Lecture Exam 2 Flashcards
1
Q
What do the following use for energy and/or carbon source: autotroph
A
Autotrophs: inorganic CO2
2
Q
What do the following use for energy and/or carbon source: heterotroph
A
Heterotrophs: organic carbon
3
Q
What do the following use for energy and/or carbon source: chemotroph
A
Chemotroph: gets its energy from chemical compounds
4
Q
What do the following use for energy and/or carbon source: phototroph
A
Phototroph: microbes that photosynthesizes (uses sun for energy)
5
Q
What do we call any substance that must be provided to an organism?
A
essential nutrient
6
Q
Why do bacteria require trace elements?
A
involved in enzyme function and maintenance of protein structure
7
Q
What is the energy source, carbon source, and example organism for each: photoautotroph
A
energy source: sunlight
carbon source: CO2
photosynthetic organisms (algae, plants, cyanobacteria)
8
Q
What is the energy source, carbon source, and example organism for each: photoheterotroph
A
energy source: sunlight
carbon source: organic
purple and green photosynthetic bacteria
9
Q
What is the energy source, carbon source, and example organism for each: chemoautotroph
A
energy source: organic compounds
carbon source: CO2
methanogens
10
Q
What is the energy source, carbon source, and example organism for each: chemoheterotroph
A
energy source: metabolic conversion of the nutrients from other organisms
carbon source: organic
protozoa, fungi, many bacteria, animals
11
Q
How do each get the energy and carbon that they need: chemolithotrophs
A
inorganic compounds (minerals)
12
Q
How do each get the energy and carbon that they need: saprobes
A
metabolizing the organic matter of dead organisms
13
Q
How do each get the energy and carbon that they need: parasites
A
utilizing the tissues, fluids of a live host
14
Q
Define the following: ectoparasite
A
parasites that live on body
15
Q
Define the following: endoparasite
A
live in organs and tissue
16
Q
Define the following: intracellular parasite
A
live within cells
17
Q
Define the following: obligate parasites
A
unable to grow outside of a living host
18
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: carbon
A
how element is obtained: different depending on nutritional classification
- heterotroph: organic carbon sources
- autotroph: use CO2
used to make: to make all macromolecules
19
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: hydrogen
A
how element is obtained: acquired through organic compounds and several inorganic compounds (water, salts, natural gases)
used to make: to make all macromolecules
20
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: oxygen
A
how element is obtained: organic compounds and inorganic salts such as sulfates, phosphates, nitrates, and water
used to make: to make all macromolecules
21
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: nitrogen
A
how element is obtained: most bacteria decompose proteins
- some use NH4+ or NO3-
used to make: proteins and nucleic acids
22
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: phosphorous
A
how element is obtained: PO43- is a source of phosphorous found in rocks and oceanic mineral deposits
used to make: nucleic acids (DNA, RNA, ATP) and cell membranes
23
Q
For each macromolecule, how do bacteria obtain that element, and why are they needed by the cell: sulfur
A
how element is obtained: most bacteria decompose proteins
- some use SO42- or H2S
used to make: amino acids and vitamins
24
Q
What are the oxygen requirements and an example organism and disease it causes for each: obligate aerobe
A
oxygen requirement: require O2
example organism and disease it causes: Pseudomonas aeruginosa
- infections in burn victims and patients w/ CF
25
What are the oxygen requirements and an example organism and disease it causes for each: microaerophile
oxygen requirement: require low O2 concentration
example organism and disease it causes: Helicobacter pylori
- causes ulcers
26
What are the oxygen requirements and an example organism and disease it causes for each: obligate anaerobe
oxygen requirement: cease growth or die in O2
example organism and disease it causes: Clostridium perfringens
- causes gas gangrene
27
What are the oxygen requirements and an example organism and disease it causes for each: facultative anaerobe
oxygen requirement: grow w/ or w/o O2. but grows better w/ oxygen (use it)
example organism and disease it causes: Escherichia coli
- UTI
28
What are the oxygen requirements and an example organism and disease it causes for each: aerotolerant anaerobe
oxygen requirement: can grow in O2, but don't use it (can grow w/ or w/o O2)
example organism and disease it causes: Streptococcus pyogenes
- causes strep throat
29
A microorganism that does not have catalase or superoxide dismutase would find it difficult to live in an environment with _____?
