Salpingitis : Inflammation or infection of a tube; usually the Fallopian tubes between the ovaries and uterus.

Saprobe : An organism that uses non-living organic matter for energy sources.

Saprobe/Saprophyte : An organism that uses dead organic matter as a source of nutrients.

Saprophytic : Nonpathogenic.

SB : Southern blot (DNA hybridization).

SBA : Suprapubic bladder aspiration.

SBE : Subacute bacterial endocarditis.

SBP : Spontaneous bacterial peritonitis.

s.c. : Subcutaneous.

Scale up : Conversion of an industrial process from a small laboratory setup to a large commercial fermentation.

Scarlet fever : Characteristic reddish skin rash resulting from an exotoxin produced by cells of Streptococcus pyogenes.

Schizogony : Stage in the asexual cycle of the malaria parasite that takes place in the red blood cells of humans.

Schlichter test : Synonym for the serum bactericidal level test.

Schuffner's dots : Tiny, red-staining granules in the cytoplasm of red blood cells infected with either Plasmodium vivax or P. ovale; true stippling (using Giemsa stain).

Sclerosing cholangitis : Recurrent or persistent obtrusive jaundice due to extensive, destructive fibrosis of the bile ducts; frequently progresses to cirrhosis, liver failure, or portal hypertension; most common in young men.

Sclerotic : Hard, indurated.

Scolex (pl. Scolices) : Head portion of a tapeworm; may attach to the intestinal wall by suckers or hooklets.

Scotochromogens : Mycobacteria that are pigmented even in the absence of exposure to light.

Scutulum (pl. scutulum) : Cup-shaped crust of hyphae and spores in favus of the skin.

SD : Standard deviation(s).

Seatworm : Another name for pinworm (Enterobius vermicularis).

Secondary antibody response : Antibody made upon second (subsequent) exposure to antigen; mostly of the class IgG.

Secondary metabolite : A product excreted by a microorganism near the end of the growth phase or during stationary phase.

Secondary structure : The initial pattern of folding of a polypeptide or a polynucleotide, usually the result of hydrogen bonding.

Secretion vector : A DNA vector in which the protein product is both expressed and secreted (excreted) from the cell.

Sed rate, SR : Sedimentation rate.

Selection : Placing organisms under conditions where the growth of those with a particular genotype will be favored.

Selective medium : A medium which allows the growth of certain types of microorganisms in preference to others. For example, an antibiotic-containing medium allows the growth of only those microorganisms which are resistant to this antibiotic.

Semiconservative replication : DNA synthesis yielding new double helices, each consisting of one parental and one progeny strand.

SEM : Scanning electron micrograph.

Sensitivity : Ability of a test to detect all true cases of the condition being tested for; absence of false-negative results. (Also see "specificity").

Septate : Hyphae with cross-walls.

Sepsis : The presence of pathogenic microorganisms or toxins in the blood or tissues.

Septic abortion : Infection of the mother after the abortion of a fetus; can involve the uterus and become a widespread systemic infection.

Septic embolus : Clot (blood or other occlusive material) carried by the blood which contains infectious agents; often leads to systemic infection. Its occurrence can be sudden.

Septic shock : Acute circulatory failure caused by toxins of microorganisms; often leads to multiple organ failure and is associated with a relatively high mortality.

Septicemia : Infection of the bloodstream by microorganisms.

Septum (pl. septa) : A crosswall (partition) dividing a parent cell into two daughter cells during binary fission or occurring between adjacent cells in the hyphae.

Septicemia (sepsis) : Systemic disease associated with presence of pathogenic microorganisms or their toxins in the blood.

Sequela (pl. sequelae) : A condition that occurs as a result of a disease process.

Sequestrum : A detached or dead piece of bone within a cavity, abscess, wound, or area of osteomyelitis.

Sereny test : Test for bacterial invasiveness; involves applying a suspension of the organism to the conjunctiva of a small mammal and observing for development of conjunctivitis.

Serology : The study of antigen-antibody reactions in vitro.

Serosanguineous : Like serous but with some blood present grossly.

Serous : Like serum.

