w10 micro Flashcards
nutrient media
support growth of microbes
enriched meda
nutrient media-blood or serum have even added to enhance growth.
-blood agar and chocolate agar are enriched media
selective media
- dyes
- antibiotics
- chemicals
- inhibit growth of most mircroorganisms other than specific CLINICALLY SIGNIFICANT microorganisms.
ex: mannitol salt selective inhibits most microbes due to high salt: allows growth of staphylococcus media
differential media
substances or indicators that will differentiate one type of bacteria from another.
ex: macConkey agar is selective and differential. -prevents growth of skin bacteria but allows growth of enteric bacteria – enteric bacteria differentiated by the way they ferment lactose in the media. - lactose fermenters turn pink, non lactose fermenters don’t change colour.
chrome agar
differential nutrient medium that allows bacteria species to grow in different colours
MLA QC
- label media with medium type and expiry date
- storing media at appropriate temp
- FIFO
- stored at 4 degrees
dehydration media
- purchased
- tightly closed lids so moisture from air isn’t absorbed
- stored at room temp
List of ingredients of culture media 14
peptone meat infusion sodium chloride buffers carbohydrates pH indicator Yest extract agar blood serum antibiotics chemicals egg media
peptone, ingredient of culture media
nutrient source of carbon and nitrogen- mix of amino acids from casein, soy meal and gelatine- soluble in eater and does not coagulate when heated
meat infusion ingredient of culture media
-enhance growth of bacteria, made from lean meat -brain, heart, muscle– provides: amino acids, carbohydrates, vitamins, trace elements
not altered by autoclave
sodium chloride, ingredient of culture media
make media isotonic-prevents hemolysis in blood agar
buffers in culture media
generally phosphate buffers( not in all media)
maintain constant pH from metabolic waste
carbohydrates in culture media
glucose added as nutrient
-others added to determine if bacteria are able to ferment them and produce acid
pH indicator in culture media
added to media with specific carbs to determine if they have been fermented during growth. (fermentation=metabolic acids=colour change)
Yeast extract in culture media
b vitamens
-added in dehydrated form or added as sterile solution after autoclave
agar in culture media
seaweed- gel used in solid media.
-heat to boiling to dissolve into solution then poured into agar plates- cools and solidifies at 42 degrees
blood in culture media
nutrients promotes variety of bacteria growth
- sterile
- sheep or horse
- BAP blood agar plate- whole blood
- CHOC chocolate agar uses lysed blood
- LBA lakes blood agar uses blood that has been frozen and thawed to lyse red blood cells
serum in culture media
nutrient to some special media
-from bovine or horse and collected aseptically or filtered to remove bacteria
antibiotics in culture media
- inhibit growth of certain microbes (selective)
- heat sensitive or LABILE antibiotics are filtered to remove bacteria and a added as a sterile solution after autoclave
chemicals in culture media
make the selective or differential
egg media
used to grow tubercle bacilli
labelling of media
labelled with type of medium and expiration date
preparation date may be included
sterilizing with microbiological filters
filters: sterilize heat sensitive ingrediants
membrane filters: cellulose esters or plastic polymers- filters with variety of pore sizes: filters with large pores will remove bacteria, small pores will remove viruses
-most use gravity and negative pressure or positive pressure may be used to force fluid through filter
how does moist heat kill microorganisms?
kills by coagulation of microbial portents
- coagulation results in break of hydrogen bonds holding protein together, once bonds broken no longer alive
- requires heat and moisture
no longer viable meaning
no longer alive
temperature and killing microbes
- boiling and free flowing steam effective with proteins
- max temp 100 degrees celsius
- some spores can live-extend time or temp
how can sterilization be accomplished in a short amount of time
steam under pressure and a high temperature
what is a steam autoclave
large insulated pressure cooker -contorls temp and pressure
-higher pressure of steam results in higher temp
temperatures and pressure of autoclave
15 pounds of pressure psi 121 degrees celsius
20 pounds of pressure psi 126 degrees celsius
30 pounds of pressure psi 135 degrees celsius
** most labs operate at 15 pounds of pressure and a temp of 121 degrees celsius for 15 minutes
what does condensation of steam in autoclave do?
- condenses to a smaller volume causing more steam to be drawn into items being sterilized—PENETRATION
- steam condenses, latent heat of condensation (heat that went into the production of steam) is released , the heat and the moisture coagulates microbial protein-STERILIZATION
parts of an autoclave
jacket- steam filled, surrounds chamber, insulation- keeps constant temp, **heat from jacket allows autoclave to dry after sterilization since steam removed from chamber but not jacket
Chamber-steam entering diverted by baffle to prevent direct hit on cool objects. - air and water heavier than steam removed by discharge channel
ejector valve-allows water and air to leave, traps steam resulting in pressure buildup
door-lock device-wont open if pressure in chamber
pressure gauge
thermometer-located below chamber in discharge channel- if temp is 121 in discharge channel it would be 121 in chamber - monitor temp carefully- critical for killing microbes
liquids in autoclave
- leak proof container that can withstand heat- pyrex -plastics melt
- no plastics =melt
- lids: -screw caps LOOSE -cotton plugs -caps hard plastic or metal
- container should have room for expansion during sterilization -filled to 80%
glassware and autoclaving
pipettes-cotton or wool in top can be autoclaved if contaminated.
test tube- use proper closures (cotton plugs, metal caps, plastic caps)
beakers/cylinders/bottles-tops covered- brown wrapping paper and held inlace with autoclave or masking tape
biohazardous waste and autoclave
microbiology cultures are autoclaved before disposal- rendered non-viable and safer for transport. culture media, petri plates and tubes are collected in special plastic autoclave bags or buckets
autoclave cycles
- usual temp 121
- time 15 mins-** large volumes require longer heating periods
- 1500ml in a 2000 ml flask would need 30 mins to autoclave
- exhaust cycle-steam removed from chamber by fast or slow exhaust
