NS1 antigen test
NS1 antigen test, is a test for dengue, introduced in 2006. It allows rapid detection on the first day of fever, before antibodies appear some 5 or more days later, it has been adopted for use in some 40 nations. The method of detection is through enzyme-linked immunosorbent assay. India has introduced in 2010 the NS1 test costing 1,600 rupees at a private hospital in Mumbai; the medical use of the NS1 antigen test can be defined to diagnose dengue infections and is effective to 1st day detection. Additionally, NS1 assay is useful for differential diagnostics in regards to flaviviruses. NS1 is present in the serum of infected persons directly at the onset of clinical symptoms in primary dengue infection and produces a strong humoral response, it is detectable before the appearance of IgM antibodies. DENV by NS1 antigen is laboratory confirmation of dengue in people assessing clinical aspects. Serological tests such as an immunoglobulin M antibody capture–enzyme-linked immunosorbent assay and viral RNA detection by reverse transcriptase can be used to diagnose Dengue fever.
Dengue virus Dengue fever
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
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
Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, therefore allows visualization of the distribution of the target molecule through the sample; the specific region an antibody recognizes on an antigen is called an epitope. There have been efforts in epitope mapping since many antibodies can bind the same epitope and levels of binding between antibodies that recognize the same epitope can vary. Additionally, the binding of the fluorophore to the antibody itself cannot interfere with the immunological specificity of the antibody or the binding capacity of its antigen. Immunofluorescence is a used example of immunostaining and is a specific example of immunohistochemistry; this technique makes use of fluorophores to visualise the location of the antibodies. Immunofluorescence can be used on tissue sections, cultured cell lines, or individual cells, may be used to analyze the distribution of proteins and small biological and non-biological molecules.
This technique can be used to visualize structures such as intermediate-sized filaments. If the topology of a cell membrane has yet to be determined, epitope insertion into proteins can be used in conjunction with immunofluorescence to determine structures. Immunofluorescence can be used as a "semi-quantitative" method to gain insight into the levels and localization patterns of DNA methylation since it is a more time consuming method than true quantitative methods and there is some subjectivity in the analysis of the levels of methylation. Immunofluorescence can be used in combination with other, non-antibody methods of fluorescent staining, for example, use of DAPI to label DNA. Several microscope designs can be used for analysis of immunofluorescence samples. Various super-resolution microscope designs that are capable of much higher resolution can be used. To make fluorochrome-labeled antibodies, a fluorochrome must be conjugated to the antibody. An antigen can be conjugated to the antibody with a fluorescent probe in a technique called fluorescent antigen technique.
Staining procedures can apply to both fixed antigen in the cytoplasm or to cell surface antigens on living cells, called "membrane immunofluorescence". It is possible to label the complement of the antibody-antigen complex with a fluorescent probe. In addition to the element to which fluorescence probes are attached, there are two general classes of immunofluorescence techniques: primary and secondary; the following descriptions will focus on these classes in terms of conjugated antibodies. There are two classes of immunofluorescence techniques and secondary. Primary immunofluorescence uses a primary antibody, chemically linked to a fluorophore; the primary antibody recognizes the target molecule and binds to a specific region called the epitope. The attached fluorophore can be detected via fluorescent microscopy, depending on the messenger used, will emit a specific wavelength of light once excited. Direct immunofluorescence, although somewhat less common, has notable advantages over the secondary procedure.
The direct attachment of the messenger to the antibody reduces the number of steps in the procedure, saving time and reducing non-specific background signal. This limits the possibility of antibody cross-reactivity and possible mistakes throughout the process. However, some disadvantages do exist in this method. Since the number of fluorescent molecules that can be bound to the primary antibody is limited, direct immunofluorescence is less sensitive than indirect immunofluorescence and may result in false negatives. Direct immunofluorescence requires the use of much more primary antibody, expensive, sometimes running up to $400.00/mL. Secondary immunofluorescence uses two antibodies. Multiple secondary antibodies can bind a single primary antibody; this provides signal amplification by increasing the number of fluorophore molecules per antigen. This protocol is more complex and time-consuming than the primary protocol above, but allows more flexibility because a variety of different secondary antibodies and detection techniques can be used for a given primary antibody.
This protocol is possible because an antibody consists of two parts, a variable region and constant region. It is important to realize that this division is artificial and in reality the antibody molecule is four polypeptide chains: two heavy chains and two light chains. A researcher can generate several primary antibodies that recognize various antigens, but all share the same constant region. All these antibodies may therefore be recognized by a single secondary antibody; this saves the cost of modifying the primary antibodies to directly carry a fluorophore. Different primary antibodies with different constant regions are generated by raising the antibody in different species. For example, a researcher might create primary antibodies in a goat that recognize several antigens, employ dye-coupled rabbit secondary antibodies that recognize
Proteus is a genus of Gram-negative Proteobacteria. Proteus bacilli are distributed in nature as saprophytes, being found in decomposing animal matter, manure soil, the mammalian intestine, human and animal feces, they are opportunistic pathogens responsible for urinary and septic infections nosocomial. Three species—P. Vulgaris, P. mirabilis, P. penneri—are opportunistic human pathogens. Proteus includes pathogens responsible for many human urinary tract infections. P. mirabilis causes wound and urinary tract infections. Most strains of P. mirabilis are sensitive to ampicillin and cephalosporins. P. vulgaris is not sensitive to these antibiotics. However, this organism is isolated less in the laboratory and only targets immunosuppressed individuals. P. vulgaris occurs in the intestines of humans and a wide variety of animals, in manure and polluted waters. P. mirabilis, once attached to the urinary tract, infects the kidney more than E. coli. P. mirabilis is found as a free-living organism in soil and water.