Serum : Cell-and fibrinogen-free fluid remaining after whole blood clots.

Serum bactericidal level : Lowest dilution of a patient's serum that kills a standard inoculum of an organism isolated from that patient; this, of course, is related to antibiotic level achieved in the patient serum and the bactericidal activity of the drug being employed.

Serum sickness : An immune complex disease that occurs approximately 1 to 2 weeks after a foreign serum or protein has been introduced into the body; local or systemic reactions can occur.

Sessile : Attached directly to a hypha without a stalk (conidiophore).

Sexual state : The portion of the life cycle in which the organism reproduces by the union of two nuclei. Also known as the perfect state.

Sexually transmitted disease (STD) : A disease whose usual means of transmission is by sexual contact.

SF : Synovial fluid.

SH : Serum hepatitis.

Sheath1 : A secreted, tubular structure formed around a chain of cells or around a bundle of filaments; cells within a sheath may or may not subsequently separate from the sheath.

Sheath2 : A layer of outer membrane covering the bacterial flagella.

Shine-Dalgarno sequence : A short stretch of nucleotides on a prokaryotic mRNA molecule upstream of the translational start site, that serves to bind to ribosomal RNA and thereby bring the ribosome to the initiation condon on the mRNA.

Shock : Marked decrease in blood pressure; rapid pulse, decreased kidney function (Plasmodium falciparum infection, rupture of hydatid cyst, bee stings).

Shuttle vector : A DNA vector which can replicate in two different organisms, used for moving DNA between unrelated organisms.

SIADH : Syndrome of inappropriate (secretion) antidiuretic hormone.

Sickle-cell anemia : A genetic trait which confers resistance to malaria but which causes a reduction in numbers of red blood cells.

Sigmoidoscopy : Visual examination of the rectum and sigmoid flexure of the colon by using a lighted tube; often performed for suspect amebiasis cases (Entamoeba histolytica).

Signal sequence (signal peptide) : A short stretch of amino acids found at the beginning of proteins that are typically rich in hydrophobic amino acids which helps transport the entire polypeptide through the membrane.

Signature sequence : Short oligonucleotides of unique sequence found in 16S ribosomal RNA of a particular group of prokaryotes.

Single-cell protein : Protein derived from microbial cells for use as food or a food supplement.

Sinus : Suppurating tract; paranasal sinus, hollows, or cavities near the nose (e.g., frontal and maxillary sinuses).

Sinusitis : Inflammation of the sinus cavities, often leading to headaches or nasal congestion.

Site-directed mutagenesis : The insertion of a different nucleotide at a specific site in a DNA molecule using synthetic DNA methodology.

16S rRNA : A large polynucleotide (about 1500 bases) which functions as a part of the small subunit of the ribosome of prokaryotes and from whose sequence evolutionary information can be obtained; the eukaryotic counterpart is 18S rRNA.

Slant : See definition of "butt." The slant is the upper surface of the medium in the tube described. It is exposed to air in the tube.

Slime layer : A diffused layer of polysaccharide exterior to the bacterial cell wall. Compare with capsule and glycocalyx.

Slime mold : A nonphototrophic eukaryotic microorganism lacking cell walls, which aggregate to form fruiting structures (cellular slime molds) or simply masses of protoplasm (acellular slime molds).

snRNP : Small nuclear ribonucleoproteins.

SOB : Shortness of breath.

Sodium polyanethol sulfonate : An antimicrobial used in the presumptive identification of anaerobic bacteria. Most anaerobic gram-positive cocci are resistant to this antimicrobial; however, P. anaerobius is susceptible. P. micros may show a small zone of inhibition.

Solid-phase immunosorbent assay (SPIA) : ELISA test in which the capture antigen or antibody is attached to the inside of a plastic tube, microwell, or to the outside of a plastic bead, in a filter matrix, or some other solid support. Allows faster interaction between reactants and more concentrated visual end products than ELISA test performed in liquid.

Somatic : Pertaining to the body (of a cell) (e.g., the somatic antigens of Salmonella species).

Somnolent : Drowsy.

