B : Biochemical Assay.

B cells : Lymphocytes involved in antibody production.

B-lymphocytes (or B cells) : Bursa-derived lymphocytes important in humoral immunity.

Babesiosis : Occasionally a disease of humans caused by a blood protozoan of various animals; tick borne; organism morphology similar to that of young rings of Plasmodium falciparum; more severe in compromised patients.

Bacillus : A bacterial genus in which members are rod-shaped, gram-positive, endospore-forming, and, depending on species, aerobic or facultatively anaerobic. Type species

Bact : Bacterium

Bacteremia : Presence of viable organisms in blood.

Bacteria : All prokaryotes that are not members of the domain Archaea.

Bacterial vaginosis : Noninflammatory condition in vagina characterized by foul-smelling vaginal discharge and presence of mixed bacteria.

Bactericidal : Term used to describe a drug that kills microorganisms.

Bacteriochlorophyll : A Magnesium-containing porphyrin that resembles but is not identical to the chlorophull of cyanobacteria, eucaryotic algae, and green plants. It occurs in anoxygenic phototrophic bacteria.

Bacteriocins : Antibiotic-like substances, produced by bacteria, that exert a lethal effect on other bacteria.

Bacteriophage : Virus that infects a bacterial cell, sometimes bringing about its lysis.

Bacteriostatic : Term used to describe a drug that inhibits growth of an organism without killing it.

Bacterium : The transient appearance of bacteria in the blood.

Bacteriuria : Presence of bacteria in urine.

Bacteroid : A swollen, deformed Rhizobium cell, found in the root nodule; capable of symbiotic nitrogen fixation.

Bacteroides bile esculin agar (BBE) : This medium contains 20% bile that selects for the bile tolerant Bacteroides fragilis group. BBE agar is used for the rapid isolation and presumptive identification of members of the B. fragilis group and Bilophila spp. This medium also contains the antibiotic gentamicin to inhibit most aerobic organisms. Members of the B. fragilis group will turn the medium brown to black by hydrolysis of the esculin contain in the medium.

Bacteriostatic : Inhibiting the growth or multiplication of bacteria.

BAL : Bronchoalveolar lavage.

Band form : Older trophozoites of Plasmodium malariae that may stretch across red blood cells in the form of a band.

BAP : Blood Agar Plate.

Barophile : An organism able to live optimally at high hydrostatic pressure.

Barotolerant : An organism able to tolerate high hydrostatic pressure, although growing better at normal pressures.

Basal medium : A(n) (unsupplemented) medium which allows the growth of many types of microorganisms which do not require any special nutrient supplements, e.g. nutrient broth.

Base composition : In reference to nucleic acid, the proportion of the total bases consisting of guanine plus cytosine or thymine plus adenine base pairs. Usually expressed as a guanine + cytosine (G+C) value, e.g. 60% G+C.

Basidiospore : A sexual spore formed on a structure known as a basidium. Characteristic of the class Basidiomycetes.

Basidium (pl. basidia) : A cell frequently club-shaped usually bearing four external basidiospores as a result of sexual reproduction.

Basket nucleus : Nuclear structure that may be seen in Iodamoeba butschlii cysts (occasionally trophozoites); in well-stained organisms, fibrils may be seen running between the karyosome and the chromatin granules. The "basket of flowers" has been described as follows

Baylisascaris procyonis : A common roundworm of raccoons (ingestion of infective eggs from the environment) that cause larva migrans (central nervous system). Human cases present with eosinophilic meningoencephalitis (two fatal cases in the Unites States).

BCG : Bacille Calmette-Guerin, an attenuated strain of Mycobacterium tuberculosis used for immunization.

bcr : Breakpoint cluster region.

Benign tertian malaria : Malaria caused by Plasmodium vivax.

Beta-lactamases : Enzymes that destroy penicillins and/or cephalosporins and are produced by a variety of bacteria.

BFP : Biological false-positive (in syphilis tests).

Bibasilar : Pertaining to the bases of both lungs.

bid : Twice a day (bis in die).

Bifurcated : Divided into two branches.

Bilharziasis : Another name for schistosomiasis; often used to indicate infection with either Schistosoma mansoni or S. haematobium.

Bilateral : Pertaining to both sides of a symmetrically shaped tissue, organ, or the entire body; for example, the right and left lungs are bilateral organs.

Bile sensitivity : An organsims ability to grow in the presence of 20% bile.

Biliary tree : System of ducts through which bile is transported.

Binary fission : The division of one cell into two (typically similar or identical ) cells by the formation of a septum. It is the commonest form of cell division in bacteria. If the daughter cells are not similar (in size) to the parent cell, it is called asymmetrical binary fission. Asymmetrical binary fission occurs e.g. in Caulobacter.

Binomial nomenclature : The system of having two names (genus and specific epithet, also called Latin binomial) for each organism.

Biochemical oxygen demand (BOD) : The oxygen-consuming property of a body of water determined by taking a sample of water, aerating it well, placing it in a sealed bottle, incubating for a standard period of time (usually 5 days at 20 degrees C.), and determining the residual oxygen in the water at the end of incubation.

Bioconversion : In industrial microbiology, use of microorganisms to convert an added chemical to a chemically modified form.

Biofilm : Microbial colonies encased in an adhesive, usually polysaccharide material, and attached to a surface.

Biogeochemistry : Study of microbially mediated chemical transformations of geochemical interest, e.g. nitrogen or sulfur cycling.

