D

Dandruff: An infection often as a result of the yeast Malassezia furfur.
Delirium: A state of mental confusion often associated with a high fever.
Dengue fever: A disease caused by an arbovirus transmitted by the bites of the Aedes aegypti and A. albopictus (Asian Tiger) mosquito and also known as 'break-bone fever". It is second only to malaria among the insect-borne diseases.
Dental plaque: Consists of bacterial cells encased in a matrix of extracellular polymers and saivary products that adhere to the teeth.
Deoxyribose: The 5-carbon sugar present in DNA.
Dermatitis: Skin inflammation marked by redness, pain, and/or itching.
Dermatomycoses: Fungal diseases of the skin.
Dermatophytes: Fungal parasites that invade keratinized tissue of the skin and nails, causing such diseases as athlete's foot and ringworm. Dermatophyte fungi typically cause scaly lesions that tend to be circular.
Dessication: Drying.
Detergents: Compounds similar to soap, but not made from fats. Because of their ability to emulsify dirt, they are used as cleaning agents, but are not disinfectants.
Dialysis: The use of a machine acting as an 'artificial kidney' by filtering the blood or fluid introduced into the abdominal cavity.
Diapedesis: The process in which leukocytes pass out of the blood and into inflamed tissues by squeezing between cells of capillary walls.
Diarrhea: More than one liquid bowel movement and a common symptom of many diseases, including typhoid, dysentery, and cholera. Transient attacks may be caused by species of Samonella, Campylobacter, Listeria, or certain strains of E. coli and can be a life-threatening disorder. The actual cause of death is from dehydration and the loss of electrolytes. It can be caused by bacterial toxins, tainted food or water, infections, ingesting infectious agents, or adverse reactions to drugs. The important thing is to replace fluids lost with those containing electrolytes -- juices, soups, teas, etc. It is also important to refrain from high-fiber foods and caffeine, which stimulate the intestines. Using probiotics can reestablish the normal bacterial flora in the bowel, alleviating some types of diarrhea. Because diarrhea is a common side effect of radiation treatments and antibiotics, probiotics can be a preventative measure when taken along with the treatments. Carob powder diluted in tea or juice is also effective, especially for children. In addition, a preparation of apple pectin and chamomile extract may also reduce diarrheal episodes. Diarrhea differs somewhat from dysentery.
Dichotomous: Divided into two.
Dideoxynucleotide: A nucleotide lacking the 3'-hydroxyl group on the deoxyribose sugar and used in the Sanger method of DNA sequencing.
Dimorphic: Existing in two forms. Thus, a dimorphic fungus is a fungus that lives part of the time as a mold and part of the time in yeast form.
Diptera: An order of insects that is comprised of at least 100,000 different kinds of flies, mosquitoes, midges, gnats, and dozens of others. The only common characteristics is that they have a single pair of wings and unusually large eyes. It is reported that flies can carry up to two million bacteria each (who counted them was not part of the report).
Diptheria: The disease produced from the bacterium Corynebacterium diphtheriae, causing fever and swelling of the membranes in the throat, inhibiting breathing and swallowing. The toxins can also cause myocarditis. Infection is contracted through the bite of a carrier, droplet inhalation, or the ingestion of contaminated food, milk, water, etc.
Diphtheroids: Gram-positive bacilli of the genus Corynebacterium, commonly found on body surfaces. They are frequently contaminating bacteria found in clinical specimens. They are usually the result of a phage that has infected a diphtheria bacterium.
Diploid: Having a pair of each characteristic chromosome of a species. In man, the diploid number is forty-six.
Disinfection: The act of reducing the number of pathogenic organisms from objects or in materials so that they pose no threat of disease.
Disinfectant: A chemical germicide used to disinfect surfaces. Most are not geared for use on the human skin. Examples include ammonium, chlorine, and phenolic (used in hospitals). For use on the skin, alcohol and hydrogen peroxide are the ones used most often.
Disseminated intravascular coagulation (DIC): The activation of blood-clotting factors and platelets inside the blood vessels throughout the body. It may be triggered by infection, burns, snake bite, or other factors and may result in uncontrolled bleeding because of the depletion of these elements.
Disseminated stronglyloides: A sometimes fatal systemic condition caused by the nematode Strongyloides stercoralis.
Dissemination: The development of a generalized infection from a localized one, involving additional organ systems secondary to the primary focus of infection, as in the case of "strep throat" when the bacteria find their way into the blood to cause any number of other Streptococcal infections throughout the body.
DNA (deoxyribonucleic acid): A natural polymer that carries the genetic information determining the character of an organism. DNA is made up of four chemicals -- adenine, guanine, cytosine, and thymine -- that form the basis of each individual's genetic form. These basic chemicals are assembled in sequences that dictate how they will act. Genes are basically short segments of DNA strung together in such a finely tuned manner that the slightest change can cause major disruption in the human body. Recombinant DNA is a DNA molecule containing DNA that originated from two or more sources.
DNA ligase: An enzyme which can join two pieces of complimentary DNA together.
Domain: The highest level of biological classification superseding kingdoms. The three domains of biological organisms are Bacteria, the Archaea, and the Eukarya. It is also used to describe a region of a protein having a distinct function.
DPT vaccine (diphtheria, pertussis, tetanus): A blend of three vaccines to prevent the diseases of diphtheria, whooping cough, and tetanus.
Droplets: Particles consisting of dried mucus in which microorganisms are embedded.
Drug allergy: An abnormal sensitivity to a medication, usually manifested by rash and, sometimes, fever.
Duodenal: Pertains to the portion of the small intestine that attaches directly to the stomach. In adults, the duodenum is about 25 cm in length.
Dysentery: A serious diarrhea accompanied by mucus and blood, along with severe abdominal cramping, fever, and pain. Bacterial sources usually include strains of Shigella causing intestinal inflammation, pain, and copious watery stools that often contain blood, mucous, and pus resulting in rapid dehydration. Dysentery is the word coined by Hippocrates for bloody diarrhea, which was described in the earliest of histories. It has killed almost as many soldiers throughout history as were killed in combat. It can be caused by an amoeba (Entamoeba histolytica), as well as a bacterium. E. histolytica is also known to travel through the bloodstream in prolonged cases to cause dangerous abscesses in the liver and brain.