About 10–15% of kidney stones are struvite stones, caused by alkalinization of the urine by the action of the urease enzyme of Proteus bacterial species. Proteus species do not ferment lactose, but have shown to be capable glucose fermenters depending on the species in a triple sugar iron test. Since it belongs to the family Enterobacteriaceae, general characters are applied on this genus, it is catalase - and nitrate-positive. Specific tests include positive phenylalanine deaminase tests. On the species level, indole is considered reliable, as it is positive for P. vulgaris, but negative for P. mirabilis. Most strains produce a powerful urease enzyme, which hydrolyzes urea to ammonia and carbon monoxide. Species can be motile, have characteristic "swarming" patterns. Underlying these behaviors are the somatic O and flagellar H antigens, so named based on Kauffman–White classification; this system is based on historic observations of Edmund Weil and Arthur Felix of a thin surface film produced by agar-grown flagellated Proteus strains, a film that resembled the mist produced by breath on a glass.
Flagellated variants were therefore designated H forms. The cell wall O-antigen of certain strains of Proteus, such as OX-2, OX-19, OX-k, crossreact with several species of Rickettsiae; these Proteus antigens can be used in laboratory to detect the presence of antibodies against certain Rickettsiae members in patient's serum. This test is called Weil-Felix reaction after its originators. Dienes phenomenon
An antibody known as an immunoglobulin, is a large, Y-shaped protein produced by plasma cells, used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the fragment antigen-binding variable region; each tip of the "Y" of an antibody contains a paratope, specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly. Depending on the antigen, the binding may impede the biological process causing the disease or may activate macrophages to destroy the foreign substance; the ability of an antibody to communicate with the other components of the immune system is mediated via its Fc region, which contains a conserved glycosylation site involved in these interactions. The production of antibodies is the main function of the humoral immune system.
Antibodies are secreted by B cells of the adaptive immune system by differentiated B cells called plasma cells. Antibodies can occur in two physical forms, a soluble form, secreted from the cell to be free in the blood plasma, a membrane-bound form, attached to the surface of a B cell and is referred to as the B-cell receptor; the BCR is found only on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms. Antibodies are glycoproteins belonging to the immunoglobulin superfamily.
They constitute most of the gamma globulin fraction of the blood proteins. They are made of basic structural units—each with two large heavy chains and two small light chains. There are several different types of antibody heavy chains that define the five different types of crystallisable fragments that may be attached to the antigen-binding fragments; the five different types of Fc regions allow antibodies to be grouped into five isotypes. Each Fc region of a particular antibody isotype is able to bind to its specific Fc Receptor, thus allowing the antigen-antibody complex to mediate different roles depending on which FcR it binds; the ability of an antibody to bind to its corresponding FcR is further modulated by the structure of the glycan present at conserved sites within its Fc region. The ability of antibodies to bind to FcRs helps to direct the appropriate immune response for each different type of foreign object they encounter. For example, IgE is responsible for an allergic response consisting of mast cell degranulation and histamine release.
IgE's Fab paratope binds to allergic antigen, for example house dust mite particles, while its Fc region binds to Fc receptor ε. The allergen-IgE-FcRε interaction mediates allergic signal transduction to induce conditions such as asthma. Though the general structure of all antibodies is similar, a small region at the tip of the protein is variable, allowing millions of antibodies with different tip structures, or antigen-binding sites, to exist; this region is known as the hypervariable region. Each of these variants can bind to a different antigen; this enormous diversity of antibody paratopes on the antigen-binding fragments allows the immune system to recognize an wide variety of antigens. The large and diverse population of antibody paratope is generated by random recombination events of a set of gene segments that encode different antigen-binding sites, followed by random mutations in this area of the antibody gene, which create further diversity; this recombinational process that produces clonal antibody paratope diversity is called VJ or VJ recombination.
The antibody paratope is polygenic, made up of three genes, V, D, J. Each paratope locus is polymorphic, such that during antibody production, one allele of V, one of D, one of J is chosen; these gene segments are joined together using random genetic recombination to produce the paratope. The regions where the genes are randomly recombined together is the hyper variable region used to recognise different antigens on a clonal basis. Antibody genes re-organize in a process called class switching that changes the one type of heavy chain Fc fragment to another, creating a different isotype of the antibody that retains the antigen-specific variable region; this allows a single antibody to be used by different types of Fc receptors, expressed on different parts of the immune system. The first use of the term "antibody" occurred in a text by Paul Ehrlich; the term Antikörper appears in the conclusion of his article "Experimental Studies on Immunity", published in October 1891, which states that, "if two substances give rise to two different Antikörper they themselves must be different".
