- Salmonella
- A major species of the bacteria family Enterobacteriaceae, associated with gastroenteritis, enteric fever, and osteomyelitis. There are more than 2,200 different species of the Salmonella bacteria.
- San Joaquin fever (Valley Fever)
- A potentially fatal disease (coccidioidomycosis) caused by inhaling spores of the fungus Coccidioides immitis. Those travelling in dusty areas are at risk for infection, with most people being unaware of any infection. Some will have mild flulike symptoms, while others develop a type of desert rheumatism. With a weakened immune system, symptoms can last for days or years, with conditions travelling to other areas of the body involving the lymph nodes, bones, liver, brain, etc. By this time, nearly two-thirds will die, not knowing the original cause.
- Saprophyte
- An organism that lives on dead or decaying matter, but does not produce infectious disease.
- Sarcodina (amoebas)
- Protozoa that move by extending a section of their cytoplasm (called a pseudopodium or false foot) in one direction, causing the remainder to follow.
- Scalded skin syndrome
- An infection caused by staphylococci producing large, soft vesicles over the body.
- Scarlet fever
- A disease caused by group A streptococcal toxins (Streptococcus pyogenes), characterized by fever and a bright red rash. It is more common in children, producing sore throat, fever, rash, and the swelling of cervical lymph nodes. Infection is transmitted via droplet inhalation or the ingestion of contaminated foods, especially milk.
- Schistosomes
- Blood flukes.
- Schistosomiasis
- A chronic disease, usually in the bladder or liver, caused by Schistosoma parasitic flukes. Humans contract the disease by eating snails that carry the larva released into fresh water often contaminated by human waste.
- Scolex
- The head of a tapeworm that attaches to the intestinal wall.
- Sebaceous glands
- Small glands located in the skin that secrete oils to the skin surface.
- Secondary response
- The humoral immune response that occurs when an antigen is recognized by memory cells. It is more rapid and stronger than a primary response.
- Sepsis
- A life-threatening acute illness caused by blood stream invasion of microorganisms, producing various combinations of symptoms: low blood pressure, destruction of blood-clotting elements, and failure of lungs, kidneys, and other organs.
- Septic shock
- The collapse of the normal blood pressure caused by blood stream invasion of microorganisms (sepsis). Frequently, the lungs, kidneys, and other organs fail as a result. This collapse can be caused by fungi and viruses, but the most frequent cause is bacteria. In the US alone, fifteen to twenty thousand people die each year from septic shock. Those who have had their spleens removed are the most susceptible to a sudden onslaught of infectious microbes. Diabetics can go septic when their kidneys or feet become infected, as can those with heart or lung diseases that quickly produce pneumonia. Septic shock can strike those following surgical procedures on germ-filled intestines. Some of the most dangerous blood infections happen to those going through chemotherapy because it leaves the immune system vulnerable to attack. During very serious illnesses when the immune system is struggling to regain strength, the bone marrow can push out immature white cells or band forms which are not ready to perform their duties.
- Septicemia
- A condition in which an infecting microorganisms (pathogens) rapidly multiply in the bloodstream. Septicemia is used synonymously with bacteremia, and was once commonly called blood poisoning. This is a negative prognostic sign, suggesting that the host may be losing its battle with the infecting agent.
- Septum (plural septa)
- A crosswall or membrane between compartments. The presence or absence of septa determines the classification of molds. When present, septa divide fungal hyphae into complete cellular units.
- Sequela
- A condition or illness directly relating to an earlier condition, but which develops some time after the first illness.
- Serotype
- A strain of bacteria with a unique antigen such that it induces antibody specific for that organism. It is also a subdivision of a particular species.
- Serology
- The test tube study of antigen-antibody reactions.
- Serratia
- A genus of the bacteria family Enterobacteriaceae. The most frequent form is S. marcescens, which produces red-pigmented colonies grown at room temperature. For a long time, it was considered a non-pathogen, but it is now recognized as a cause of pneumonia, cystitis, and other such infections that are often antimicrobial-resistant.
- Serum
- The colourless, fluid component of blood remaining after the solid elements have been separated out.
