Lab Exam 3

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1

Why do we use Synder's agar?

It's simpler than the plate count in that the tube of agar is simply read for a color change. If the agar retains its original color, it means susceptibility to caries is low.

2

Why do we use Rogosa's agar?

It inhibits the growth of other oral flora, but will not affect the growth of the lactobacilli.

3

What is the Sabouraud Dextrose agar for?

Allows for the growth of fungi and inhibits most bacteria with its low pH.

4

What organism are we expecting to cultivate in the Lactobacillus study and mold slide culture lab?

Lactobacillus acidophilus.

5

What stain did you use on the fungi?

Lactophenol cotton blue

6

What was the purpose of the coccal flora lab?

Attempt to isolate some of the gram-positive cocci which are part of the transient (temporary) and resident (permanent) population of coccal bacteria in the human nasopharynges.

7

What was the purpose of the Bacterial Examination of Water and Submerged slide culture lab?

Look for the detection of fecal contamination, one that is concerned with the identification of E. coli according to its biochemical characteristics.

8

What was the purpose of the milk and food lab?

To learn the importance of sanitary quality.

9

What is the purpose of the microbiological reduction by hand washing lab?

To learn about the resident (normal flora) or transient (contaminating) organisms.

10

What media was used for the coccal flora lab?

Blood agar, tryptic soy broth, and Mannitol salt agar.

11

What organisms are mentioned in the coccal flora lab?

Staphylococcus aureus, streptococcus pyogenes, and streptococcus pneumonia.

12

Blood Agar is:

Trypticase soy agar with sheep blood added, about 5%. The nutrient in the medium is enriched by the blood which is required by the most fastidious organisms. Blood also serves as the indicator of hemolysis.

13

Define Tryptic soy broth:

Like the above medium, but without the blood and agar. Though it is a general purpose medium and is not specific for the growth of cocci, for our purposes it will suffice as the enrichment medium.

14

Define Mannitol Salt agar:

Selective and differential medium for the growth of staphylococci. The high salt concentration of this medium inhibits the growth of most bacteria, while the staph grow uninhibited. As the mannitol is fermented the pH of the medium is lowered and the medium turns yellow, which is typical of Staphylococcus aureus, (and under heavy inoculation Enterococcus faecalis), but not Staphylococcus epidermidis.

15

Define Differential medium:

Allows one to distinguish between different types of organisms.

16

Define Subculture:

Picking off one of each type of colony.

17

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Staphylococcus aureus.

Gram-positive cocci occurring in clumps or bunches, and the action of it on mannitol salt agar is yellow.

18

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Staphylococcus epidermidis.

No change in color, but has growth.

19

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Streptococcus pyogenes.

Chains and pairs of gram-positive cocci.

20

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Streptococcus mitis.

gram positive cocci appearing in pairs and chains, but has a lighter color stain

21

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Streptococcus pneumonia.

Gram positive cocci appearing in pairs and chains, but has a darker color stain

22

What organisms are talked about in Bacterial Examination of Water and Submerged Slide Culture lab?

Escherichia coli, Enterococcus faecalis.

23

What media is used in the Bacterial Examination of Water and Submerged Slide Culture lab?

Durham tubes of double strength lactose broth, Durham tubes of single strength lactose broth, EMB agar, Endo agar.

24

Sabouraud dextrose agar:

Allows for the growth of fungi and inhibits most bacteria with its low pH.

25

Selective medium:

Allows for growth of only one type of organism

26

Saprophyte:

fungus that lives on dead or decaying organic matter.

27

State the scientific name of the microbe most commonly associated with dental caries:

Lactobacillus acidophilus

28

Name a medium selective for the growth of the lactobacilli

Synder's test agar

29

Name the acid commonly produced by the lactobacilli

Lactic acid

30

State the relationship between the number of lactobacilli in oral flora and the incidence of dental caries

If the number of lactobacilli is high, then the incidence of dental caries are high as well.

31

What is this part of the mold mycelium?

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Septa

32

What is this part of the mold mycelium?

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Hyphae

33

What is this part of the mold mycelium?

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Reproductive spores

34

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Staphylococcus aureus.

Gram positive cocci occurring in clumps or bunches (beta hemolytic) and the action of it on mannitol salt agar is yellow.

35

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Staphylococcus epidermidis.

Beta hemolytic, gram positive cocci with the action on mannitol salt agar being no change in color, but has growth

36

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Streptococcus pyogenes

Chains and pairs (beta hemolytic) of gram-positive cocci

37

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Streptococcus mitis.

Alpha hemolytic, gram positive cocci appearing in pairs and chains but has a lighter color stain than Streptococcus pneumoniae

38

State the morphology, staining reaction, hemolytic activity and action on mannitol salt agar for Staphylococcus pneumonia.

Is alpha hemolytic, gram positive cocci appearing in pairs and chains and has a darker stain color than streptococcus mitis.

39

Which bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus mitis, Streptococcus (Diplococcus) pneumonia) are able to grow on the MSA plate?

Staphylococcus aureus and Staphylococcus epidermidis

40

What reactions/growth do you expect to see for the organisms used in the Coccal Flora lab?