However, the term was not accepted and several other terms for antibody were proposed.
Phenol is an aromatic organic compound with the molecular formula C6H5OH. It is a white crystalline solid, volatile; the molecule consists of a phenyl group bonded to a hydroxy group. It requires careful handling due to its propensity for causing chemical burns. Phenol was first extracted from coal tar, it is an important industrial commodity as a precursor to useful compounds. It is used to synthesize plastics and related materials. Phenol and its chemical derivatives are essential for production of polycarbonates, Bakelite, detergents, herbicides such as phenoxy herbicides, numerous pharmaceutical drugs. Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 mL. Homogeneous mixtures of phenol and water at phenol to water mass ratios of ~2.6 and higher are possible. The sodium salt of phenol, sodium phenoxide, is far more water-soluble. Phenol is weakly acidic and at high pHs gives the phenolate anion C6H5O−: PhOH ⇌ PhO− + H+ Compared to aliphatic alcohols, phenol is about 1 million times more acidic, although it is still considered a weak acid.
It reacts with aqueous NaOH to lose H+, giving the salt sodium phenoxide, whereas most alcohols react only partially. One explanation for the increased acidity over alcohols is resonance stabilization of the phenoxide anion by the aromatic ring. In this way, the negative charge on oxygen is delocalized on to the ortho and para carbon atoms through the pi system. An alternative explanation involves the sigma framework, postulating that the dominant effect is the induction from the more electronegative sp2 hybridised carbons. In support of the second explanation, the pKa of the enol of acetone in water is 10.9, making it only less acidic than phenol. Thus, the greater number of resonance structures available to phenoxide compared to acetone enolate seems to contribute little to its stabilization. However, the situation changes. A recent in silico comparison of the gas phase acidities of the vinylogues of phenol and cyclohexanol in conformations that allow for or exclude resonance stabilization leads to the inference that about 1⁄3 of the increased acidity of phenol is attributable to inductive effects, with resonance accounting for the remaining difference.
The phenoxide anion has a similar nucleophilicity to free amines, with the further advantage that its conjugate acid does not become deactivated as a nucleophile in moderately acidic conditions. Phenolate esters are more stable toward hydrolysis than acid anhydrides and acyl halides but are sufficiently reactive under mild conditions to facilitate the formation of amide bonds. Phenol exhibits keto-enol tautomerism with its unstable keto tautomer cyclohexadienone, but only a tiny fraction of phenol exists as the keto form; the equilibrium constant for enolisation is 10−13, which means only one in every ten trillion molecules is in the keto form at any moment. The small amount of stabilisation gained by exchanging a C=C bond for a C=O bond is more than offset by the large destabilisation resulting from the loss of aromaticity. Phenol therefore exists entirely in the enol form. Phenoxides are enolates stabilised by aromaticity. Under normal circumstances, phenoxide is more reactive at the oxygen position, but the oxygen position is a "hard" nucleophile whereas the alpha-carbon positions tend to be "soft".
Phenol is reactive toward electrophilic aromatic substitution as the oxygen atom's pi electrons donate electron density into the ring. By this general approach, many groups can be appended to the ring, via halogenation, acylation and other processes. However, phenol's ring is so activated—second only to aniline—that bromination or chlorination of phenol leads to substitution on all carbon atoms ortho and para to the hydroxy group, not only on one carbon. Phenol reacts with dilute nitric acid at room temperature to give a mixture of 2-nitrophenol and 4-nitrophenol while with concentrated nitric acid, more nitro groups get substituted on the ring to give 2,4,6-trinitrophenol, known as picric acid. Aqueous solutions of phenol are weakly acidic and turn blue litmus to red. Phenol is neutralized by sodium hydroxide forming sodium phenate or phenolate, but being weaker than carbonic acid, it cannot be neutralized by sodium bicarbonate or sodium carbonate to liberate carbon dioxide. C6H5OH + NaOH → C6H5ONa + H2OWhen a mixture of phenol and benzoyl chloride are shaken in presence of dilute sodium hydroxide solution, phenyl benzoate is formed.
This is an example of the Schotten-Baumann reaction: C6H5OH + C6H5COCl → C6H5OCOC6H5 + HClPhenol is reduced to benzene when it is distilled with zinc dust, or when phenol vapour is passed over granules of zinc at 400 °C: C6H5OH + Zn → C6H6 + ZnOWhen phenol is reacted with diazomethane in the presence of boron trifluoride, anisole is obtained as the main product and nitrogen gas as a byproduct. C6H5OH + CH2N2 → C6H5OCH3 + N2When phenol reacts with iron chloride solution, an intense violet-purple solution is formed; because of phenol's commercial importance, many methods have been developed for its production. The dominant current route, accounting for 95% of production, is the cumene process, which uses benzene and propene as feedstock and involves the partial oxidation of cumene vi