- Sexually transmitted diseases
- Such diseases include HIV/AIDS, syphilis, gonorrhea, Hep B, chlamydia, PID, genital herpes and warts, and infection by the human papillomavirus. Among the industrialized nations, the US has the highest rates of sexually transmitted diseases. Microbial pathogens that are sexually transmissible can come from bacteria, viruses, fungi, or protozoa. Those from bacteria include the following: Neisseria gonorrhoeae; Ureaplasma urealyticum, Gardnerella vaginalis; Haemophilus ducreyi; Calymmatobacterium granulomatis; Treponema pallidum; Chlamydia trachomatis; and, occasionally, from Group B Streptococcus; Shigella species; and Campylobacter jejuni. Those from viruses include the following: HIV; Herpes simplex II; Papillomavirus; Cytomegalovirus; and, occasionally, from Molluscum contagiosum; and Hepatitis A and B. Those from fungi or protozoa include the following: Trichomonas vaginalis; and, occasionally, from Giardia lambia; Candida albicans; Endamoeba histolytica; and Cryptosporidium.
- Shigella
- A Shigellae bacterial genus of the family Enterobacteriaceae responsible for human infections associated with intestinal diseases and having a high mortality rate.
- Shock
- A medical condition manifested by a decreased blood pressure, circulatory insufficiency, and a weakened pulse that can be life-threatening.
- SIDA
- The common name for AIDS outside the US, based on the Spanish sindromo inmuno-deficiencia adquirido and the French syndrome immuno-deficitaire acquis.
- Silvadene
- An antibiotic cream applied to burned or severely damaged skin.
- Sinus
- An opening or space in a tissue. Infectious processes often produce a nonhealing sinus which may connect between tissues or even to the outside.
- Slime layer
- A diffuse exterior layer of polysaccharides, loosely bound to the cell wall that protects the cell against drying, helping to trap nutrients, and, sometimes, binding cells together.
- Slow virus infections
- Infections of the brain produced by imperfect viruses or unusual infectious agents and preceded by incubation periods of many years. (e.g., AIDS, SSPE, CJD)
- Smallpox
- A disease caused by the Variola species virus belonging to the family Poxviridae genus Orthopoxvirus. It has essentially been eradicated from the world, but concerns are now rising as to its use as a biological weapon since most of the world’s population has never been exposed to cause immunity.
- Smallpox vaccine
- A live-virus vaccine made from cowpox that confers protection against smallpox.
- Sonogram
- A procedure, also known as an echogram, sonograph, or ultrasonogram, is a technique in which sound waves are transmitted to hard-to-reach places in the body, and their echoes are recorded and studied.
- Sous vide
- A risky procedure whereby meals are cooked, chilled, and stored in vacuum for weeks, prior to reheating and eating.
- Sparganosis
- An invasive infection by a larval tapeworm, often of the eye, contracted by applying a poultice made of raw animal flesh, often frogs.
- Species
- A group of organisms with many common characteristics; a collection of closely related strains sufficiently different from all other strains to be recognized as a distinct unit.
- Spirillum (plural spirilli)
- Bacteria that have a curved or spiral shape.
- Sporicide
- Kills spores.
- Spirochaetes
- Highly coiled bacteria and a general term applied to any organism of the order Spirochaetales, which cause such diseases as syphilis and yaws. Treponemes have fine, regular spirals and do not stain with Gram’s or other simple stains. They have not been cultured in a laboratory, but can cause infections in some animals. Leptospires have regular spirals, finer than treponemes, and are the same except that they can grow in special media in the lab. Borrelia have coarse irregular spirals that readily stain with ordinary dyes and can be grown in a lab.
- Spirometra
- A species of larval tapeworm that causes Sparganosis.
- Spore
- A dormant form of microbe capable of enhanced resistance to heat, drying, and disinfection. Spores are tiny, hard, inert, globular derivatives of bacteria, formed under inclement conditions to enable survival. They are not dangerous in themselves, but can return to growing bacteria that can cause harm. A spore is the asexual reproductive cell produced by fungi.
- Sporozoa (singular sporozoon)
- A type of protozoa that include Plasmodium and Toxoplasma, responsible for the diseases of malaria and toxoplasmosis.
