92-440: An infection is the detrimental colonization of a host organism by a foreign species. Infection , infected , or infectious may also refer to: Infection An infection is the invasion of tissues by pathogens , their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease , also known as a transmissible disease or communicable disease ,
184-554: A plastic surgeon . There are several methods that can be implemented to achieve primary closure of a wound, including suture , staples , skin adhesive , and surgical strips . Suture is the most frequently used for closure. There are many types of suture, but broadly they can be categorized as absorbable vs non-absorbable and synthetic vs natural. Absorbable sutures have the added benefit of not requiring removal and are often preferred in children for this reason. Staples are less time-consuming and more cost effective than suture but have
276-456: A prion . The benefits of identification, however, are often greatly outweighed by the cost, as often there is no specific treatment, the cause is obvious, or the outcome of an infection is likely to be benign . The diagnosis is aided by the presenting symptoms in any individual with an infectious disease, yet it usually needs additional diagnostic techniques to confirm the suspicion. Some signs are specifically characteristic and indicative of
368-422: A runny nose . In certain cases, infectious diseases may be asymptomatic for much or even all of their course in a given host. In the latter case, the disease may only be defined as a "disease" (which by definition means an illness) in hosts who secondarily become ill after contact with an asymptomatic carrier . An infection is not synonymous with an infectious disease, as some infections do not cause illness in
460-425: A colonization is often only a matter of circumstance. Non-pathogenic organisms can become pathogenic given specific conditions, and even the most virulent organism requires certain circumstances to cause a compromising infection. Some colonizing bacteria, such as Corynebacteria sp. and Viridans streptococci , prevent the adhesion and colonization of pathogenic bacteria and thus have a symbiotic relationship with
552-516: A complementary therapy in wound healing; however, there is no high quality research supporting its use as an evidence based clinical intervention. More than 400 species of plants are identified as potentially useful for wound healing. Only three randomized controlled trials, however, have been done for the treatment of burns. From the Classical Period to the Medieval Period , the body and
644-469: A disease and are called pathognomonic signs; but these are rare. Not all infections are symptomatic. In children the presence of cyanosis , rapid breathing, poor peripheral perfusion, or a petechial rash increases the risk of a serious infection by greater than 5 fold. Other important indicators include parental concern, clinical instinct, and temperature greater than 40 °C. Many diagnostic approaches depend on microbiological culture to isolate
736-399: A disease. This amplification of nucleic acid in infected tissue offers an opportunity to detect the infectious agent by using PCR. Third, the essential tools for directing PCR, primers , are derived from the genomes of infectious agents, and with time those genomes will be known if they are not already. Thus, the technological ability to detect any infectious agent rapidly and specifically
828-481: A few of the many factors known to affect the rate of wound healing. Wounds can be broadly classified as either acute or chronic based on time from initial injury and progression through normal stages of wound healing. Both wound types can further be categorized by cause of injury, wound severity/depth, and sterility of the wound bed. Several classification systems have been developed to describe wounds and guide their management. Some notable classification systems include
920-423: A hospital stay. Lastly, a community-acquired infection is one in which the infection is acquired from a whole community. One manner of proving that a given disease is infectious, is to satisfy Koch's postulates (first proposed by Robert Koch ), which require that first, the infectious agent be identifiable only in patients who have the disease, and not in healthy controls, and second, that patients who contract
1012-524: A host with depressed resistance ( immunodeficiency ) or if they have unusual access to the inside of the body (for example, via trauma ). Opportunistic infection may be caused by microbes ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract , and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridioides difficile colitis ) or from
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#17331107646941104-502: A host. As bacterial and viral infections can both cause the same kinds of symptoms, it can be difficult to distinguish which is the cause of a specific infection. Distinguishing the two is important, since viral infections cannot be cured by antibiotics whereas bacterial infections can. There is a general chain of events that applies to infections, sometimes called the chain of infection or transmission chain . The chain of events involves several steps – which include
1196-434: A link between virulence and transmissibility. Diagnosis of infectious disease sometimes involves identifying an infectious agent either directly or indirectly. In practice most minor infectious diseases such as warts , cutaneous abscesses , respiratory system infections and diarrheal diseases are diagnosed by their clinical presentation and treated without knowledge of the specific causative agent. Conclusions about
