ECG : Electrocardiagram.

Echinulate : Surface covered with spiny surfaces.

Ecology : Study of the interrelationships between organisms and their environments.

Ecosystem : A community of organisms and their natural environment.

Ectoparasite : Organism that lives on or within skin.

Ectoplasm : Outer layer of the cytoplasm of a cell.

Ectothrix : Outside of hair shafts.

Eczema : An itchy, scaly, blistery, or raised rash often seen in children and associated with irritation of the skin.

Edema : Excessive accumulation of fluid in tissue spaces.

EEG : Electroencephalogram.

Effusion : Fluid escaping into a body space or tissue (e.g., pleural effusion).

Egg yolk agar (EYA) : This medium is used to detect the presence of enzymes including lecithinase, lipase, and protease.

Eh : Oxidation-reduction potential.

EIA : Enzyme immunoassay.

Electron acceptor : A substance that accepts electrons during an oxidation-reduction reaction. An electron acceptor is an oxidant.

Electron donor : A substance that donates electrons in an oxidation-reduction reaction. An electron donor is a reductant.

Electromyography : Test used to represent electrical currents associated with muscles.

Electron-transport phosphorylation : Synthesis of ATP involving a membrane-associated electron transport chain and the creation of a proton-motive force. Also called oxidative phosphorylation.

Electrophoresis (EP) , is a technique for separation of ionic molecules (principally proteins) by the differential migration through a gel according to the size and ionic charge of the molecules in an electrical field. Smaller molecules with a more negative charge will travel faster and further through the gel toward the anode of an electrophoretic cell when high voltage is applied. Similar molecules will group on the gel. They may be visualized by staining and quantitated, in relative terms, using densitometers which continuously monitor the photometric density of the resulting stain.

Electroporation : The use of an electrical pulse to enable cells to take up DNA.

Elementary body : The infectious stage of Chlamydia or a cellular inclusion body of a viral disease.

Elephantiasis : Condition caused by inflammation and obstruction of the lymphatic system, resulting in hypertrophy and thickening of the surrounding tissues usually involving the extremities and external genitalia (often as a result of filariasis).

ELISA : Enzyme-linked immunosorbent assay.

Elution : Process of extraction by means of a solvent.

EM : Electron microscopy.

EMB : Eosin-methylene blue (agar plate).

Embden-Meyerhof-Parnas pathway (Embden-Meyerhof pathway; EMP pathway) : A pathway that degrades glucose to pyruvate; the six-carbon stage converts glucose to fructose-1,6-bisphosphate, and the three-carbon stage produces ATP while changing glyceraldehyde-3-phosphate to pyruvate. Compare with Entner-Doudoroff pathway.

Emesis : vomiting.

Emetic : Inducing vomiting.

EMIT : Enzyme-multiplied Immunoassay.

Empyema : Accumulation of pus in a body cavity, particularly empyema of the thorax or chest.

Enanthema : A mucous membrane eruption; typically occurs in relation to the skin eruptions that are symptoms of acute viral or coccal disease.

Encapsulation : Active process of walling off a parasite by the host through the formation of a connective tissue capsule (trichinosis).

Encephalitis : Inflammation of the brain.

Encystment : Formation of a resistant external wall by protozoa to enable them to survive drying and adverse environmental conditions; encysted forms are infective to humans.

Endemic : The constant presence of a disease or infectious agent within a given geographic area; it may also refer to the usual prevalence of a given disease within such area. Hyperendemic expresses a constant presence at a high level of incidence, and holoendemic a high level of prevalence with infections beginning early in life and affecting most of the population, e.g., malaria in some places. (See Zoonosis.)

Endergonic : A chemical reaction requiring input of energy to proceed.

Endocarditis : A serious infection of the endothelium of the heart, usually involving leaflets of the heart valves where destruction of valves or distortion of them by formation of vegetations may lead to serious physiological disturbances and death: also, an inflammation of the endocardial surface (much less common).

Endocervix : Mucous membrane of the cervical canal.

Endocytosis : A process in which a particle such as a virus is taken intact into an animal cell. Phagocytosis and pinocytosis are two kinds of endocytosis.

Endogenous : Developing from within the body.

Endogenous (or indigenous) anaerobes : Anaerobes that comprise part of the indigenous microflora of animals (including humans).

Endometritis : Inflammation or infection of the lining of the uterus.

Endoparasite : Parasite that lives within the body.

Endophthalmitis : Inflammation of internal tissues of eye; may rapidly destroy the eye.

Endoplasm : Inner portion of the cytoplasm of a cell.

Endoplasmic reticulum (ER) : An extensive array of internal membranes in eukaryotes.

Endoscopy : Procedure involving the passing of a flexible hollow tube into the esophagus or rectum for the purpose of visualizing portions of the gastrointestinal tract; also useful for obtaining diagnostic samples.

Endospore : A thick-walled spore formed in a bacterial cell. It is very resistant to being killed by heat and various other chemical and physical agents. Endospores are best verified by demonstrating that cultures survive a temperature of 70-80 C for 10 min.

