E2L12: Control of Micro Org

Question 1

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

Answer 1

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

Question 2

Define “cidal”.

Answer 2

• “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

Question 3

Define “static”.

Answer 3

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

Question 4

Define “inhibitor”.

Answer 4

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

Question 5

Define “ineffective”.

Answer 5

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

Question 6

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

Answer 6

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

Question 7

Name some chemicals for the control of microorg.

Answer 7

Alcohol, bleach, and phenol compounds

Question 8

Alcohol Concentrations that are effective

Answer 8

• 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.

Question 9

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

Answer 9

Takes about 15 minutes to be cidal.

But, alcohol also evaporates quickly, so…

Question 10

What alcohol concentration will be effective against spores?

Answer 10

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

Question 11

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

Answer 11

15 minutes w/o sunscreen.

Question 12

Name some ways of physical methods to control microorg.

Answer 12

Radiation, heat

Question 13

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

Answer 13

• 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.

Question 14

Talk about the effect of time on agent efficacy.

Answer 14

• all methods aren’t instant

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

Question 15

Why don’t we use alcohol to disinfect skin?

Answer 15

• evaporates quickly

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

For every 10C increase, it doubles the RXN rate

Question 18

What is room temperature? Body temperature?

Answer 18

• 25C

- 37C

Question 19

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

Answer 19

You decrease the rate of RXN by half.

Question 20

Talk about Botulism.

Answer 20

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

Question 21

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

Answer 21

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

Question 22

Define “heat labile”.

Answer 22

“Destroyed by heat”

Question 23

Talk about phenols.

Answer 23

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

Question 24

Why is S. aureus so bad?

Answer 24

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

Question 25

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

Answer 25

0.1% / indef. / bacteriostatic 1% / 20-30 min / cidal 5% / 2-3 min / cidal * no higher than 5% b/c caustic

Question 26

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

Answer 26

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

Question 27

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 ```

Answer 27

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

Question 28

Why don't 900,000 die each time?

Answer 28

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

Question 29

What are some ways of reducing the bacterial load?

Answer 29

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

Question 30

Which is more resistant? G+ or G-?

Answer 30

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

Question 31

Which is more resistant? Veggie cells or spores?

Answer 31

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

Question 32

Which lasts longer? HIV/AIDS or Hepatitis B?

Answer 32

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

Question 33

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

Answer 33

1.5 days inside, typ. 6 hrs outside.

Question 34

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

Answer 34

- 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

Question 35

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

Answer 35

- penetration (larger volume, longer; bigger density, longer) - inactivation (inactivate chem) - pH (optimal conditions) - enzymes (breaking down)

Question 36

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

Answer 36

Agar, b/c more dense. | If it doesn't penetrate to the center, it's not completely effective.

Question 37

Define "colloids".

Answer 37

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

Question 38

Give some examples of colloids.

Answer 38

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

Question 39

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

Answer 39

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

Question 40

Talk about colloids and chlorine treatment.

Answer 40

- 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.

Question 41

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

Answer 41

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

Question 42

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

Answer 42

- Halogens (ex: Iodide --> betadine) work best in ACIDIC - -> ppl's skin is ACIDIC - -> BUT! lots of US H2O is ALKALINE

Question 43

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

Answer 43

- 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.

Question 44

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

Answer 44

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

Question 45

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?

Answer 45

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.