You should see the darkly staining staphylococci, if it is yellow then you see staphylococcus aureus. if there is no change in the msa plate, you have staphylococcus epidermidis. You can have a mixature of the 2 organisms as well.

41

What organisms are mentioned in the Coccal Flora lab?

Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumonia, Streptococcus mitis and Staphylococcus epidermidis

42

DSLB:

Durham tubes of double strength lactose broth

43

SSLB:

Single strength lactose broth

44

Durham tube:

A regular slip cap culture tube with a serological tube inverted inside. If coliforms are present in the water sample, they will ferment the lactose resulting in gas production.

45

What organisms are mentioned in the Bacterial Examination of Water lab?

Escherichia coli and Enterococcus faecalis

46

EMB agar:

selective stain for Gram-negative bacteria. EMB contains dyes that are toxic for Gram positive bacteria and bile salt which is toxic for Gram negative bacteria other than coliforms.

47

Endo agar:

microbiological growth medium with a faint pink colour. Most gram-negative organisms grow well in this medium, while growth of gram-positive organisms is inhibited.

48

Coliform is:

a gram negative intestinal bacillus, essentially nonpathogenic, facultative anaerobic and capable of fermenting the carbohydrate lactose.

49

Autotroph is:

an organism that can form nutritional organic substances from simple inorganic substances such as carbon dioxide

50

Describe the reaction of E. coli on both EMB and Endo agar.

Escherichia coli was found on the Endo agar plate and it had an abundance of growth. There was growth on the EMB agar plate, but we didn't find any signs of Escherichia coli as there wasn't an abundance of growth.

51

State the results of the bacteriologic examination of water study

That the DSLB tube had a gas pocket, while both SSLB tubes did not have a gas pocket.

52

State the results of the submerged slide culture exercise

We were able to see gram-negative bacillus bacterium on the slide.

53

What is the difference between the presumptive and confirmed test and why do we perform both?

A presumptive test is the results that we assume the result, a confirmed test is the actual result. We do both because the confirmation test cost more than the presumptive test, so we do the presumptive test in order to see if the confirmed test is even needed.

54

What result are we looking for in the Durham tubes?

Gas production

55

Describe the materials and method employed in the bacteriologic examination of water exercise.

1 DSLB 2 SSLB tubes. 1 plate of EMB agar, 1 plate of Endo agar.

After we do the presumed test (seeing if there is gas production in one of the Durham tubes), we do the confirmed test where we streak the plates (EMB & Endo).

56

Describe the materials and methods employed in the submerged slide culture exercise.

1 piece of masking tape (about one foot long), 2 microscope slides, 1 piece of wire about 10 inches long, 2 250 ml beakers, 150 mls of acid-alcohol (pour into one of the beakers).

Dip the slides into the 250ml beaker containing acid-alcohol for 5 minutes. Place the slides in a beaker of distilled water for 4 minutes, then dry with a paper towel. Holding the slides together, make a frame of masking tape all the way around the slides. Leave an exposed surface in the center area of both slides. Tape the wire to one side and bend the other side. Immerse the slide culture with the hook on the edge in the provided, large beaker of stream water.

57

What is the purpose of the submerged slide culture?

To examine the morphologies and the staining reactions of the microbes present.

58

How did we visualize the organisms on the slide for the Bacterial Examination of Water and Submerged Slide Culture?

Wet mount slide and gram stain.

59

Resident microbe:

microbes on the skin of the hands that are normal flora

60

Transient microbes:

microbes on the skin of the hands that are contaminating organisms

61

State the results of the hand scrubbing experiment

For the results of the hand scrubbing experiment, beaker 1 had 646 microbes per ml, beaker 2 had 417 microbes per ml, beaker 3 had 198 microbes per ml, beaker 4 had zero microbes per ml, and beaker 5 had 118 microbes per ml. Beaker 4 didn't have enough microbes in order to be counted which was probably due to the agar being too hot when poured or that the beaker wasn't stirred enough. This experiment showed how even though a person washes their hands effectively, they can still have microbes on them.

62

What was the media used for the Microbiological Reduction by Hand washing experiment?

Veal infusion agar

63

Veal infusion agar is:

used for the cultivation of fastidious pathogenic bacteria

64

What organisms are the veal infusion agar selective/differential for?

E. coli

65

Who are the 2 main skin organisms?

Normal flora or contaminating microbes

66

What food did we use in the food lab?

Lettuce

67

What would you expect to find on the lettuce that hadn't been washed yet?

E. coli or salmonella

68

What media did we use in the milk and food experiment?

Tryptone glucose extract agar

69

Tryptone glucose extract agar is:

non-selective medium containing pancreatic digest of casein, beef extract, and glucose, which provide vital amino acids, nitrogen, carbon compounds, carbohydrates, essential minerals, and trace substances to promote the growth of a variety of microorganisms.

70

Would you expect to see a high number or organisms in the milk we use?

No, because it's checked and regulated by the FDA.

71

Tryptone glucose extract agar is used for:

Food, water, and dairy products

72

What reactions/growth do you expect to see for the organisms used in the milk and food experiment?

Milk having none or barely no growth/microorganisms, and food having little growth/colonies.

73

What food processing procedure ensures that the milk will not have a high microbe count?

Pasturizing