Microbiology Laboratory Questions Essay Example | Topics and Well Written Essays - 500 words

Microbiology Laboratory Questions - Essay Example It ferments inulin and produces virulence in mice. While viridans streptococci are optochin resistant, bile insoluble and non-capsulated. They do not ferment inulin and do not produce virulence in mice. (Ross, 1999. p 276) Answer 4. The Quellung reaction was first described by Neufeld (1902). The word â€Å"Quellung† means swelling in German. The polysaccharide antigen in the bacterial capsules reacts with the specific antibody produced in sensitized laboratory animals. This reaction causes the capsule to enlarge and become opaque. This can then be observed microscopically. Several bacterial species namely, Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Salmonella and Group B Streptococci show a positive test for this reaction. (Fischer et al.) Answer 5. The bacterial capsule plays a vital role in virulence and pathogenesis. It protects the bacterium against the host immune processes like phagocytosis. Also, the capsule provides sites for cellular attachment to the host (Hammerschmidt, 2005). Answer 6. Streptococci grow best on nutrient agar enriched with 5-10% blood, heated blood or serum. The optimum temperature for growth is 37oC though growth can occur between the temperature range of 22-42oC. S. pneumoniae grows optimally in air or hydrogen with 5-10% CO2. Incubation period is 24 hours (Ross, 1999. p 264) Answer7. Blood agar may be defined both as an enriched and differential medium used for culture of fastidious organisms. A differential medium enables to distinguish one microorganism from another based on the growth properties on the same medium. Blood agar differentiates microorganisms based on their hemolytic properties. Hemolysis is of three types alpha or partial, beta or complete and gamma or no hemolysis. A good example of use of blood agar as a differential medium is seen in grouping Streptococci. S. pneumoniae and viridans streptococci are alpha hemolytic, Group A S.