Source of infection : The person, animal, object or substance from which an infectious agent passes to a host. Source of infection should be clearly distinguished from source of contamination, such as overflow of a septic tank contaminating a water supply, or an infected cook contaminating a salad. (See Reservoir).

Southern Blot (SB) describes the technique first developed by the Scottish molecular biologist Edward M. Southern which now bears his name. Specimen DNA is denatured, treated with restriction enzymes to result in DNA fragments and then the single-stranded DNA fragments are separated by electrophoresis. The electrophoretically separated fragments are then blotted to a nitrocellulose membrane, retaining their electrophoretic position, and hybridized with radiolabeled single-stranded DNA fragments with the sequences complementary to those being sought. The resulting double-stranded DNA bearing the radiolabel is then, if present, detected by autoradiography.

sp. gr., SG. s.g. : Specific gravity.

Sparganum : A migrating tapeworm larva that invades the subcutaneous tissues with inflammation and fibrosis (Diphyllobothrium and Spirometra spp.).

Special potency disks : Used to aid in the presumptive identification process. These disks include: kanamycin, vancomycin, colistin, and sodium polyethol sulfonate antibiotic disks. Nearly all gram negative organisms are resistant to vancomycin. Knamycin and colistin disks help identify gram negative organisms down to the genus level. Sodium polyanethol sulfonate is used for gram-positive cocci. Peptostreptococcus anaerobius is sensitive to the SPS disk, while all other gram-positive cocci are only slightly resistant to this disk.

Species : In microbiology, a collection of closely related strains sufficiently different from all other strains to be recognized as a distinct unit.

Specific epithet : The label (or designation) of a particular species in the binomial nomenclature system. For example, "coli" is the specific epithet of Escherichia coli.

Specific Gravity : A laboratory measurement that allows for comparison of the weight (density) of a liquid with that of distilled water; frequently used to determine the relative concentration or dillution of urine.

Specificity : Ability of a test to correctly yield a negative result when the condition being detected is absent; absence of false-positive results. (Also see "sensitivity").

Spheroplast : A spherical, osmotically sensitive cell derived from a bacterium (or any cell with cell wall) by loss of some but not all of the rigid wall layer. If all the rigid wall layer has been completely lost, the structure is called protoplast.

Spherule : Large, round, thick-walled structure containing spores; characteristic of coccidioides immitis in infected host material under direct microscopic examination. Spherules do not grow in routine artificial mycology media.

SPIA : Solid-phase immunosorbent assay.

Spicule : Accessory reproductive structure in male nematodes; useful in identification to the species level.

Spinae : Hollow conical appendages observable by light microscopy and having cross-strains when viewed by electron microscopy.

Spiral Hypha : Coiled or corkscrew-like turns in a hypha.

Spirillum (plural : spirilli)1: A bacterium with a spiral shape which is relatively rigid (i.e. not flexible, compare with spirochaete.

Spirillum2 : The bacterium in the genus Spirillum.

Spirochaete (spirochete) : A gram-negative bacterium characterized by the flexibly spiral shape and the possession of axial filaments.

Splenectomy : Removal of the spleen.

Splenomegaly : Enlargement of the spleen (leishmaniasis, schistosomiasis, malaria).

Splinter hemorrhages : Effects of vaculitis in trichinosis; tiny linear hemorrhages in nail beds (larval migration).

Spongiform : Pertaining to a spongelike appearance; when this is noted in brain tissue, it is indicative of the presence of Creutzfeldt-Jakob disease or another slow viral disease.

Spontaneous generation : The hypothesis that living organisms can originate from nonliving matter.

Sporangia : Spore-containing structures.

Sporangiophore : A specialized hyphal branch or stalk bearing a sporangium.

Sporangiospore : An asexual spore produced in a sporangium.

Sporangium : A sac or cell with the entire contents becoming converted into a number of asexual spores by cleavage.

Spore : Propagule that develops by sexual reproduction (ascospore, basidiospore, zygospore) or by asexual means within a sporangium (sporangiospore). Those most commonly seen in the clinical laboratory are usually enclosed in a sac-like structure (as opposed to conidia which are free, not enclosed).

