Nom : Numéro d`étudiant : . Examen de mi

Numéro d’étudiant :
Nom :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
Cet examen comporte deux parties. La première partie d’une valeur de 20 points comporte de
20 questions à choix de réponses. Assurez-vous d’indiquer vos réponses sur cette feuille.
S.V.P., UTILISEZ DES LETTRES MAJUSCULES pour indiquer vos réponses.
La deuxième partie d’une valeur de 10 points comporte 6 questions à courtes réponses.
Assurez-vous de répondre à SEULEMENT 4 DES 6 questions, sinon seulement que les
réponses aux quatre premières questions seront corrigées.
1
B
2
A
3
B
4
C
5
D
6
A
7
D
8
B
9
A
10
D
11
C
12
D
13
A
14
D
15
C
16
B
17
B
18
C
19
B
20
C
21
C
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
Partie I: Indiquez vos choix de réponses sur la feuille réponse.
1. Choose the correct association between the expected effect of the addition of a macrolide at
each of the growth phases of a bacterial culture.
A.
B.
C.
D.
Lag — after a period of time the cells would initiate the exponential phase.
Exponential — the cells would go in stationary phase.
Stationary — the cells would go in death phase.
None of these associations are correct.
2. A bacterial culture went from 1 X 103 to 1 X 106 cells/ml in 12 hours. According to this data,
what are the total number of generations, the generation time (g) and the growth rate
constant (k), respectively?
A.
B.
C.
D.
~10 generations, ~72 minutes and ~0.83 generations/hour.
~12 generations, ~60 minutes and ~1.0 generations/hour.
~15 generations, ~75 minutes and ~0.80 generations/hour.
~20 generations, ~36 minutes and ~1.7 generations/hour.
3. The optical density of a broth culture of B. subtilis (a large rod) is compared to that of an
E.coli broth culture (a small rod). If both cultures have the same optical density, which of the
following conclusions is correct?
A.
B.
C.
D.
The number of bacteria in both broths must be the same.
The E.coli broth must contain more cells than the B. subtilis broth.
The B. subtilis broth must contain more cells than the E.coli broth.
None of these conclusions are correct.
4. Which of the following germicides would be effective against spores of Clostridium difficile?
A.
B.
C.
D.
Alcohols.
Halogens.
Aldehydes.
Detergents.
5. This image shows a microscopic examination of a water
sample that was sterilized by ultraviolet light. What
conclusion can be drawn based on what is observed ?
A.
B.
C.
D.
The water is contaminated.
The water is sterile.
The sterilization did not work.
None of these conclusions can be drawn from this image.
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
6. Which of the following conclusion about broad spectrum antibiotics is FALSE?
A.
B.
C.
D.
They are recommended for definitive therapies.
They generally have a low therapeutic index.
They are not recommended if the identity of the infectious agent is known.
They include the carbapenems.
Refer to the following image to answer questions 7-8.
2000
2012
A
B
A
B
C
D
C
D
These images represent sensitivity tests to different antibiotics of the same bacterial species
isolated in the year 2000 and 2012.
7. What can you conclude about antibiotic « B »?
A.
B.
C.
D.
It would not be recommended anymore to treat infections by this bacteria.
The MIC decreased in 2012.
The MBC was higher in 2000.
Its MIC remained lower than that of antibiotic « A ».
8. If all these antibiotics have the same toxic dose, which one maintained the highest
therapeutic index?
A.
B.
C.
D.
A.
B.
C.
D.
9. Ten liters of medium are inoculated a 10 o’clock in the morning. Six hours later, at 16
o’clock, the culture reached stationary phase. If the generation time of this bacteria is 30
minutes, at what time was the population density of this culture half of that obtained at
stationary phase?
A.
B.
C.
D.
At 15 h 30.
At 13 h 30.
At 13 h 25.
At 11 h 45.
10. Which of the following germicide (s) damages proteins?
A.
B.
C.
D.
Aldehydes.
Phenols.
Alcohols.
All of them.
Numéro d’étudiant :
Nom :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
11. Choose the correct sequence as it relates to binary fission.
A.
B.
C.
D.
Septum formation, DNA replication, cell elongation, division.
DNA replication, septum formation, cell elongation, division.
DNA replication, cell elongation, septum formation, division.
Cell elongation, DNA replication, septum formation, division.
Log of the number of cells
Refer to the following graph to answer questions 12-15.
