1
Q
What is defined culture media vs complex culture media?
A
- defined: know composition, component, amount, made with specific chemicals ex. sugars, amino acids, vitamins
- complex: do not, uses complex nutrient sources ex. glucose, peptones
2
Q
What is transport media? Lacks what?
A
- maintains cell sample without death or division
- uses buffers and salts
- usually liquid
- lacks carbon, nitrogen, organic GFs
3
Q
What is enrichED media? ___ encouraging?
A
- contains general nutrient supplements ex. yeast extract for precursor molecules
- usually liquid
- “Generally encouraging”
4
Q
What is enrichMENT media? ___ encouraging?
A
- for growth of specific microbe, becomes dominant
- used in clinical labs
- “Specifically encouraging”
5
Q
Explain fecal sample of Salmonella and how an enrichment media would be used?
A
- Sample contains hi levels of normal microflora, low levels of pathogen
- So, enrichment media keeps microflora in lag phase and promotes logarithmic growth of Salmonella
6
Q
What is selective media? ___ inhibiting?
A
- Encourages growth of an organism, inhibits others
- solid agar
- “Specifically inhibiting”
7
Q
What is differential media?
A
- Has indicators to distinguish between organisms that you encouraged the growth of
- Color changes with acid production/lowered pH
8
Q
Mannitol salt agar and Hektoen agar are examples of what two media types?
A
- Differential and selective media
9
Q
What is blood agar? What happens to RBC?
A
- Enriched and differential culture medium with base nutrients and blood to grow bacteria and detect haemolysin activity
- Haemolysins (bacterial enzymes) act on animal RBC
- Zone of haemolysins around RBC
- Want to see if cells produce haemolysins (which destroy red blood cells)
10
Q
What is a-haemolysis? beta? gamma?
A
- partial lysis of RBC
- complete lysis
- non-haemolytic/no break down of RBC
11
Q
What is growth curve? Different phases and their characteristics/what is taking place?
A
- theoretical growth of bacterial culture under ideal conditions
- Lag phase: variable
- Exponential phase: bacteria divides until media can’t support it anymore
- Stationary phase: nutrients run out or toxin build up
- Death/decline: neg. slope
- Long term stationary: stronger bacteria survive by being resistant and using nutrients from dead counterparts
12
Q
How to keep a culture continous?
A
- Use open system where nutrients are coming in, dead cells/waste taken out
13
Q
What are primary metabolites? Secondary metabolites?
A
- Primary are needed for microbe growth and produced during lag phase
- Secondary are not essential and accummulate during stationary phase
14
Q
How to measure microbial growth directly? Downsides?
A
- Directly with counting chamber and microscope
- Directly by measuring turbidity (more light scattered or absorbed with more sample)
- Although fast, can’t tell if dead or alive AND just an estimation
15
Q
How to measure indirect microbial growth?
A
- Put sample on agar plate –> incubate –> count
- Each live cell should give rise to one colony
- Gives you viable count although takes longer
16
Q
What is an endospore?
A
- Forms with a cell
- Survival structure (highly resistant, dormant)
- Layers of protection
- Highly ordered sequence of events for formation
17
Q
How does endspore form?
A
- Vegitative cell divides via binary fission (growth has stopped)
- DNA is dense, divides assymmetrically
- Larger compartment engulfs the smaller one
- Forespore formed
- Protective coat formed, forespore is dehydrated
- Parent cell degrades and endospore is released
18
Q
What physically determines resistance?
A
- Coat, thick layers
- Inner membrane, impermeable
19
Q
What chemically determines resistance? (in the core, 3 things)
A
- Low water content
- Lower pH, more acidic
- Hi DPA and Ca2+ (help with dehydration and resistance to heat)
20
Q
What do DPA and Ca2+ do in the endospore core?
A
- They combine to form a lattice
- dehydrate, make heat resistance
21
Q
What chemically determines resistance in the cortex of the endospore?
A
- Decreased peptidoglycan cross-linking index
- (Peptidoglycan more dense in vegetative cells)
- helps it be more flexible –> maintains dehydration, help with metabolic dormancy, and heat resistance
- Ca2+ and DPA
22
Q
Describe the activation, germination, and outgrowth stages for a endospore?
A
- During activation endospore is prepared
- During germination the coat starts to break (no resistance from outside elements) AND the endospore swells up to take up more water
23
Q
What is microorganism death?
A
- Can’t multiply under any conditions
24
Q
What is sterilization? Bactericidal vs bacterostatic?
