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Microbiology > E2L12: Control of Micro Org > Flashcards

E2L12: Control of Micro Org Flashcards

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1
Q

At what point during a bacterium’s life cycle are penicillins and cephalosporins most effective?

A

Since they work on cell wall synthesis, penicillins and cephalosporins are most effective during the log growth phase.

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2
Q

Define “cidal”.

A
  • “Kills”
  • best option –> everything DIES, MWUAHAHA
  • esp. good for immunocompromised (includes: diabetes, cancer, organ transplant recipients, AIDS patients, etc)
  • have 100 cells, all 100 die
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3
Q

Define “static”.

A
  • Does NOT kill, Does STOP growth
  • rate of bacterial growth is stopped
  • if you have competent immune system, gives you time to fight infection
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4
Q

Define “inhibitor”.

A
  • Does NOT kill, Does NOT stop growth
  • -> SLOWS GROWTH DOWN
  • gives time for competent immune system to work
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5
Q

Define “ineffective”.

A
  • Doesn’t work at all, lmao
  • all org. survive and multiply at normal rate
  • -> ex: alcohol, can’t destroy spores –> ineffective
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6
Q

What are some factors that affect the efficacy of the disinfectant/sterilant agent?

A

a) Amount
- -> chemical: concentration (typ. more is better)
- -> physical: intensity (more is better)
b) Time
- -> the longer, the better
c) Temperature
- -> incr. temp., incr. efficacy

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7
Q

Name some chemicals for the control of microorg.

A

Alcohol, bleach, and phenol compounds

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8
Q

Alcohol Concentrations that are effective

A
  • Rubbing alcohol (70%), either ethanol/isopropyl
  • Hand sanitizers (65%)
  • Lab (80-95%, depending on dilution)
  • 100% is NOT effective, b/c still need H2O in order to be effective (precipatate proteins), even on veggie cells
  • As long as below 95% alcohol, [high] = better, [low] = ineffective.
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9
Q

How long does it take for alcohol to be effective against veggie cells?

A

Takes about 15 minutes to be cidal.

But, alcohol also evaporates quickly, so…

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10
Q

What alcohol concentration will be effective against spores?

A

TRICK QUESTION: NONE, ALCOHOL WILL NEVER BE KILL SPORES, CAN NEVER BE A STERILANT!!!

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11
Q

What’s the recommended time to be out in the sun w/o any protection?

A

15 minutes w/o sunscreen.

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12
Q

Name some ways of physical methods to control microorg.

A

Radiation, heat

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13
Q

An example of radiation includes microwaves, talk about the intensity required.

A
  • Microwaves from the sun aren’t intense enough to do anything to you.
  • If can incr. intensity (like, in a microwave oven), then will be effective.
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14
Q

Talk about the effect of time on agent efficacy.

A
  • all methods aren’t instant

- this can be seen when looking at growth curve –> log death phase doesn’t drop straight down

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15
Q

Why don’t we use alcohol to disinfect skin?

A
  • evaporates quickly

- chlorhexidine is now recommended by the CDC since it stays on longer, but more $$$

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16
Q

How long is an autoclave cycle? At what temperature? Does it disinfect or sterilize?

A
  • 15 minutes, but lab will run it for 20 min for safety
  • 121.5 C
  • Sterilizes
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17
Q

What is the correlation between temperature and the rate of reaction?

A

For every 10C increase, it doubles the RXN rate

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18
Q

What is room temperature? Body temperature?

A
  • 25C

- 37C

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19
Q

What happens to the reaction rate if the temperature goes down by 10C?

A

You decrease the rate of RXN by half.

20
Q

Talk about Botulism.

A
  • cause: Clostridium botulinum
  • typ. food poisoning from damaged canned foods
  • G+, spore producing, bacillus
  • kill with high temp, the better
21
Q

List the 5 temperatures discussed in class, how long it takes to kill spores, and effectiveness on spores. (Chart)

A 
100C / 5-9 hrs / ineff.
113C / 1 hr / sporicidal
116C / 30 min / sporicidal
121.5C / 15 min / sporicidal
135C / 3 min / sporicidal
22
Q

Define “heat labile”.

A

“Destroyed by heat”

23
Q

Talk about phenols.

A
  • better than alcohols, but not perfect
  • > 5% [phenol] = caustic (burns)
  • was really good for Staph. aureus that everything else was compared to it
24
Q

Why is S. aureus so bad?

A
  • found on yo skin, in nose
  • staph infections can be worse than your original reason for coming to hospital
  • can contaminate needles during injections
25
Q

List the 3 phenol concentrations, their times at RT, and their effect on bacteria. (Chart)

A

0.1% / indef. / bacteriostatic
1% / 20-30 min / cidal
5% / 2-3 min / cidal

  • no higher than 5% b/c caustic
26
Q

What are some factors pertaining to the organism itself that affect the ability to control the microorg?

