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Hsci 212 > Week 3 > Flashcards

Week 3 Flashcards

1
Q

What are the three phases in the laboratory cycle

A

Pre-analytic phase
Analytic phase
Post-analytic phase

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2
Q

What is pre-analytic phase

A

All steps before the sample is ready for testing

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3
Q

What is analytical phase

A

The testing step including necessary quality control

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4
Q

What is post-analytical phase

A

Interpretation, reporting, and receipt of results

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5
Q

Some info regarding gram positives

A

More rigid wall -> can withstand elements

Live in external environments like the skin

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6
Q

Some info regarding gram negatives

A

Flexible, porous/plumpy (due to 2 membranes) -> sophisticated osmoregulation

Live in watery/moist settings like the GI Tracy or catheters

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7
Q

What are three bacteria that can’t be seen with gram stain and why

A

Those within host cells
- chlamydia spp
Those without cell wall
- mollicutes like mycoplasma spp
Those not large enough to be seen w/ light microscopy
- spirochetes like borrelia spp

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8
Q

How do we identify bacteria organisms

A

Mass spectroscopy via MALDI-TOF

Molecular based methods like PCR

Select biochemical/table top tests

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9
Q

How does MALDI-TOF work and what does it stand for

A

matrix-assisted laser desorption ionization time of flight

Uses lasers to ionize proteins from bacterial isolates

Ionized molecules travel at different speeds in vacuumed based on proteins mass to charge ratio

Different speed spectra are captured to a screen

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10
Q

Limitation of MALDI-TOF

A

Some species have similar or same spectra which MALDI can’t differentiate

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11
Q

if MALDI-TOF can’t differentiate what do we use

A

Biochemicals such as bile solubility for streptococcus pneumoniae (soluble) vs streptococcus mites/oralis(not soluble)

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12
Q

When is the PCR method for determining bacteria used

A

Single plex
-when looking for a specific target
Multiples
-when looking for multiple pathogens which can cause same disease

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13
Q

What is Antimicrobial susceptibility testing (AST)

A

Methods for determining if a bug is resistant to drug
Growing a bug in vitro with defined concentration of drug to examine growth

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14
Q

Minimum inhibitory concentration (MIC) is

A

The lowest concentration of a drug that inhibits growth of a bug

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15
Q

What are 3 AST methods

A

Broth microdilution testing
Gradient strip diffusion
Disk diffusion testing

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16
Q

What is broth microdilution

A

Testing bacterial isolates against serial dilutions of a drug and measuring the MIC

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17
Q

Is broth microdilution manual or automated

A

Both but automated is easier and more reliable (less human error)

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18
Q

Is gradient diffusion manual or automated

A

Manual

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19
Q

What is gradient diffusion

A

Using an antimicrobial-impregnated strip with graded concentration which is placed on a of the bacteria
This forms an ellipse where the bacteria is “repelled” and where this slips meets the strip is the MIC

Often called E-test due to original brand of strips

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20
Q

What is disk diffusion

A

Aka Kirby-Bauer method
Uses circular disk with standard [] of drug which is placed overnight in an plate of the bacteria and then the diameter of the inhibition zone is measured and if its too small the bacteria is resistant

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21
Q

What is selective reporting

A

Practice of reporting the most relevant antibiotics to the providers
-safest and most effective drugs for the bug and/or patient
-drugs available

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22
Q

What is the issue with selective reporting

A

Does not account for exceptions in individual cases

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23
Q

What are the bacterial requirements for growth

A

Sources of energy (sugars, fatty acids)
Metal ions such as iron
Optimal environment
-temp
-pH
-O2

