quiz microbio

Question 1

The action of catalase results in

Answer 1

the decomposition of hydrogen peroxide to water and oxygen.
H2O2→ H2O + ½ O

Question 2

catalyse procedure

Answer 2

Using a sterile loop, pick up some bacterial cells and smear onto a small area of a slide

Place a drop of hydrogen peroxide on the bacterial cells. and observe for (gas/bubbles) this indicates the presence of catalase.

Question 3

hemolysis

Answer 3

Blood agar is a differential media, differentiating between those that are able to lyse red bloodcells and those that cannot.

.

Question 4

hemolysis procedure

Answer 4

inoculate a blood plate. Perform a T streak.
2. Inoculate organism onto the appropriate section of the plate. Incubate the plate for 24 hours in
a candle jar (decreased oxygen) at 37oC.

Question 5

amylase

Answer 5

catalyzes the breakdown of starch (a branched polymer of glucose) to maltose (a disaccharide).

Question 6

amylase procedure

Answer 6

Divide a Starch agar plate into sections.
2. Inoculate organism using the loop to draw a straight line onto the plate.
3. Incubate at 37oC for 24-48 hours.
4. Flood the plate with iodine. Starch, in the presence of iodine turns the media blue-black.
Organisms able to produce amylase will show a clear zone of no color around the culture, due
to breakdown of the starch. Organisms which do not hydrolyze starch will have a blue-black
color to the medium up to the edge of the growth.

Question 7

coagulase

Answer 7

Coagulase is a cell surface associated virulence factor of certain organisms, in particular certain
Staphylococci. In infected tissues coagulase may protect a bacterium from the normal defenses of the
host by coating itself with host proteins. Coagulase catalyzes the conversion of fibrinogen to fibrin
forming an insoluble clot. The clot formation assay, indicating the action of coagulase, is indicative of
pathogenic strains of Staphylococci.

Question 8

coagulase procedure

Answer 8

Procedure
1. Inoculate 0.5ml of diluted (1:4) rabbit plasma with a loopful of culture of from a fresh plate
2. Incubate at 37oC; check after 2-4 hours, but continue incubation for up to 24 hours.
3. Check for coagulation by tilting the tubes; coagulated plasma will stay as a clot in the bottom of
the tube

Question 9

BACITRACIN SUSCEPTIBILITY

Answer 9

Initial presumptive identification is done by growth on a blood agar plate, looking for characteristic -hemolysis.

Furtheridentification can be done by determining the sensitivity of the -hemolytic organism to the antibiotic
bacitracin. Although most group A streptococci are sensitive, some strains (2-7%) may give false
negative results (resistant to bacitracin); similarly other streptococci (5-15%) may be susceptible to
bacitracin. However, a -hemolytic, bacitracin sensitive organism is characteristic of Streptococcus
pyogenes.

Question 10

Bacterian susceptibility procedure

Answer 10

Procedure
1. Perform a T streak on a Blood Agar.
2. Carefully place a bacitracin disc, on Section I. Press gently using sterile forceps to ensure the
discs are on the medium.
3. Incubate for 24 hours at 37oC in candle jar.
4. Record your results for zone of inhibition

Question 11

OPTOCHIN SUSCEPTIBILITY

Answer 11

. -hemolytic organisms suspected as being S. pneumoniae can
be differentiated from other -hemolytic organisms (normal flora) by their sensitivity to optochin
(ethylhydrocupreine hydrochloride).

Question 12

OPTOCHIN SUSCEPTIBILITY procedure

Answer 12

Procedure
1. Perform a T streak on a Blood Agar.
2. Carefully place a optochin disc, on Section I. Press gently using sterile forceps to ensure the
discs are on the medium.
3. Incubate for 24 hours at 37oC in candle jar.
4. Record your results for zone of inhibition.

Question 13

FURAZOLIDONE SUSCEPTIBILITY

Answer 13

some coagulase-negative staphylococci (i.e. not Staphylococcus aureus) are resistant to furazolidone. The result for this test is based on the zone of inhibition therefore, it is important to measure the zone of inhibition.
Resistant microorganisms can still show a zone of clearing between
6mm to 9mm.
In order to identify Staphylococcus spp. correctly, a zone of inhibition has to be greater than 15mm.

Question 14

FURAZOLIDONE SUSCEPTIBILITY procedure

Answer 14

1. Inoculate a TSA plate with an unknown isolate by the T-streak method.
2. Carefully place a furazolidone disc in the first section. Press gently using sterile forceps to ensure
   the discs are on the medium.
3. Incubate for 24 hours at 37oC.
4. Record your results. A positive test for Staphylococcus is indicated by a zone of no growth around the furazolidone disc (≥15mm

Question 15

UREASE

Answer 15

Urease catalyzes the breakdown of urea by the removal of two ammonia molecules from each urea
molecule.

