Microbiology Exam Ii/part Ii

Front 1

Physical, chemical, and mechanical methods...

Back 1

To destroy or reduce undesirable microbes in a given area (decontamination)

Front 2

Primary targets are microorganisms capable of causing infection or spoilage, such as...

Back 2

Vegetative bacterial cells and endospores

Protozoan trophozoites and cysts

Fungal hyphae and spores, yeast

Worms

Viruses and prions

Front 3

Sterilization

Back 3

A process that destroys all viable microbes, including viruses and endospores

Front 4

Disinfection

Back 4

A process to destroy vegetative pathogens, not endospores; inanimate objects

Front 5

Antiseptic

Back 5

Chemicals applied directly to exposed body surfaces

Front 6

Sanitation

Back 6

Any cleansing technique that mechanically removes microbes

Front 7

Highest resistance microbes

Back 7

Prions, bacterial endospores

Front 8

Moderate resistance

Back 8

Psudomonas sp.

Mycobacterium tuberculosis

S. aureus

Protozoan cysts

Front 9

Least resistance

Back 9

Most bacterial vegetative cells

Fungal spores and hyphae, yeast

Enveloped viruses

Protozoa trophozoites

Front 10

Microbial death

Back 10

Permanent loss of reproductive capability, even under optimum growth conditions

Front 11

Factors that affect death rate

Back 11

Number of microbes

Composition of microbes in the population

Temp and pHof environment

Concentration or dosage of agent

Mode of action of the agent

Presence of solvents, organic matter, or inhibitors

Front 12

Practical concerns in microbial control

Back 12

Does the application require sterilization?

Is the item to be reused?

Can the item withstand heat, pressure, radiation, or chemical?

Is method suitable?

Will agent penetrate to the necessary extent?

Is the method cost- and labor-efficient and is it safe?

Front 13

Cellular targets of physical and chemical agents

Back 13

Cell wall and cell membrane

Front 14

Cell wall

Back 14

Becomes fragile and cell lyses; some antimicrobial drugs, detergents, and alcohol

Front 15

Cell membrane

Back 15

Loses integrity; detergents or surfactants

Front 16

Cellular targets of physical and chemical agents

Back 16

Protein and NA synthesis: prevention of replication, transcription, translation, peptide bond formation, protein synthesis, chloramphenicol, UV radiation, formaldehyde

Proteins: disrupt or denature proteins, alcohols, phenols, acids, heat

Front 17

Methods of physical control

Back 17

Heat-moist and dry

Cold temperatures

Desiccation

Radiation

Filtration

Front 18

Bacterial endospores are most/least resistant and usually require temperatures above/below boiling

Back 18

Most and above

Front 19

Thermal death time

Back 19

Shortest length of time required to kill all test microbes at a specified temp

Front 20

Thermal death point

Back 20

Lowest temperature required to kill all microbes in a sample in 10 minutes

Front 21

Steam under pressure

Back 21

Sterilization

Front 22

Autoclave

Back 22

15 psi/121C/10-40 minutes

Steam must reach surface of item being sterilized

Item must not be heat or moisture sensitive

Mode of action-denaturation of proteins, destruction of membranes, and DNA

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Tyndallization

Back 23

Intermittent sterilization for substances that cannot withstand autoclaving

Items exposed to free-flowing steam for 30-60 minutes, incubated for 23-24 hours and then subjected to steam again

Repeat cycle for 3 days

Used for some canned foods and lab media

Front 24

Boiling water

Back 24

Boiling at 100C for 30 minutes to destroy non-spore forming pathogens

Disinfection

Front 25

Pasteurization

Back 25

Heat is applied to oil potential agents of infection and spoilage w/o destroying the food flavor or value

63C-66C for 30 minutes

71.6C for 15 seconds

Not sterilization-kills non-spore-forming pathogens and lowers overall microbe count; does not kill endospores or many nonpathogenic microbes

Front 26

Dry heat

Back 26

Using higher temps than moist heat

Front 27

Incineration

Back 27

Flame or electric heating coil

Ignites and reduces microbes and other substaces

Front 28

Dry ovens

Back 28

150-180C

Coagulate proteins

Front 29

Microbiostatic

Back 29

Slows the growth of microbes

Refrigeration 0-15C and freezing 0C

Used to preserve food, media, and cultures

Front 30

Desiccation

Back 30

Gradual removal of water from cells, leads to metabolic inhibition

Not effective microbial control-many cells retain ability to grow when water is reintroduced

