Microbio Lecture 13 Control of growth Study

Sepsis

refers to bacterial contamination

Asepsis

absence of significant contamination

aseptic surgery tech.- prevent the microbial contamination of wounds

Sterilization

removing and destroying all microbial life

Commercial sterilization

killing Clostridium botulinum endospores in canned goods

Clostridium botulinum

rod shaped- endospores are resilient

Botulism

food borne disease- often contaminated canned food

Botulinum toxin- BOTOX- neuro toxin

- respiration failure, paralysis, digestion, eye muscle

used to treat cerebral palsy, spasms, cosmetic issues

Disinfection

destroying harmful microorganisms on inanimate surfaces/environments

Antisepsis

destroying harmful microorganisms from living tissue

Degerming

mechanical removal of microbes from a limited area (ex. washing hands)

Sanitization

lowering microbial counts on eating utensils to safe levels

Biocide- germicide

treatment that kill microbes

Bacteriostatsis

inhibiting, not killing, microbes (stops growth)

The usual definition of sterilization is the removal or destruction of all forms of microbial life; how could there be practical exceptions to this simple definition?

idk

Rate of microbial death- effectiveness of treatment depends on

number of microbes, environment (org. matter, temp., biofilms), time of exposure, microbial characteristics (endospores, cell wall)

Effective of treatment depends on # of microbes bc

the death rates are the same, but it takes 3 min to kill low pop., 6 min to kill high pop.

How is it possible that a solution containing a million bacteria would take longer to sterilize than one containing a half-million bacteria?

because the death rates may be the same, so it takes longer to kill more bacteria

Kill microbes Microbial control agents does what- damage to plasma membrane

damage to plasma membrane- causes leakage of cellular contents, interferes with cell growth

Kill microbes Microbial control agents does what

damage to plasma membrane, proteins (enzymes), nucleic acids

Would a chemical microbial control agent that affects plasma membranes affect humans?

yes because we have plasma membranes

Heat denatures

enzymes

Thermal death point

lowest temperature at which all cells in a liquid culture are killed in 10 min

Thermal death time

minimal time for all bacteria in a liquid culture to be killed at a particular temperature

Decimal reduction time

minutes to kill 90% of a specific population of bacteria at a given temperature

Moist heat coagulates

or denatures proteins

Autoclave- steam under pressure

121C at 15 psi for 15 min, kills all organisms (except prions) and endospores steam must contact item’s surface!!

preferred method for sterilization in healthcare environments

Pasteurization

reduces spoilage organisms and pathogens in milk and juices

High temperature short time

72C for 15 sec

Thermoduric

organisms survive, but are unlikely to cause disease or to spoil refrigerated milk

UHT- ultra high temperature treatments

will sterilize milk, creamer, and juice- can be stored w/out refrigeration

rapid heating to 140C for 4 sec., then rapid cooling

Dry heat sterilization

flaming, incineration,

hot air sterilization- oven 170C for 2 hours

Filtration

passage of substance thru screenlike material

used for heat sensitive materials

high efficiency particulate air (HEPA) filters

remove microbes > 0.3 micrometers in diameter

Membrane filters

remove microbes > 0.22 micrometers

pore sizes as small as >0.05 micrometers are available to filter out viruses and large proteins

Physical Methods of microbial control- LOW temp has

bacteriostatic effect- refrig., deep freezing, lyophilization (freeze drying

Physical methods mic. control- high pressure

denatures proteins, alters carb. struc.

Physical methods of mic. control- desiccation

absence of water prevents metabolism

Physical methods of mic. control- osmotic pressure

uses high concen. of salts/sugars to create hypertonic environment- causes plasmolysis

Radiation- Ionizing radiation is what

X rays, gamma rays, electron beams

Radiation- Ionizing radiation description

–Ionizes water to create reactive hydroxyl radicals

–Damages D N A by causing lethal mutations

–Used by food industry (spices, certain meats, vegetables)

–Sterilization of pharmaceuticals, disposable dental and medical supplies, mail

Gamma rays

penetrate deeply but require hours to sterilize

high energy electron beams

less penetration, but fast (seconds)

Radiation- nonionizing radiation (UV, 260 nm)

–Damages D N A by creating thymine dimers

–U V C “germicidal” lamps used in hospital rooms, nurseries, operating rooms, cafeterias

–Effective, but doesn’t penetrate; good for surfaces

–Must avoid contact with eyes and skin

Radiation- visible blue light

470 nm- kills a wide range of bacteria due to the formation of singlet oxygen

Radiation- microwave

kills by heat, not especially antimicrobial

Physical ways of controlling growth

Heat: Moise, Pasteurization (HTST, UHT), Dry heat

Filtration: HEPA and other filters

Low temp- Cidal or static

High pressure

Desiccation

Osmotic

Radiation

How is microbial growth in canned foods prevented?

idk

Why would a can of pork take longer to sterilize at a given temperature than a can of soup that contained pieces of pork?

idk

What is the connection between the killing effect of radiation and hydroxyl radical forms of oxygen?

hydroxyl radicals (\(\bullet \text{OH}\)), which then chemically destroy vital cellular components like DNA.