Question 16

urease procedure

Answer 16

inoculate the surface of a Urea agar slant with your organism in a zig-zag pattern.
2. Incubate the slants for 24 hours at 37oC. Continue incubation for up to 4 days.
3. A positive result will be seen by a deep-pink to red color in the slant

Question 17

Catalase is an important enzyme for organisms growing aerobically by

Answer 17

prevents the accumulation of
toxic metabolites (H2O2) that form during oxidation-reduction reactions of the respiratory chain.High intracellular levels of such compounds could kill the cell.

Question 18

Some bacteria are able to _____ red blood cells, which results in a zone of clearing around a bacterial
colony

Answer 18

lys

Question 19

gamma hemolysis

Answer 19

no lysis or significant change in the appearance of the medium surrounding
the cells

Question 20

alpha hemolysis

Answer 20

a zone of partial clearing due to incomplete lysis if the red blood cells. A
greenish halo around the bacteria due to reduction of hemoglobin to methemoglobin, suggested to
be due at least in part to the action of hydrogen peroxide.

Question 21

beta

Answer 21

a clear zone of hemolysis is present around the colony. There is complete
destruction of the cell and hemoglobin

Question 22

Bacteria are not able to transport starch into the cell. how do they overcome this,

Answer 22

organisms that are able to hydrolyze starch do so by hydrolyzing sugar to maltose. Maltose is then
able to enter the cell and be utilized by the bacterium

Question 23

urea enzyme does what

Answer 23

detoxification of waste products,
supplying a source of nitrogen (via ammonia) for amination reactions producing amino acids and
nucleotides.

Question 24

the assay medium for urease activity contains a high concentration of ____ and a pH indicator.

Answer 24

urea

Question 25

The ammonia released by the urease reacts in solution to form _____ which results in an increase in the pH of the medium

Answer 25

ammonium carbonate

Question 26

Staphylococci are susceptible to _________while micrococci are resistant.

Answer 26

furazolidone

Question 27

_______ is a quinine derivative that has a detergent-like action capable of causing lysis of S. pneumoniae

Answer 27

Optochin

Question 28

identification of pathogenic -hemolytic streptococci, in particular ______________, is important in the diagnosis of disease

Answer 28

Streptococcus pneumoniae

Question 29

Identification of ________ (Streptococcus pyogenes) is required for the prompt therapy of patients.

Answer 29

group A streptococci

Question 30

Not all -hemolytic organisms are

Answer 30

group A streptococci.

Question 31

Denitrification is the process in which

Answer 31

nitrate is reduced to molecular nitrogen

Question 32

Some organisms are able to use nitrates, instead of oxygen as the terminal electron acceptor, in a process known as

Answer 32

anaerobic respiration

Question 33

he reduction of nitrate to nitrite is detected by

Answer 33

assaying for the presence of the product (nitrite)

Question 34

he agar inhibits diffusion of oxygen, favoring ___________ therefore utilization of anaerobic respiration

Answer 34

anaerobic growth,

Question 35

in nitrate reduction and denitrification after incubation, reagents A (________) and B (________) are added to the nitrate broth medium.

Answer 35

sulfanilic acid , a-naphthylamine

Question 36

The presence of a color reaction (red) indicates the presence of _____, due to ___

Answer 36

nitrite, formation of nitrous acid HNO2 from nitrite which reacts with sulfanilic acid and a-naphthylamine

Question 37

procedure for nitrite reduction and denitrification

Answer 37

inoculate broth, incubate for 24-48 hours at 37 degrees examine dirham tube for evidence of gas. add 3-5 drops of solution A and 3-5 drops of solution B to all nitrate broths development of red color means precense of nitrite. so tis positive. add small amount of zinc dust to tubes that are negative. A red color obtained by addition of zinc is a true negative for nitrate reduction. If no red color develops after addition of zinc, then the nitrite has been further reduced to ammonia, molecular nitrogen or other reduced nitrogenous compounds. This is therefore a positive test for nitrate reduction

Question 38

zince does what to nitrate

Answer 38

reduces nitrate to nitrite

Question 39

how long should it take color to turn red in nitratre reduction and denitrification

Answer 39

30 sec

Question 40

Some organisms ferment pyruvate resulting in production of 2,3 _____

Answer 40

butanediol

Question 41

voges proskauer test an intermediate in this pathway is the compound ______

Answer 41

acetoin

Question 42

voges proskauer test Organisms that utilize this pathway produce smaller amounts of

Answer 42

mixed acids, generally insufficient to result in a positive methyl red test.

Question 43

2,3-Butanediol is not a very reactive compound so in the VP test the presence of the ______ is assayed.