oxygen
30
What is superoxide dismutase used for (what reaction)? What types of organisms produce superoxide dismutase? Why?
used to neutralize superoxide ions into hydrogen peroxide
used by organisms that grow in the presence of O2 because superoxide ions are highly reactive and can damage and destroy a cell
31
What is catalase used for (what reaction)? What types of organisms produce catalase? Why?
used to neutralize hydrogen peroxide
used by organisms that use O2 as a FEA. Hydrogen peroxide is neutralized into H20 and O2 because it is toxic to cells
32
What is peroxidase used for (what reaction)? What types of organisms produce peroxidase? Why?
used to neutralize hydrogen peroxide into water
used by organisms that grow in O2 but don't use it
they use peroxidase instead of catalase because they don't use O2 and don't need to produce more
33
What is a capnophile? What is an example of an organism that is a capnophile?
organisms that grow best at a higher CO2 concentration that is normally present in the atmosphere
Streptococcus pneumoniae
34
Define the following terms: minimum growth temperature
the lowest temp that permits a microbe's continued growth and metabolism
35
Define the following terms: optimum growth temperature
an intermediate between the minimum and maximum that promotes the fastest rate of growth and metabolism
36
Define the following terms: maximum growth temperature
highest temperature at which growth and metabolism can proceed before proteins are denatured
37
What are the following for the temperature requirements of an organism: psychrophile
name means:
growth range:
optimal growth temperature:
example pathogenic organism and disease it causes:
where organism is found (grows):
name means: cold lover
growth range: 0-20 degrees C
optimal growth temperature: below 15 degrees C
example pathogenic organism and disease it causes: N/A
where organism is found (grows): cold temperature/refrigerator
38
What are the following for the temperature requirements of an organism: psychrotroph
name means:
growth range:
optimal growth temperature:
example pathogenic organism and disease it causes:
where organism is found (grows):
name means: cold eater
growth range: 0-30 degrees C
optimal growth temperature: 15-30 degrees C
example pathogenic organism and disease it causes: Listeria monocytogenes (causes listeriosis)
where organism is found (grows): deli meat, milk, unpasteurized cheese
39
What are the following for the temperature requirements of an organism: mesophile
name means:
growth range:
optimal growth temperature:
example pathogenic organism and disease it causes:
where organism is found (grows):
name means: moderate lover
growth range: 10-50 degrees C
optimal growth temperature: 20-45 degrees C
example pathogenic organism and disease it causes: Escherichia coli (causes sepsis, UTI, food poisoning)
where organism is found (grows): inhabit animals and plants as well as soil, and H2O in temperate, subtropical, and tropical regions
40
What are the following for the temperature requirements of an organism: thermophile
name means:
growth range:
optimal growth temperature:
example pathogenic organism and disease it causes:
where organism is found (grows):
name means: heat lover
growth range: 45-80 degrees C
optimal growth temperature: 50-60 degrees C
example pathogenic organism and disease it causes: N/A
where organism is found (grows): sunlit soil and water associated with volcanic activity, compost piles, and hot springs
41
Do most psychrotrophs cause human disease? Why or why not?
no, they do not grow at human body temperature
42
What problems do psychrotrophs cause for humans?
usually cause food spoilage and listeriosis can cause fetuses to be stillborn or contract meningitis
43
Which temperature requirement organisms cause the most food spoilage and human disease? Why?
mesophiles; they grow best at human body temperature
44
Why can a fever be useful for the body?
increases body temperature and mesophiles suffer (around 39 degrees C)
45
What are thermoduric microbes?
organisms that can survive short exposure to high temperatures but are normally mesophiles
46
What pH range do most bacteria grow at? What pH range do most molds and yeast grow at?"
bacteria: 6.5-7.5
molds and yeast: 5-6
47
Define the following terms: acidophile
grow in acidic environments
48
Define the following terms: neutrophile
grow in neutral pH environments
49
Define the following terms: alkaliphiles
grow in alkaline (basic) environments
50
Which pH requirement organisms are likely to be the case for most food microbes (that cause spoilage)?
acidophiles
51
Which pH requirement organisms are likely to be the case for most normal microbiota (flora)?
neutrophiles
52
What happens to most bacteria when placed in hypertonic environments (in a solution with high concentration of salt or sugar)
plasmolysis occurs; cell membrane will collapse in and inhibit microbial growth
53
What is the term for organisms that require high osmotic pressure?
extreme or obligate halophiles
54
What is the term for organisms that tolerate high osmotic pressure? What is an example organism?
facultative halophiles
55
What is synergy? What is an example of a synergistic interaction among microbes?