1288-518: A number of basic dyes due to the electrostatic attraction between negatively charged cellular molecules and the positive charge on the dye. A cell is normally transparent under a microscope, and using a stain increases the contrast of a cell with its background. Staining a cell with a dye such as Giemsa stain or crystal violet allows a microscopist to describe its size, shape, internal and external components and its associations with other cells. The response of bacteria to different staining procedures
1380-558: A number of factors, each of which is important to consider in order to establish a proper diagnosis and treatment plan. In addition to collecting a thorough history, the following factors should be considered when evaluating any wound: A thorough wound evaluation, particularly evaluation of wound depth and removal of necrotic tissue, should be performed only by a licensed healthcare professional in order to avoid damage to nearby structures, infection, or worsening pain. Additional diagnostic tests may be needed during wound evaluation based on
1472-404: A particular pathogen at all (no matter how little) but also is often used in a sense implying a clinically apparent infection (in other words, a case of infectious disease). This fact occasionally creates some ambiguity or prompts some usage discussion; to get around this it is common for health professionals to speak of colonization (rather than infection ) when they mean that some of
1564-493: A pathogen from the appropriate clinical specimen. In a microbial culture, a growth medium is provided for a specific agent. A sample taken from potentially diseased tissue or fluid is then tested for the presence of an infectious agent able to grow within that medium. Many pathogenic bacteria are easily grown on nutrient agar , a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into
1656-429: A pathogen. A fluorescence microscope is then used to detect fluorescently labeled antibodies bound to internalized antigens within clinical samples or cultured cells. This technique is especially useful in the diagnosis of viral diseases, where the light microscope is incapable of identifying a virus directly. Other microscopic procedures may also aid in identifying infectious agents. Almost all cells readily stain with
1748-432: A patient's blood or other body fluids for antigens or antibodies that indicate presence of a specific pathogen that the doctor suspects. Other techniques (such as X-rays , CAT scans , PET scans or NMR ) are used to produce images of internal abnormalities resulting from the growth of an infectious agent. The images are useful in detection of, for example, a bone abscess or a spongiform encephalopathy produced by
1840-470: A persistent infection by infecting different cells of the body. Some viruses once acquired never leave the body. A typical example is the herpes virus, which tends to hide in nerves and become reactivated when specific circumstances arise. Persistent infections cause millions of deaths globally each year. Chronic infections by parasites account for a high morbidity and mortality in many underdeveloped countries. For infecting organisms to survive and repeat
1932-547: A process in which the wound is allowed to fill-in over time through natural physiologic processes. When healing by secondary intention, granulation tissue grows in from the wound edges slowly over time to restore integrity of the skin. Healing by secondary intention can take up to months, requires daily wound care, and leaves an unfavorable scar, thus primary closure is always preferred when possible. As an alternative, wounds that cannot be closed primarily can be addressed with skin grafting or flap reconstruction , typically done by
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#17331107646942024-403: A result of an infectious disease with immunosuppressive activity (such as with measles , malaria or HIV disease ). Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host. While a primary infection can practically be viewed as the root cause of an individual's current health problem, a secondary infection
2116-471: A result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however, many serious diseases are caused by organisms acquired from the environment or that infect non-human hosts. Opportunistic pathogens can cause an infectious disease in
2208-503: A risk of worse scarring if left in place for too long. Adhesive glue and sutures have comparable cosmetic outcomes for minor lacerations <5 cm in adults and children. The use of adhesive glue involves considerably less time for the doctor and less pain for the person. The wound opens at a slightly higher rate but there is less redness. The risk for infections (1.1%) is the same for both. Adhesive glue should not be used in areas of high tension or repetitive movements, such as joints or
2300-411: A severe illness affecting the brain, remain undiagnosed, despite extensive testing using the standard of care ( microbiological culture ) and state-of-the-art clinical laboratory methods. Metagenomic sequencing-based diagnostic tests are currently being developed for clinical use and show promise as a sensitive, specific, and rapid way to diagnose infection using a single all-encompassing test. This test
2392-417: A specific identification of an infectious agent only when such identification can aid in the treatment or prevention of the disease, or to advance knowledge of the course of an illness prior to the development of effective therapeutic or preventative measures. For example, in the early 1980s, prior to the appearance of AZT for the treatment of AIDS , the course of the disease was closely followed by monitoring