Sporoformer : A bacterial species capable of producing Endospores; examples of Spore-forming anaerobes are Clostridium spp. and Sarcina ventriculi.

Sporocyst : An elongated sac without a mouth or other distinct internal or external structure, formed after the miracidium infects a snail. May give rise to cercariae (schistosomes) or rediae (Paragonimus spp.).

Sporogony : Stage in the sexual cycle in the malarial parasite that takes place in the mosquito.

Sporophore : A specialized hypha that develops spores.

Sporozoa : Nonmotile parasitic protozoa.

Sporozoite : Slender, spindle-shaped organism that is the infective stage of the malarial parasite; it is inoculated into humans by an infected mosquito and is the result of the sexual cycle of the malarial parasite in the mosquito.

Spurious parasite : Organisms that parasitize mosquito; the result of the sexual cycle in the mosquito.

Sputum : Material discharged from the surface of the lower respiratory tract air passages and expectorated (or swallowed).

Stab culture : Culture in which the inoculation of a tube or solid medium is made by stabbing with a needle to encourage anaerobic growth in the bottom.

Stalk : A nonliving ribbon-like or tubular appendage, excreted by a bacterial cell, that mediates attachment to a surface. (Contrast with prostheca).

Staph : Staphylococcus.

Stat : Statim (Latin); immediately.

Stationary phase : Stage in the growth cycle of a bacterial culture in which the vegetative cell population equals the dying population.

STD : Sexually transmitted disease; skin test dose.

Steatorrhea : Malabsorption characterized by the presence of fat in the stool (giardiasis, strongyloidiasis, cryptosporidiosis, isosporiasis).

Stem cell : Fetal cells that give rise to bone marrow, blood cells, and B and T cells.

Stereoisomer : A mirror image form of a molecule. Both have the same molecular and structural formula but different in their stereo arrangement of molecular positions.

Sterigma (sterigmata) : A small pointed hyphal branch or structure which supports a sporangium, a conidium, or basidiospore.

Sterigmata : Term formerly used to denote phialides of Aspergillus and other genera. More accurately refers to denticles produced by Basidiomycetes.

Sterile (sterility) : Free of living microorganisms (the state of being sterile).

Sterilization : Treatment resulting in death of all living organisms and viruses in a material.

Steroid : Any tetracyclic hydrocarbon which is derived from perhydrocyclopentanophenanthrenea. Important examples of steroids are cholesterol, and sterol; several hormones are also steroids such as sex hormones and corticosteroid hormones. Even vitamin D is based on the steroid structure.

Sterol : Any steroid-based alcohol having a hydrocarbon (aliphatic) side-chain of 8-10 carbons at the 17-beta position and a hydroxyl group (-OH) at the 3-beta position (that's why it's an alcohol). Cholesterol is one type of sterol. Because of its hydrophilic property at the -OH end and hydrophobic at the hydrocarbon side chain, it can be incorporated into the lipid bilayers of the cytoplasmic membrane. However, sterols only exist in the cytoplasmic membranes of eukaryotes while in prokaryotes, virtually all do not have sterol in their membranes except mycoplasmas, a group of bacteria lack cell walls.

Stolon : A horizontal hypha, or runner, that grows along the surface of the medium, often bearing rhizoids that penetrate the medium and sporangiophores that ascend into the air.

Stop codon : A codon which signals the termination of translation.

Streptobacilli : Rods that remain attached in chains after cell division.

Strep : Streptococcus.

Streptococci : Cocci that remain attached in chains after cell division.

Strain : A population of cells all descended from a single cell; also a clone.

Stridorous cough : Cough associated with laryngeal blockage which results in a a characteristic high-pitched cough.

Strobila : Entire chain of tapeworm proglottids, excluding the scolex and neck.

Stromatolites : Laminated microbial mats, typically built from layers of filamentous and other microorganisms which can become fossilized.

STS : Serologic test for syphilis.

Subcarinal : Refers to the area below the ridge that separates the right and left main bronchi at their junction with the trachea.

