Medical diagnosis is the process of determining which disease or condition explains a person's symptoms and signs. It is most referred to as diagnosis with the medical context being implicit; the information required for diagnosis is collected from a history and physical examination of the person seeking medical care. One or more diagnostic procedures, such as diagnostic tests, are done during the process. Sometimes posthumous diagnosis is considered a kind of medical diagnosis. Diagnosis is challenging, because many signs and symptoms are nonspecific. For example, redness of the skin, by itself, is a sign of many disorders and thus does not tell the healthcare professional what is wrong, thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns; the process is made easy by a sign or symptom, pathognomonic. Diagnosis is a major component of the procedure of a doctor's visit.
From the point of view of statistics, the diagnostic procedure involves classification tests. The first recorded examples of medical diagnosis are found in the writings of Imhotep in ancient Egypt. A Babylonian medical textbook, the Diagnostic Handbook written by Esagil-kin-apli, introduced the use of empiricism and rationality in the diagnosis of an illness or disease. Traditional Chinese Medicine, as described in the Yellow Emperor's Inner Canon or Huangdi Neijing, specified four diagnostic methods: inspection, auscultation-olfaction and palpation. Hippocrates was known to make diagnoses by smelling their sweat. A diagnosis, in the sense of diagnostic procedure, can be regarded as an attempt at classification of an individual's condition into separate and distinct categories that allow medical decisions about treatment and prognosis to be made. Subsequently, a diagnostic opinion is described in terms of a disease or other condition, but in the case of a wrong diagnosis, the individual's actual disease or condition is not the same as the individual's diagnosis.
A diagnostic procedure may be performed by various health care professionals such as a physician, physical therapist, healthcare scientist, dentist, nurse practitioner, or physician assistant. This article uses diagnostician as any of these person categories. A diagnostic procedure does not involve elucidation of the etiology of the diseases or conditions of interest, that is, what caused the disease or condition; such elucidation can be useful to optimize treatment, further specify the prognosis or prevent recurrence of the disease or condition in the future. The initial task is to detect a medical indication to perform a diagnostic procedure. Indications include: Detection of any deviation from what is known to be normal, such as can be described in terms of, for example, physiology, pathology and human homeostasis. Knowledge of what is normal and measuring of the patient's current condition against those norms can assist in determining the patient's particular departure from homeostasis and the degree of departure, which in turn can assist in quantifying the indication for further diagnostic processing.
A complaint expressed by a patient. The fact that a patient has sought a diagnostician can itself be an indication to perform a diagnostic procedure. For example, in a doctor's visit, the physician may start performing a diagnostic procedure by watching the gait of the patient from the waiting room to the doctor's office before she or he has started to present any complaints. During an ongoing diagnostic procedure, there can be an indication to perform another, diagnostic procedure for another concomitant, disease or condition; this may occur as a result of an incidental finding of a sign unrelated to the parameter of interest, such as can occur in comprehensive tests such as radiological studies like magnetic resonance imaging or blood test panels that include blood tests that are not relevant for the ongoing diagnosis. General components which are present in a diagnostic procedure in most of the various available methods include: Complementing the given information with further data gathering, which may include questions of the medical history, physical examination and various diagnostic tests.
A diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease. Diagnostic tests can be used to provide prognostic information on people with established disease. Processing of the answers, findings or other results. Consultations with other providers and specialists in the field may be sought. There are a number of methods or techniques that can be used in a diagnostic procedure, including performing a differential diagnosis or following medical algorithms. In reality, a diagnostic procedure may involve components of multiple methods; the method of differential diagnosis is based on finding as many candidate diseases or conditions as possible that can cause the signs or symptoms, followed by a process of elimination or at least of rendering the entries more or less probable by further medical tests and other processing until, aiming to reach the point where only one candidate disease or condit
Osler's nodes are painful, raised lesions found on the hands and feet. They are associated with a number of conditions, including infective endocarditis, are caused by immune complex deposition, their presence is one definition of Osler's sign. Osler's nodes result from the deposition of immune complexes; the resulting inflammatory response leads to swelling and pain that characterize these lesions. The nodes are indicative of subacute bacterial endocarditis. 10–25% of endocarditis patients will have Osler's nodes. Other signs of endocarditis include Janeway lesions; the latter, which occur on the palms and soles, can be differentiated from Osler's nodes because they are non-tender. Osler's nodes can be seen in Systemic lupus erythematosus Marantic endocarditis Disseminated gonococcal infection Distal to infected arterial catheter Osler's nodes are named after Sir William Osler who described them in the early 20th century. Picture of Osler's nodes and Janeway's lesions
Streptococcus mutans is a facultatively anaerobic, gram-positive coccus found in the human oral cavity and is a significant contributor to tooth decay. It is part of the "streptococci", an informal general name for all species in the genus Streptococcus; the microbe was first described by J Kilian Clarke in 1924. This bacterium, along with the related species Streptococcus sobrinus, can cohabit the mouth: Both contribute to oral disease, the expense of differentiating them in laboratory testing is not clinically necessary. Therefore, for clinical purposes they are considered together as a group, called the mutans streptococci; this grouping of similar bacteria with similar tropism can be seen in the viridans streptococci, another group of Streptococcus species. S. mutans is present in the human oral microbiota, along with at least 25 other species of oral streptococci. The taxonomy of these bacteria remains tentative. Different areas of the oral cavity present different ecological niches, each species has specific properties for colonizing different oral sites.
S. mutans is most prevalent on the pits and fissures, constituting 39% of the total streptococci in the oral cavity. Fewer S. mutans. Bacterial-fungal co-coaggregation can help to increase the cariogenic potential of S.mutans. A symbiotic relationship with S.mutans and Candida Albicans leads to increased glucan production and increased biofilm formation. This therefore amplifies the cariogenic effect of S.mutans. Oral streptococci have both harmful bacteria. However, under special conditions commensal streptococci can become opportunistic pathogens, initiating disease and damaging the host. Imbalances in the microbial biota can initiate oral diseases. Early colonizers of the tooth surface are Neisseria spp. and streptococci, including S. mutans. They must adhere sufficiently to the dental hard tissues; the growth and metabolism of these pioneer species changes local environmental conditions, thereby enabling more fastidious organisms to further colonize after them, forming dental plaque. Along with S. sobrinus, S. mutans plays a major role in tooth decay, metabolizing sucrose to lactic acid using the enzyme glucansucrase.
The acidic environment created in the mouth by this process is what causes the mineralized tooth enamel to be vulnerable to decay. S. mutans is one of a few specialized organisms equipped with receptors that improve adhesion to the surface of teeth. Sucrose is used by S. mutans to produce a sticky, dextran-based polysaccharide that allows them to cohere, forming plaque. S. mutans produces dextran via the enzyme dextransucrase using sucrose as a substrate in the following reaction: n sucrose → n + n fructoseSucrose is the only sugar that bacteria can use to form this sticky polysaccharide. However, other sugars—glucose, lactose—can be digested by S. mutans, but they produce lactic acid as an end product. The combination of plaque and acid leads to dental decay. Due to the role S. mutans plays in tooth decay, many attempts have been made to create a vaccine for the organism. So far, such vaccines have not been successful in humans. Proteins involved in the colonization of teeth by S. mutans have been shown to produce antibodies that inhibit the cariogenic process.
A molecule synthesized at Yale University and the University of Chile, called Keep 32, is supposed to be able to kill S. mutans. Another candidate is a peptide called C16G2, synthesised at UCLA, it is believed that Streptococcus mutans acquired the gene that enables it to produce biofilms through horizontal gene transfer with other lactic acid bacterial species, such as Lactobacillus. Surviving in the oral cavity, S. mutans is the primary causal agent and the pathogenic species responsible for dental caries in the initiation and development stages. Dental plaque the precursor to tooth decay, contains more than 600 different microorganisms, contributing to the oral cavity's overall dynamic environment that undergoes rapid changes in pH, nutrient availability, oxygen tension. Dental plaque adheres to the teeth and consists of bacterial cells, while plaque is the biofilm on the surfaces of the teeth. Dental plaque and S. mutans is exposed to "toxic compounds" from oral healthcare products, food additives, tobacco.
