Chapter 13-Control microbial growth Flashcards

1
Q

Controlling microbial growth (PHYSICAL METHODS)

A

heat, filtration, irradiation, washing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Controlling microbial growth (CHEMICAL METHODS)

A

antimicrobials chemicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Biosafety levels

A

BSL 4-microbes dangerous and exotic posing high risk (frequently fatal)
BSL 3-microbes are indigenous and exotic and cause serious or potentially lethal diseases
BSL 2-microbes are indigenous and have varying severity (moderate risk)
BSL 1-microbes are not known to cause disease (minimal risk)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the factors that influence the level of control needed?

A

Identify the situation:
daily life, hospitals, microbiology labs, various industrious

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Fomite

A

inanimate object used by humans that can transmit microbes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the most difficult microbes to eliminate?

A

1-Bacterial endospores: resistant to heat, drying, some chemicals (ex. clostridium botulinum)
2-Protozoan cysts and oocytes: survives harsh conditions, excreted in feces (ex. giardia)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the most difficult microbes to eliminate? cont.

A

3-Mycobacterium species: cell wall structure initiates resistance, contains mycolic acid=more resistance, waxy lipid
4-Pseudomonas species: can grow in presence of many chemical disinfectants, has many R plasmids
5-Naked viruses: lack envelope, resistant to chemical killing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Critical items

A

MUST BE STERILE: used inside body, penetrate tissue (ex. surgical instruments, catheters, IV fluids)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Semi critical items

A

Contacts mucous me membrane, nonintact skin, doesn’t penetrate body tissues, sterile but not penetrating (ex. GI scopes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Noncritical items

A

contacts unbroken skin; must be clean (ex.bed linens, furniture, stethoscope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

D value

A

time required to reduce population of microbes by 90% (larger starting population will take longer to eradicate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Methods of control (1-4)

A

1.Sterilization: eliminates all forms of life
2.Disinfection:inactivated most microbes on fomite surface using antimicrobial chemicals or heat
3.Pasteurization: reduces # of spoilage organisms and pathogens
4.Decontamination: rescues pathogens to a level considered “safe”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Methods of control 5-8

A

5.Sanitation: reduces microbial populations to acceptable levels for public health
6.Degerming: significantly reduce microbial numbers (hand washing)
7.Antiseptic: antimicrobial chemical safe for use on skin (hydrogen peroxide, alcohol)
8.Preservation: slows/inhibits growth of microbes in food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Aseptic technique

A

Prevents contamination on sterile surfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Sterilization

A

complete removal/ killing of all vegetative cells, endospores, and viruses from target item or environment
-physical (heat) or chemical (chemicals that achieve sterilization) means
-labs, medical, food industry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Autoclave

A

-Charles Chamberland
-pressurized steam
-effective against endospores

17
Q

When is sterilization requires?

A

lab glassware, surgical instruments, canning process

18
Q

Dry Heat

A

Inceration-bacterial loops
Dry heat ovens- sterilizing glass ware

19
Q

Pasteurization

A

Kills pathogens and reduce number of spoilage causing microbes while maintaining food quality
-HTST: high temperature short time 72°C for 15 seconds
-UHT: ultra high temperature 138°C for 2 sec

20
Q

Refrigeration/Freezing

A

-slows metabolism of bacteria
-does not sterilize foods but can decrease- some microbes live in these conditions

21
Q

Radiation

A

Causes damage to DNA and potentially plasma membranes-inhibits replication, some endospores can be resistant

22
Q

Filtration of air

A

HEPA filter removes nearly all microbes from air (bacteria will get trapped)

23
Q

Filtration of liquid

A

Traps microbes on filter for heat sensitive fluids

24
Q

Germicidal chemicals

A

Sterilants: treat heat sensitive critical instruments
High level disinfectants: treat semi critical instruments (GI scopes)
Intermediate level disinfectants: disinfect non critical instruments (stethoscopes)
low level disinfectants:general purpose (floors,walls)

25
Selecting the appropriate germicidal chemical:
Toxic- How toxic is the chemical Presence of organic matter Compatibility with material being treated-tile/fabric Residue Cost and availability Ease of use Storage/stability-shelf stable Environmental risk-Where to dump
26
Alcohols
Kill bacteria, fungi- not endospores -Denature proteins (inhibiting cell metabolism) disrupt membranes leading to cell lysis (ex. antiseptic for hands, alcohol pads before vaccine)
27
Aldehydes
Inactivates enzymes and nucleic acids, kills bacteria/fungi, viruses, endospores (ex. formaldehyde, formalin)
28
Ethylene oxide
Gaseous sterilizing agent-fabric, pillows, pacemakers -cold sterilization for heat sensitive items
29
Bishiguanides
Antiseptics before surgery (surgeon hand scrub) (ex. chlorhexidine-common ingredient in skin scream, mouthwash, disinfectant) -not effective against mycobacterium, non enveloped viruses, spores
30
Halogens
Chlorine, sodium hypochlorite (bleach), iodine, betadine
31
Heavy metals
Kill microbes by binding to proteins which inhibits enzymatic activity -non specific way of killing bacteria ex. silver, copper, zinc
32
Phenolic
compound in mouthwashes and throat lozenges, disrupt membrane and denature proteins
33
Why was triclosan banned?
People had same chance of getting sick than with triclosan
34
What are the targets in bacterial cells that are affected by germicidal chemicals?
-Cytoplasmic membrane -Proteins -DNA **Most chemicals denature/inactivate proteins
35
Disk diffusion assay
Testing for the effectiveness of germinal chemicals: ZOI indicates how effective antimicrobial is against microbe