Control of Microbial Growth

Question 1

why should microbial growth be controlled? (3)

Answer 1

• To prevent spread of pathogens and disease in hospitals, nursing homes, medical offices, homes, etc.
• To prevent food contamination and spoilage at home and elsewhere
• To prevent microbial degradation of materials in industry or in homes

Question 2

what does sterile mean?

Answer 2

something is sterile if it is free of all viable microorganisms (by removal or killing)

Question 3

what is sterilization?

Answer 3

process of killing and/or removing all microorganisms in a material or object, including any spores

Question 4

what is disinfection?

Answer 4

the process of decreasing the number of viable microorganisms on an inanimate object/surface to a level that presents a minimum possibility of disease transmission or contamination (99.99 %)

Question 5

what are antisepsis? (3)

Answer 5

• disinfection of living tissues
• antiseptics usually are applied to surface of body, that prevents microorganisms from multiplying; it must not be caustic/toxic to tissues
• can work either by killing or inhibiting their growth or metabolism

Question 6

What is sanitization/sanitizer? (2)

Answer 6

• reduction of microbial population to levels deemed safe (based on public health standards)
• a sanitizer is an agent that kills 99.99% of all microorganisms in contaminated area (mostly used on inanimate objects)

Question 7

what is an antimicrobial agent?

Answer 7

• any physical or chemical agent that either kills microorganisms or inhibits their growth
• specifically, there are antibacterial, antiviral, antifungal, antiprotozoal

Question 8

what does microbiocidal mean

Answer 8

• antimicrobial agent that kills microorganisms

- Specifically it could be bacteriocidal, viricidal, fungicidal

Question 9

what does microbiostatic mean?

Answer 9

• antimicrobial agent that inhibits the growth of microorganisms
• specifically it could be bacteriostatic, viristatic, fungistatic

Question 10

slides 6 and 7

Answer 10

take a look

Question 11

death for microorganisms=………

Answer 11

inability to reproduce (loss of ability to reproduce)

Question 12

different antimicrobial agents can act in different ways to kill or inhibit. List these different ways (5)

Answer 12

1.) alter physical state of cytoplasm –i.e., damage
2.) ribosomes (cells)
inactivate enzymes – destroy proteins (cells and viruses)
3.) disrupt cell membrane (CM) (cells)
-alter CM permeability
-lyse CM
-affect transport
4.) disrupt cell wall –> lysis (cells)
5.) destroy or damage DNA or damage DNA or RNA (cells and viruses)

Question 13

are microorganisms killed instantly?

Answer 13

no

Question 14

Population death usually occurs _____

Answer 14

exponentially

Question 15

measure of agents killing efficiency is done by…

Answer 15

-decimal reduction time – time to kill 90%
-must be sure persister cells (viable but nonculturable (VBNC) condition) are dead
once they recover they may regain the ability to reproduce and cause infection
(slides 9-11)

Question 16

what are some Conditions Influencing the Effectiveness of Antimicrobial Agent Activity? (5 things; describe them)

Answer 16

1. ) Population size
   - larger populations take longer to kill than smaller populations
2. ) Population composition
   - microorganisms differ markedly in their sensitivity to antimicrobial agents
3. ) Concentration or intensity of an antimicrobial agent
   - usually higher concentrations or intensities kill more rapidly
   - but relationship is not linear
4. ) Duration of exposure
   - longer exposure –>more organisms killed
5. ) Local environment
   - many factors (e.g., pH, viscosity, and concentration of organic matter) can profoundly impact effectiveness
   - organisms in biofilms are physiologically altered and less susceptible to many antimicrobial agents

Question 17

what are the physical methods for controlling microbial growth?

Answer 17

slides 16 and 17

Question 18

describe moist heat (2)

Answer 18

-Destroys viruses, fungi, and bacteria
-Degrades nucleic acids, denatures proteins, and disrupts membranes
(chart on slide 18)

Question 19

describe Steam Sterilization (4)

Answer 19

• Carried out above 100oC which requires saturated steam under pressure
• Uses an autoclave
• Effective against all types of microorganisms (including spores!)
• Quality control - includes strips with Geobacillus stearothermophilus

Question 20

slides 20 and 21

Answer 20

too hard to make into a card but know this stuff

Question 21

what is filtration?

what are filters normally made of?

Answer 21

• pass liquid or gas through screen-like subs w/pores small enough to retain microbes, but let gas or liquid pass thru-filter out bacteria, fungi (0.44 µM or 0.22 µM pore size)
• usually use cellulose or nitrocellulose membrane filters, aka membrane filters for liquids
• other filters, sterilize air -> HEPA (high effiiciency particulate air)

Question 22

why is filtration used?

Answer 22

-used to sterilize heat sensitive liquids or gasses which cannot be autoclaved (ie, certain medias, enzymes, antibiotics

Question 23

what are membrane filters?

Answer 23

porous membranes with defined pore sizes that remove microorganisms primarily by physical screening
(slides 23-26)

Question 24

what are some ways we filter the air? (3)

Answer 24

-Surgical masks
-Cotton plugs on culture vessels
-High-efficiency particulate air (HEPA) filters
(used in laminar flow biological safety cabinets)

Question 25

describe ionizing radiation

Answer 25

-destroys bacterial endospores
-Gamma irradiation, X-irradiation and electron beams - high energy and cause the production of ions in water (ie, -OH) and other materials
-Ionizing radiation can sterilize (at high doses) or disinfect at lower doses
-damages and denature proteins and DNA
-Ionizing radiation can penetrate packaging; used to sterilize sealed medical equipment, food, and other things that can’t get hot or wet (ie, autoclaved)
(slides 28-30)

Question 26

describe nonionizing radiation (4)

Answer 26

-Ultraviolet radiation – lower in energy, does not produce ions; can’t penetrate packaging, can’t penetrate into spores; it does kill vegetative cells (260 nm damages DNA primarily)
-Best considered a type of disinfection; UV is useful in decontamination of surfaces
-Cannot penetrate solid, opaque, or light-absorbing surfaces
-Has been used for water treatment
(slides 32)

Question 27

what is dessication?

Answer 27

remove H2O from microorganisms: drying vegetative cells stops metabolic activity

Question 28

what are some examples of dessication?

Answer 28

1.) used to preserve some foods, chemicalss
2.)dry fruits, beef jerkey, bread, dry grains to preserve
2.) diff. microbes can survive for diff times after dessication
ie, Neisseria gonorrhoeae die w/in min after dessication
-Mycobac.tuberculosis -viable for hours or even days
-endospores viable indefinately

Question 29

what is Lyophilization?

Answer 29

(freeze-drying) – dry out material with vacuum at same time lowering the temperature below freezing – for foods, cell lines
-form of dessication

Question 30

what are 2 other forms of dessication not discussed already? describe them

Answer 30

1. ) High salt or sugar –hypertonic environment dessicates microorganisms
   ie: jelly, jam, salted fish
2. ) Smoking (cooking) – heat, drying plus toxic combustion products

Question 31

slides 36-39

Answer 31

look over 36 for sure

Question 32

describe phenolics (6)

Answer 32

-Derived from phenol (first disinfectant)
-Commonly used as laboratory and hospital disinfectants
-Denature proteins and disrupt cell membranes
-Effective in presence of organic material, and long lasting
-Disagreeable odor and can cause skin irritation
-Triclosan is used in hand sanitizers
(slide 40 for picture)

Question 33

describe alcohols

Answer 33

(slides 41 and 42)

Question 34

Halogens are any of these 5 elements

Answer 34

fluorine, chlorine, bromine, iodine, and astatine

**they are important antimicrobial agents