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24
Q

What is an extremophile

A

A microorganism which can survive harsh conditions such as pH or temp extremes

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25
At what range of temperatures do most microorganisms grow
Mid-range temp
26
What is a microorganism called when it grows at mid-range temperatures
Mesophilic
27
At what pH do most microorganisms grow
Neutral
28
Obligate aerobes
Require oxygen to perform aerobic respiration
29
Obligate anaerobes
Cannot survive in oxygen (carry out fermentation)
30
What are the 4 phases of the bacterial growth curve
Lag phase, log phase, stationary phase, death or decline phase
31
What is the lag phase in the bacterial growth curve
No increase in # of bacteria
32
What is the log phase in the bacterial growth curve
Exponential increase in # of bacteria
33
What is the stationary phase in the bacterial growth curve
Plateau in # of living bacteria, rate of division is equal to rate of death
34
What is the death or decline phase in the bacterial growth curve
Exponential decrease in # of living bacterial cells
35
What part of the growth curve is best to target bacteria with antibiotics
The log phase since you are limiting growth and the bacteria are preforming lots of interruptible activities such as protein, DNA and cell wall synthesis
36
What physical methods have humans used to control microbial growth
Heat, pasteurization, refrigeration, alter acidity, dessication
37
What is dessication
The addition of solutes such as sugar or salts to draw water out of the cell since it wants to move from low solute[] to high solute[]
38
What are the differences between prokaryotic and eukaryotic cells
Prokaryotic - single chromosome no nucleus -cell wall with peptidoglycan -no membrane bound organelles - 70S ribosomes made of 30S and 50S - binary fission Eukaryotic - multiple chromosomes with nucleus -no cell wall other than fungi with chitin -Membrane bound organelles - 80S ribosomes (some 70S in plants) - use meiosis and mitosis
39
What type of toxicity is wanted in antimicrobials
Selective toxicity
40
What is selective toxicity in antibiotics
Selectively kills or inhibits growth of microbial targets with minimal or no harm to host
41
What are the two types of antibiotics
Bactericidal and bacteriostatic
42
bactericidal
Kills target bacteria
43
Bacteriostatic
Cause reversible inhibition of bacterial growth, the growth will resume when drug is not taken
44
What is an example of a bactericidal antibiotic
Penicillin
45
What is an example of a bacteriostatic antibiotic
Aminoglycoside
46
What is spectrum of activity in antimicrobials
The extent and diversity of bacteria that the antibiotic targets
47
What does it mean to be a narrow spectrum antibiotic
Only target a subset of bacterial pathogens
48
What does it mean to be a broad spectrum antibiotic
Target wide variety of bacterial pathogens
49
What are the advantages of broad spectrum
Useful when you don’t know what you are treating Good for an infection where there are more than one bacteria involved May be useful for antimicrobial resistance
50
Broad spectrum disadvantages
Kills good and bad microbes Can lead to superinfection
51
What is a superinfection
A secondary infection in someone with a preexisting infection, it is opportunistic so also called opportunistic infections
52
Advantages of narrow spectrum
Less effect on microbiome Generally lower chance of superinfection Less selection pressure for antimicrobial resistance
53
Who and how were antibiotics discovered
Alexander Fleming accidentally left out a petri plate of bacteria and noticed that mould had grown, and where it had grown the bacteria was unable to reproduce into this area. This lead to penicillin
54
How does penicillin work
By binding to PBP which disrupts peptidoglycan strands and due to osmatic pressure leads to cell lysis
55
What is PBP and how does it help bacteria
Is is a protein called penicillin-binding protein which helps crosslink peptidoglycan strands
56
What is the term for antibiotics similar to penicillin which block crosslinking of peptidoglycan
Beta-lactam antibiotics
57
Beta-lectam antibiotics have what chemical structure
A beta-lectam ring connected to R groups which allow for varying characteristics
58
Penicillin and other beta-lectam antibiotics are primarily only effective against
Gram positive bacteria due to the large peptidoglycan cell wall
59
What was the first antibiotic to target gram negative bacteria
Streptomycin which was isolated from Streptomyces griseus
60
How do antibiotics like streptomycin act as antibiotics
They inhibit prokaryotic ribosomes to stop protein production
61
What are the 5 targets exploited by antibiotics
Cell wall, DNA synthesis, Cell membrane, Ribosomes (30S, 50S), metabolic pathways
62
Antibiotics which disrupt the cell wall are
Beta-lectams and glycopeptides
63
Antibiotics which target the plasma membrane are
Polymyxins and lipopeptides
64
Antibiotics which target metabolic pathways are
Sulfonamides and trimethoprims
65
Antibiotics which target ribosomes are
Aminoglycosides for 30S Macrolides for 50S
66
Antibiotics which target DNA synthesis are
Fluoroquinolones
67
Antibiotics which target RNA synthesis are
Rifamycin
68
Antibiotic resistances arise from
Random mutations which are selected for and passed to subsequent generations or shared through horizontal gene transferring
69
What are the bacterial mechanisms for resistance
Efflux pumps Blocked penetration Inactivation by enzymes Target modification
70
Drug modification or inactivation is
When a bacteria has genes which code for enzymes that modify an antimicrobial so it no longer functions
71
An example of drug modification is
Beta-lactamase which destroys beta lactam antibiotics
72
How do we combat beta lactamase
Using a beta-lactamase inhibitor
73
How do efflux pumps contribute to resistance
Bacteria actively transports antimicrobial drug out of cell, may transport many antibiotics
74
How does blocked penetration contribute to resistance
By decreasing the amount of antibiotic which enters the cell by decreasing transporters on outer membranes
75
How does target modification contribute to resistance
By changing the structure of the antimicrobials target Eg -changing ribosomes -changing metabolic enzymes -changing penicillin binding proteins
76
What is an MDR bacteria or a superbug
Multidrug resistant bacteria which has more than one resistance mechanism so its resistant to multiple antimicrobials
77
How do we combat antimicrobial resistance
Infection prevention/vaccination Minimizing inappropriate antibiotic use in humans and animals Research new antimicrobials
78
What is another way to treat against bacteria
Bacteriophages
79
What are bacteriophages
Viruses which selectively target and kill bacteria
80
How do bacteriophages work
Attach to bacteria and infect it with viral genome which is integrated into the bacteria’s DNA and can be passed to other bacteria during horizontal gene transfer, this dna causes the bacteria’s to produce more bacteriophages which kill the bacteria when released.

Hsci 212 (6 decks)

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