- Sputum
- Consists of mucous secretions, together with cells, bacteria, viruses, and parasites, brought up from the lungs, bronchi, and trachea, and ejected through the mouth, in contrast to saliva which is the secretions of the salivary glands.
- SSPE (subacute sclerosing panencephalitis)
- A very rare and slow-forming infection of the brain caused by a defective measles virus. Other members of the group include the following: progressive rubella panencephalitis, caused by the German measles virus; kuru, a fatal disease of cannibals in New Guinea; and Creutzfeld-Jakob disease, the human form of “mad cow disease.”
- Staphylococcus (staph)
- A genus of the family Micrococcaceae. Infections are usually the result of two species – S. aureus and S. epidermidis. They are particularly prevalent in hospitals and care facilities, where infection rates rival those of E. coli outbreaks. Staphylococcus aureus is a gram-positive spherical bacterium that causes abscesses of the skin and that can invade the blood stream and infect any organ. It is also the cause of toxic shock syndrome associated with super-absorbent tampons.
- Sterilant
- A germacide that kills all microorganisms and not just the harmful ones we call germs.
- Stool Samples
- Fecal matter collected to be studied in a laboratory to aid in a diagnosis. About one-third of the dry weight of fecal material consists hundreds of both live and dead bacteria. A thorough anaylsis of one small sample of human feces could take over a year to complete. This explains why a lab is given a short list of suspect organisms to narrow down the search and the amount of time to be taken.
- Strain
- A subgroup or subtype of a species having one or more characteristics that distinguish it from other subgroups of that species.
- Streptococcus (strep)
- A genus of the family Micrococcaceae, as is the Staphylococcus bacteria, and are most often found as the normal flora of healthy people. According to the Lancefield system, they are divided into eighteen major groups designated A through R. Group A is responsible for most of the fatal illnesses, including the “flesh eating” infections, as well as strep throat, scarlet fever, and rheumatic fever. Group B generally cause such diseases as neonatal meningitis and sepsis. Groups C and G are responsible for the occasional wound infection and pharyngitis. Group D (enterococci) are mainly responsible for urinary tract infections, bacteremia, and endocarditis. Viridans streptococci contains about ten species responsible for about 70% of all cases of bacterial endocarditis. Streptococcus mutans plays a central role in the initiation of cavities.
- Streptokinase (fibrinolysin)
- An enzyme produced by streptococci that digest fibrin, dissolving blood clots.
- Strongyloides
- A nematode or small roundworm.
- Substrates
- Components of a medium used by the microbes for growth and also the chemicals used by enzymes for their action.
- Subtype
- A designation used to distinguish among members of a species that have one or more differentiating characteristics.
- Superantigens
- Substances that are able to activate many immune functions at once, producing harmful effects, including fever, shock, and organ failure. Pyrogenic exotoxins function as superantigens.
- Superinfection
- A secondary infection that develops in addition to a previous infection; an infection that occurs as a result of antibiotic treatment.
- Suppressor T cells
- Lymphocytes controlled by the thymus gland, which suppresses the immune response.
- Suppuration
- An accumulation of white blood cells resulting in the formation of pus.
- Symbiosis
- An association of two different organisms involving some degree of interdependence. The partners of such an association are symbionts. (contrast commensalism)
- Syndrome
- A number of symptoms occurring together that characterize a specific disease.
- Synergistic
- The capacity of working together, as in two organisms which are able to produce a response greater than they could alone.
- Syphilis
- A disease caused by a spiral-shaped bacterium (spirochete), a member of the family Spirochaetaceae. Three genera of spirochetes contain species that are able to cause disease in humans: Treponema (syphilis), Borrelia (relapsing fever), and Leptospira (leptospirosis). The last two diseases are caused by spirochetes that infect ticks or lice and transmitted to humans through their bites. Syphilis is a disease transmitted sexually or in the womb and caused by a corkscrew-shaped bacterium, producing chronic infection of the brain, blood vessels, and other organs.
- Systemic (dissemination)
- Pertains to the whole body and such infections that are not localized to one area but are carried throughout the body, usually via the bloodstream.
