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Bacteriology/ Mycology > Identification, Disinfection > Flashcards

Identification, Disinfection Flashcards

1
Q

When you see a bacterial result that says 1+ what does that mean?

A

1+ means it grew in the 1st column only

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2
Q

When you see a bacterial result that says 4+ what does that mean?

A

4+ means it grew in all four quadrants.

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3
Q

What is Macconkeys agar usually used for? What is a common Macconkeys used?

A

Used more for hearty/ enteric bacteria.
Common is blood macconkeys.

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4
Q

On a Macconkys agar, what does a red colony indicate?

A

Bacteria is a Lactose utilizers

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5
Q

On a Macconkys agar, what does a white colony indicate?

A

The bacteria are lactose non- utilizers

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6
Q

Why is this image have pink leaking out past where the colonies are present? What is the likely bacteria growing on this plate?

A

Ecoli produces so much acid, even the non inoculated areas are turning red. This is how you can tell its ecoli on this plate

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7
Q

What bacteria will not grow on MacConkeys Agar Plates?

A

Gram positives will not, this plate is selective against gram positive bacteria. It also differentiates lactose utilizers.

Some gram negatives also wont grow here, like respiratory bacteria.

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8
Q

What are some characteristics of Surface colonies on agar plates?

A
  • Surface
  • Whole colony
  • Elevation
  • Margin
  • Size
  • Color
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9
Q

What are some terms used to describe the Surface of colonies on agar plates?

A

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

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10
Q

What are some terms used to describe the whole colony on agar plates?

A

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

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11
Q

What are some terms used to describe the elevation of a colony on agar plates?

A

Elevation: flat; raised; convex; pulvinate, umbonate

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12
Q

What are some terms used to describe the margins of colonies on agar plates?

A

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

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13
Q

What are some terms used to describe the size of colonies on agar plates?

A

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

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14
Q

What are some terms used to describe the color of colonies on agar plates?

A

Color: pigmentation;
e.g. Staphylcoccus aur

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15
Q

How can you identify spores in gram stains?

A

(refractile to Gram stain —> colorless hole in cell

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16
Q

What color will gram positive bacteria stain in gram staining? Why?

A

Gram-positive bacteria have a thick
peptidoglycan cell wall and appear blue/violet

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17
Q

What color will gram negative bacteria stain in gram staining? Why?

A

Gram-negative bacteria have a thin
peptidoglycan wall, but have a –lipid-rich outer membrane, and appear red after Gram staining.

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18
Q

What are the two motility tests that can be done for bacteria?

A
  1. Wet mount: direct microscopic observation
  2. Motility culture medium: soft agar stab
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19
Q

What is an example of a bacterial serological test?

A
  • Slide agglutination: simple, inexpensive
  • ELISA, counterimmunoelectrophoresis: complex, expensive
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20
Q

What would be a reason to use a serology over a plated culture?

A

Some can’t be isolated on media ( I.e rickettsia) so you can test serology

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21
Q

How are amino acids catabolized following hydrolysis?

A
  1. ) Deamination- Deaminase
  2. ) Desulfurylation- Desulfurylase
  3. ) Decarboxylation- Decarboxylase
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22
Q

How can a researcher obtain a sample that is an isolation of a homogenous culture?

A
  • Pure culture techniques; streak and pour plates
  • Use of selective and differential culture media
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23
Q

What metabolic by products create unique biochemical footprints?

A
  • Carbohydrate utilization
  • Protein degradation
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24
Q

What is decontamination?

A

• Decontamination: A reduction in potentially pathogenic organisms to a level that is safe to handle.

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25
Q

What is disinfection?

A

• Disinfection: Eliminate most if not all pathogenic organisms. Clean after

26
Q

What is sterilization?

A

• Sterilization: Elimination of all living organisms

27
Q

Why is mycobacteria so resistant?

A

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

28
Q

How does moist heat help to kill bacteria?

A

Moist heat denatures proteins and if proteins dont work bacteria dies

29
Q

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

A
  • Good for metal objects
  • Contents under pressure
  • No plastic
30
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.

31
Q

What are the limitations to sterilization with dry heat?

A

Limited to inanimate objects/ heat resistant objects

32
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

33
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

34
Q

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

A

Interact 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

35
Q

What does HEPA filters filter up to? What percent of particles is this? Where can you find them?

A

• HEPA = high . . . .
efficiency particulate air filter = 99.999% of 0.12 micron particles
• face masks, sterile hoods, room air filters

36
Q

What are alkaylating agents? What can it be used to sterilize?