In the case of organisms, members cooperate and share nutrients
- mixed communities of bacteria and other microbes that are attached to a surface and each other
56
Describe the following types of media and what they are used for: chemically defined
exact chemical composition is known
- used for certain assays and provide growth factors for fastidious organisms
57
Describe the following types of media and what they are used for: complex media
extracts and digests of yeasts, meat, or plants
- used for general growth, salt balance, solidifying agents, varies batch to batch
58
Describe the following types of media and what they are used for: reducing
contain chemicals that combine O2 to deplete it
- used for the cultivation of anaerobic bacteria
59
Describe the following types of media and what they are used for: selective
contain inhibitors to suppress growth; used to suppress unwanted microbes and encourage desired microbes
60
Describe the following types of media and what they are used for: differential
allows distinguishing of colonies of different microbes on the same plate
61
True or false: microbial growth refers to an increase in the size of the microbial cell. Explain.
false; microbial growth refers to an increase in number of cells
62
Describe the process of binary fission
1) one cell becomes two
2) parent cell enlarges
3) duplicates its chromosomes
4) starts to pull its cell envelope together to the center of the cell
5) cell wall eventually forms a complete central septum
63
What is the term for the time required for a cell to divide and its population double?
generation time
64
What is the typical generation time for most bacteria?
30-60 minutes
65
What are the 4 phases of growth and describe each phase: phase one
lag phase
- high metabolic activity
- cell adapt to new environment
- can last for 1 hour to several days
- no increase in population size
66
What are the 4 phases of growth and describe each phase: phase two
log phase
- fastest rate of division
- exponential growth
- BR > DR
- population increases
67
What are the 4 phases of growth and describe each phase: phase three
stationary phase
- BR = DR (no change in pop size)
- exhaustion of nutrients, accumulation of wastes, and harmful changes in pH
68
What are the 4 phases of growth and describe each phase: phase four
death phase
- BR < DR
- cells die at exponential rate
69
During which phase of the growth curve are endospores most likely to be produced?
stationary phase
70
Describe three methods to analyze population size without actually culturing the bacteria
1) Turbidity: clear nutrient solution becomes turbid as microbes grow in it
- the greater the turbidity, the larger the population size
2) direct cell count: measured microscopically
- coulter counter: electronically scans a fluid as it passes through a tiny pipette
- flow cytometer: works similarly to a coulter counter, but can measure cell size and differentiate between live and dead cells
3) genetic probing: uses real time PCR to quantify bacteria and other organisms present in environmental or tissue samples
71
What is the term for the sum of all chemical reactions in an organism?
metabolism
72
For catabolism describe the following:
a) it is used to build or break down molecules
b) does it use a hydrolysis or dehydration reaction
c) are the reactions exergonic or endergonic
a) breaks down molecules
b) hydrolysis
c) exergonic (energy released)
73
For anabolism describe the following:
a) it is used to build or break down molecules
b) does it use a hydrolysis or dehydration reaction
c) are the reactions exergonic or endergonic
a) build molecules
b) dehydration
c) endergonic reaction (energy must be put in)
74
Describe endergonic and exergonic reactions. Give an example of each
endergonic: energy is put in to build products
- photosynthesis
exergonic: energy is released to break bonds
- cellular respiration
75
If a chemical bond is formed, does this release or store energy?
stores energy
76
Does an exergonic or an endergonic reaction require a high amount of potential energy for the reaction to occur? Why?
exergonic reactions because there is a lot of stored potential energy in bonds that are to be released
77
What are the three types of metabolic pathway patterns? Give an example for each.