A
  • load (# of cells)
  • kind of org
  • -> G- vs G+
  • -> Veggies vs Spores
  • -> Viruses
  • age of org
27
Q

How many org. die during a single time interval?

time / # viable cells (log) / deaths/unit / total deaths
0 / 10^6 / 0 / 0
2 / 10^5 / 900,000 / 900,000
4 / 10^4 / 90,000 / 990,000
6 / 10^3 / 9,000 / 999,000
8 / 10^2 / 900 / 999,900
10 / 10^1 / 90 / 999,990
12 / 10^0 = 1 / 9 / 999,999
15 / 0 / 1 / 100,000
A

Since it’s a log scale, every time interval is has 1 log, which means 90% death occurs.

28
Q

Why don’t 900,000 die each time?

A

The dead shield and protect the lives ones, basically a physical barrier. The higher the load, the longer it takes to kill.

29
Q

What are some ways of reducing the bacterial load?

A
  • scrub/wash
  • remove some bacteria
  • -> disinfection will be more effective if load is reduced 1st
30
Q

Which is more resistant? G+ or G-?

A

G-, b/c of the outer membrane component of their cell wall.

31
Q

Which is more resistant? Veggie cells or spores?

A

Spores, you need 121.5C for 15 min. Veggies, on the other hand, only require 100C for 15 minutes.

32
Q

Which lasts longer? HIV/AIDS or Hepatitis B?

A

Hep B!!! Can last up to 1 WEEK on a surface, even if blood dries up.

33
Q

How long can AIDS survive inside a cell? Outside a cell?

A

1.5 days inside, typ. 6 hrs outside.

34
Q

Compare/contrast young, mature, and old bacteria susceptibility.

A
  • stationary phase (mature) most resistant b/c slow metabolism and cell wall already
  • log growth (young) most susceptible, penicillin/cephalosporins work best at this time to prevent cell wall formation
  • log death (old) susceptible b/c already damaged from their own toxins
35
Q

What are some factors pertaining to the nature of the environment that affect the ability to control microorg?

A
  • penetration (larger volume, longer; bigger density, longer)
  • inactivation (inactivate chem)
  • pH (optimal conditions)
  • enzymes (breaking down)
36
Q

Density affects penetration. Which is more difficult to penetrate? Broth or agar?

A

Agar, b/c more dense.

If it doesn’t penetrate to the center, it’s not completely effective.

37
Q

Define “colloids”.

A

Any particles that are too large to dissolve, but small enough to remain suspended, can inactivate chemicals.

ex: NOT salt/sugar –> they dissolve
ex: bacteria –> yes, b/c they don’t dissolve –> cloudy

38
Q

Give some examples of colloids.

A

Bacteria, blood (RBC, WBC, platelets), feces, vomit (particles and liquid)

39
Q

What is normally done first when there’s a blood or vomit spill?

A

Typ. mopped up 1st, and disposed in biohazard bucket to reduce load b4 mopping

40
Q

Talk about colloids and chlorine treatment.

A
  • common way of treating H2O
  • if Cl- attach to bacteria, kills it
  • if Cl- attach to pOOP, nope –> inactivated
  • [chlorine] has to be high enough to get residual effect of 0.5-1ppm.
41
Q

If Cl- binds to feces, does it kill bacteria?

A

No! That’s why you make sure you add enough to attach to all bacteria as well as fecal matter.

42
Q

Why is pH important to consider in the control of microorg?

A
  • Halogens (ex: Iodide –> betadine) work best in ACIDIC
  • -> ppl’s skin is ACIDIC
  • -> BUT! lots of US H2O is ALKALINE
43
Q

How are enzymes important to consider in the control of microorg?

A
  • Enzymes break down antibiotics
  • -> ex: the kidney’s renal dipeptidases break down most carbapenems (type of antibiotic), so something extra must be added to slow down the carbapenem break down.
44
Q

If something kills all the bacteria within 15 minutes, if you leave it longer, will it matter?

A

No, it won’t matter because everything’s dead at that point. However, 6 min better > 4 min, 4 min better > 2 min, etc.

45
Q

Suppose you have 100ml of blood on the counter top. Then, you add 100ml of 70% alcohol on top of the blood. What is the [alcohol] now and why does it matter?

A

At that point, the [alcohol] would be 35% which would be ineffective. This is why it’s still important to test the various concentrations and their corresponding efficacies.

Microbiology (9 decks)

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