Yeast infections caused by Candida species may occur on moist areas of the skin such as in nappy rash. Bites Wound infections due to bites tend to reflect the microorganisms present in the saliva and oral cavity of the human or animal that created the bite wound. Human bites may become infected with a variety of aerobic and anaerobic bacteria that are part of the normal oral flora. The majority of animal bites are from dogs and cats, and the most common bacteria recovered from these cultures is Pasteurella multocida.
Although rare, there is a risk of a rabies viral infection with bites from unvaccinated animals and should be considered if the bite occurs outside Australia although even in the wild the prevalence of rabies is low. In Australia, if bitten or scratched by a bat, then prophylaxis against Australian Bat Lyssa Virus should be considered by your health care provider. Trauma Trauma is a wide category of injuries caused by physical force. It includes everything from burns to injuries from motor vehicle accidents, crushing injuries, cuts from knives and other sharp instruments, and gunshot wounds.
The type of infections that trauma victims acquire depend primarily on the environment in which the injury took place, the extent of the injury, the microorganisms present on the skin of the affected person, the microorganisms the person is exposed to during wound healing, and the person's general health and immune status. Wounds that are initially contaminated such as with the dirt that may be acquired during a motor vehicle accident or that involve extensive damaged tissue - such as a severe burn - are at an increased risk of becoming infected.
A deep puncture wound could allow anaerobic bacteria such as Clostridium tetani the cause of tetanus to grow. Because most people in Australia are immunised against tetanus, this is a rare event but need to be considered. Routine vaccination of adults every 10 years is no longer recommended but you should discuss this with your health care provider. Re-vaccination is often done in the emergency room where patients are treated after incurring a deep wound that may need stitches particularly if more than 5 years has elapsed since the last dose.
Superficial burns do not usually become infected, unless other systemic factors are present. When infection does occur, the most commonly reported microbes from a burn wound in the days immediately following the injury are S. Later, Gram-negative organisms such as Pseudomonas aeruginosa or coliforms, e. Bite wounds often contain more exotic flora, reflecting the source of the bite. Staphylococcus spp , Peptostreptococcus spp and Bacteroides spp are the most common microorganisms in wounds from human and animal bites.
However, when infection does occur, antibiotic-resistant organisms, such as methicillin resistant Staphylococcus aureus MRSA and vancomycin resistant enterococci, are more commonly encountered, reflecting hospital-acquired flora. Diabetic foot infections are frequently associated with S. However, the clinical significance of the type of microorganism present is reduced if there are limited signs of infection, which is common in people with infected diabetic ulcers.
Deeper penetrating wounds are associated with a wider range of bacteria, representing the increased likelihood of foreign bodies in the wound. Referral is often necessary for exploration of the wound if it fails to heal. There is some debate as to whether the type of bacteria or the overall density of the bacteria affects healing rates more significantly. It is likely that both factors play a role, however, the more widespread opinion is that organism type has the greater effect on wound healing.
It is thought that aerobic or facultative pathogens in particular, such as S. Laboratories may provide either a quantitative or semi-quantitative result for bacterial load. A quantitative result gives the estimated number of organisms per gram of tissue or per mm 3. Organism load above per gram of tissue or per mm 3 is considered significant, and is likely to reduce healing times significantly.
Susceptibility testing is performed for all of the potential pathogens isolated from the swab. This may not always be the case, e. When an organism is reported as resistant to a particular antibiotic it is important to assess the clinical response, if treatment has already commenced, with consideration given to changing the antibiotic if necessary.
In slower-developing infections or wounds that have failed to resolve over time, antibiotic choice should be directed by the relevant susceptibilities provided by the laboratory analysis. If empiric antibiotic treatment is prescribed, i. Susceptibility differs by geographical area, as well as in different rest homes or long-term care facilities, e.
MRSA is more common in some locations. For information on nationwide susceptibilities and resistance, see: www. In addition to antibiotic treatment, wound cleansing, surgical debridement and correct dressing is essential to reduce the microbial load, and likelihood of infection. Its frequent use led to increased bacterial resistance to mupirocin, and as a result, mupirocin became a prescription-only medicine. Mupirocin remains active against some MRSA strains and as such, it is recommended that it should be reserved for use only when susceptibility testing shows MRSA to be present.
If signs of infection are not reduced 48 — 72 hours after initiation of antibiotic treatment for an acute wound, a swab should be taken to reassess the wound flora and relevant susceptibilities. If a wound fails to heal within four to six weeks following treatment, particularly if antibiotics were used, discussion with a wound specialist is recommended.
In some cases, a non-healing wound may raise the suspicion of malignancy and this should be investigated.
Chronic wounds can degenerate into malignancy, and conversely a malignancy may present as, or be mistaken for, a chronic wound. Primary malignancy should be considered in a patient with an ulcer which has developed over a relatively short time. A pearly, shiny nodule with prominent capillary networks is also common. A basal cell carcinoma may also present as an eczema-like patch.
Only advanced cancers appear as wound-like, having outgrown their blood supply and eroded. The ulcer is usually present for more than six months, but may be present for up to several decades, as it slowly undergoes malignant change.
The most common resulting malignancy is a squamous cell carcinoma, 19 which is a slow-growing cancer derived from the epithelial cells.
A punch biopsy of the wound should be taken if there is a suspicion of any malignancy; particularly if the wound has been present for longer than three months or developed rapidly and has not responded to treatment or is increasing in size.