Linear: A->B->C (starch hydrolysis)
Branched: A-> B OR C (oxidation vs. fermentation)
Circular: A->B->C->A (kreb cycle)
78
Why are some organisms able to do metabolic processes and other organisms cannot do those processes? For example, yeast can do alcohol fermentation and you cannot. Why can't you do alcohol fermentation?
Metabolic pathways are determined by enzymes and enzymes are encoded by genes
79
What is the advantage of organisms performing metabolism? Which class of macromolecule provides most of the energy in the cell?
allows for controlled storage and release of energy often in the form of ATP; oxidation of carbohydrates
80
What is it about ATP's structure that allows it to store lots of potential energy? What happens to ATP when this energy is transferred to something else?
Lots of energy stored in bond between phosphate groups
- because of the negative charges that repel each other
- when the bond is broken, energy is released
81
True or false: organism store their energy in the cell as ATP. Why did you choose that answer
false; we do not store ATP but we store energy rich molecules such as glycogen, starch, and fats for coupled reactions
82
Define the following terms: collision theory
molecules or atoms must make physical contact in order for a chemical reaction to occur
83
Define the following terms: activation energy
the amount of energy required to get a reaction started
84
Define the following terms: reaction rate
the frequency of collisions containing sufficient energy to bring about a reaction
85
What are the ways that a reaction rate can be increased?
- raise the temperature
- stir
- increase pressure
- increase concentration of reactants
- add an enzyme
86
An ____ is a type of protein that accelerates the rate at which a chemical reaction takes place in an organism
enzyme
87
What types of macromolecules are enzymes usually?
globular proteins
88
Do specific enzymes usually catalyze only one reaction or many reactions?
one reaction
89
Lactose is the _____ of the enzyme _____
substrate; lactase
90
How do enzymes work?
catalyze chemical reactions by lowering activation energy
91
What is the region of the enzyme called that binds to the substrate?
active site
92
Define the following parts of an enzyme: apoenzyme
protein portion of enzyme
93
Define the following parts of an enzyme: cofactors
may be inorganic or organic coenzyme; non-protein portion
94
Define the following parts of an enzyme: holoenzyme
apoenzyme + cofactor: whole, active enzyme
95
Define the following parts of an enzyme: active site
location where substrate binds
96
Define the following parts of an enzyme: allosteric site
"other space"
97
What are the two types of cofactors?
inorganic (minerals) or organic (vitamins)
98
Describe the mechanism of enzymatic action (4 steps)
1) substrate contacts the active site
2) temporary enzyme - substrate complex forms
3) substrate is transformed into product
4) products are released and enzyme remains unchanged and available
99
List the factors that influence enzymatic activity. Briefly describe how each factor affects enzymatic activity.
Temperature: there is an optimal temperature range based on enzyme
pH: optimal pH range for optimal enzyme activity
Substrate concentration: an increase in substrate concentration increase reaction rate until saturation is reached
I
nhibitors: molecules that inhibit enzymes
- competitive inhibition
- noncompetitive inhibition
100
What is the difference between competitive and noncompetitive inhibition?
Competitive inhibitor: compete with substrate for active site
Noncompetitive inhibitor: do not compete with substrate for active site
101
Which type of inhibitor can be reversed by increasing the substrate concentration?
competitive inhibitor can be reversed by increasing substrate concentration
102
Which type of inhibitor has a structure that is similar to the normal substrate?
competitive inhibitor has a structure that is similar to the normal substrate
103
How does sulfanilamide inhibit the synthesis of folic acid? Why is this important?
sulfanilamide is a competitive inhibitor and binds to the active site of the enzyme that converts PABA to folic acid -> bacteria don't synthesize folic acids or nucleic acids -> inhibits bacterial growth
104
Describe feedback (end-product) inhibition and how it works,
- pathway end-product inhibits enzyme activity
- excess end-product binds to allosteric site on first enzyme
- active site deforms
- pathway shuts down
- as end product concentration decreases, active sites reform and pathway resumes
- quick but short term
105
For exoenzymes and endoenzymes, discuss the following:
a) where are these enzymes used (inside or outside the cell)
b) are the substrates usually large or small
c) what are those types of enzymes used for
exoenzymes:
a) secreted outside cell
b) usually larger substrates
c) usually to help metabolize unusual food sources or larger food or used to neutralize harmful chemicals
endoenzymes:
a) inside the cell
b) usually smaller substrates
c) essential to metabolism
106
Compare constitutive and induced (adaptive) enzymes
constitutive
- always present, always produced
- essential
induced (adaptive)
- produced when only substrate is present
- conserves energy
107
What are the RNA-based enzymes called in the nucleus that are responsible for splicing RNA?