Subcoastal retractions : Inward movement of the area between the ribs, associated with an increased respiratory effort.

Subcutaneous : Situated or occurring directly under the skin.

Substrate : A substance on which an enzyme acts.

Substrate-level phosphorylation : Synthesis of high-energy phosphate bonds through reaction of inorganic phosphate with an activated (usually) organic substrate.

Subterminal spore : An endospore located somewhere other than the end of the cell.

Sulfatara : A hot, sulfur-rich, generally acidic environment, commonly inhabited by hyperthermophilic Archaea.

Sulfate-reducing bacterium : A prokaryote which is able to reduce sulfate SO42- (as a terminal electron acceptor) using electrons donated from organic acids, fatty acids, alcohols or hydrogen (electron donors).

Sulfur granule : Small colony of organisms with surrounding clublike material; yellow-brown; resembles grain of sulfur.

Superantigen : Molecules produced by microbes (viruses, bacteria, and perhaps parasites) that act independently to stimulate T-cell activities, including cytokine release. Among the most potent T-cell mitogens, superantigen stimulation can result in anergy, or alternatively, systemic immune system activation.

Supercoil : Highly twisted form of circular DNA.

Superinfection : Strictly speaking, this refers to a new infection superimposed on another being treated with an antimicrobial agent. The new infecting agent is resistant to the therapy initially employed and thus survives and causes persistence of the infection (now resistant to the treatment) or a new infection at a different site. Term is also used to indicate persistence or colonization with a new organism without any evidence of resulting infection.

Superoxide anion : A harmful derivative of oxygen capable of oxidative destruction of cell components.

Superoxide dismutase : A family of enzymes that catalyzes the conversion of two superoxide anions into a molecule of oxygen (02) and a molecule of hydrogen peroxide (H2O2).

Supine : Refers to lying on the back with the face directed upward.

Suppressor : A mutation that restores wild-type phenotype without altering the original mutation, usually arising by mutation in another gene.

Suppuration : Formation of Pus.

Suppurative : Producing Pus.

Suppurative lymphadenopathy : Enlarged, tender lymph nodes from which pus is draining.

Suprapubic bladder aspiration (SBA) : Obtaining urine by direct needle puncture of the full bladder through the abdominal wall above the pubic bone.

Surveillance of disease : As distinct from surveillance of persons (see Quarantine), surveillance of disease is the continuing scrutiny of all aspects of occurrence and spread of a disease that are pertinent to effective control.

Susceptible : A person or animal not possessing sufficient resistance against a particular pathogenic agent to prevent contracting infection or disease when exposed to the agent.

Suspect : In infectious disease control, illness in a person whose history and symptoms suggest that he or she may have or be developing a communicable disease.

Swimmer itch : Dermatitis caused by skin penetration of humans by cercariae of schistosomes (normally infect birds and semiaquatic animals).

Symbiosis : Close association between two different organisms; living together.

Sympodial growth : Conidiogenous structure that continues to increase in length by forming a new growing point just below each new terminal conidium, often resulting in a geniculate (bent) appearance.

Syncope : Fainting or loss of consciousness due to a temporary deficiency of blood supply to the brain (Dracunculus infections).

Syncytia : Structure resulting from fusion of cell membranes of several cells to form a multinucleated cellular structure; usually the result of viral infection of the cells.

Syndrome : Set of symptoms occurring together (e.g., nephrotic syndrome).

Synergism : Combined effect of two or more agents that is greater than the sum of their individual effects.

Synergy : When the actions of two or more processes, structures, or agents are combined to yield a result that is greater than the sum of each individually; for example, antibiotics can be synergistic.

Synonym : Another name considered acceptable for a species or taxonomic group.

Synovial fluid : Viscid fluid secreted by the synovial membrane; formed in joint cavities, bursae, and so forth.

Syntropy : A nutritional situation in which two or more organisms combine their metabolic capabilities to catabolize a substance not capable of being catabolized by only one of the two organisms.

Syphilis : A chronic human disease caused by Treponema pallidum. Infection generally occurs by direct contact with lesions of syphilis.

Systemic : Involving the entire body.