling feeling or sound detected on palpation of tissues that is due to gas within the tissues. It is not necessarily related to gas gangrene (Clostridium perfringens specific) as other infecting organisms can form gas in tissues / WICP, page 10
Critical colonisation / A point at which microorgansims are increasing in numbers in tissues or an open wound but not releasing virulence factors (or toxins) to cause infection. It may be related to delayed healing but is hard to define.
Cytotoxic / Chemical agentswhicjh are directly toxic to cells, preventing their reproduction or growth and causing cell death. This includes disinfectants which do kill bacteria but are also toxic to healthy tissues / AWCN
Debridement / The removal of necrotic or foreign material from and around a wound to optimise wound healing. There are many different methods that can be used to debride a wound. They can be broadly classified as surgical/sharp, mechanical, biological, enzymatic and autolytic.
Sharp debridement is the removal of dead or necrotic tissue or foreign material from and around a wound to expose healthy tissue using a sterile scalpel, scissors or both.
Mechanical debridement involves methods such as wet-to-dry dressings, wound irrigation, and similar techniques that physically remove debris from a wound.
Biological debridement broadly describes the application of sterile larvae to the wound area.
Enzymatic debridement involves the topicalapplication of endogenous enzymes.
Autolytic debridement is a process that spontaneously separates necrotic tissue and eschar from healthy tissue; it occurs to some extent in all wounds.
Evidence supporting one method over another is lacking. / David Leaper, World Wide Wounds 2002, plus Schultz, Sibbald, Falanga et al, WRR 2003;11:1-28
Dehiscence / The separation of a surgical incision or sutured wound exposing underlying tissues but not necessarily exposing deep contents of a body cavity. Used in the past to describe burst abdomen or chest where all layers of a surgical wound separate with exposure of viscera It is a surgical complication that results from poor wound healing. Risk factors includeinfection, age, diabetes, underlying disease such as cancer, obesity, immunosuppression, poor suture or surgical technique. / IWII committee
Delayed healing / Healing progresses at a slower rate than expected. As a guide:
■ in open surgical wounds healing mainly by epithelialisation, the epithelial margin advances at about 5mm per week
■ clean pressure ulcers with adequate blood supply and innervation should show signs of healing within two to four weeks
■ a reduction in venous leg ulcer surface area of >30% during the first two weeks of treatment is predictive of healing
A chronic wound might be defined as a failure to heal after 6 weeks despite optimal conditions (such as adequate debridement and dressings, pressure relief, diabetic control, adequate arterial inflow or compression in pressure, diabetic, arterial or venous ulcers) / WICP, page 10
Erythema / Redness or inflammation of the skin or mucous membranes that is the result of dilation and congestion of superficial capillaries. It can be caused by invasive bacteria such as -haemolytic streptococci / Mosby’s PDQ for Wound Care (2009). Mosby-Elsevier, St. Louis, MO.
Endotoxin / A toxin that forms an integral part of the cell wall of certain bacteria (Gram negative rods in particular) and is only released upon destruction of the bacterial cell.
Endotoxins are less potent and less specific than most bacterial toxins but can cause pyrexia and sepsis.
Exotoxin / A toxin that is released from an actively growing cell, is heat labile and often proteinaceous in nature. It has a specific target and can be used to form toxoids which are used in vaccines. Many are important virulence factors in pathogenic bacteria e.g. Panton Valentine Leukocidin (PVL) of Staphylococcus aureuswhich can cause a necrotising cellulitis and pneumonia
Foreign body / Every foreign body has the potential to act as a nidus for infection and to impair wound healing. The majority of wound debris may be removed through meticulous, copious irrigation. However, direct visualization and removal with instruments may be required. Objects can either be inert (nonreactive) or organic (reactive). Examples of inert objects include bullets, needles, and metal objects. While these may cause chronic pain, they may not provoke an inflammatory response. Organic materials—such as wood, bone, stone, rubber, and soil—may cause infection and must be completely removed. Their presence in tissues can logarithmically reduce the numbers of organisms needed to cause an infection / Atlas of Emergency Medicine
Genotype / The genetic constitution (the genome) of a cell, an individual or an organism. The genotype is distinct from its expressed features, or phenotype. The genotype of a person is her or his genetic makeup. It can pertain to all genes or to a specific gene.