ribozymes
108
For redox reactions, what type of reactions are used for the loss of electrons and what type of reactions are used for the gain of electrons
oxidation: loss of electrons
reduction: gain of electrons
109
What are the reactants and products of cellular respiration?
reactants: glucose and oxygen
products: carbon dioxide, water, and ATP
110
What is the source of electrons in cellular respiration? What reactant became oxidized and which reactant became reduced?
glucose is source of electrons
- glucose oxidized
- oxygen is reduced
111
What are the electron carriers in cellular respiration? Are they oxidized or the reduced, electron carriers energy rich?
coenzymes
- reduced molecules are energy rich
- oxidized molecules are energy poor
112
Define the term phosphorylation. Name and describe the three mechanisms of phosphorylation involved in ATP synthesis.
phosphorylation: making ATP from ADP
1) substrate level phosphorylation: transferring a phosphate from a substrate onto ADP-> ATP
2) oxidative phosphorylation: uses redox reaction to form ATP (ETC)
3) photophosphorylation: using light energy to form ATP (photosynthesis)
113
Compare aerobic respiration, anaerobic respiration, and fermentation.
a) # of ATP
b) oxygen required
c) method of phosphorylation
d) FEA
e) organic or inorganic products
aerobic respiration
a) 30-32
b) yes
c) oxidative phosphorylation
d) o2
e) inorganic
anaerobic respiration
a) 3-29
b) no
c) substrate level phosphorylation
d) non o2 compound (so42-, NO3-, CO32-)
e) inorganic
fermentation
a) 2
b) no
c) substrate level phosphorylation
d) organic compounds (pyruvate, acetaldehyde)
e) organic
114
What is the function of oxygen in aerobic cellular respiration? What would happen if there is no oxygen?
Final electron acceptor; electrons will not be able to move down the electron transport chain
115
Glycolysis and the Kreb cycle produces very little ATP compared to the electron transport chain. What is the important product produced during those steps and why is that product important?
glycolysis: 2NADH
kreb cycle: 6NADH
helps to carry electrons used in ETC
116
Describe what happens in the electron transport chain and how this generates the bulk of the ATP during aerobic cellular respiration
occurs in the cristae of the mitochondrion in eukaryotes.
- electron carriers alternate reduced and oxidized states on as they accept and donate electrons
- energy produced from this process drive hydrogen against their concentration gradient from the mito matrix in eukaryotes and cytoplasm in prokaryotes to intermembrane space in eukaryotes and periplasmic space in prokaryotes
- hydrogens in outer space are then pumped back into origin through ATP synthase producing ATP
117
What activates ATP synthase to produce ATP
energy produced from electron transport chain
118
Where do the steps of cellular respiration take place in eukaryotic cells?
a) glycolysis - cytosol
b) intermediate step - going into mitochondrion
c) kreb cycle - mito matrix
d) electron transport chain - mito matrix + intermembrane space
119
Where do the steps of cellular respiration take place in prokaryotic cells?
a) glycolysis - cytosol
b) intermediate step - cytosol
c) kreb cycle - cytosol
d) electron transport chain - cytoplasm + periplasmic space
120
The reactions of fermentation function to produce ______ molecules for use in glycolysis
NAD+
121
True or false: anaerobic respiration is called fermentation
false; fermentation and anaerobic respiration are two different processes in which fermentation uses organic FEA and produces organic products while respiration uses inorganic FEA and produces inorganic products
122
What are the two types of fermentation? What are the final electron acceptors in each type? What type of organisms do each type?
