Extra Qs Flashcards
Are molecular identification methods based on the organism’s genotype or phenotype. And what about biochemical tests
- Molecular identification = genotype
- Biochemical = phenotype
What does a PCR test do. And the 3 main steps
- Amplifying specific regions of DNA
- Denaturing, annealing, elongation
What does Lancefield group system do
Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls
Name some bacteria that can be cultured on blood agar
strep pyogenes, hameophylius influenza, Neisseria species
What agar can bacteria that ferment lactose be selected for
MacConkey agar
What agar can salmonella be cultured on
XLD agar
What agar is used for urine samples
CLED agar
Out of staph and strep, which lacks catalase activity
streptococci
What indicator is used in urease test. If positive, what is the colour change
- from yellow to pink
- phenol red is used
what indicator is used in a DNAase test. What is the colour change
- Toluidine blue
- turns pinkish in the presence of free nucleotides or oligonucleotides that are released by degradation of the DNA
5 main steps in a gram stain
- Heat fix bacteria to slide
- Flood with crystal violet
- Rinse and flood with iodine
- Decolourise with acetone
- Safranin counterstain
In acidic conditions, hydroxyapatite dissolves because ions are removed from solution. Which ions are likely to be removed?
OH- and (PO4)3-
Relationship of IP and Ksp at critical pH
They are equal
What type of microorganism does Sabouraud dextrose select for and why
Fungal
Low pH of media suppresses bacterial growth
What is the antibacterial mechanism of action of chlorhexidine?
Disrupts cell walls
Chlorhexidine is broad spectrum and could be bactericidal or bacteriostatic depending on the concentration
Cultivating in an anaerobic or aerobic environment will grow the most intra oral microbes
Anaerobic
What could be added to Mitis -Salivarius growth medium to make it selective for Streptococcus mitis or Streptococcus salivarius?
Tellurite. Growth of mitis
What agar grows candida
Sabouraud agar
What bacteria causes sore throat and inflamed pharynx
Streptococcus pyogenes
Which carbohydrate is fermented in the Snyder test?
glucose
what is germination
the process of reactivation of spore form to vegetative form
what does Clavulanic acid do
Inactivates beta lactamase to prevent bacteria inhibiting the beta lactam in antibiotics. Combined with pencillins to prevents antibiotic resistance.
[Co-amoxiclav]
name some antibacterial toothpaste ingredients
Chlorhexidine, essential oils, tannous fluoride, Triclosan, Cetylpyridium chloride
name 2 spore forming species
clostridium and bacillus
When culturing microorganisms on agar plates, why is it important the plate is placed in the incubator top down.
To stop condensation settling on the agar surface
What is a virulence factor
- features of or molecules produced by bacteria, viruses, fungi and protozoa
- Help pathogenic microorganisms to (1) invade the host, (2) cause disease, and (3) evade host defences
What does a leukotoxin do and what bacteria is it produced by
- Toxic to leukocytes
- A type of exotoxin
- Aggregatibacter actinomycetemcomitans
the 3 components of an enveloped virus
- Nucleocapsid - Nucleic acid (DNA or RNA) and protein shell
- Lipid layer from host with envelope glycoproteins / spike proteins
What effect would incubating sub gingival plaque bacteria anaerobically be on the number of colonies which formed?
There would probably be more cfu. The reason is that the nearly all the bacteria in the mouth are either facultatives (do not need oxygen but can grow in its presence) or strict anaerobes. So, a plate incubated aerobically will only grow the facultatives whereas a plate incubated anaerobically will grow the facultatives as well as the anaerobes. However, there are some strict aerobes that would not grow anaerobically, so it is not clear cut.
what bacteria used in Snyder test. What pH is the growth medium
lactobacilli
pH 5
fermenting glucose and making lactic or acetate acid
Why the number of CFU may not be the same as the number of cells in a culture
- Some cells may be dead/non viable
- Some may be unable to grow on the particular medium
- cells often tend to clump or form chains and, if not dispersed, multiple cells will make a single CFU.