Front 31

Lyophilization

Back 31

Freeze drying; preservation

Front 32

Ionizing radiation

Back 32

Deep penetrating power that has sufficient energy to cause electrons to leave their orbit, breaks DNA

Gamma X-rays, cathod rays used to sterilize medical supplies and food products

Front 33

Nonionizing radiation

Back 33

Little penetrating power so it must be directly exposed

UV light creates pyrimidine dimers, which interfere with replication

Front 34

Filtration

Back 34

Physical removal of microbes by passing a gas or liquid through filter

Used to sterilize heat sensitive liquids and air in hospital isolation units and industrial clean rooms

Front 35

Chemical agents in microbial control

Back 35

Disinfectants, antiseptics, sterilants, and preservatives

Front 36

Some desirable qualities of chemicals

Back 36

Rapid action in low concentration

Solubility in water or alcohol, stable

Broad spectrum, low toxicity

Penetrating

Noncorrosive and nonstaining

Affordable and readily available

Front 37

High-level germicides

Back 37

Kill endospores; may be sterilants

Devices that are not heat sterilizable and intended to be used in sterile environments (body tissues)

Front 38

Intermediate-level germicides

Back 38

Kill fungal spores (not endospores), tubercle bacillus, and viruses

Used to disinfect devices that will come in contact with mucous membranes but are not invasive

Front 39

Low-level germicides

Back 39

Eliminate only vegetative bacteria, vegetative fungal cells, and some viruses

Clean surfaces that touch skin but not mucous membranes

Front 40

Factors that affect germicidal activity of chemicals

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Nature of the material being treated

Degree of contamination

Time of exposure

Strength and chemical action of the germicide

Front 41

Germicidal categories

Back 41

Halogens, phenolics, chlorhexidine, alcohols, hydrogen peroxide, aldehydes, gases, detergents and soaps, heavy metals, dyes, acids and alkalis

Front 42

Halogens

Back 42

Chlorine-Cl2, hypochlorites, and chloramines

Denature proteins by disrupting disulfide bonds

Intermediate level

Unstable in sunlight, inactivated by organic matter

Water, sewage, wastewater, inanimate objects

Front 43

Iodine

Back 43

I2, iodophore (betadine)

Interferes with disulfide bonds of proteins

Intermediate level

Milder medical and dental degerming agents, disinfectants, ointments

Front 44

Phenolics

Back 44

Disrupt cell walls and membranes and precipitate proteins

Low to intermediate level

Bactericidal, fungicidal, virucidal, not sporicidal

Example: Lysol

Ticlosan-antibacterial additive to soaps

Front 45

Chlorhexidine

Back 45

A surfactant and protein denaturant with broad microbicidal properties

Low to intermediate level

Hibiclens, hibitane

Used as skin degerming agents for preoperative scrubs, skin cleaning, and burns

Front 46

Alcohols

Back 46

Ethyl, isopropyl in solutions of 50-95%

Act as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi

Intermediate level

Front 47

Hydrogen Peroxide

Back 47

Produce highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas-toxic to anaerobes

Antiseptic at low concentrations; strong solutions are sporicidal

Front 48

Aldehydes

Back 48

Kill by alkylating protein and DNA

Glutaraldehyde in 2% sol used as sterilant for heat sensitive instruments (high level)

Formaldehyde: disinfectant, preservative, toxicity limits use

Formalin-37% aqueous solution

Intermediate to high level

Front 49

Gases and Aerosols

Back 49

Ethylene oxide, propylene oxide

Strong alkylating agents

High level

Sterilize and disinfect plastics and prepackaged devices, foods

Front 50

Detergents and Soaps

Back 50

Quaternary ammonia compounds act as surfactants that alter membrane permeability of some bacteria and fungi

Very low level

Front 51

Soaps

Back 51

Mechanically remove soil and grease containing microbes

Front 52

Heavy metals

Back 52

Solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins

Oligodynamic action

Low level

Merthiolate, silver nitrate, silver

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Dyes as Antimicrobial Agents

Back 53

Aniline dyes are very active against gram-positive species of bacteria and various fungi

Sometimes used for antisepsis and wound treatment

Low level, narrow spectrum of activity

Front 54

Acids and Alkalis

Back 54

Low level of activity:

Organic acids prevent spore germination and bacterial and fungal growth

Acetic acid inhibits bacterial growth

Propionic acid retards molds

Lactic acid prevents anaerobic bacterial growth

Benzoic and sorbic acid inhibit yeast