alcohol fermentation
a) organic FEA
b) yeast cells
lactic acid fermentation
a) organic FEA
b) in animal cells (muscles) and some bacteria, like lactobacillus
123
Define the following terms: sterilization
process of destroying all microbial life on an object (including endospores)
124
Define the following terms: disinfection
process of reducing or inhibiting microbes on non-living (inanimate) surfaces
125
Define the following terms: antisepsis
process of reducing or inhibiting microbes on living tissue
126
Define the following terms: degerming
removing microbes from a limited area
127
Define the following terms: sanitization
lowering microbial counts on eating surfaces and utensils
128
Define the following terms: bacteriocide
kills bacteria
129
Define the following terms: bacteriostatic
inhibits bacteria
130
Washing your hands would be an example of what type of microbial control? Why?
degerming; not removing all organisms but an attempt to lower microbial count
131
What pattern does the rate of microbial death show (i.e constant, logarithmic, sporatic, etc)? What is the kill time of a chemical dependent on?
constant; kill time is proportional on number of microbes present
132
How does moist heat sterilization work? What is an autoclave, what is it used for, and what is the minimum operating conditions?
If you tightly wrapped forceps in foil (and the steam could not contact the forceps), would the forceps be sterilized?
it denatures proteins; steam under pressure; used to sterilize culture media, instruments, dressing, intravenous equipment, applications, sponges, etc at 121 degrees C for 15 min at 15 PSI
no: autoclave only effective if in direct contact with steam
133
If you wanted to reduce spoilage organisms and pathogens in milk, juice, and wine, what physical control method should you use? Why? Does this method sterilize the juice?
pasteurization; heating food too much can change the taste of the food
it does not sterilize the juice as not all microbes are removed in the heating process
134
Does dry heat or moist heat sterilize more quickly?
moist heat sterilizes things more quickly
135
For each of the following control methods, list the way that the method controls microbial growth and indicate whether it is bacteriostatic or bactericidal: low temperature
inhibits growth; bacteriostatic
136
For each of the following control methods, list the way that the method controls microbial growth and indicate whether it is bacteriostatic or bactericidal: high pressure
denatures proteins; bactericidal
137
For each of the following control methods, list the way that the method controls microbial growth and indicate whether it is bacteriostatic or bactericidal: desiccation
removes water and prevents metabolism; bacteriostatic
138
For each of the following control methods, list the way that the method controls microbial growth and indicate whether it is bacteriostatic or bactericidal: osmotic pressure
high sugar/salt causes plasmolysis; bacteriostatic
139
Which group of organisms are more resistant to osmotic pressure?
molds and yeasts
140
How do surface tension depressants work?
loosen contamination from surfaces
141
What is the best method to sterilize liquid solutions that may be damaged by heat (for example, medications)
filtration
142
How does filtration work?
it is the passage of liquid or gas through screen like material to filter out microbes
143
How does high energy/ionizing radiation work to control microbial growth? What is high energy/ionizing reagent used for?
ionizes water, creates free radicals that damage DNA
144
How does UV radiation control microbial growth? Is it bacteriostatic or bactericidal? Can it be used to disinfect solutions inside a sealed glass bottle? Why or why not?
Disinfects surfaces only as it is not very penetrating and damages DNA by causing a thymine thymine dimer which is a mutation in the DNA that leads to cancer
It will not be effective as it has trouble penetrating the surface
145
What are the factors influencing the effectiveness of control agents?
a) number of microbes present
b) concentration and age of agent
c) temperature and pH
d) presence of organic matter
e) diffusibility
f) age of cells
g) species
146
Do most chemical agents achieve sterility?
no; different species and stages have different susceptibilities to physical and chemical control
147
List organisms from the most resistant to the least resistant to antimicrobial chemicals. For each one, explain why they would be resistant (or not resistant) to antimicrobial chemicals
Prions: not alive and are heat resistant proteins
Endospores: tough keratin shell
mycobacteria: waxy cell wall w/ 60% mycolic acid
cysts of protozoa: thick wall on the outside made of chitin
vegetative protozoa: have a pellicle (like a cell wall)
gram negative bacteria: outer membrane with porins
fungi: cell wall w/ chitin
viruses w/o envelopes: no envelope to be dissolved by lipid soluble antimicrobial
gram positive bacteria: not resistant
viruses w/ lipid envelopes: not resistant
148
What is selective toxicity and why is it important
the property of some antimicrobial agents to be toxic to a microorganism and less non/toxic to the host
149
What organisms produce the majority of antimicrobial drugs?
