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Bacteriology/Mycology > Lecture 2 - Identification, Disinfection > Flashcards

Lecture 2 - Identification, Disinfection Flashcards

1
Q

What are the two basic types of bacteriological culture medium?

A
  1. Defined/simple (e.g. minimal salts).
  2. Enriched/complex (e.g. nutrient broth).
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2
Q

What is an example of differential media?

A

MacConkey agar, Blood agar

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3
Q

What is an example of selective media?

A

Selenite broth, MacConkey Agar

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4
Q

What is an example of enriched media?

A

Blood agar

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5
Q

What is an example of transport media?

A

Stuart’s media

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6
Q

Describe streaking

A

Go in a clockwise rotation. (quadrant 1-4).
E.g. Ecoli 1+ (only in 1 quadrant), Ecoli 4+ (in all four quadrants).

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7
Q

Will gram positive bacteria grown in MacConkey Agar?

A

No

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8
Q

How can the surface of a colony be described?

A

Surface: smooth & glistening; rough;
granular; wrinkled dry & powdery

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9
Q

How can an entire colony be described?

A

Whole colony: circular, filamentous;
irregular; rhizoid; punctiform

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10
Q

How can the elevation of a colony be described?

A

Elevation: flat; raised; convex;
pulvinate, umbonate

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11
Q

How can the margins of a colony be described?

A

Margin: entire, undulate, curled,
lobate, serrate, filamentous

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12
Q

How can the size of a colony be described?

A

Size: diameter in mm; pinpoint;
small, medium and large

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13
Q

How can the color of a colony be described?

A

Color: pigmentation;
e.g. Staphylcoccus aureus

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14
Q

Decribe the two types of Motility Tests

A
  1. Wet mount: direct
    microscopic observation . to see if it’s motile
    .
    .. … . .. .
    Neg. Pos.
    .
    .
    Nonmotile Motile
  2. Motility culture medium:
    soft agar stab –> if motile it will spread out
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15
Q

Describe the different types of Serological Tests used for Bacterial Identification. Explain the rationale behind these tests

A

Rationale: each species has unique antigenic components , eg.
H- antigens = flagella = protein
O- antigens = LPS = polysaccharides
K- antigens = capsule = polysacch. or protein
• Types of tests:
- Slide agglutination: simple, inexpensive
Used for initial screening of colonies that may be Salmonella
ELISA, counterimmunoelectrophoresis: complex, expensive

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16
Q

Name some common serological assays

A

ELISA, latex agglutination, Western Blotting,
Older assays not commonly used any more

Don’t need to isolate pathogen - can use patient’s serum!
Counter-immunoelectrophoresis, radioimmunoassay,
complement fixation, fluorescent antibody, etc.
ELISA, latex agglutination, Western Blotting,
Older assays not commonly used any more

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17
Q

Detecting Carbohydrate Utilization

A

Medium with a ph indicator
if ph drops, turns medium yellow

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18
Q

How can you differentiate between fermentors and non-fermentors?

A

lactose and sucrose are 10 x the concentration of glucose so it is easy to differentiate fermenters from non-fermenters

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19
Q

Reactions Produced on TSI Medium
Non-fermenters = entire medium stays?

A

red

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20
Q

Reactions Produced on TSI Medium
Non lactose fermentors - stain is what color?

A

if only ferments glucose, not lactose or sucrose, only butt turns yellow b/c not enough acid to turn aerobic area yellow.

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21
Q

Reactions Produced on TSI Medium
Lactose/sucrose fermentors - medium is what color?

A

so muhc acid produced turns eveyrthng yellow.

if too much acid turns butt black

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22
Q

Bromthymol Blue is useful for ?

A

pH indicator in Oxidative phosphorylation medium
ferments = yellow
utilizes amino acids = turns blue
nothing = stays green

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23
Q

Physical Agents
• Temperature: moist, dry, incineration
• Radiation: ultraviolet, gamma, X-rays
• Mechanical: sonication, filtration

A
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24
Q

What is the purpose of Decontamination?

A

Cleaning and any additional steps required to
eliminate risk of infection while handling
devices or attire. A reduction in potentially
pathogenic organisms to a level that is safe to
handle.

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25
Q

What is the purpose of Disinfection?

A

Elimination of most if not all PATHOGENIC
organisms, including spores. Most effective
when preceded by cleaning.

26
Q

What is the purpose of Sterilization

A

Elimination of ALL living organisms

27
Q

What is the purpose of incineration?

A

• Incineration - > 300o C until completely oxidized
- fast, but expensive
- useful in elimination of pathogen contaminated
materials e.g. bandages, carcasses, tissues

28
Q

What is the purpose of Ionizing Radiation (Ozone)?

A

Interact with macromolecules and cause
disruption of covalent bonds!
• Useful in sterilization of inanimate, heat sensitive materials e.g. syringes, catheters O2- . oxygen radical X-rays, gamma-rays OH. hydroxyl radical
Short lived radicals

29
Q

What is the purpose of Liquid Filtration?

A

Choose filter with avg. pore size of 0.2 microns.
• Exclude most bacteria - avg. smallest dimension is 0.5 microns.
• Applications: sterilize liquids which are heat sensitive.

30
Q

What is the purpose of Air Filtration

A

HEPA = high efficiency
particulate air filter = 99.999% of 0.12 micron particles

31
Q

What Chemical Agents can be used?