2484-420: A thorough evaluation is performed, all wounds should be properly irrigated and debrided . Proper cleansing of a wound is critical to prevent infection and promote re-epithelialization. Further efforts should be made to eliminate/limit any contributing factors to the wound (e.g. diabetes, pressure, etc.) and optimize the wound's healing ability (i.e. optimize nutritional status). The end goal of wound management
2576-432: A visible mound on the surface of the plate called a colony , which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its strain ), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit
2668-448: A wound impossible without adequate debridement. Debridement can be achieved in several ways: The end goal of wound care is to re-establish the integrity of the skin , a structure which serves as a barrier to the external environment. The preferred method of closure is to reattach/reapproximate the wound edges together, a process known as primary closure/healing by primary intention. Wounds that have not been closed within several hours of
2760-534: A wound, is a critical consideration when evaluating a wound. In the United States, the CDC's Surgical Wound Classification System is most commonly used for classification of a wound's sterility, specifically within a surgical setting. According to this classification system, four different classes of wound exist, each with their own postoperative risk of surgical site infection: Wound presentation will vary greatly based on
2852-509: Is a sequela or complication of that root cause. For example, an infection due to a burn or penetrating trauma (the root cause) is a secondary infection. Primary pathogens often cause primary infection and often cause secondary infection. Usually, opportunistic infections are viewed as secondary infections (because immunodeficiency or injury was the predisposing factor). Other types of infection consist of mixed, iatrogenic , nosocomial , and community-acquired infection. A mixed infection
Infection (disambiguation) - Misplaced Pages Continue
2944-457: Is a critical aspect of wound care because devitalized tissue, particularly necrotic tissue, serves as nutrients for bacteria thereby promoting infection. Additionally, devitalized tissue creates a physical barrier over a wound which limits the effectiveness of any applied topical compounds and prevents re-epithelialization. Lastly, devitalized tissue, especially eschar, prevents accurate assessment of underlying tissue, making appropriate assessment of
3036-500: Is active but does not produce noticeable symptoms may be called inapparent, silent, subclinical , or occult . An infection that is inactive or dormant is called a latent infection . An example of a latent bacterial infection is latent tuberculosis . Some viral infections can also be latent, examples of latent viral infections are any of those from the Herpesviridae family. The word infection can denote any presence of
3128-695: Is also capable of absorbing excess fluid as to avoid skin maceration or bacterial growth. Several wound dressing options are available, each tailored to different kinds of wounds: Ideally, wound dressings should be changed daily to promote a clean environment and allow for daily evaluation of wound progression. Highly exudative wounds and infected wounds should be monitored closely and may require more frequent dressing changes. Negative pressure wound dressings can be changed less frequently, every 2–3 days. Wound progression over time can be monitored with transparent sheet tracings or photographs , each of which produce reliable measurements of wound surface area. There
3220-620: Is an illness resulting from an infection. Infections can be caused by a wide range of pathogens , most prominently bacteria and viruses . Hosts can fight infections using their immune systems . Mammalian hosts react to infections with an innate response, often involving inflammation , followed by an adaptive response. Specific medications used to treat infections include antibiotics , antivirals , antifungals , antiprotozoals , and antihelminthics . Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections
3312-423: Is an infection that is caused by two or more pathogens. An example of this is appendicitis , which is caused by Bacteroides fragilis and Escherichia coli . The second is an iatrogenic infection. This type of infection is one that is transmitted from a health care worker to a patient. A nosocomial infection is also one that occurs in a health care setting. Nosocomial infections are those that are acquired during
3404-422: Is an initial site of infection from which organisms travel via the bloodstream to another area of the body. Among the many varieties of microorganisms , relatively few cause disease in otherwise healthy individuals. Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect. The appearance and severity of disease resulting from any pathogen depend upon
3496-499: Is any injury whereby the integrity of the skin has been disrupted and the underlying tissue is exposed. A closed wound, on the other hand, is any injury in which underlying tissue has been damaged but the overlying skin is still intact. Fractures can be classified as either open or closed, depending on whether the integrity of the overlying skin has been disrupted or preserved, respectively. Several classification systems have been developed to further characterize soft tissue injuries in
3588-406: Is closure of the wound which can be achieved by primary closure, delayed primary closure, or healing by secondary intention, each of which is discussed below. Pain control is a mainstay of wound management, as wound evaluation, wound cleansing, and dressing changes can be a painful process. Proper cleansing of a wound is critical in preventing infection and promoting healing of any wound. Irrigation
