Lecture 5

Question 1

What is the coagulase test?

Answer 1

Method of identifying staphylococcus aureus, which uses fibrin to cause a clot seen in plasma

Question 2

What are the 3 types of enzymatic assays studied in class?

Answer 2

Coagulase test, Oxidase test, Catalase test

Question 3

What is the oxidase test?

Answer 3

Identifies some aerobic bacteria as they produce cytochrome C which means they can be treated with oxidase reagent N,N,N’,N’,-tetramethyl-p-phenylenediamine to cause a dark blue stain

Question 4

What is the Catalase test?

Answer 4

Differentiates between Staphylococci and streptococci as staphylococci use catalase to cause bubbling when treated with hydrogen peroxide

Question 5

What is the assay studied in class based on metabolic reactions?

Answer 5

Microbact strips

Question 6

What are microbact strips?

Answer 6

A strip that has different colour changing tests for specific enzymes in positions located throughout the strip used to identify many different types of bacteria

Question 7

What is an antibiotic susceptibility test?

Answer 7

A test performed on lawn agar plates with an antibiotic disc which differentiates microbes as only those with antibacterial resistance will survive

Question 8

What is a selective agar test?

Answer 8

When the agar gel contains inhibitors to discourage growth of certain organisms

Question 9

What is a differential agar test?

Answer 9

A test where the agar contains indicators allowing organisms to be indentified

Question 10

What is the mannitol salt agar test?

Answer 10

Test for staphylococcus aureus, high salt content prevents growth of most bacteria and mannitol can only be metabolized by staphylococcus aureus which results in a pH change, which causes the indicator to change fro red to yellow

Question 11

What is the Sabouraud Agar test?

Answer 11

Selecitve for fungi as low pH prevents bacterial growth

Question 12

What is the eosin-methylen blue agar test?

Answer 12

Selects for gram negative bacteria, as the dye kille positive bacteria, lactose fermenters appear pink

Question 13

What is the MacConkey Agar test?

Answer 13

Selects for gram negative intestinal pathogens, uses bile salt so only enteric bacteria can grow, lactose ferementers are pink

Question 14

What is the blood agar plate test?

Answer 14

Differential test for hemolytic reactions,
Alpha: Colonies appear green, occurs in streptococcos pneumonia, represents some haemolysis
Beta: Total haemolysis, yellow appearance, Streptococcos pyogenes
Gamma: No haemolysis

Question 15

What is the cystine-lactose-electrolyte deficient agar test?

Answer 15

Grows urinary pathogens, lack of electrolytes prevents movement and lactose ferementers appear yellow

Question 16

What is the Bile-Esculine agar test?

Answer 16

Selects for enteric bacteria as oxgall inhibits non-enteric bacteria. Bacteria which hydrolyse Esculine appear dark brown

Question 17

What are the methods of bacterial identification based off antibody-antigen interaction studied in class?

Answer 17

Cell Agglutination, Latex bead agglutination, Western Blot, Immunofluorescence microscopy

Question 18

What is Cell agglugation?

Answer 18

Antibodies recognize cell surface receptors and form visuable clumps

Question 19

What is Latex bead agglutination?

Answer 19

Antibodies are bound to beads resulting in clumping occurring on the bead

Question 20

What is the western blot technique?

Answer 20

Identification for proteins or antibodies, proteins undergo gel electrophoresis and are then fixed. Specific proteins are then identified via an antibody, which then has a 2nd marker antibody attach to it

Question 21

What is fluorescent microscopy?

Answer 21

Using two antibodies to highlight a component of the cell, using the principal of the western blot test

Question 22

What is a anti-streptolysin O assay?

Answer 22

Red blood cells are mixed with streptolysin O and patient serum, if the solution turns remains clear then there has been a recent S.pyogenes infection and the patient may develop rheumatic fever

Question 23

What is restriction fragment length polymorphism?

Answer 23

Use of restriction enzymes to check for changes in the DNA sequence as a change will result in a different length of DNA being formed as the recognition site will have changed locations

Question 24

What is polymerase chain reaction?

Answer 24

A method of amplifying a small amount of DNA through use of a heat stable polymerase

Question 25

What does the Ziel- Neelsen stain test for?

Answer 25

Acid fast microorganisms, used to identify microorganisms that cannot be stained with the grams stain such as mycobacterium

Question 26

What feature of bacteria does the grams stain use to differentiate species?

Answer 26

The cell wall complex

Question 27

How does the gram stain work?

Answer 27

Crystal Violet penetrates all things, the iodine treatment then causes this to form crystals which become trapped in the peptidoglycans of gram +ve organisms resulting in only the gram -ve organisms losing the crystals when the decolourising agent is added, safranin is then used as a counter stain to allow gram negative bacteria to be seen

Question 28

What is the lactophenol cotton blue stain?

Answer 28

Used for visualization of fungi,
Lactophenol used as mounting fluid,
Phenol kills cells before lysis occurs
Cotton blue stains chitin in cell wall