A

Alkylating agents - gaseous and liquids
• formaldehyde (formalin), glutaraldehyde, ethylene oxide
• extremely reactive with carboxyl, hydroxyl and
sulfhydryl groups of proteins —-> alkylate = addition
of hydroxyl, methyl, or ethyl groups or cross-linking of
reactive groups
• sterilizing research or hospital equipment that is
sensitive to heat: plastic syringes, equipment
O
Protein X
Protein Y

32
Q

What does MEC stand for?

A

MEC-minimum effective concentration of a
germicide required to achieve advertised microbicidal activity.

33
Q

A Low-level disinfectant is a germicide that kills most ________ bacteria and ____-_______ and ______ sized viruses.

A

Germicide that kills most vegetative bacteria and lipid-enveloped and medium size viruses.

34
Q

What is an Intermediate level disinfectant?

A

It kills all
microbial pathogens except spores

35
Q

What is a High level disinfectant?

A

kills all microbial
pathogens except large number of bacterial spores

36
Q

In general, disinfectants have a gradient of microbicidal activity
on bacteria of different cell types:

A

Gram Positive < Gram Negative < Acid Fast < Spore Formers

37
Q

Alcohols, such as ethanol, isopropanol, denature?

A

proteins and solubilize lipids

38
Q

Alkalies - sodium hydroxide, 1-2%; “lyse”
• destroys ?
• used on ?

A

cell walls and cell membranes, inanimate objects not sensitive to alkaline pH

39
Q

Heavy metals - HgCl2 (0.001%), AgNO3, and copper
• metals function to poison ______ activities by interacting with ______ groups of ______ residues.
• the basis for merthiolate and mercurochrome used as
skin antiseptics?

A

enzyme, sulfhydryl, cysteine

“burns” open tissue as it is
solubilized in alcohol !!!

40
Q

Oxidizing agents
• Halogens - iodine and chlorine inactivate enzymes by converting functional ____
groups to oxidized ____ forms; can attack ____ groups, ______ groups and ______ residues;

A

-SH, S-S, -NH, indole, tyrosine

41
Q

Surface active agents - induce a reduction of ______ or
_______ _____ e.g. _______ agents, _______.

A

surface, interfacial tension, wetting, detergents

42
Q

Anionic agents are _____ or ____ acids with a ______ charge

A

soaps, fatty, negative

43
Q

Phenolic compounds, such as ______, _____, and _______, cause membrane ________ and protein _______. Usually mixed with _____ to increase penetration. Not usually inactivated by ______ ______. No longer used because of its ______.

Lysol is _____. ______ is incorporated into soaps, antiperspirants, toothpastes, filters.

A

phenol, creosol, hexachlorophene, disruption, denaturation, soap, organic matter, toxicity, creosol; hexachlorophene

44
Q

Aldehydes: the most commonly used are ?

A

glutaraldehyde,
ortho-Phthalaldehyde, and formaldehyde

FOG

45
Q

Glutaraldehyde is a high level _______ that is compatible
with many materials, and so is the agent of choice for
______ disinfection for ______ materials.

A

disinfectant, chemical, hospital

46
Q

ortho-Phthalaldehyde is a ____% solution for ___ min is a high
level disinfectant, is also compatible with many materials,
is more active that ____ against mycobacteria.

A

0.55, 12, GAH

47
Q

Formaldehyde

A

high level disinfectant used as a liquid or
gas. Not used as commonly as previously due to irritation
and potential carcinogenicity.

48
Q

Why is mycobacteria so resistant?

A

• Mycobacteria -> glycolic acids on the surface make it hearty so it is much more resistant .

49
Q

How does moist heat help to kill bacteria?

A

Moist heat denatures proteins and if proteins dont work bacteria dies

50
Q

What is an autoclave good for? What cannot be autoclaved?

A

• Good for metal objects
• Contents under pressure
• No plastic

51
Q

Which is quicker at disinfection/ sterilization, dry or moist heat? what is the difference in time?

A

Dry Heat 1-2 hours slower than moist heat.

52
Q

What are the limitations to sterilization with dry heat?

A

Limited to inanimate objects/ heat resistant objects

53
Q

What is incineation? What is the benefits/ cons?

A

• Incineration: Until completely oxidized ( > 300 degrees celcius)
◦ Fast but expensive
◦ useful to eliminate pathogen contaminants/ ect.

useful in elimination of pathogen contaminated
materials e.g. bandages, carcasses, tissues

54
Q

What area in the radiant energy spectrum has the best bacterial effect? What is the practical methods of sterilization? Impractical?

A

• < 300 nm large bacterial effect
• UV is practical
• xray/ gamma will work but not practical

> 300 nm - little bacteriocidal effect < 300 nm - large bacteriocidal effect

55
Q

How does ionizing radiation ( ozone) work to kill bacteria? What can it be used for? Is it common?

A

nteract with macromolecules and cause disruption of covalent bonds!
• Useful in sterilization of inanimate, heat sensitive materials e.g. syringes, catheters.
Again, not practical so not used often

56
Q

What is sonification? Is sonification common?

A

Bubbles bombard cells and lyse them. No it is not common

57
Q

What are the physical means of disinfection?

A

Physical means include temperature, radiation, filtration &
sonication.

58
Q

Why does an autoclave sterilize efficiently?

A

• An autoclave sterilizes efficiently because of efficient transfer
of latent heat from water to object.

59
Q

What is the most effective way to clean?

A

Remove organic material first before using antiseptic. Antiseptic wont be very effective if there is organic material present. The organic material will be protective.

60
Q

What % alcohol is effective against strep. pyogenes?

A

100% is not very effective against streptococcus pyogenes.
◦ Lower concentrations are until about 50 %
◦ 60% and 95 % is the optimal concentrations

Bacteriology/Mycology (40 decks)

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