Gram stain / A method of differentiating bacterial species into two groups, Gram- and Gram+, based on the chemical and physical properties of their cell walls. Staphylococci and streptococci are Gram positive cocci; E.coli and pseudomonas are Gram negative rods
Hypertrophic scar / An abnormal scar in which there is excess scar tissue formed, especially across a joint surface. The reddened scar tissue does not exceed the original size the wound. Hypertrophic scars tend to regress spontaneously
Induration / Hardening and swelling of the skin and subcutaneous tissues around a wound due to inflammation, which may be secondary to infection. The oedema and “tumor” of inflammation / WICP, page 10
Infection / Multiplication and invasion of an infectious agent within the body tissues causing signs and symptoms of disease. In wound care the most common are Gram positive cocci, such as staphylococci; and Gram negative rods, such as pseudomonas
Inflammation / Redness, warmth, swelling and pain (the Celsian rubor, calor, tumor and dolor) and decreased function (the mediaeval addition of function laesa) seen in injured, infected or irritated tissues. Inflammation is also the first mechanism used as a type of nonspecific immune response. In wound care it usually pertains to infection
Invasion / The process whereby an infectious agent (in wound careusually bacteria) enters the hostcells or tissues and spreads in the body (as cellulitis, lymphangitis and bacteraemia).
Keloid scar / Keloids represent excess scar formation that grows beyond the borders of the original wound and does not tend to resolve spontaneously. Keloids tend to form in persons with darker skin pigmentation and can form as late as a year after injury.
Lymphangitis / Inflammation of lymph vessels, seen as red skin streaks running proximally from a site of infection. Most often seen with streptococcal and staphylococcal infections / WICP, page 10
Micro-organism / Organisms that are microscopic or invisible to the naked eye, including bacteria, fungi, viruses, and parasites
Multi-organ dysfunction syndrome / MODS is the presence of altered organ function in a patient who is acutely ill such that homeostasis cannot be maintained without intervention. Primary MODS is the direct result of a well-defined insult in which organ dysfunction occurs early and can be directly attributable to the insult itself. Secondary MODS develops as a consequence of a host response and is identified within the context of SIRS and sepsis. Patients with uncontrolled wound infection (e.g. in pressure sores) may develop sepsis, organ failure and death
Opportunistic
Pathogen / An infectious agent capable of causing disease when the hosts’ immune system is impairedPathogen / An infectious agent capable of causing an infectious disease.
Phenotype / The observable characteristics or traits of an organism such as morphology, development or behaviour
Pathogenicity / The ability of a microorganism to cause disease, also called virulence
Planktonic bacteria / Free floating bacteria that is not attached to a surface
Prophylaxis / An agent used to prevent the spread of disease or condition. Classically an antibiotic given once, IV, at induction of anaesthesia to prevent surgical site infection
Purulent / Containing or comprised of pus. Pus is a collection of infected material, usually living and dead leukocytes
Quorum sensing / A type of decision making process used by decentralized groups to co-ordinate behaviour. Many species of bacteria use quorum sensing to co-ordinate their gene expression according to the local density of their population
Resistance / The ability of a micro-organism to not be effected by antimicrobial agents by blocking their cellular action or by the production of an enzyme to inactivate the agent
Sepsis / Defined as systemic inflammatory response syndrome (SIRS) in the presence of a known or suspected infection. The body may develop this excessive inflammatory response to microbes in the blood, urine, lungs, skin, or other tissues such as infected wounds or ulcers. An incorrect lay term for sepsis is blood poisoning, or septicaemia;both terms are now redundant
Similar syndromes may follow burns or pancreatitis with the systemic response to endotoxins and expression of cytokines
Multiple organ dysfunction syndrome (MODS) may result (eg, lactic acidosis, acute respiratory distress syndrome, oliguria, obtundation). Septic shock is refractory hypotension in addition, despite adequate fluid resuscitation / American College of Chest Physicians/Society of Critical Care Medicine Consensus Panel
Surgical site infection / Definitions of surgical site infection include:
- Superficial incisional SSI: Infection involves only skin and subcutaneous tissue of incision.
- Deep incisional SSI: Infection involves deep tissues, such as fascial and muscle layers.
- Organ/space SSI: Infection involves any part of the anatomy in organs and spaces other than the incision, which was opened or manipulated during operation.
Systemic Inflammatory Response Syndrome / Systemic inflammatory response syndrome (SIRS) may follow a variety of clinical insults, including infection, pancreatitis, ischemia, multiple trauma, tissue injury, hemorrhagic shock, or immune-mediated organ injury.
It is defined as two of:
Tachycardia >90 beats/min; Tachypnoea> 20 breaths/min
WBC >12x 109/l or <4x109/l; temp >38oC or <36oC
Tensile strength / The tensile strength of a wound is a measurement of its load capacity per unit area. The bursting strength of a wound is the force required to break a wound regardless of its dimension. Bursting strength varies with skin thickness. Peak tensile strength of a wound occurs approximately 60 days after injury. A healed wound only reaches approximately 80% of the tensile strength of unwounded skin.
Virulence / Virulence is the quantitative or relative ability of the agent to cause disease
WICP = Harding et al, Wound Infection in Clinical Practice, MEP 2008
International Wound Infection Institute - Glossary of terms in wound infection – October 2009