Biological safety cabinet : Enclosure in which one can work with relatively dangerous organisms without risk of acquiring or spreading infection caused by them. These cabinets, also called biosafety hoods, vary in design according to nature of agents to be worked with. The simpler ones maintain a negative pressure within the work area and a laminar air curtain, both of which operate to prevent escape of organisms form interior of hood. Air that is exhausted may be passed through a high-efficiency bacterial filter that will trap all microorganisms that are anticipated or may be passed through a furnace that will incinerate any organisms.

Bioluminescence : Light generation by living organisms.

Biomass : A general term to indicate the total weight (usually dry weight) of a microorganism in a culture or an environment.

Biopsy : Removal of tissue from a living body for diagnostic purposes (e.g., lymph node biopsy).

Bioremediation : Use of microorganisms to remove or detoxify toxic or unwanted chemicals from an environment.

Biosynthesis : The production of needed cellular constituents from other (usually simpler) molecules.

Biotechnology : The use of living organisms to carry out defined chemical processes for industrial application.

Biotin : Small vitamin with two binding sites, one of which can bind covalently with nucleic acid leaving the other free to form a strong bond with the protein avidin, which in turn can be bound to enzymes. The system is used as a label for nucleic acid probe detection.

Biotype : Biological or biochemical type of an organism. Organisms of the same biotype will display identical biological or biochemical characteristics. Certain key markers are used to define and recognize biotypes in tracing the spread of organisms in the environment and in epidemics or outbreaks.

Biseriate : With reference to the genus Aspergillus, phialide is supported by a metula as opposed to a uniseriate phialide which forms directly on the vesicle. (See Uniseriate.)

Black smoker : Thermal vent emitting very hot (270-380 degrees C.) water and minerals.

Blackwater fever : Condition in which the diagnostic symptom is passage of reddish or red-brown urine, which indicates massive intravascular hemolysis (Plasmodium falciparum).

Blastic : Development of a conidium by enlargement at first by de novo growth prior to delimitation by a septum.

Blastoconidium : A spore formed by budding, as in yeasts.

Blastomycosis : An acute or chronic mycosis which usually affects man and animals (e.g. dogs). Blastomycosis is caused by a fungus called Blastomyces dermatitidis and occurs in North America, Africa and Israel. Infection apparently occurs by inhalation of spores from the fungus, although B. dermatitidis has proved difficult to isolate from environmental habitats.

Blepharitis : Inflammation of eyelids.

Blepharoplast : A small, dark-staining body near the base of the flagellum that is associated with fibrillar portions of the flagellum (blood flagellates).

Blind loop : A condition in which continuity of the bowel has been interrupted in such a way that a segment of bowel receives material from high in the bowel in the usual way but cannot empty normally because it ends in a blind sac. This leads to proliferation of microorganisms, especially anaerobes, in the blind loop of bowel and may produce profound pathophysiologic effects. There are other situations in which there may be bacterial overgrowth in a segment of the bowel by other mechanisms.

B lymphocyte : A cell of the immune system that differentiates into an immunoglobulin-producing cell.

BM : Bowel movement.

Bothrium : One of the two shallow grooves on the scolex of Diphyllobothrium latum.

Breakpoint : Level of an antibacterial drug achievable in serum; organisms inhibited by this level of drug are considered susceptible. In certain situations, clinicians strive to achieve serum or body fluid levels several times that of the breakpoint.

Brewing : The manufacture of alcoholic beverages such as beer from the fermentation of malted grains.

Brightfield microscopy : Conventional microscopy in which the object to be viewed is illuminated from below.

Bronchial washings : Fluid that may be aspirated from bronchial tree during bronchoscopy.

Bronchial lavage : Similar to bronchial washings but this term implies instillation of a larger volume of fluid before aspiration. Alveolar organisms may be present in the lavage.

Bronchiolitis : Inflammation of the bronchioles (conducting airways of less than 1 mm).

Bronchitis : Inflammations of mucous membranes of bronchi; often caused by infectious agents, viruses in particular.

Bronchoscopy : Examination of bronchi through a bronchoscope, a tubular illuminated instrument introduced through the trachea (windpipe).

Bronchospasm : Episodic constriction of smooth muscles lining the bronchi in response to some kind of irritant or stimulus.

Brucella blood agar (BRU) : This medium contains 5% sheep blood for the enrichment of obligate and facultative anaerobic organisms. Brucella blood agar contain no inhibitory substances and should be used for the recovery of all clinical isolates.

BSC : Biological safety cabinet.

Bubo : Inflammatory enlargement of lymph node, usually in the groin or axilla.

Buccal cavity/capsule : The space between the oral opening and beginning of the esophagus in nematodes; useful diagnostically in rhabditiform larvae (Strongyloides stercoralis, hook-worm).

Buccal teeth/plates : Toothlike structure in the mouth cavity of the adult hookworms of the genus Ancylostoma (compared with buccal plates found in the mouth cavity of the genus Necator).

Budding : A form of reproduction in which a new cell is formed as an outgrowth from the parent cell.

Buffy coat : Layer of white blood cells and platelets above red blood cell mass when blood is sedimented.

Bullae : Large blebs or blisters, filled with fluid, in or just beneath the epidermal layer of skin.

BUN : Blood urea nitrogen.

Bursa : Umbrellalike expansion of the cuticle at the posterior end of male nematodes; it is supported by muscular rays and aids in copulation (hookworms, trichostrongyles).

Bursitis : Inflammation of a bursa, which is a small sac lined with synovial membrane and filled with fluid interposed between parts that move on each other.

Butt : Lower portion or medium in a tube that has the medium dispensed in such a way that the lower portion fills the tube entirely while the upper portion is distributed in the form of a slanted surface leaving an air space between the slant and the opposite wall of the tube.

Butyrous : Butterlike consistency.

BV : Bacterial vaginosis.