3680-510: Is currently available. The only remaining blockades to the use of PCR as a standard tool of diagnosis are in its cost and application, neither of which is insurmountable. The diagnosis of a few diseases will not benefit from the development of PCR methods, such as some of the clostridial diseases ( tetanus and botulism ). These diseases are fundamentally biological poisonings by relatively small numbers of infectious bacteria that produce extremely potent neurotoxins . A significant proliferation of
3772-412: Is defined as constant flow of a solution over the surface of a wound. The goal of irrigation is not only to remove debris and potential contaminants from a wound, but also to assist in visual inspection of a wound and hydrate the wound. Irrigation is typically achieved with either a bulb or syringe and needle/catheter. The preferred solution for irrigation is normal saline which is readily accessible in
Infection (disambiguation) - Misplaced Pages Continue
3864-406: Is followed by the inflammatory phase which typically lasts 1 to 3 days. Proliferation is the third stage of wound healing and lasts from a few days up to a month. The fourth and final phase of wound healing, remodeling/ scar formation, typically lasts 12 months but can continue as long as 2 years after the initial injury. Acute wounds can further be classified as either open or closed. An open wound
3956-503: Is injured. All multicellular organisms are colonized to some degree by extrinsic organisms, and the vast majority of these exist in either a mutualistic or commensal relationship with the host. An example of the former is the anaerobic bacteria species, which colonizes the mammalian colon , and an example of the latter are the various species of staphylococcus that exist on human skin . Neither of these colonizations are considered infections. The difference between an infection and
4048-432: Is moderate evidence that honey is more effective than antiseptic followed by gauze for healing wounds infected after surgical operations. There is a lack of quality evidence relating to the use of honey on other types of wounds, such as minor acute wounds, mixed acute and chronic wounds, pressure ulcers, Fournier's gangrene, venous leg ulcers, diabetic foot ulcers and Leishmaniasis. Therapeutic touch has been implicated as
4140-467: Is not an enzyme and has no metabolic function. Serological methods are highly sensitive, specific and often extremely rapid tests used to identify microorganisms. These tests are based upon the ability of an antibody to bind specifically to an antigen. The antigen, usually a protein or carbohydrate made by an infectious agent, is bound by the antibody. This binding then sets off a chain of events that can be visibly obvious in various ways, dependent upon
4232-417: Is not preferred since these solutions are toxic to tissue and inhibit wound healing. The exact volume of irrigation used will vary depending on the appearance of the wound, although some sources have reported 50–100 mL of irrigation per 1 cm of wound length as a guideline. Debridement is defined as removal of devitalized or dead tissue, particularly necrotic tissue, eschar , or slough. Debridement
4324-425: Is referred to as infectious diseases . Infections are caused by infectious agents ( pathogens ) including: The signs and symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue , loss of appetite, weight loss, fevers , night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes , coughing , or
4416-404: Is referred to as colonization. Most humans are not easily infected. Those with compromised or weakened immune systems have an increased susceptibility to chronic or persistent infections. Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections . Entrance to the host at host–pathogen interface , generally occurs through the mucosa in orifices like
4508-501: Is similar to current PCR tests; however, an untargeted whole genome amplification is used rather than primers for a specific infectious agent. This amplification step is followed by next-generation sequencing or third-generation sequencing , alignment comparisons , and taxonomic classification using large databases of thousands of pathogen and commensal reference genomes . Simultaneously, antimicrobial resistance genes within pathogen and plasmid genomes are sequenced and aligned to
4600-439: Is that microbial colonization is very common even in environments that humans think of as being nearly sterile . Because it is normal to have bacterial colonization, it is difficult to know which chronic wounds can be classified as infected and how much risk of progression exists. Despite the huge number of wounds seen in clinical practice, there are limited quality data for evaluated symptoms and signs. A review of chronic wounds in
4692-577: Is used in the taxonomic classification of microbes as well. Two methods, the Gram stain and the acid-fast stain, are the standard approaches used to classify bacteria and to diagnosis of disease. The Gram stain identifies the bacterial groups Bacillota and Actinomycetota , both of which contain many significant human pathogens. The acid-fast staining procedure identifies the Actinomycetota genera Mycobacterium and Nocardia . Biochemical tests used in
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#17331107646944784-588: The Journal of the American Medical Association 's "Rational Clinical Examination Series" quantified the importance of increased pain as an indicator of infection. The review showed that the most useful finding is an increase in the level of pain [likelihood ratio (LR) range, 11–20] makes infection much more likely, but the absence of pain (negative likelihood ratio range, 0.64–0.88) does not rule out infection (summary LR 0.64–0.88). Disease can arise if
