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Microbio Lab > Lab Review > Flashcards

Lab Review Flashcards

1
Q

3 general methods to kill germs

A 
1 physical (heat, radiation)
2 chem (alcohol, bleach)
3 bio (antibiotics, phage)
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2
Q

which structure is mostly damaged by UV light

A

DNA

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3
Q

What type of lesion UV makes in the DNA of bacteria and what does it lead to?

A

thymine dimers which leads to mutation in DNA

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4
Q

What is the most lethal form of UV light and what is its wavelength?

A

UV-C (100-280 nm wavelength)

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5
Q

Indicate the wavelength of UV light emitted by germicidal lamp.

A

254 nm

used for sterilization of air, surfaces, water, operating rooms

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6
Q

definition of antibiotic

A

a type of antimicrobial agent that is made by a microorganism and kills or inhibit other microorganisms

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7
Q

How is the efficacy of antibiotics measured?

A

Kirby-Bauer method

-tests the sensitivity of bacteria to antibiotics.

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8
Q

type of agar used for Kirby-Bauer test

A

Muller-Hinton agar

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9
Q

most appropriate way of washing hands to remove germs property

A

Warm water and soap for 20 seconds

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10
Q

Mannitol Salt agar (MSA) is example of what type of medium

A

Selective & differential medium

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11
Q

What component of the Mannitol salt agar (MSA) makes it selective

A

7.5% salt which is much higher salt concentration

normal saline is 0.9% salt

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12
Q

type of bacteria that grow on MSA

A

Gram-positives

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13
Q

What component of MSA makes it differential and what 2 groups of bacteria get differentiated

A

Mannitol (sugar alcohol) for GRAM POS

differentiates mannitol fermenters(phenol Red to yellow)

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14
Q

staphylococci changed the color of MSA to yellow

A

Staph aureus changed the color to yellow

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15
Q

Where do S. aureus and S. epidermidis found in human

A

S. epidermidis is found on the skin of 100% human population

S. aureus is found in about 25% of human population around nares (it prefers moist surfaces)

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16
Q

Eosin Methylene Blue (EMB) is example of what type of medium

A

Selective & differential

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17
Q

component of EMB makes it selective

A

Eosin and Methylene blue dyes

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18
Q

type of bacteria grow on EMB

A

Gram-negative

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19
Q

component of EMB makes it differential and what 2 groups of Gram-negative bacteria get differentiated

A

The sugar lactose which allows for differentiation between non-lactose fermenters, and heavy lactose fermenters (E. Coli)

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20
Q

What is EMB used for mostly in diagnostic laboratories

A

For detection of fecal coliforms, specifically E. Coli

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21
Q

coliform bacteria

A

bacteria that live in the environment of the intestine of many animals and humans.

Fecal coliforms such as E. Coli live primarily within intestine of all warm- and cold-blooded animals.

22
Q

What does presence of E. coli in water or food is indication of

A

fecal contamination

23
Q

What type of colonies E. coli makes on EMB and why

A

Dark green sheen colonies because E. coli is a rapid lactose fermenter

24
Q

typhoid pathogen

A

salmonella typhi

25
Q

How is Hydrogen peroxide (H2O2) is produced in bacterial cells and how does it damage the bacteria

A

H2O2 is produced by the electron transport chain during the reduction of oxygen by oxidases that reduce oxygen to for
m H2O2. It is considered a Reactive Oxygen Species (ROS) which can damage bacterial DNA, RNA, and proteins.

26
Q

reactive oxygen species (ROS) and what type of biological molecules are damaged by it

A

Also called oxygen radicals or free radicals, ROS are types of unstable molecules that contain oxygen and can easily react with other molecules in a cell. A buildup of ROS in cells may cause damage to DNA, RNA, and proteins, and may cause cell death.

27
Q

Which enzyme neutralizes H2O2. Show the reaction

A

catalase

2 H2O2 > 2 H2O + O2

28
Q

test result indicates that the organism is catalase positive

A

Generation of gas bubbles is indicative of organism being catalase

29
Q

catalase positive bacteria

A

STAPHYLOCOCCI

30
Q

function of cytochrome oxidase in bacteria

A

It is the final enzyme of electron transport chain that reduces oxygen to form H2O

31
Q

purpose of oxidase test in bacteria

A

To see if the bacterium has cytochrome oxidase in its electron transport chain

32
Q

What color does oxidase agent turns to if bacterium has cytochrome oxidase

A

DARK BLUE/PURPLE

33
Q

Which category of bacteria can be distinguished using oxidase test

A

Gram-negative rods such as pseudomonas aeruginosa

34
Q

serum

A

liquid part of the blood after it clots

35
Q

serological testing

A

using serum to specifically detect antigens or antibodies in patient’s serum

36
Q

What component of serum is commonly used in serological testing

A

antibodies

37
Q

ELISA

A

Enzyme Linked immunosorbent assay. It is a very commonly used test to use the specificity of antibodies to detect the antigen in laboratory.

38
Q

direct an indirect ELISA

A

Direct ELISA detects antigens in the patient’s serum, but Indirect ELISA detects antibodies in the patient’s serum

39
Q

INDIRECT ELISA steps

A

1 antigen of interest
2 antibody fr patient’s serum
3 antihuman antibody w colorgenic enzyme

40
Q

DIRECT ELISA

A

1 antibody
2 antigen fr patients serum
3 same antibody w colorgenic enzyme

41
Q

titer

A

measurement of how much antibody an organism has produced that recognizes a particular antigen.

42
Q

indirect elisa example

A

HIV test

43
Q

direct elisa example

A

pregnancy test for HCG hormone(antigen)

44
Q

What is the purpose of standard plate count

A

The method is used around the world for estimation of the number of live microbes in a sample which is called Colony Forming Units (CFU)

45
Q

How is the standard plate count is performed

A

First, a serial dilution of the sample is made and from each dilution, an aliquot is transferred onto agar plates and after 24 hours of incubation, the number of colonies (CFU) in each plate is counted and the number of bacteria in the original sample can be calculated by multiplying the number of colonies of the plate by the dilution factor

46
Q

Plates containing how many colonies (CFU) are the most appropriate ones for calculation of number of bacteria in the sample

A

30-300 colonies

47
Q

epidemiology

A

study of causes, distribution, + disease in population

48
Q

outbreak

A

sudden + unexpected start of an infectious disease in an area

49
Q

3 ways food can be contaminated by harmful microbes

A

1 improper processing
2 improper storage/transport
3 improper preparation + handling

50
Q

tolerable amt of microbes in milk

A

300,000

Microbio Lab (3 decks)

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