Endosymbiosis : The hypothesis that mitochondria and chloroplasts are the descendants of ancient prokaryotic organisms from the domain Bacteria.

Endothelium : Squamous epithelium lining blood vessels.

Endothrix : A fungus growing inside the hair shaft producing arthroconidia.

Endotoxin : Substance containing lipopolysaccharide complexes found in the cell wall of bacteria, principally gram-negative bacteria; felt to play an important role in many of the complications of sepsis such as shock, DIC, and thrombocytopenia.

Engineering controls : Physical devices, such as needle resheathing holders and sharps containers, that help to remove biohazardous material from the workplace.

ENL : Erythema nodosum leprosum.

Enrichment culture : Use of selective culture media and incubation conditions to isolate microorganisms directly from nature.

Enrichment media : Contains the necessary nutrients for growth of all organisms contained in the specimen. No inhibitory factors are contained within these media. May also be referred to as nonselective media.

ENT : Ear, nose, and throat.

Enterics : The common name for bacteria in the family Enterobacteriaceae.

Enteric bacteria : A large group of gram-negative, rod-shaped bacteria characterized by a facultatively aerobic metabolism. Many of them are commonly found in the intestines of animals.

Enteric fever : Typhoid fever; paratyphoid fever.

Enterobacteriaceae : A select group of aerobic, oxidase negative organisms.

Enteroinvasive : Capable of invading the mucosal surface and sometimes the deeper tissues of the bowel.

Enteropathogenic : Escherichia coli (EPEC): Specific serotypes of E. coli isolated from feces of patients with diarrhea, usually associated with nursery epidemics.

Enterotoxigenic : Producing an enterotoxin (e.g., enterotoxigenic Escherichia coli).

Enterotoxin : Toxin affecting the cells of the intestinal mucosa.

Entner-Doudoroff pathway (ED pathway) : A pathway that converts glucose to pyruvate and glyceraldehyde-3-phosphate by producing 6-phosphogluconate and then dehydrating it.

Enzootic : Referring to a temporal pattern of disease occurrence in an animal population that is marked by predictable regularity with little change over time; for example, the pattern of hantavirus infection in deer mice.

Enzyme : A protein functioning as a catalyst in living organisms, which promotes specific reactions or groups of reactions.

Enzyme Immunoassay (EIA) , is the general term for an expanding technical arsenal of testing which allows a full range of quantitative analyses for both antigen and antibodies. These tests use color-changed products of enzyme-substrate interaction (or inhibition) to measure the antigen-antibody reaction. Examples of EIA procedures (EMIT, ELISA, MAC, MEIA) follow.

Enzyme-Linked Immunosorbent Assay (ELISA) , is a sensitive, heterogeneous (multiple phase) analytical technique for quantitation of antigen or antibody in which enzyme-labeled antibody or antigen is bound to a solid support (e.g., tubes, beads, microtiter plate wells, plastic tines or fins). After addition of patient specimen and substrate, antigen, antibody or complex are detected by a color change indicating the presence of the product of an enzyme-substrate reaction. Direct ELISA is a technique for measuring antigen using competition for antibody binding sites between enzyme-labeled antigen and patient antigen. Indirect ELISA, or enzyme immunometric assay, measures antibody concentrations using bound antigen to interact with specimen antibodies. Enzyme-labeled reagent antibodies can be isotype-specific (i.e., capable of determining the presence of IgG, IgA, IgM, IgE classes which react with the antigen of interest). The specificity of indirect ELISA assays for IgM isotypes in some infectious diseases is limited by false-positive results due to IgM rheumatoid factor in the presence of IgG-specific antibodies.

Enzyme Multiplies Immunoassay Technique (EMIT) , is a homogeneous (single phase) EIA procedure in which the antigen being measured competes for a limited number of antibody binding sites with enzyme labeled antigen. The reagent antibody has the ability to block enzymatic activity when bound with the reagent enzyme-antigen complex preventing it's formation of product in the presence of substrate. The free antigen-enzyme complexes resulting from competition with measured antigen in the sample forms color-change products proportional to the concentration of antigen present in the specimen.

Eosinophilia : Formation of large numbers of eosinophilic leukocytes caused by some type of immune response; usually found in helminth infections, particularly with tissue invasion (visceral larva migrans, trichinosis, filariasis, schistosomiasis, ascariasis, strongyloidiasis).

Eosinophilic cerebrospinal fluid pleocytosis : Increased eosinophils in cerebrospinal fluid (Angiostrongylus and Baylisascaris infections; coenurosis, cysticercosis, echinococcosis; Fasciola, Gnathostoma, Paragonimus, Schistosoma, Toxocara, Toxoplasma, and Trichinella infections; possibly: Dirofilaria, Onchocerca, and Ascaris infections).

Eosinophilic meningitis : Inflammation of membranes of brain or spinal cord accompanied by an increased number of eosinophils, usually associated with particular helminth infections (angiostrongyliasis, gnathostomiasis, cysticercosis, and schistosomiasis).