4876-468: The oral cavity , nose, eyes, genitalia, anus, or the microbe can enter through open wounds. While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids. Wound colonization refers to non-replicating microorganisms within the wound, while in infected wounds, replicating organisms exist and tissue
4968-447: The polymerase chain reaction (PCR) method will become nearly ubiquitous gold standards of diagnostics of the near future, for several reasons. First, the catalog of infectious agents has grown to the point that virtually all of the significant infectious agents of the human population have been identified. Second, an infectious agent must grow within the human body to cause disease; essentially it must amplify its own nucleic acids to cause
5060-403: The "strep test", they can be inexpensive. Complex serological techniques have been developed into what are known as immunoassays . Immunoassays can use the basic antibody – antigen binding as the basis to produce an electro-magnetic or particle radiation signal, which can be detected by some form of instrumentation. Signal of unknowns can be compared to that of standards allowing quantitation of
5152-704: The CDC's Surgical Wound Classification, the International Red Cross Wound Classification , the Tscherne classification , the Gustilo-Anderson classification of open fractures, and the AO soft tissue grading system. An acute wound is any wound which results from direct trauma and progresses through the four stages of wound healing along an expected timeline. The first stage, hemostasis , lasts from minutes to hours after initial injury. This stage
5244-435: The ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen. However, a host's immune system can also cause damage to the host itself in an attempt to control the infection. Clinicians, therefore, classify infectious microorganisms or microbes according to the status of host defenses – either as primary pathogens or as opportunistic pathogens . Primary pathogens cause disease as
5336-458: The basis of a biochemical diagnosis of an infectious disease. For example, humans can make neither RNA replicases nor reverse transcriptase , and the presence of these enzymes are characteristic., of specific types of viral infections. The ability of the viral protein hemagglutinin to bind red blood cells together into a detectable matrix may also be characterized as a biochemical test for viral infection, although strictly speaking hemagglutinin
5428-463: The case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". Eukaryotic parasites may also be grown in culture as a means of identifying a particular agent. In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make
5520-472: The causative agent, Trypanosoma cruzi in a patient, which therefore makes it difficult to definitively make a diagnosis. In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi , an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of T. cruzi within its gut. Another principal tool in
5612-436: The cause of the disease are based upon the likelihood that a patient came in contact with a particular agent, the presence of a microbe in a community, and other epidemiological considerations. Given sufficient effort, all known infectious agents can be specifically identified. Diagnosis of infectious disease is nearly always initiated by medical history and physical examination. More detailed identification techniques involve
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#17331107646945704-426: The cause, appearance, and age of a wound. The goal of wound care is to promote an environment that allows a wound to heal as quickly as possible, with emphasis on restoring both form and function of the wounded area. Although optimal treatment strategies vary greatly depending on the specific cause, size, and age of a particular wound, there are universal principles of wound management that apply to all wounds. After
5796-436: The classification of the wound, therefore it is essential that wounds be thoroughly evaluated by a healthcare professional for proper management. In normal physiology, all wounds will undergo a series of steps collectively known as the wound healing process, which include hemostasis, inflammation, proliferation, and tissue remodeling. Age, tissue oxygenation, stress, underlying medical conditions, and certain medications are just
5888-431: The composition of patient blood samples, even though the outcome would not offer the patient any further treatment options. In part, these studies on the appearance of HIV in specific communities permitted the advancement of hypotheses as to the route of transmission of the virus. By understanding how the disease was transmitted, resources could be targeted to the communities at greatest risk in campaigns aimed at reducing
5980-484: The culture of infectious agents isolated from a patient. Culture allows identification of infectious organisms by examining their microscopic features, by detecting the presence of substances produced by pathogens, and by directly identifying an organism by its genotype. Many infectious organisms are identified without culture and microscopy. This is especially true for viruses, which cannot grow in culture. For some suspected pathogens, doctors may conduct tests that examine
6072-400: The destruction of the virus. Instrumentation can be used to read extremely small signals created by secondary reactions linked to the antibody – antigen binding. Instrumentation can control sampling, reagent use, reaction times, signal detection, calculation of results, and data management to yield a cost-effective automated process for diagnosis of infectious disease. Technologies based upon