Answer 43

intermediate acetoin

Question 44

In the presence of atmospheric oxygen and potassium hydroxide, acetoin is converted to ______- with a-naphthol serving as a catalyst

Answer 44

diacetyl,

Question 45

in VOGES-PROSKAUER TEST what color do you get if positive

Answer 45

pink-red color

Question 46

in VOGES-PROSKAUER TEST how long do you have to wait

Answer 46

24-48 hours

Question 47

in VOGES-PROSKAUER TEST what happenes if there is a short incubation times

Answer 47

will not allow for sufficient to accumulate acetoin

Question 48

VOGES-PROSKAUER TEST procedure

Answer 48

1. Inoculate 3 ml of MR/VP broth medium. 2. Incubate at 37oC for 24-48 hours. 3. Add 30 drops of a-naphthol. Mix thoroughly. 4. Add 10 drops of 40% KOH. Mix well. 6. Incubate the tubes in a slanted position (increases surface area) for up to 60 minutes with a slightly loose cap. Do not exceed 60 minutes, as a false positive test may be obtained. (Do not keep shaking tube during incubation.) 7. Development of a pink-rose color is a positive VP tes

Question 49

BILE ESCULIN TEST procedure

Answer 49

inoculate the slant using an inoculating loop and inoculating needle. 2. Make a zig-zag pattern on the surface of the slant, and stab the butt of the slant using an inoculating needle. 3. If you are working off a blood agar plate, then incubate slant in candle jar, if not then incubate in aerobic conditions at 37oC

Question 50

Fermentation of glucose can occur via a number of pathways, one of which, the mixed acid ____________, results in the formation of a very low pH due to production of strong acids

Answer 50

fermentation pathway,

Question 51

glucose fermentation via the mixed acid fermentation results in the formation of stable acid end products such as

Answer 51

acetic, lactic, succinic and formic acids.

Question 52

Production of strong acids is detected by addition of

Answer 52

methyl red

Question 53

methyl red has a ph range of

Answer 53

6.0 (yellow)-4.4(red)

Question 54

o maintain the red color on addition of methyl red, large quantities of strong, stable acids must be produced from the _________

Answer 54

carbohydrate source

Question 54

Organisms not producing stable acids in methyl red testing result in formation of a change in color of the pH indicator to _____

Answer 54

yellow

Question 56

Mythel red procedure

Answer 56

inoculate 3 ml of MR/VP broth medium. 2. Incubate at 37oC for 48-96 hours. 3. Add 5 drops of methyl red pH indicator. 4. Development of a stable red color at the surface of the medium indicates the presence of sufficient acids to lower the pH to 4.4. This is a positive methyl red (mixed acid fermentation) test. (Do not keep shaking tube during incubation.)

Question 57

Most microorganisms obtain their energy by either

Answer 57

respiration (aerobic or anaerobic) or fermentation

Question 58

CARBOHYDRATE FERMENTATION (ACID & GAS PRODUCTION procedure

Answer 58

1.Collect tubes of phenol red broth base + sugar (mannitol, glucose). Make sure the Durhamtube does not contain any air bubbles. 2. Inoculate each organism in to each sugar. 3. Incubate at 37oC for 24-48 hours. 4. Determine the production of acid or acid and gas

Question 59

Organisms are able to use carbohydrates differently depending on the _____ at its disposal

Answer 59

complement of enzymes the cell has

Question 60

In fermentation, the substrate acts as the ___________ such that there is no net change in the oxidation state of the product(s) relative to the starting substrate.

Answer 60

electron acceptor

Question 61

In general, fermentation pathways are named for __________ , a property which is widely used in the identification of bacteria.

Answer 61

characteristic end products

Question 62

Examples of fermentation pathways are:

Answer 62

ethanol fermentation, lactic acid, fermentation, mixed acid fermentation, butanol, fermentation and butanediol fermentation

Question 63

Fermentations are assayed in a __________ broth tube containing an inverted Durham tube to detect production of gas (CO2).

Answer 63

phenol red

Question 64

The growth tube contains:

Answer 64

fermentation broth-which has all the nutrients required for growth of the microorganism a specific carbohydrate for fermentation a pH indictor which changes color at an acidic pH.

Question 65

Fermentation is indicated by the presence of ______ , i

Answer 65

acid (media will turn yellow)

Question 66

CARBOHYDRATE FERMENTATION in some cases there may also be evolution of _____ which will be collected in the _______

Answer 66

gas; durham tube

Question 67

Lack of fermentation does not _________; some microorganism can use othernutrients (such as peptides) as energy sources.

Answer 67

indicate absence of growth

Question 68

in carbohydration femrentation peptides are broken down into amino acids which can be converted to _______ by deamination which are then metabolized.

Answer 68

ketoamino acids

Question 69

CARBOHYDRATE FERMENTATION reactions result in release of ammonia which accumulates as _____________.

Answer 69

(alkaline) ammonium hydroxide

Question 70

release of ammpnia which makes ammonium hydroxide may also occur if the tubes are

Answer 70

incubated too long and all the fermentable sugar is used up

Question 71

CARBOHYDRATE FERMENTATION it is important to read the results in ________ otherwise some of the broths may revert in color due to the presence of alkaline products

Answer 71

24hr-48hr