A
- Completely remove or destory all microorganisms
- Use of physical or chemical methods to do so
- Non-selective
- Kills vs inhibits
25
Describe autoclave as a physical control? How long does it take?
- Uses moist heat
- The water molecules in steam transfer energy which leads to killing cells quicker
- With more pressure the temp and boiling point inc
- 131 C for 15 mins, kills all cells and endospores
26
Generally describe heat as a physical control?
- Max temp of bacterial growth is 68 C
- Endospores require 100 C to get rid of which is considered sterilization
27
E.g. of items you can put in autoclave? Can't?
- Can: glassware, most culture media, pharmaceutical prep
- Can't: toxic chemicals (phenol), heat-labile compounds (anti-biotics)
28
Describe boiling water as a physical control? How long?
- Uses moist heat
- 100 C for 15 mins
- Kills all cells, NOT endospores
29
Describe pasteurization as a physical control? Flash pasteurization?
- 63 C for 30 mins
- 71 C for 15 secs
- Don't kill all cells or endospores
30
What are dry heat physical controls? How long?
- Flaming and incineration (kills endospores)
- Hot air oven (160 C for 2 hrs, kills everything)
31
Freezing as physical control?
- Freezing (Min temp 8 C, slows down metabolism)
- Can kill some bacteria
- Salty things don't freeze well
- Does not kills endospores
32
Ultra hi temp as physical control?
- 140 C for 1 sec
- Kills everything
33
What terms are used for assessing efficacy of heat treatments?
- Thermal death point
- Thermal death time
- Decimal reduction time
34
What is thermal death point? How would you know what it is?
- Lowest temp to kill all cells within 10 mins
- Bacteria in liquid culture
- Look at first sector with no growth, then you could run an experiment with different increments of temp
35
Why is a control sector on agar plate important?
- In case you used the wrong agar or the bacteria had a diff. thermal death point and didn't grow
- Want to test original culture for viability
36
What is thermal death time? How is this done?
- Length of time to kill all bacterial cells
- Choose a temp and take samples at certain time points
- Streak agar plate and check if there's growth after incubation
- E.g., TDT of 8 min at 60 C
37
What is decimal reduction time? (D-value)? What does ten-fold reduction mean?
- Length of time for a ten-fold reduction in bacteria
- Measure sample, spread out, count colonies
- ten-fold = 90% killed = 1 log diff
38
What is K?
- Death rate constant and slope of the curve
- Can be calculated from an equation
- K = 2.3/t x log10 (Nt/N0)
39
What is filtration? (as physical sterilizaiton method)
- Mechanical removal
- Liquid or air can pass through
- Pores are too small for bacteria and endospores, but not for other stuff
- Around 0.20 µm
40
What is a depth filter?
- Random array of fibers
- Traps endospores in depth of fibers
- Hi dirt handling capacity, traps contaminated solutions, pre-filter, and can filter air
- Limitation: random
41
What is membrane filter? Overcome disadvantage how?
- Thin, distinct pores
- Most common
- Limitation: if hi contamination then all bacteria sit on the surface and block filter
- Overcome by changing frequently or by using depth filter
42
What is nucleopore filter?
- Pores and holes are carefully defined
- Prepare samples for electron microscopy
- Liquid passes through filter into sterile beaker
43
What is HEPA filter?
- Protects specimen, user, and environment
- Removes most of particles through physical retention or electrostatic interactions
44
Examples of solutions that can be filtered?
- Tissue culture media (used to grow viruses), serum, antibiotic solutions, gases
- Some of these are heat sensitive or have small volumes and don't want to be put through membrane filter
45
What is non ionizing radiation?
- E.g., UV rays
- Wavelength damages DNA in the cells by forming pyrimidine dimers or directly damaging protein
- Does NOT kill bacterial endospores
- Used for large volumes of liquids, benches, air
46
What is nucleotide excision repair?
- Enzymes used to remove damaged nucleotides
- DNA polymerase I fills gap
- DNA ligase joins fragments
47
What is direct repair?
- Photo reactivation used
- Visible light and photolyase
- Reverses damage to DNA from UV light
48
What is recombinational repair?
- Damaged DNA corrected through Rec A
49
What is SOS repair?
- Transcriptional repressor protein is destroyed
- Error prone
50
UV radiation effects on gram neg. vs gram pos. bacteria?
- Gram neg. tend to die quickly (like E. coli)
- Gram pos. differs in sensitivity, esp. if they form an endospore
51
What is ionizing radiation?
