Micro Ch. 17

Front 1

2 types of radiation

Back 1

ionizing and ultraviolet

Front 2

ultraviolet (UV) used for:

Back 2

Ultraviolet (UV) used for reducing microbial contaminants on
surfaces (germicidal)

DNA damage (breaks, Disinfection of exposed surfaces,
modifications) air, water

Front 3

ionizing radiation

Back 3

gamma-rays, X-rays, electron beams – used
for sterilization of medical devices and food

Front 4

microwave

Back 4

Heat, possible other effects Sterilization of disposable
medical devices

Front 5

electron beam

Back 5

Damage to DNA and proteins
via electrons
Sterilization of medical devices,
food, pharmaceuticals

Front 6

Gamma rays
(ionizing radiation)

Back 6

Damage to DNA and proteins
via electrons and radicals
Sterilization of medical devices,
bulk foods

Front 7

Decimal reduction value = D10

Back 7

amount of radiation
needed for a 10-fold reduction in viable cells.

Front 8

Standard killing dose for radiation sterilization is

Back 8

12 X D 10

Front 9

Many liquids and gasses are heat sensitive. They cannot be sterilized with heat.
• _____ can be used instead.

Back 9

filtration:
the liquid or gas is passed through a filter whose pores are too small
for microbes but large enough for the liquid or gas

Front 10

sheets or mats of fibrous paper,
cellulose, or glass. Resist clogging. Often used
as prefilters for larger particles. Ex: HEPA filters

Back 10

depth filters

Front 11

____ – used for sterilization, have
uniform pore size; made of cellulose acetate,
nitrocellulose, or polysulfone.
• commonly used in
microbiology labs have 0.2 μm and 0.45 μm
pore size

Back 11

membrane filters

Front 12

Two main categories of antimicrobial agents:

Back 12

• Non-chemotherapeutic agents & chemotherapeutic agents

Front 13

non-chemotherapeutic agents

Back 13

(e.g., antiseptics, disinfectants, sterilizers,
sanitizers); non-selective: they have similar effects on all cells; used to inhibit or
kill microbes on living sufaces (topically) or inanimate objects, but too toxic for
internal use inside the human body. Often collectively called germicides.

Front 14

chemotherapeutic agents

Back 14

(antibiotics) selective agents: kill specific microbes
without killing the host; can be used internally to control microbes that cause
infectious diseases.

Front 15

non-chemotherapeutic agents are often called

Back 15

germicides

Front 16

Sterilizers

Back 16

Kill all living organisms, including spores
ex: Ethylene oxide (gas); bleach, formaldehyde (gas)

Front 17

Disinfectants:

Back 17

Kill microbes or pathogens from inanimate surfaces, may
not kill spores
ex: bleach, ethanol (60-85%), iodine-containing solutions

Front 18

Sanitizers:

Back 18

Reduce, but may not eliminate microbes (food industry, etc.)
ex: chlorine compounds and cationic detergents

Front 19

Antiseptics:

Back 19

Antimicrobial compounds that are nontoxic enough to be
used ON living tissues
ex: ethanol (60-85%), iodine-containing solutions, hydrogen
peroxide (3%), silver nitrate

Front 20

-static

Back 20

“-static”: antimicrobials that inhibit microbial
growth without killing them, e.g., bacteriostatic,
fungistatic

Front 21

-cidal

Back 21

“-cidal”: antimicrobials that kill microbes, e.g.,
bacteriocidal, fungicidal, virucidal, sporicidal

Front 22

-lytic

Back 22

“-lytic”: antimicrobials kill lytic : that microbes by
lysing them, e.g., bacteriolytic

Front 23

Microbial factors:

Back 23

Population size
• Population and community
composition
• Encasement within surface
biofilms

Front 24

Antimicrobial treatment factors:

Back 24

• Antimicrobial concentration (may be
“-static” at certain concentrations
and “-cidal” at higher
concentrations)
• Duration of exposure of the
microorganisms
• Temperature of treatment
• Presence of other organic materials
• Level of microbial resistance to the
antimicrobial agent g

Front 25

Measurement of antimicrobial activity

Back 25

1) Tube dilution assay; 2) Disk agar diffusion assay

Front 26

Tube dilution assay

Back 26

to detect the
Minimal Inhibitory Concentration
(MIC)
• A series of increasing
concentrations of the antimicrobial
agent are added to the culture
broth medium. Each tube is equally
inoculated and incubated to allow
microbial growth to proceed.
• Growth (turbidity) occurs in those
tubes containing the antimicrobial
at concentrations below the MIC.
• Tube cultures are non-turbid (clear,
no growth) at MIC and higher
concentrations of the antimicrobial agent

Front 27

Antibiotic disc agar diffusion method:

Back 27

The test organism is spread on the culture
plate medium in an agar plate, then sterile
antibiotic discs are applied.
• After incubation, the organism produces a
confluent “lawn” of growth except in zones of
inhibition around discs containing antibiotics
to which the organism is susceptible.

Front 28

modes of action of anticeptics****

Back 28

-lipid solvent and protein denaturation
-disrupts cell membrane
-interact with phospholipids of cell membrane
-oxidizing agent
-iodinates tyrosine residues of protien: oxidizing agent
-disrupts cell membrane
-protein precipitant

Front 29

modes of action of sterilants, disinfectants, and sanitizers

Back 29

-lipid solvent and protein denaturant
-interacting with phospolipids
-oxidizing agent
-