6164-428: The diagnosis of infectious disease is microscopy . Virtually all of the culture techniques discussed above rely, at some point, on microscopic examination for definitive identification of the infectious agent. Microscopy may be carried out with simple instruments, such as the compound light microscope , or with instruments as complex as an electron microscope . Samples obtained from patients may be viewed directly under
6256-456: The emergency department, although recent studies have shown no difference in emergency department infection rates when comparing normal saline to potable tap water . Irrigation can also be achieved with a diluted 1% povidone iodine solution, but studies have again shown no difference in infection rates when compared to normal saline. Irrigation with antiseptic solutions, such as non-diluted povidone iodine, chlorhexidine , and hydrogen peroxide
6348-445: The environment as a result of traumatic introduction (as in surgical wound infections or compound fractures ). An opportunistic disease requires impairment of host defenses, which may occur as a result of genetic defects (such as chronic granulomatous disease ), exposure to antimicrobial drugs or immunosuppressive chemicals (as might occur following poisoning or cancer chemotherapy ), exposure to ionizing radiation , or as
6440-426: The expression of symptoms is often atypical, making a clinical diagnosis based on presentation more difficult. Thirdly, diagnostic methods that rely on the detection of antibodies are more likely to fail. A rapid, sensitive, specific, and untargeted test for all known human pathogens that detects the presence of the organism's DNA rather than antibodies is therefore highly desirable. There is usually an indication for
6532-403: The growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of viruses : the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In
6624-484: The host's protective immune mechanisms are compromised and the organism inflicts damage on the host. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, Clostridium tetani releases a toxin that paralyzes muscles, and staphylococcus releases toxins that produce shock and sepsis . Not all infectious agents cause disease in all hosts. For example, less than 5% of individuals infected with polio develop disease. On
6716-598: The host, preventing infection and speeding wound healing . The variables involved in the outcome of a host becoming inoculated by a pathogen and the ultimate outcome include: As an example, several staphylococcal species remain harmless on the skin, but, when present in a normally sterile space, such as in the capsule of a joint or the peritoneum , multiply without resistance and cause harm. An interesting fact that gas chromatography–mass spectrometry , 16S ribosomal RNA analysis, omics , and other advanced technologies have made more apparent to humans in recent decades
6808-532: The identification of infectious agents include the detection of metabolic or enzymatic products characteristic of a particular infectious agent. Since bacteria ferment carbohydrates in patterns characteristic of their genus and species , the detection of fermentation products is commonly used in bacterial identification. Acids , alcohols and gases are usually detected in these tests when bacteria are grown in selective liquid or solid media. The isolation of enzymes from infected tissue can also provide
6900-413: The infection cycle in other hosts, they (or their progeny) must leave an existing reservoir and cause infection elsewhere. Infection transmission can take place via many potential routes: The relationship between virulence versus transmissibility is complex; with studies have shown that there were no clear relationship between the two. There is still a small number of evidence that partially suggests
6992-755: The infectious agent also develop the disease. These postulates were first used in the discovery that Mycobacteria species cause tuberculosis . Wound A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over time due to underlying disease processes such as diabetes mellitus , venous/arterial insufficiency, or immunologic disease . Wounds can vary greatly in their appearance depending on wound location, injury mechanism, depth of injury, timing of onset ( acute vs chronic ), and wound sterility, among other factors. Treatment strategies for wounds will vary based on
7084-399: The infectious agent does not occur, this limits the ability of PCR to detect the presence of any bacteria. Given the wide range of bacterial, viral, fungal, protozoal, and helminthic pathogens that cause debilitating and life-threatening illnesses, the ability to quickly identify the cause of infection is important yet often challenging. For example, more than half of cases of encephalitis ,
7176-402: The infectious agent, reservoir, entering a susceptible host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place. Infection begins when an organism successfully enters the body, grows and multiplies. This
7268-462: The initial injury or wounds that are concerning for infection will often be left open and treated with dressings for several days before being closed 3–5 days later, a process known as delayed primary closure. The exact duration of time from initial injury in which delayed primary closure is preferred over primary closure is not clearly defined. Wounds that cannot be closed primarily due to substantial tissue loss can be healed by secondary intention,
7360-425: The light microscope, and can often rapidly lead to identification. Microscopy is often also used in conjunction with biochemical staining techniques, and can be made exquisitely specific when used in combination with antibody based techniques. For example, the use of antibodies made artificially fluorescent (fluorescently labeled antibodies) can be directed to bind to and identify a specific antigens present on