While S. mutans grows in the biofilm, cells maintain a balance of metabolism that involves production and detoxification. Biofilm is an aggregate of microorganisms in which cells adhere to a surface. Bacteria in the biofilm community can generate various toxic compounds that interfere with the growth of other competing bacteria. S. mutans has over time developed strategies to colonize and maintain a dominant presence in the oral cavity. The oral biofilm is continuously challenged by changes in the environmental conditions. In response to such changes, the bacterial community evolved with individual members and their specific functions to survive in the oral cavity. S. mutans has been able to evolve from nutrition-limiting conditions to protect itself in extreme conditions. Streptococci represent 20% of the oral bacteria and determine the development of the biofilms. Although S. mutans can be antagonized by pioneer colonizers, once they become dominant in oral biofilms, dental caries can develop and thrive.
The causative agent of dental caries is associated with its ability to
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Firmicutes. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted; the term was coined in 1877 by Viennese surgeon Albert Theodor Billroth, by combining the prefix "strepto-", together with the suffix "-coccus" Most streptococci are oxidase-negative and catalase-negative, many are facultative anaerobes. In 1984, many bacteria grouped in the genus Streptococcus were separated out into the genera Enterococcus and Lactococcus. Over 50 species are recognised in this genus; this genus has been found to be part of the salivary microbiome. In addition to streptococcal pharyngitis, certain Streptococcus species are responsible for many cases of pink eye, bacterial pneumonia, endocarditis and necrotizing fasciitis. However, many streptococcal species are not pathogenic, form part of the commensal human microbiota of the mouth, skin and upper respiratory tract.
Streptococci are a necessary ingredient in producing Emmentaler cheese. Species of Streptococcus are classified based on their hemolytic properties. Alpha-hemolytic species cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar. Beta-hemolytic species cause complete rupture of red blood cells. On blood agar, this appears. Gamma-hemolytic species cause no hemolysis. Beta-hemolytic streptococci are further classified by Lancefield grouping, a serotype classification; the 20 described serotypes are named Lancefield groups A to V. This system of classification was developed by Rebecca Lancefield, a scientist at Rockefeller University. In the medical setting, the most important groups are the alpha-hemolytic streptococci S. pneumoniae and Streptococcus viridans group, the beta-hemolytic streptococci of Lancefield groups A and B. Table: Medically relevant streptococci When alpha-hemolysis is present, the agar under the colony will appear dark and greenish due to the conversion of hemoglobin to green biliverdin.
Streptococcus pneumoniae and a group of oral streptococci display alpha-hemolysis. Alpha-hemolysis is termed incomplete hemolysis or partial hemolysis because the cell membranes of the red blood cells are left intact; this is sometimes called green hemolysis because of the color change in the agar. S. pneumoniae, is a leading cause of bacterial pneumonia and occasional etiology of otitis media, sinusitis and peritonitis. Inflammation is thought to be the major cause of how pneumococci cause disease, hence the tendency of diagnoses associated with them to involve inflammation; the viridans streptococci are a large group of commensal bacteria that are either alpha-hemolytic, producing a green coloration on blood agar plates, or nonhemolytic. They possess no Lancefield antigens. Beta hemolysis, sometimes called complete hemolysis, is a complete lysis of red cells in the media around and under the colonies: the area appears lightened and transparent. Streptolysin, an exotoxin, is the enzyme produced by the bacteria which causes the complete lysis of red blood cells.
There are two types of streptolysin: Streptolysin O and streptolysin S. Streptolysin O is an oxygen-sensitive cytotoxin, secreted by most group A Streptococcus, interacts with cholesterol in the membrane of eukaryotic cells, results in beta-hemolysis under the surface of blood agar. Streptolysin S is an oxygen-stable cytotoxin produced by most GAS strains which results in clearing on the surface of blood agar. SLS affects immune cells, including polymorphonuclear leukocytes and lymphocytes, is thought to prevent the host immune system from clearing infection. Streptococcus pyogenes, or GAS, displays beta hemolysis; some weakly beta-hemolytic species cause intense hemolysis when grown together with a strain of Staphylococcus. This is called the CAMP test. Streptococcus agalactiae displays this property. Clostridium perfringens can be identified presumptively with this test. Listeria monocytogenes is positive on sheep's blood agar. Group A S. pyogenes is the causative agent in a wide range of group A streptococcal infections.
These infections may be invasive. The noninvasive infections tend to be less severe; the most common of these infections include impetigo. Scarlet fever is a noninvasive infection, but has not been as common in recent years; the invasive infections caused by group A beta-hemolytic streptococci tend to be more severe and less common. This occurs when the bacterium is able to infect areas where it is not found, such as the blood and the organs; the diseases that may