EP : Electrophoresis.

EPEC : Enteropathogenic Escherichia coli.

Epidemic : Disease that spreads rapidly and infects many people in a community or area (usually within a short time frame). The number of cases indicating presence of an epidemic will vary according to the infectious agent, size and type of population exposed, previous experience or lack of exposure to the disease, and time and place of occurrence; epidemicity is thus relative to usual frequency of the disease in the same area, among the specified population, at the same season of the year. A single case of a communicable disease long absent from a population or the first invasion by a disease not previously recognized in that area requires immediate reporting and epidemiologic investigation; two cases of such a disease associated in time and place are sufficient evidence of transmission to be considered an epidemic. (See Report of a Disease and Zoonosis).

Epidemiology : The study of the incidence and prevalence of disease in populations.

Epidermal : Pertaining to the outer layer of the skin.

Epididymitis : Inflammation of the epididymis characterized by fever and pain on one side of the scrotum; seen as a complication of prostatitis and cystitis.

Epigastric : Relating to the area of the abdomen that lies between the margins of the ribs.

Epiglottitis : Inflammation of the epiglottis, a structure that prevents aspirating swallowed food and fluids into the tracheobronchial tree; a serious infection because the swollen epiglottis may block the airway.

Epimastigote : Developmental stage of the family Trypanosomatidae. The base of the flagellum is in front of the nucleus; as the flagellum passes through the body to emerge as the free flagellar potion, it is attached to the body by the undulating membrane (old term: crithidia).

Epithelium : Tissue composed of contiguous cells that forms the epidermis and lines hollow organs and all passages of the respiratory, digestive, and genitourinary systems.

Epitope : Antigenic determinant.

ERCP : Endoscopic retrograde cholangiopancreatogrophy.

Erysipelas : An acute cellulitis caused by group A streptococci.

Erythema : Redness of the skin from various causes.

Erythema infectiosum : A mild facial rash in children that has a "slapped cheek" appearance; usually caused by parvovirus B19.

Erythema migrans : Characteristic radial skin lesion of Lyme disease.

Erythrasma : A minor, superficial skin infection caused by Corynebacterium minutissimium.

Erythrocytes : A synonym for red blood corpuscle.

Erythrocytic cycle : Developmental cycle of malarial parasites within red blood cells.

Eschar : A dry scar, particularly one related to a burn.

Esculin : A coumarin glyoside contained in Bacteroides bile esculin agar.

Esopagitis : Inflammation of the esophagus.

ESR : Erthrocyte sedimentation rate.

Et : Ethyl.

ETEC : Enterotoxigenic Escherichia coli. Strains of E. coli that produce a choleralike toxin; have been implicated as causes of diarrhea.

Ethmoid sinus : Air-filled cavity in the ethmoid bone located below the orbit of the eye and beside the nose.

Etiology : Cause or causative agent.

Eugonic : Growing luxuriantly (bacterial cultures).

Eukarya : The phylogenetic domain containing all eukaryotic organisms.

Eukaryote : A cell or organism having a unit membrane-bound (true) nucleus and usually other organelles.

Eukaryotic : Organisms with a true nucleus, in contrast to bacteria and viruses.

Evolutionary distance : In phylogenetic trees, the sum of the physical distance on a tree separating organisms; this distance is inversely proportional to evolutionary relatedness.

Exanthem : Skin eruption as symptom of an acute disease, usually viral.

Excoriate : Tp physically scratch or remove the skin.

Exergonic reaction : A chemical reaction that proceeds with the liberation of energy.

Exoantigen test : In vitro immunodiffusion test method for identifying fungal hyphae as Histoplasma, Blastomyces, or Coccidioides.

Exoerythrocytic cycle : Portion of the malarial life cycle occurring in the vertebrate host in which sporozoites, introduced by infected mosquitoes, penetrate the parenchymal liver cells and undergo schizogony, producing merozoites, which then initiate the erythrocytic cycle.

Exogenous : From outside the body.

Exon : The coding sequences in a split gene. Contrast with intron, the intervening noncoding region.

Exotoxin : A toxin produced by a microorganism that is released into the surrounding environment.

Exponential growth : Growth of a microorganism where the cell number doubles within a fixed time period.

Exponential phase : A period during the growth cycle of a population in which growth increases at an exponential rate.

Expression : The ability of a gene to function within a cell in such a way that the gene product is formed.

Expression vector : A cloning vector that contains the necessary regulatory sequences to allow transcription and translation of a cloned gene or genes.

Extensor surface : The surface of a joint involved in extension or straightening of a limb.

Extradermatomal : Not confined to one dermatome.

Extradural : Referring to the outer side of the dura mater.

Extramedullary cranial ganglion : Outside the medulla oblongata (brain stem), in reference to the cranial nerves.

Extreme halophile : An organism whose growth is dependent on large amounts (generally >10%) of NaCl.

Exudate : Fluid that has passed out of blood vessels into adjacent tissues or spaces; high protein content.