7452-491: The normal stages of wound healing are interrupted. Chronic wounds are most commonly a result of disruption of the inflammatory phase of wound healing, however errors in any phase can result in a chronic wound. The exact duration of time which distinguishes a chronic wound from an acute wound is not clearly defined, although many clinicians agree that wounds which have not progressed for over three months are considered chronic wounds. Wound sterility, or degree of contamination of
7544-531: The number of new infections. The specific serological diagnostic identification, and later genotypic or molecular identification, of HIV also enabled the development of hypotheses as to the temporal and geographical origins of the virus, as well as a myriad of other hypothesis. The development of molecular diagnostic tools have enabled physicians and researchers to monitor the efficacy of treatment with anti-retroviral drugs . Molecular diagnostics are now commonly used to identify HIV in healthy people long before
7636-455: The onset of illness and have been used to demonstrate the existence of people who are genetically resistant to HIV infection. Thus, while there still is no cure for AIDS, there is great therapeutic and predictive benefit to identifying the virus and monitoring the virus levels within the blood of infected individuals, both for the patient and for the community at large. Symptomatic infections are apparent and clinical , whereas an infection that
7728-514: The other hand, some infectious agents are highly virulent. The prion causing mad cow disease and Creutzfeldt–Jakob disease invariably kills all animals and people that are infected. Persistent infections occur because the body is unable to clear the organism after the initial infection. Persistent infections are characterized by the continual presence of the infectious organism, often as latent infection with occasional recurrent relapses of active infection. There are some viruses that can maintain
7820-539: The pathogens are present but that no clinically apparent infection (no disease) is present. Different terms are used to describe how and where infections present over time. In an acute infection, symptoms develop rapidly; its course can either be rapid or protracted. In chronic infection, symptoms usually develop gradually over weeks or months and are slow to resolve. In subacute infections, symptoms take longer to develop than in acute infections but arise more quickly than those of chronic infections. A focal infection
7912-408: The posterior trunk. After a wound is irrigated, debrided, and, if possible, closed, it should be dressed appropriately. The goals of a wound dressing are to act as a barrier to the outside environment, facilitate wound healing, promote hemostasis, and act as a form of mechanical debridement during dressing changes. The ideal wound dressing maintains a moist environment to optimize wound healing but
8004-421: The setting of an underlying fracture: Any wound which is arrested or delayed during any of the normal stages of wound healing is considered to be a chronic wound . Most commonly, these are wounds which develop due to an underlying disease process such as diabetes mellitus or arterial/venous insufficiency. However, it is important to note that any acute wound has the potential to become a chronic wound if any of
8096-477: The soul were believed to be intimately connected, based on several theories put forth by the philosopher Plato . Wounds on the body were believed to correlate with wounds to the soul and vice versa; wounds were seen as an outward sign of an inward illness. Thus, a man who was wounded physically in a serious way was said to be hindered not only physically but spiritually as well. If the soul was wounded, that wound may also eventually become physically manifest, revealing
8188-457: The target antigen. To aid in the diagnosis of infectious diseases, immunoassays can detect or measure antigens from either infectious agents or proteins generated by an infected organism in response to a foreign agent. For example, immunoassay A may detect the presence of a surface protein from a virus particle. Immunoassay B on the other hand may detect or measure antibodies produced by an organism's immune system that are made to neutralize and allow
8280-559: The taxonomically classified pathogen genomes to generate an antimicrobial resistance profile – analogous to antibiotic sensitivity testing – to facilitate antimicrobial stewardship and allow for the optimization of treatment using the most effective drugs for a patient's infection. Metagenomic sequencing could prove especially useful for diagnosis when the patient is immunocompromised . An ever-wider array of infectious agents can cause serious harm to individuals with immunosuppression, so clinical screening must often be broader. Additionally,
8372-503: The test. For example, " Strep throat " is often diagnosed within minutes, and is based on the appearance of antigens made by the causative agent, S. pyogenes , that is retrieved from a patient's throat with a cotton swab. Serological tests, if available, are usually the preferred route of identification, however the tests are costly to develop and the reagents used in the test often require refrigeration . Some serological methods are extremely costly, although when commonly used, such as with
8464-411: The use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. Chagas disease is the most significant example, because it is difficult to directly demonstrate the presence of
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