bacteria in the genera Streptomyces and bacillus
150
List the desirable characteristics of antimicrobial drugs
-selectively toxic: toxic to microbe and less toxic to host
- relatively soluble: able to get to difficult tissues to reach
- not too expensive
- easily produced
- hypoallergenic
- administration and dosage: taken orally vs. through an IV
- low toxicity: doesn't do damage to kidneys and liver
- does not lead to antibiotic resistance
- remains in tissues long enough to have an effect
151
What is the difference between a narrow spectrum drug and a broad spectrum drug?
broad spectrum
- antibiotic that is effective against a wide variety of organism (both gram + and gram-)
- norfloxacin
narrow spectrum
- antibiotic that is effective against only specific types of organisms
- penicillin: targets peptidoglycan and is effective against gram +
152
What is a superinfection and how can it occur?
an infection following a previous infection usually by microorganisms that have become resistant to the antibiotics used earlier
153
Why is it so difficult to target a pathogenic virus without damaging the host's cells?
live within host cells
- they are not living
154
Why is it so difficult to target a protozoan without damaging the host's cells?
eukaryotic and animal like
155
Why is it so difficult to target a fungus without damaging the host's cells?
eukaryotic
156
Why is it so difficult to target a helminth without damaging the host's cells?
eukaryotic and animal cells
157
Why are antibiotics with a very broad spectrum of activity not as useful as one might first think?
they destroy normal microbiota that may be good for us as well as the bad bacteria
158
What is the difference between antimicrobial agents that are bacteriostatic versus those that are bactericidal?
bactericidal: kill microbes directly
bacteriostatic: inhibits microbes from growing
159
If you have an infection with a gram negative organism, should you choose a drug that is bactericidal or bacteriostatic?
bacteriostatic; gram negative bacteria have an outer membrane w/ lipid A that is an endotoxin
if bacteria were to burst it would release lipid A which could send the patient into shock
160
Name and discuss the five modes of antimicrobial inhibition. For each of the 5 modes:
a) the drugs target of inhibition
b) describe why this mode would, or would not be, considered selectively toxic
c) describe if this mode would be bacteriostatic or bactericidal
d) list several example drugs for each mode
1) protein synthesis inhibitors acting on ribosomes
a) 70S ribosomes
b) selectively toxic; bacteria use 70S ribosomes and our cells use 80S
c) bacteriostatic; prevents bacteria from producing proteins
d) Azithromycin, Clindamycin, Tetracyclines
2) cell wall inhibitors
a) bacteria cell wall; block synthesis and repair
b) selectively toxic; bacteria have a cell wall and human cells do not
c) bactericidal; w/o cell wall to help grow in size when dividing bacteria will die
d) penicillin, cephalosporins, vancomycin
3) cytoplasmic membrane
a) cause loss of selective permeability
b) no; bacterial cell membranes are similar to ours (phospholipid bilayer)
c) bactericidal
d) polymyxins, daptomycin
4) DNA/RNA
a) nucleic acids
b) yes; bacteria have circular chromosomes and we have linear chromosomes
c) bacteriostatic; inhibit replication and transcription
d quinolones, rifampin
5) Folic acid synthesis in cytoplasm
a) block pathway and inhibit metabolism
b) yes; bacteria synthesize folic acid but we get it from diet
c) bacteriostatic
d) sulfonamides, trimethoprim
161
Which class of antimicrobial drugs contain a beta-lactam ring? How do these drugs inhibit microbial growth? Which group of organisms do those drugs target?
penicillin; prevent the cross linking of peptidoglycans, interfering with cell wall construction; target gram positive and some gram negative
162
What is the problem with natural penicillin?
susceptible to penicillinase
163
Which enzyme do bacteria produce that makes them resistant to penicillin? How does this enzyme work to make bacteria antibiotic resistant?
penicillinase; cuts beta lactam ring which makes bacteria resistant to penicillin
164
What advantage do semi-synthetic penicillins have over natural penicillins?
contain chemically added side chains, making them resistant to penicillinase
165
What do the following antimicrobial drugs have in common, in terms of their structure: penicillin, cephalosporin, and ampicillin
they contain a beta-lactam ring
166
What are two polypeptide antibiotics that inhibit cell wall synthesis? What is each one used for?
bacitracin: topical antibiotic used for skin infections
- used to kill gram positive bacteria on our skin
vancomycin: used to be a last line drug for MRSA
- now is a first line drug
167
What disease is isoniazid and ethambutol used to treat? How do they work?
tuberculosis
Isoniazid: inhibits mycolic acid synthesis
Ethambutol: inhibits incorporation of mycolic acid
168
How do streptomycin, tetracycline, and chloramphenicol all inhibit microbial growth?