- E.g., x-rays, gamma rays
- Indirectly kills by inducing reactive chemical radicals and breaking molecules into ions
- Kills endospores
- Short wavelengths, hi energy used
- Free (reactive) radicals interact with bacteria
- Can sterilize products in packaging, lab products, sewage treatment, food preservation
52
What are disinfectants?
- Kill microorganisms
- Can't apply to living tissues, toxic
- Strong
53
What are antiseptics?
- Kill or inhibit growth of microorganisms
- Non-toxic, can be applied to to tissue
54
What are preservatives?
- Pharmaceutical or food prep
- Prevent microbial spoilage
55
What can you use chemical control methods for?
- Antisepsis of skin
- Disinfect equipment
- Clean spills
56
What are some conditions that influence antimicrobial agent effectiveness?
- Pop. size
- Properties of chemical agent
- Microbe type
- Environment
- Toxicity
57
How does pop size effect chemical reduction of microorganisms?
- During a time interval only a fraction die, same amount killed every minute
- Death curve is logarithmic
- Time to reach sterility depends on initial bacterial load
- Ex: if 90% killed in 1 min, another 90% of remaining killed in next min
58
How do chemical agent properties affect chemical reduction?
- DIlution: concentration affects efficiency
- Too high can be bad too
- 70% ethanol is ideal because the water enhances it
- pH: zone with most activity and lowest killing time
59
How does type of microbe affect chemical reduction?
- Phase of growth: in metabolic phase it's the most efficient because they'll take in more chemicals from their environment
- Bacteria with polymer, capsule, or lipids outside of the cell limit diffusion of chemicals into the cell
- Cell wall or membranes can be altered in harsh environments
- Cellular aggregation/biofilms: when clumped together middle cells have more protection
- Resistant structures: like endospores which can be resistant
60
What are more resistant types of viruses? Least resistant?
- Endospores --> mycobacteria --> small viruses or non lipid --> fungi --> vegetative bacteria --> enveloped or medium viruses
61
How do environmental factors affect chemical reduction?
- Organic materials: impacts antimicrobial capacity/neutralizes it, e.g. body fluids or food
- Temperature: influences chemical rxn, warm is better b/c with a higher rate --> more death --> steeper neg. slope
62
How does toxicity of the agent affect chemical reduction?
- Want to balance so it kills but not harmful
- Have to manage the use according to the specific bacteria and specific location
63
Criteria for the ideal chemical control agent? (12)
- High antimicrobial activity, broad spectrum of it
- Stability for longer storage
- Homogeneity, don't want ingredients settling out
- Solubility in different solutions like water, oil, or fatty layer based
- Detergent activity: breaks down stuff
- Doesn't damage surfaces
- Minimum inactivation by organic material
- Active at normal temp, doesn't need to be heated
- Nice: deodorizes, low cost
64
Describe alcohol as a chemical agent?
- Non toxic
- Doesn't kill endospores, poor penetration
- Used as antiseptic on skin, in tinctures
- Denatures proteins and membranes by disrupting lipids in the cell membrane
65
Describe aldehydes as a chemical agent?
- Kills endospores and vegetative cells
- Toxic
- Preserves tissues, enabling
- Inactivates proteins and enzymes by adding alkyl group
66
Describe quaternary ammonium compounds as a chemical agent?
- Non-irritant
- Detergent action
- Don't kill endospores
- Inactivated by organic matter
- Used in soaps, detergents, skin antispetics
- Physical removes microorganisms, disrupts membranes
67
Describe halogens and hydrogen peroxide as a chemical agent?
- Wide activity
- Inactivated by organic matter and have short life
- Used for water chlorination and skin antiseptic
- Oxidizes vital biochemicals
- Hydrogen peroxide isn't as common b/c there are better alternatives
68
Describe heavy metals as a chemical agent?
- Toxic
- Used to be put in eyes of newborns
- Put in dressings
- Reacts with sulphydral groups
- Silver ion cells bind to and denature proteins
69
Describe phenols and phenolic derivatives as a chemical agent?
- Wide spectrum of activity
- Endospores don't get killed
- Irritant, can be toxic
- Can use at home, mouthwashes, hospitals
- Denatures proteins, disrupts membranes
70
Describe sterilizing gases as a chemical agent?
- Kill endospores
- Explosive and toxic
- Used for pre-wrapped disposable items
- Strong alkylating agent
70
Trigene is an example of doing what?
- Using a combination of different active ingredients in lower concentrations to kill more things
71
Examples of natural antimicrobial compounds?
- Garlic, honey, tea tree oil
MICROBIO
flashcards
Decks in class (5)
# Cards
