M1 | Fundamentals of Microbial Control

sterilization

removal or destruction of all forms of microbial life, including endospores but with the possible exception of prions

prions

sterilization is removal or destruction of all forms of microbial life, including endospores but with the possible exception of [BLANK]

sterilant

a sterilizing agent is called a

steam under pressure or sterilizing gas (like ethylene oxide)

sterilization is usually done by

ethylene oxide

sterilizing gas

commercial sterilization

limited heat treatment

absolute sterility

The heat treatment required to ensure [BLANK] would unnecessarily degrade the quality of the food

clostridium botulinum

Food is subjected only to enough heat to destroy, in canned goods, the endospores of [BLANK] —> can produce a deadly toxin

• complete sterilization

• body’s normal defenses

[BLANK] is often not required in some settings, for example: the [BLANK] can cope with a few microbes entering a surgical wound

pathogenic microbes

A drinking glass or a fork in a restaurant requires only enough microbial control to prevent the transmission of possibly [BLANK] from one person to another

not germinate and grow under normal storage conditions

More-resistant endospores of thermophilic bacteria may survive, but they will:

disinfection

Usually refers to the destruction of vegetative pathogens on inanimate objects

vegetative

non endospore forming

ultraviolet radiation, boiling water, or steam

disinfection use chemicals or physical methods like:

inert surface or substance

Most commonly applied to the use of a chemical (a disinfectant) to treat an:

disinfectant

chemical for disinfection

antisepsis

disinfection treatment directed at living tissue

antiseptic

chemical for antisepsis

hydrogen peroxide, ethyl alcohol, Lysol

3 examples of antiseptic

degerming

mechanical removal in limited area

degerming

when someone is about to receive an injection the skin is swabbed with alcohol, is an example of:

sanitization

To lower microbial counts to safe public health levels and minimize the chances of disease transmission from one user to another

• high-temperature washing

• dipping into a chemical disinfectant

sanitization may be done with

-cide

kill

biocide or germicide

kills MGs

fungicide

kills fungi

virucide

inactivates viruses

stat or stasis

to stop or to steady

bacteriostasis

inhibiting bacterial growth

sepsis

decay or putrid

aseptic

an object or area is free of pathogens

asepsis

absence of significant contamination

die at a constant rate

When bacterial populations are heated or treated with antimicrobial chemicals, they usually [BLANK].

90%

rate of microbial death in 1 minute if heated or treated with antimicrobial chemicals

constant

If the death curve is plotted logarithmically, the death rate is [BLANK]

• microbial characteristics

• environmental influence

• acidity

• number of microbes

• time of exposure

give 5 factors that influence the effectiveness of antimicrobial treatment | M E A N T

Microbial characteristics

factor that affects the choice of chemical and physical control methods

various degrees of resistance

MOs have [BLANK] to physical and chemical control methods

G(-)

Which is more are generally more resistant to physical and chemical control methods, G(+) or G(-) bacteria?

• cyst-forming protozoa

• endospore-forming bacteria

these 2 are more resistant than their vegetative counterparts

• prions

• bacterial endospores

• mycobacteria

• protozoan cyst

• vegetative protozoa

• G(-) bacteria

• fungi

• non-lipid virus

• G(+) bacteria

• lipid viruses

give the decreasing order of microbial resistance

Creutzfeldt-Jakob Disease

ex. of disease caused by prions

bacillus atrophaeus

ex. of disease caused by bacterial spores

cryptosporidium

ex. of disease caused by coccidia

• mycobacterium tuberculosis

• mycolicibacter terrae

ex. of disease caused by mycobacteria

• polio

• coxsackie

ex. of disease caused by non-lipid or small viruses

• aspergillus

• candida

ex. of disease caused by fungi

• s. aureus

• p. aeruginosa

ex. of disease caused by vegetative bacteria

• HIV

• herpes

• hepatitis B

ex. of disease caused by lipid or medium-sized viruses

Environmental influence

factor that pertains to how most disinfectant work somewhat better in warm solution

Acidity

factor that pertains to heat being measurably more effective

Number of microbes

factor that means the more microbes there are to begin with, the longer it takes to eliminate the entire population