Streptomycin: changes shape of 30S portion, causing code on mRNA to be read incorrectly
Tetracyclines: interfere with attachment of tRNA to mRNA ribosome complex
Chloramphenicol: binds to 50S portion and inhibits formation of peptide bond
169
What does rifamycin target as an antibiotic and what disease is it used to treat? Why?
inhibits mRNA synthesis; used for TB as it penetrates tissues to get to walled off bacteria in scar tissue in lungs
170
What drug is used topically, is combined with bacitracin and neomycin in nonprescription ointments, and works by injury to the cell membrane? Does this target Gram + or Gram - bacteria?
polymyxin B; gram - bacteria
171
What is the term for the effect of two drugs together is greater than the effect of either alone?
drug synergy
172
What two drugs are synergistic and target folic acid synthesis? How do they work?
trimethoprim and sulfamethoxazole: inhibits folic acid synthesis by competitively binding to the enzyme of PABA production - a folic acid precursor
173
What three factors must be known before antimicrobial therapy can be administered?
1) the identity of the microorganism causing the infection
2) the degree of the microorganism's susceptibility to various drugs
3) the overall medical condition of the patient
174
What is the Kirby Bauer method used for and how does it work? What would a plate look like if the organism is sensitive to the antibiotic? What would it look like if the organism is resistant to the antibiotic?
used to determine the appropriate antibiotic for treatment; measure zones of inhibition and compare to standardized table
- sensitive: large clearing around antibiotic
- resistant: no clearing or really small clearing around antibiotic
175
What are the advantages of using the kirby bauer method?
- most common
- easy, cheap, little skill required
- standardized
176
If there is clearing around an antibiotic disk, does that mean that the bacteria is definitely dead in that area? Why or why not? How could you test if the bacteria in that area are dead?
no; bacteria may be in a dormant state as they could produce endospores
you could do an endospore stain to see if bacteria are able to produce endospores
177
Describe how the E test works and what it is used to determine.
a gradient diffusion method
- plastic strip (epsilometer) coated with an increasing concentration of drug
- determines the minimal inhibitory concentration (lowest antibiotic concentration preventing bacterial growth)
178
What is the therapeutic index (TI)? Is a lower or higher TI considered to be a safer drug
the ratio of the dose of the drug that is toxic to humans as compared to its minimum effective (therapeutic) dose
- the smaller the ratio, the greater the potential for toxic drug reactions
- TI = 1.1 risky
- TI = 10 safer
179
What are the four mechanisms of resistance to antibiotics?
1) reduced permeability: the antibiotic is less likely to get in
- porins in outer membrane of gram negative bacteria may reduce making it harder for antibiotic, mutation in porin, or change in cell wall structure (produce capsule or slime to protect bacteria)
2) restricts access of antibiotics: efflux pumps push antibiotics back out of cell
3) antibiotic target site alteration: prevents antibiotic from binding to target molecule caused by mutation (ex. PABA -> folic acid; sulfanilamide no longer effective as binding site changes)
4) antibody inactivation or modification: enzymes produced that either cut beta lactam ring or modify antibody enzymes to no longer be active
180
What are the three ways that bacteria can acquire the genes needed for antibiotic resistance? Describe each method for how it works.
vertical gene transfer: occurs during reproduction between generations of cell
- mutation (ex. in enzymes that inhibit antibiotic enzymes)
horizontal gene transfer: transfer of genes between cells of the same generation (resistance genes being passed from one to another)
- transformation: naked DNA transferred from dead donor into competent recipient
- transduction: virus (bacteriophage) acts as genetic vector, passing DNA from donor to recipient
- conjugation: the transfer of genetic material from one cell to another involving cell-to-cell contact
