lab quiz 4/5
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What instrument is used in the urine culture test?
A volumetric loop
How does the urine culture test work?
- Urine is streaked onto the agar in a zigzag pattern
- Following a period of incubation, the resuling bcterial colonies are counted and original cell population density (OCD) is calculated.
Application or urine culture test
- Urine culture is a common method of detecting and quantifying UTIs.
- It is frequently combined with selective media for specific identification of members of enterobacteriaceae or streptococcus.
How does UV radiation mutate DNA?
- When DNA absorbs UV radiation 1t 254 nm, the energy is used to form new cvalent bonds between adjacent pyrimidines: cytosine-cytosine, cystosine-thymine, or thymine-thymine.
- These are known as "pyrimidine dimers," with thymine dimers being the most common
- These dimers distort the DNA molecule and interfere with DNA replication and trnscription.
What are some mechanisms that bacteria have t repair DNA damage.
- E. Coli have light repair or photoreactivation, which the repair enzyme, DNA photolyase is activated by a visible light and monomerizes the dimer by reversing the original reaction.
- The 2nd E. Coli repair mechanism, excision repair or dark repai, involves a number of enzymes.
- The thymine dimer distorts the sugar-phosphate back-boneof the strand. This is detected by an endonuclease that breaks two bonds, eight nucleotides in the 5' direction from the imer, and ht other four nucleotides in the 3' direction.
- A helicase removes the 13 nucleotide fragman,living single-stranded DNA.
Application of UV radiation damage and repair
- Because uv radiation has a lethal effect on bacterial cells, it can be used in decontamination.
- Its use is limited, however, because it penetrates materials such as glass and plastic poorly.
- In addition, bacterial cells have mechanisms to repair UV damage`
Process for UV radiation test
Innoculate plates, number them, put them under UV light, after propor ammount of time examine growth patterns
What type of wbc increases in an active infection?
Which wbcs are granulocytes
Which wbcs are agranulocytes
- - Most abundant WBCs in blood.
- - They leave the blood nad enter tissues to phagocytize foreign material.
- - An increase in neutrophils in the blood is indicative of a systemic bacterial infection.
- - Mature neutrophils sometimes are referred to as segs because their nucleus usually is semented into two to five lobes.
- - Because of the variation in nuclear appearance, they also are called polymorphonuclear neutrophils (PMNs). Immature neutrophils lack this segmentation and are referred to as bands.
- - The distinction between bands (immature neutrophils) and segs (mature neutrophils) is useful b/c a patient with an active infection increases neutrophil production, which reates a higher percentage of the band (immature) type.
- - Neutrophils are 12-14 um in diameter, about twice the size of an erythrocyte (RBC).
- - Their cytoplasmic granules are neutral-staining and thus do not have the inteste clor of other granulocytes when prepared with Wright’s or Giemsa stain.
- Basophils are the least abundant WBC in normal blood.
- - They are structurally similar to tissue mast cells and produce some of the same chemicals (histamine and heparin) but are derived from different stem cells in bone marrow.
- - They are 12-15 um in diameter.
- - The nucleus usually is obscured by the dark-staining cytoplasmic granules, but it either has 2 lobes or is unlobed.
- - Eosinophils are phagocytic, and their numbers increase during allergic reactions and parasitic infections.
- - They are 12-15 um in diameter (about twice the size of a RBC) and generally have two lobes in their nucleus. Their cytoplasmic granules stain red in typical preparations.
- - Monocytes are the blood form of macrophage.
- - They are the largest leukocytes, being two to three times the size of RBCs at 12-20 um.
- - Their nucleus is horseshoe-shaped, and the cyptoplasm lacks prominent granules, but may appear finely granular.
- - Lymphocytes are cells of the immune system.
- - Two functional types of lymphocytes are the T-cell, involved in cell-mediated immunity, and the B-cell which converts to a plasma cell when activated and produces antibodies.
- - The nucleus usually is spherical and takes up most of the cell.
- - Lymphocytes are approximately the same size as RBCs or up to twice their size.
- - The larger ones form a third functional group of lymphocytes, the null cell, many of which are natural killer (NK) cells that kill foreign or infected cells without antigen-antibody interaction.
How many wbcs are counted in a differential white cell count?
Application of differential blood cell count
- A differential blood cell count is done to determine approximate numbers of the various leukocytes in blood.
- Excess or deficiency of all or a specific group is indicative of certain states. Even though differential counts are automated now, it is good training to perform one "the old fashioned way" using a blood smear and a microscope to get an idea of the principle behind the technique
- Abundance in blood (%): 55-65
- Diameter: 12-15
- Nucleus: 2-5 lobes
- Granules: Present, but stain poorly; contain antimicrobial chemicals
- Functions: Phagocytosis and digestion of bacteria
- Abundance in blood (%): 1-3
- Diameter: 12-15
- Nucleus: 2 lobes
- Granules: Present and stain red; contain antimicrobial chemicals and histaminase
- Functions: Present in inflammatory reacions and immune response against some multicellular parasites (worms)
- Abundance in blood: 0.5-1
- Diameter: 12-15
- Nucleus: Unlobed or 2 lobes
- Granules: Present and stain dark purple; contain histamine and other chemicals
- Functions: Paticipate in inflammatory response
- Abundance in Blood: 25-33 %
- Diameter: 7-18
- Nucleus: Spherical (leaving little visible cytoplasm)
- Cytoplasmic granules: Absent
- Functions: Active in specific acquired immunity (as T and B cells)
- Abundance in blood: 3-7
- Diameter: 12-20
- Nucleus: Horseshoe-shaped (cytoplasm is prominent)
- Granules: Absent
- Function: phagocytosis
What forms agglutinates?
When particular antigens (such as whole cells) combine with homologous antibodies to form visible clumps
Relies on the combination of antiobodies nad naturally particulate antigens
Relies on artificially constructed systems in which agglutination will occur. These involve coating particles (such as RBCs or latex microspheres) with either antibody or antigen, depending on what is being looked for in the sample
Application of agglutination
- Agglutination reactions may be used to detect the presence of either antigen or antibody in a sample. Direct agglutinatin reactions are used to diagnose some diseases, determine if a patient has been exposed to a certain pathogen, and are involved in blood typin.
- Indirect agglutination is used in some pregnancy tests as well as in diagnosing disease.
What are you doing in the agglutination test?
You will perfomr a simple agglutination test to identify thepresenf of slamonella H antigen in a sample. You will compare this reaction to a reaction between the nonhomologous Salmonella anti-H antiserum and the Salmonella O antigen.
What indicates a positive result in the agglutination test?
Presence of agglutination
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