Microbial cultivation Flashcards
Cultivation techniques and appropriate media
It is the process of growing microorganism in culture by taking bacteria from the infection site (in vivo) and growing them in an artificial environment (in vitro)
Microbial Cultivation
Purposes of bacterial cultivation
- To grow and isolate all bacteria present in clinical specimen
- To determine which of the bacteria that grow are most like causing infection and which are likely contaminants or colonizers
- To obtain sufficient growth of clinically relevant bacteria to allow identification and characterization.
this is a mixture of nutrients needed by bacteria to grow in vitro
Culture medium
A culture may be:
a. pure culture if only one type of organism is present or
b. mixed culture if populations of different organisms are present
Phases of culture media: According to Consistency
Solid form - agar plate; with the base agarose
Liquid form - broth
Semisolid form - w/ 0.5% or less agarose content
Biphasic- solid and liquid phase may be used.
Survival of bacteria in a culture medium depends on:
Availability of essential nutrients and appropriate environmental conditions
A bacteria that needs relatively complex requirements and exceptional media components to aid its growth
A fastidious organism
is defined as any organism which has very complicated nutritional requirements, meaning it will not grow without specific factors present or in specific conditions.
bacteria that do not need special nutritional supplements and conditions to grow on agar plates.
Nonfastidious bacteria
What happens to bacteria in broth growth media
- nutrients are dissolved in water, and bacterial growth is indicated by a change in the broth’s appearance from CLEAR to TURBID
What do more growth iof bacteria in broth culture media indicate
-indicates higher cell density and greater turbidity
Thioglycollate broth is an example of what type of culture medium
Semisolid medium
- thiglycollate broth (liquid) also contains small amount of agar
Thioglycollate broth is an example of what type of culture medium
Semisolid medium
- thiglycollate broth (liquid) also contains small amount of agar
Other than amount of growth present in culture media, ________ of growth within a broth provides an indication of the type of organism present based on oxygen requirements.
- location of growth
e. g. strict anaerobes will grow at the bottom of broth tube whereas aerobes will grow near the surface.
microaerophilic organisms will grow slightly below the surface where oxygen concentration are lower than atmospheric conc.
facultative anaerobes and aerotolerant organisms will grow throughout the medium since they are unaffected by variation in oxygen content.
A medium in which a solidifying agent is added to nutrient and water
Solid medium
The most common solidifying agent
Agarose
-has a unique property of melting at high temp (>95 °C)
and re-solidify after temp falls below 50°C
The petri dishes containing the agar is referred to as
-Agar plate
Types of culture
Pure culture- comes from one type of microbe/ the same species
Mixed culture- more than one type of microbe/ more than two species maybe across kingdoms
Stock culture - unwanted microbe is present; contaminants are fungi and other bacteria
……..
Examples of Solid media - contains 2-3% agar
Triple sugar iron agar (TSI)
Blood agar plate (BAP)
Chocolate Agar plate (CAP)
Mckonkey agar plate (MAC)
Agar is a sulfated polymer made up of________________
Carbohydrates
D-galactose, 3,6-anhydro-L galactose, and D-glucuronic acid derived from red algae
Example of Liquid Medium - does not contain agar
BHI - Brain-Heart- infusion medium
TSB- Trypticate Soy broth
Thioglycolate broth
Example of Semi-Solid medium - agar content is only 0.5-1%
SIM - Sulfide indole motility media
Type of medium necessary for gas testing. When you want to know certain bacteria that produces gas
Semi-solid medium
-SIM
Three test that can be observed when using SIM or sulfide-indole motility medium which is a semi-solid medium
- Black precipitate (due to sulfide)
- Indole production (gas)
- Motility (growth outside line of inoculation)
What is the indication of bacterial growth in liquid medium
e.g. in TSB, BHI and thioglycolate
-Changes in transparency of liquid such as turbidity and cloudiness