6
o
A suspension in water of 10 spores is placed in a dry oven at 170 C. The number of viable
spores was then determined at the indicated times.
12. What is the thermal death point (TDP) of this suspension?
A.
B.
C.
D.
170oC
15 minutes.
60 minutes.
This value cannot be determined from this graph.
13. What is the approximate D value of this suspension?
A.
B.
C.
D.
10 minutes.
30 minutes.
45 minutes.
60 minutes.
14. What is the approximate thermal death time (TDT) of this suspension?
A.
B.
C.
D.
15 minutes.
30 minutes.
45 minutes.
60 minutes.
4
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
15. Amongst the following profiles, which best corresponds to what would be expected if the
experiment had been repeated with dry spores rather than in suspension?
Profile « A»
Profile « B»
Profile « C »
All these profiles would be possible.
Log of number of cells
B
Log of number of cells
A
Time (minutes)
C
Log of number of cells
A.
B.
C.
D.
Time (minutes)
Temps
(minutes)
Time (minutes)
16. Which of the following antibiotics does not ned to penetrate the cell in order to act?
A.
B.
C.
D.
Clarithromycin; a macrolide.
Polymyxin B; a peptide antibiotic.
Spectinomycin, an aminoglycoside.
Sulfadiazine; a sulfamide.
17. A reduction in the number of porins on the LPS layer would be a mechanism of acquired
resistance which would not be effective for which of these antibiotics?
A.
B.
C.
D.
Clarithromycin; a macrolide.
Polymyxine B; a peptide antibiotic.
Spectinomycin, an aminoglycoside.
Sulfadiazine; a sulfamide.
18. Which antimicrobial mode of action is not associated with maggot therapy?
A.
B.
C.
D.
Ingestion and digestion of the bacteria.
Production of antimicrobial compounds.
Digestion of dead tissue.
Stimulation of the host immune system.
19. In the same growth medium, a bacterium « A » has a µ of 0.05 whereas a bacterium « B »
has a µ of 0.15. Which of the following conclusions must be correct?
A.
B.
C.
D.
Bacterium « A » has a shorter generation time than bacterium « B ».
Bacterium « A » has a smaller k value than that of bacterium « B ».
Bacterium « B » will reach the stationary phase before bacterium « A ».
The growth yield of bacterium « B » will be higher than that of bacterium « A ».
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
20. This E test verifies the sensitivity of Staphylococcus aureus to
vancomycin which is maintained at a physiological concentration
between 0.5 and 50.0 µg/mL. Based on the illustrated results, what is the
sensitivity of S. aureus in vivo.
A.
B.
C.
D.
S. aureus is resistant.
S. aureus is sensitive.
S. aureus is of intermediate resistance.
This information cannot be determined.
21. What is the approximate concentration of the antibiotic at the point
indicated by the arrow on the E-test illustrated?
A.
B.
C.
D.
256 µg/mL
48 µg/mL
1.5 µg/mL
0.5 µg/mL
Concentrations are indicated in
µg/mL
Numéro d’étudiant :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
Partie 2. Répondre à SEULEMENT 4 DES 6 questions, sinon seulement que les premières
quatre questions qui auront été répondues seront corrigées.
1. Indicate all the structures which correspond to each of the characteristics indicated. Enter
« X » if none of the structures corresponds to the indicated characteristic. The same
answer can be used more than once.
A
B
C
D
E
F
G
H
I
Characteristic
Drug (s) that targets the membrane
Beta lactam of last generation
Penicillin
Drug with the lowest therapeutic index
Drug (s) which targets DNA synthesis
Compound, other than a macrolide, which targets protein synthesis
Bactericide drug (s) which is non bacteriolytic
Tensioactive/Emulsifying compound (s) other than alcohols
Narrow spectrum beta lactam that acts against Gram positives
Tetracycline
Structure
G
C
X
G
A
BE
AB
I
X
E
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
2. To verify the proper operation of an autoclave, broths containing 1 X 1010 spores of B.
stearothermophillus and 1 X 1010 cells of E.coli are autoclaved at 120oC. According to the
data given below, how much time would be required to reduce the number of B.
stearothermophillus and of E.coli to 1 X 10-6 cells once the broths have attained the desired
temperature? (1.0 point)
D120 of B.stearothermophilus = 30 secondes or 0.5 minutes
D100 of E.coli = 300 secondes or 5 minutes
Z of E.coli = 10oC
Ans. :
B.stearothermophilus : 480 sec. or 8 min
E.coli : 48sec. or 0.8min.
