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Movements, leaders, victories and the continuing fight for equality.
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In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Baird-Parker agar is a type of agar used for the selective isolation of gram-positive Staphylococci species.[1] It contains lithium chloride and tellurite to inhibit the growth of alternative microbial flora, while the included pyruvate and glycine promote the growth of Staphylococci.[1] Staphylococcus colonies show up black in colour with clear zones produced around them.[1]
Baird-Parker Agar From Liofilchem first published an academic article about this agar medium for the purposes of improved diagnostics and isolating coagulase-positive Staphylococci in 1962.[2] He developed this agar medium from the tellurite-glycine formulation of Zebovitz et al[3] and improved its reliability in isolating coagulase-positive staphylococci from foods. Baird-Parker added egg yolk emulsion as a diagnostic agent and sodium pyruvate to protect damaged cells and aid their recovery.[4] It is now widely recommended by national and international bodies for the isolation of coagulase-positive staphylococci.[5] Baird-Parker agar is commonly used as a method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) in food and animal feedstuffs.[6]
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Baird-Parker agar is a type of agar used for the selective isolation of gram-positive Staphylococci species. It contains lithium chloride and tellurite to inhibit the growth of alternative microbial flora, while the included pyruvate and glycine promote the growth of Staphylococci. Staphylococcus colonies show up black in colour with clear zones produced around them.
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from Penicillium moulds, principally P. chrysogenum and P. rubens. Eight species of Penicillium, in the section Chrysogena, produce penicillins. Most penicillins in clinical use are synthesised by P. chrysogenum using deep tank fermentation and then purified. A number of natural penicillins have been discovered, but only two purified compounds are in clinical use: penicillin G (intramuscular or intravenous use) and penicillin V (given by mouth). Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are still widely used today for various bacterial infections, though many types of bacteria have developed resistance following extensive use. In the United States, 10% of the population claims penicillin allergies, but because the frequency of positive skin test results decreases by 10% with each year of avoidance, 90% of these patients can eventually tolerate penicillin. Additionally, those with penicillin allergies can usually tolerate cephalosporins (another group of β-lactam) because the immunoglobulin E (IgE) cross-reactivity is only 3%. Penicillin was discovered in 1928 by the Scottish physician Alexander Fleming as a crude extract of P. rubens. Fleming's student Cecil George Paine was the first to successfully use penicillin to treat eye infection (neonatal conjunctivitis) in 1930. The purified compound (penicillin F) was isolated in 1940 by a research team led by Howard Florey and Ernst Boris Chain at the University of Oxford. Fleming first used the purified penicillin to treat streptococcal meningitis in 1942. The 1945 Nobel Prize in Physiology or Medicine was shared by Chain, Fleming and Florey. Several semisynthetic penicillins are effective against a broader spectrum of bacteria: these include the antistaphylococcal penicillins, aminopenicillins, and antipseudomonal penicillins.
Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular, and made up of non-motile and non-sporing cocci (round cells) that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause group A streptococcal infection. S. pyogenes is the predominant species harboring the Lancefield group A antigen, and is often called group A Streptococcus (GAS). The name group A (beta-hemolytic) Streptococcus is thus also used. The species name is derived from Greek words meaning 'a chain' (streptos) of berries (coccus [Latinized from kokkos]) and pus (pyo)-forming (genes), since a number of infections caused by the bacterium produce pus. The main criterion for differentiation between Staphylococcus spp. and Streptococcus spp. is the catalase test. Staphylococci are catalase positive whereas streptococci are catalase-negative. S. pyogenes can be cultured on fresh blood agar plates. The PYR test allows for the differentiation of Streptococcus pyogenes from other morphologically similar beta-hemolytic streptococci (including S. dysgalactiae subsp. esquismilis) as S. pyogenes will produce a positive test result. An estimated 700 million GAS infections occur worldwide each year. While the overall mortality rate for these infections is less than 0.1%, over 650,000 of the cases are severe and invasive, and these cases have a mortality rate of 25%. Early recognition and treatment are critical; diagnostic failure can result in sepsis and death. S. pyogenes is clinically and historically significant as the cause of scarlet fever, which results from exposure to the species' exotoxin.
Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of Staphylococcus isolates. Importantly, S. aureus is generally coagulase-positive, meaning that a positive coagulase test would indicate the presence of S. aureus or any of the other 11 coagulase-positive Staphylococci. A negative coagulase test would instead show the presence of coagulase-negative organisms such as Staphylococcus epidermidis or Staphylococcus saprophyticus. However, it is now known that not all S. aureus are coagulase-positive. Whereas coagulase-positive staphylococci are usually pathogenic, coagulase-negative staphylococci are more often associated with opportunistic infection. It is also produced by Yersinia pestis. Coagulase reacts with prothrombin in the blood. The resulting complex is called staphylothrombin, which enables the enzyme to act as a protease to convert fibrinogen, a plasma protein produced by the liver, to fibrin. This results in clotting of the blood. Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood. The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host. The fibrin coat can therefore make the bacteria more virulent. Bound coagulase is part of the larger family of MSCRAMM adhesin proteins.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.