Chapter 13-Control microbial growth

Question 1

Controlling microbial growth (PHYSICAL METHODS)

Answer 1

heat, filtration, irradiation, washing

Question 2

Controlling microbial growth (CHEMICAL METHODS)

Answer 2

antimicrobials chemicals

Question 3

Biosafety levels

Answer 3

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)

Question 4

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

Answer 4

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

Question 5

Fomite

Answer 5

inanimate object used by humans that can transmit microbes

Question 6

What are the most difficult microbes to eliminate?

Answer 6

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)

Question 7

What are the most difficult microbes to eliminate? cont.

Answer 7

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

Question 8

Critical items

Answer 8

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

Question 9

Semi critical items

Answer 9

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

Question 10

Noncritical items

Answer 10

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

Question 11

D value

Answer 11

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

Question 12

Methods of control (1-4)

Answer 12

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”

Question 13

Methods of control 5-8

Answer 13

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

Question 14

Aseptic technique

Answer 14

Prevents contamination on sterile surfaces

Question 15

Sterilization

Answer 15

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

Question 16

Autoclave

Answer 16

-Charles Chamberland
-pressurized steam
-effective against endospores

Question 17

When is sterilization requires?

Answer 17

lab glassware, surgical instruments, canning process

Question 18

Dry Heat

Answer 18

Inceration-bacterial loops
Dry heat ovens- sterilizing glass ware

Question 19

Pasteurization

Answer 19

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

Question 20

Refrigeration/Freezing

Answer 20

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

Question 21

Radiation

Answer 21

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

Question 22

Filtration of air

Answer 22

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

Question 23

Filtration of liquid

Answer 23

Traps microbes on filter for heat sensitive fluids

Question 24

Germicidal chemicals

Answer 24

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)

Question 25

Selecting the appropriate germicidal chemical:

Answer 25

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

Question 26

Alcohols

Answer 26

Kill bacteria, fungi- not endospores
-Denature proteins (inhibiting cell metabolism) disrupt membranes leading to cell lysis
(ex. antiseptic for hands, alcohol pads before vaccine)

Question 27

Aldehydes

Answer 27

Inactivates enzymes and nucleic acids, kills bacteria/fungi, viruses, endospores
(ex. formaldehyde, formalin)

Question 28

Ethylene oxide

Answer 28

Gaseous sterilizing agent-fabric, pillows, pacemakers
-cold sterilization for heat sensitive items

Question 29

Bishiguanides

Answer 29

Antiseptics before surgery (surgeon hand scrub)
(ex. chlorhexidine-common ingredient in skin scream, mouthwash, disinfectant)
-not effective against mycobacterium, non enveloped viruses, spores

Question 30

Halogens

Answer 30

Chlorine, sodium hypochlorite (bleach), iodine, betadine

Question 31

Heavy metals

Answer 31

Kill microbes by binding to proteins which inhibits enzymatic activity
-non specific way of killing bacteria
ex. silver, copper, zinc

Question 32

Phenolic

Answer 32

compound in mouthwashes and throat lozenges, disrupt membrane and denature proteins

Question 33

Why was triclosan banned?

Answer 33

People had same chance of getting sick than with triclosan

Question 34

What are the targets in bacterial cells that are affected by germicidal chemicals?

Answer 34

-Cytoplasmic membrane
-Proteins
-DNA

**Most chemicals denature/inactivate proteins

Question 35

Disk diffusion assay

Answer 35

Testing for the effectiveness of germinal chemicals: ZOI indicates how effective antimicrobial is against microbe