b. The broths were in containers with the dimensions indicated below. Indicate the order of the
heating time of the containers (from the longest to the shortest) to reach the desired
temperature. (Note that heating in the autoclave occurs from all sides) (1.0 point)
Dimensions
Length
Width
Height
Containers
A
100
10
10
4XB
25
10
10
C
25
4
100
D
40
5
40
A(0.42), B(0.48), C(0.6), D(0.5) = ABDC
c. UV sterilization, as illustrated, would be most effective for which of the containers (A, C or
D)? (0.5 points)
A
UV
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
3. The growth of three bacteria (A, B and C) was examined in the presence of different
antibiotic concentrations (Ab-X, Ab-Y and Ab-Z) (Table 1). The physiological concentartion
ranges of these antibiotics are presented in table 2. In addition, the relatioship between the
antibiotic’s concentrations and the inhibition diameters on a disc diffusion assay were
determined.
Table 1
Diameters of the inhibition zones as a
function of concentration
+: Growth
-: No growth
Table 2
a. What are the MICs for the antibiotic with the broadest spectrum for each of the bacteria?
Indicate the antibiotic and the MIC for each bacterium.
Ab-Z. A: 20, B: 40, C: ≤ 5
b. For each bacterium, indicate which antibiotic (s) they are sensitive too in vivo.
A: Y
B: Y
C: X, Z?
c. For each antibiotic, indicate the minimum diameter that must be observed on a Kirby Bauer
assay which would indicate sensitivity.
X: >100mm
Y: >40mm
Z: >5mm
d. This table shows the results of subcultures of bacterium « A » in
medium lacking any antibiotics. The indicated concentrations
are the original concentrations from which the inoculums were
obtained. Which antibiotic (s) is (are) bactericide or bacteriolytic.
Y and Z
Numéro d’étudiant :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
4. Match each of the terms or statements from list « A » to those of list « B ». Each term of list
« B » can only be used once.
List A
List B
K
Myiase
A.
Green fly
E
CDAD
B.
ZnO
C
Innate resistance
C.
Permeability
J
Glycopeptide antibiotic
D.
Exponential phase
B
Antifungal
E.
Probiotic
M
Iodine
F.
MRO
H
Ym
G.
Porin
L
Halogen
H.
Stationary phase
F
MRSA
I.
Bacteriophage
D
Binary fission
J.
Cell wall
K.
Maggots
L.
Water treatment
M.
Betadine
N.
Bacteriostatic
O.
Polymyxin
Nom :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
5. The profile illustrated is that of the growth of a bacterium in medium « X ». The number of
cells (X 107) at different time intervals were determined by direct counts and are reported on
a logarithmic scale.
a. What are the n, K, g, and µ values for the duration of the profile? (2.0 points)
n: approx. 10.5; K: approx. 3; g: approx. 20min.; µ: approx. 0.03
b. The direct counts were done on a haemocytometer slide with a counting chamber of the
following dimensions: 0.1 cm X 0.2 cm X 0.01 cm. If the counting chamber has 100
squares, what should be the average number of cells per square at the 50 minutes time
point? (0.5 points)
40
6. Refer to the growth profile in question 5 to answer the following questions. Consider that the
growth medium « X » is relatively rich, such as human blood. After 1150 minutes, the
culture was transferred to a much poorer medium in which the bacteria can grow.
a. Indicate what would be the expected effect on each of the following values: n, K, g, µ
and Yg of the culture in comparison to those obtained above. (1.25 points)
n - smaller; K - smaller, g - greater, µ - smaller, Yg, smaller.
b. Draw on the above graph, the expected profile. (1.25 points)
Numéro d’étudiant :
Nom :
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Examen de mi-session #2 de BIO3524 : Introduction à la Microbiologie
Formulas:
Area and volume :
Area = (2x (a x b)) + (2x (b x c)) + (2X (c x a))
Volume = a x b x c
Growth :
N= N0 x 2n
n=t/g
µ = ln2/g
K= n/t
n=3.3(logN-logNo)
µ = ( (log10N - log10N0) 2.303) / (t - t0)
Mortality :
-kt = ln (No/N)
D = t/(logNo – logN)
log(
Db
T T
) a b
Da
z
12