Lecture 5 Flashcards
What is the coagulase test?
Method of identifying staphylococcus aureus, which uses fibrin to cause a clot seen in plasma
What are the 3 types of enzymatic assays studied in class?
Coagulase test, Oxidase test, Catalase test
What is the oxidase test?
Identifies some aerobic bacteria as they produce cytochrome C which means they can be treated with oxidase reagent N,N,Nā,Nā,-tetramethyl-p-phenylenediamine to cause a dark blue stain
What is the Catalase test?
Differentiates between Staphylococci and streptococci as staphylococci use catalase to cause bubbling when treated with hydrogen peroxide
What is the assay studied in class based on metabolic reactions?
Microbact strips
What are microbact strips?
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
What is an antibiotic susceptibility test?
A test performed on lawn agar plates with an antibiotic disc which differentiates microbes as only those with antibacterial resistance will survive
What is a selective agar test?
When the agar gel contains inhibitors to discourage growth of certain organisms
What is a differential agar test?
A test where the agar contains indicators allowing organisms to be indentified
What is the mannitol salt agar test?
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
What is the Sabouraud Agar test?
Selecitve for fungi as low pH prevents bacterial growth
What is the eosin-methylen blue agar test?
Selects for gram negative bacteria, as the dye kille positive bacteria, lactose fermenters appear pink
What is the MacConkey Agar test?
Selects for gram negative intestinal pathogens, uses bile salt so only enteric bacteria can grow, lactose ferementers are pink
What is the blood agar plate test?
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
What is the cystine-lactose-electrolyte deficient agar test?
Grows urinary pathogens, lack of electrolytes prevents movement and lactose ferementers appear yellow
What is the Bile-Esculine agar test?
Selects for enteric bacteria as oxgall inhibits non-enteric bacteria. Bacteria which hydrolyse Esculine appear dark brown
What are the methods of bacterial identification based off antibody-antigen interaction studied in class?
Cell Agglutination, Latex bead agglutination, Western Blot, Immunofluorescence microscopy
What is Cell agglugation?
Antibodies recognize cell surface receptors and form visuable clumps
What is Latex bead agglutination?
Antibodies are bound to beads resulting in clumping occurring on the bead
What is the western blot technique?
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
What is fluorescent microscopy?
Using two antibodies to highlight a component of the cell, using the principal of the western blot test
What is a anti-streptolysin O assay?
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
What is restriction fragment length polymorphism?
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
What is polymerase chain reaction?
A method of amplifying a small amount of DNA through use of a heat stable polymerase
What does the Ziel- Neelsen stain test for?
Acid fast microorganisms, used to identify microorganisms that cannot be stained with the grams stain such as mycobacterium
What feature of bacteria does the grams stain use to differentiate species?
The cell wall complex
How does the gram stain work?
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
What is the lactophenol cotton blue stain?
Used for visualization of fungi,
Lactophenol used as mounting fluid,
Phenol kills cells before lysis occurs
Cotton blue stains chitin in cell wall