Time of exposure

factor that means chemical antimicrobial often require extended exposure to affect more resistant microbes or endospores

temperature

factor about how disinfectant work somewhat better under warm conditions

presence of organic matter

factor about what often inhibits the action of chemical microbials

mucoid matrix in biofilms

factor termed when microbes are difficult for biocides to reach effectively

nature of the suspending medium

factor termed when fats and protein are especially protective for microbes

plasma membrane

usual target of antimicrobials

• alteration of membrane permeability

• damage to proteins and nucleic acids

2 chemical actions of microbial control agents

Plasma membrane

the target of many microbial control agent

nutrients-in, wastes-out

• passage of nutrients into the cell

• elimination of wastes from the cell

Membrane actively regulates the (N I W O):

enzymes

protein vital to all cellular activities

hydrogen bonds

which are susceptible to breakage by heat or certain chemicals → breakage results in denaturation of the protein

covalent bonds

are stronger but are also subject to attack: disulfide bridges can be broken by certain chemicals or sufficient heat

DNA and RNA

carriers of cell’s genetic information

can no longer replicate, nor can it carry out normal metabolic functions such as the synthesis of enzymes

• 2 abilities mainly affected:

  • replicating

  • metabolizing

Damage to these nucleic acids (DNA and RNA) by heat, radiation, or chemicals is frequently lethal to the cell →

• heat

• filtration

• desiccation

• osmotic pressure

• radiation

5 physical methods of microbial control:

heat

kills through enzyme denaturation

3D

the resultant changes from heat to the [BLANK] shapes of these proteins, inactivate them

thermal death point

lowest temp in 10 min to be killed

• lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes

thermal death time

minimal length of time to be killed

• minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature

decimal reduction time

90% death rate in a given temp

• the time, in minutes, in which 90% of a population of bacteria at a given temperature will be killed

• moist heat sterilization

• dry heat sterilization

• hot air sterilization

3 ways to sterilize with heat:

moist heat sterilization

Kills microorganisms primarily by coagulating proteins (denaturation) → caused by breakage of the hydrogen bonds that hold the proteins in their 3D structure

• boiling

• autoclave

• pasteurization

3 examples of moist heat sterilization:

boiling

Kills vegetative forms of bacterial pathogens, almost all viruses, and fungi and their spores within about 10 minutes but endospores and some viruses, however, are not destroyed

about 10 minutes

time for boiling

autoclave

Steam under pressure; preferred method of sterilization in health care environments

autoclave

Most effective when the organisms either are contacted by the steam directly or are contained in a small volume of aqueous (primarily water) liquid

15 psi at 121°C

temp and time for autoclave

about 15 minutes

autoclave will kill all organisms and their endospores in [BLANK] but not prions

pasteurization

Kill the organisms that caused the particular spoilage problem without seriously damaging the taste of the product

60°C for 30 minutes

temp and time for pasteurization

phosphatase test

Test to determine whether products have been pasteurized

72°C for 15 seconds

high temperature short-time (HTST) pasteurization

HTST pasteurization

lowers total bacterial counts, so the milk keeps well under refrigeration

Ultra-High Temperature (UHT) Treatments

• Can be stored for several months without refrigeration

• The process avoids having the milk touch a surface hotter than the milk itself

• Liquid milk (or juice) is sprayed through a nozzle into a chamber filled with high temperature steam under pressure

140°C for 4 seconds

Ultra-High Temperature (UHT) Treatments

dry heat sterilization

• Kills by oxidation effect

• Direct flaming

• Kills all microbial forms

hot air sterilization

To sterilize instruments that easily corrode

170C maintained for nearly 2 hours

hot air sterilization

filtration

screen-like materials w/ pores for heat-sensitive materials

• some culture media

• enzymes

• vaccines

• antibiotic solutions

filtration is used to sterilize heat-sensitive materials, such as:

High-Efficiency Particulate Air Filter

filter for >0.3 μm MGs

Membrane Filter

0.1 mm thick filter

0.22 μm and 0.45 μm

membrane filter for bacteria

0.01 μm

membrane filter for viruses and some molecule

0-7C

the temperature of ordinary refrigerators wherein the metabolic rate of most microbes is so reduced that they cannot reproduce or synthesize toxins

• lyophilization

• refrigeration

• freezing

3 examples of low temperature treatment that inhibit microbial growth

low temperature treatment

Used to preserved cultures of microorganisms