The biopsy site is important. If malignancy is suspected, the biopsy site should be on the wound margin and must include tissue from the wound bed and surrounding, non-damaged skin. Staphylococcus aureus is the most frequently isolated bacterial pathogen in wounds.
Although non-pathogenic colonisation is common, 16 S. Methicillin-resistant S. There appears to be limited biological or clinical difference between MRSA and non-resistant staphylococcus with the exception of resistance. Adhesion ability, colonisation and infectivity, modes of transmission and survivability are all similar. Infections caused by MRSA are most common in hospitals, prisons, residential care and other areas where multiple people, often with lowered immune response live in close proximity.
Depending on the severity of the infection and the clinical situation, patients with MRSA infection in a wound may require referral to hospital for IV antibiotic treatment, usually with vancomycin.
Patients with soft tissue infections that can be treated in the community are usually prescribed oral co-trimoxazole or clindamycin, but discussion with a clinical microbiologist or infectious disease specialist may be useful.
Thank you to Dr Rosemary Ikram , Clinical Microbiologist, Christchurch for expert guidance in developing this article. Follow us on facebook. Decision support for health professionals ». South Island general practice support ». Practice acquisition and careers in health ». Click here to register ». Forgot your login? Login to my bpac. Remember me. Dermatology Infections Trauma and surgical procedures. Microbiological assessment of infected wounds: when to take a swab and how to interpret the results Identifying and managing infection in wounds is an important aspect of primary care practice.
In this article Characteristics of a wound When and how should a wound be swabbed? Interpreting the results of a wound swab analysis What should you do if a wound infection does not resolve? Characteristics of a wound A wound is defined as any injury that damages the skin and therefore compromises its protective function.
Wound healing Wounds heal by either primary closure, as in the case of a clean, fresh wound, with well-approximated edges which are sutured together, or by contraction and epithelialisation, such as for a wound left open due to loss of skin or contamination.
Local factors which may delay wound healing include: 3, 4 The underlying cause and severity of the wound A delay in the patient presenting for medical attention The presence of necrotic tissue in the wound — this can promote the growth of bacteria, especially anaerobes The presence of foreign bodies in the wound Impairment of the local circulation The site of the wound, e.
AIDS, or medicine, e. Colonisation versus infection All open skin wounds are colonised by bacteria, however, this does not mean that all wounds are infected. Wound infection can be classified on a spectrum of five progressively more severe stages: 1, 5 1. Contamination occurs when non-replicating bacteria enter the wound. Red flags for wound care Specific wound features or patient factors greatly increase the risk of infection or other complications.
Referral for hospital assessment should be considered if a patient presents with high risk features, such as: 7, 8, 9 Rapidly developing tissue necrosis or gangrene Extensive cellulitis, or cellulitis of the face, hands, over joints or periorbital area Systemic illness without another obvious cause Clinical signs suggestive of osteomyelitis, e.
Maybe it was not very long ago. You might also remember what happened after that. The injury might have oozed some blood, which stopped soon after to reveal reddish, damaged skin. If the injury was deep, you may have visited the doctor. The doctor would have cleaned the damaged skin and covered it with a bandage. Over the next few days, you may have observed the injured skin change colors from bright red to bluish-black, and finally, the injury would have been replaced with fresh skin.
After the damaged skin has healed, you may see a flesh-colored scar at the location of the injury. If this sounds familiar, it means that your accidental injury resulted in what is called a wound, which was followed by the normal steps of recovery known as wound healing.
It is likely that your wound eventually healed without any problems. The skin is the largest organ of the body and it acts as a protective covering shielding the body from the outer environment. The epidermis is the outermost layer of the skin, consisting of cells known as keratinocytes. The middle layer, or dermis , contains another type of skin cell known as fibroblasts, and blood vessels that carry blood to and from the skin.
The dermis also has tissue fibers that provide support to cells within the skin. Superficial wounds are injuries to only the epidermis. Deep wounds extend all the way into the dermis, causing greater damage to skin cells and tissue fibers, resulting in a gap in the skin. In deep wounds, the blood vessels also get damaged, leading to leaks, which is why these wounds bleed. So, what happens after we get hurt and how does the body respond to a wound? After an injury, the body starts repairing damaged skin through the process of wound healing, which involves a set of four well-coordinated steps Figure 1 [ 1 ].
The first step involves stopping the blood flow by formation of a blood clot at the wound, and this happens almost immediately after an injury. To form a clot, blood components interact to form a loose plug of protein strands and blood cells at the wound site. Next, large numbers of immune cells arrive at the wound site through blood vessels, releasing chemicals that start to build new tissue in the wound. In the third stage, the wound is gradually filled with new skin tissue that replaces the gap created by the injury.
This works somewhat like building blocks, in which different types of skin proteins act as a solid, sticky surface on which many layers of skin cells can attach and grow. In the final stage of wound healing, this new skin tissue gets strengthened and completely fills the wound.
This step replaces the damaged tissue with scar tissue that closely resembles normal skin. This completes the process of wound healing. The entire process of wound healing starts immediately after injury and usually takes a few weeks. However, in certain situations, wounds do not follow this coordinated repair process, taking a long time to heal or not healing at all. Why do some wounds fail to heal properly? One of the main reasons that wounds may fail to heal properly is the presence and growth of microbes , which are very tiny forms of life, in the wound.
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