A

Alkylating agents - gaseous and liquids

Alkylating agents - gaseous and liquids
• formaldehyde (formalin), glutaraldehyde, ethylene oxide
• extremely reactive with carboxyl, hydroxyl and sulfhydryl groups of proteins

sterilizing research or hospital equipment that
is sensitive to heat: plastic syringes, equipment

37
Q

What is sonification? Is sonification common?

A

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

38
Q

What are the physical means of disinfection?

A

Physical means include temperature, radiation, filtration &
sonication.

39
Q

Why does an autoclave sterilize efficiently?

A

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

40
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.

41
Q

What is the definition of cleaning?

A

• Cleaning-removal of foreign material

42
Q

What is MEC?

A

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

43
Q

What is a low level disinfectant?

A

• Low-level disinfectant-germicide that kills
most vegetative bacteria and lipid-enveloped and
medium size viruses.

44
Q

What is an intermediate level disinfectant?

A

Intermediate level disinfectant-kills all
microbial pathogens except spores

45
Q

What is a high level disinfectant?

A

High level disinfectant-kills all microbial
pathogens except large number of bacterial spor

46
Q

Which bacteria is the most susceptible to disinfectants? Which is the least? What is the order?

A

Disinfectants have a gradient of microbial activity.
• Gram positive < Gram Negative < Acid Fast < Spore Formers

47
Q

What is QAC?

A

• QAC (Quantitiative Ammonium Compounds) Most common used in hosptial.

48
Q

Which is the more resistant bacteria, gram + or gram -? What is the most resistant?

A
  • Gram negatives are more resistance than gram positives.
  • Spore formers are the most resistant,
49
Q

Spore former B subtilis is alot less resistant than many other bacteria? Why is this?

THIS IS AN FYI NOT GOING TO BE TESTED

A

• B subtilis -> is easy to kill in vegetative state. Even though it is a spore former (FYI)

50
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.

51
Q

What pH’s will kill cells? How do alkalies work?

A

extremely high or low pH will kill cells

  • destroys cell walls and cell membranes
  • used on inanimate objects not sensitive to alkaline pH
52
Q

What is mercurochrome? How do heavy metal disinfectants work?

A

metals poison enzyme activities by interacting
with sulfhydryl groups of cysteine residues.

• the basis for merthiolate and mercurochrome used
as skin antiseptics; “burns” open tissue as it is
solubilized in alcohol !!!
• Mercurochrome was used as skin antiseptic but it burns open tissue and is not safe. This is now known but was not before.

53
Q

What is an example of a oxidizing agent? how does it work? what is a common well known example?

A
  1. Oxidizing agents
    • Halogens - iodine and chlorine
    - inactivate enzymes by converting functional -SH groups to oxidized S-S forms; can attack -NH groups, indole groups and tyrosine residues;
    • Chlorine in a pool.
    • 10% bleach is what is used for pathogen spills in labs.
54
Q

What are examples of surface active agents? How do they work?

A

• anionic agent/ soaps
• Sodium lauryl sulfate
• Cationic agents
• Zephiran
◦ all work the same way, have a hydrophobic tail, is like a glycolipid and a hydrophillic area.
◦ hydrophobic portion penetrates into membrane and disrupts cell integrity

55
Q

What is phenol? Why is it not used anymore? How does it work? What are some newer alternatives?

A

Phenol very effective, since its toxic no longer used
• causes membrane disruption/ protein denaturation
◦ usually mixed with soap to increase penetration
◦ usually not inactivated by organic matter
◦ Lysol is creosol which is safer but still very effective.

56
Q

Why arent aldehydes used anymore? Were they effective? Examples?

A

Very useful, but carcinogenic

Aldehydes-the most commonly used are glutaraldehyde,
ortho-Phthalaldehyde, and formaldehyde

57
Q

What are other disinfectants that are not as effective?

A

Hydrogen peroxide • Peracetic acid • Glucoprotamine • Peroxygen compounds • Superoxidized water

58
Q

Why is hydrogen peroxide not helpful when used with staph?

A

• Staph produces catalase, so it converts H2O2 to CO2 and H2O

59
Q

Finish this sentence: Disinfection refers to the elimination of pathogens usually by ______ _______

A

Chemical means

60
Q

Chemical agents destroy bacteria by? Is resistance to these disinfectants common?

A

• Chemical agents usually lethal to all types of bacteria
- gross metabolic poisons: alter permeability, irreversibly
denature macromolecules

  • seldom does resistance develop
61
Q

What factors influencing the success of disinfectants include…

A

Factors influencing process include: bacterial species, conc.-
time – temperature, competing organic matter

62
Q

What are the major classes of disinfectants?

A

Major classes of disinfectants:

alcohols,

alkalies,

heavy metals,
halogens,

alkylating agents,

surface active agents,

phenolics

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Bacteriology/ Mycology (19 decks)

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