Culture Media Preparation (M) Flashcards
True or False.
Diff pathogenic bacteria have same nutritional needs, various types of culture media have been developed for use in diagnostic microbiology
False, because diff pathogenic bacteria have diff nutritional needs
What are fastidious bacteria?
These are bacteria that have relatively complex needs and exceptional media components must be used for growth
What are nonfastidious bacteria?
These are bacteria whereas the nutritional needs of most clinically important bacteria are relatively basic and straightforward
What is the definition of the term culture?
It is a term given to microorganisms that are cultivated in the lab for the purpose of studying them
What is the definition of the term medium?
It is a term given to the combination of ingredients that will support the growth and cultivation of microorganisms by providing all the essential nutrients required for growth (that is, multiplication) in order to cultivate these microorganisms in large #s to study them
How will the medium support the growth and cultivation of microorganisms?
By providing all the essential nutrients required for growth
What are the diff classifications of media based on their physical state?
1) Broth (liquid)
2) Agar (solid)
3) Semi-solid
4) Bi-phasic
What is the composition of broth (in terms of agar)?
No agar is present
What is the composition of agar (in terms of agar)?
0.5 - 1.5 % agar
What is the composition of semi-solid (in terms of agar)?
0.2 - 0.4 % agar
What is the composition of bi-phasic (in terms of agar)?
Both liquid and solid
What is the interpretation for the ff circumstances:
a) Clear broth
b) Turbid broth
a) Indicating no bacterial growth
b) Indicating bacterial growth
What are the classifications based on methods of dispensing?
1) Plated medium
2) Tube Media
What are the components of tube media?
1) Butt
2) Butt / Slant
3) Slant
What are the diff classifications of media (based on their functions)?
1) Enrichment media
2) Supportive media
3) Selective media
4) Differential media
5) Transport media
What is the characteristic of enrichment media?
It contains specific nutrients required for growth of particular bacterial pathogens that may be present alone or w/ other bacterial spp in a pt sx
What is the purpose of enrichment media?
This media type is used to enhance the growth of a particular bacterial pathogen from a mixture of organisms by using nutrient specificity
What are the exs of enrichment media?
1) Choc agar
2) SBA
3) Sel-F
4) Alkaline Peptone water
5) BCYE
What is the characteristic of supportive media and its function?
It contains nutrients that support growth of most nonfastidious organisms w/out giving any particular organism a growth advantage
What is an ex of supportive medium?
Thioglycollate broth
What is the characteristic of selective media and its function?
1) It contains 1 or more agents that are inhibitory to all organisms except those being sought
2) In other words, these media select for the growth of certain bacteria to the disadvantage of others
Does selective media contain inhibitory agents?
Yes
What are the inhibitory agents present in selective media?
1) Dyes
2) Bile salts
3) Alcohols
4) Acids
5) Antibiotics
What are the exs of selective media?
1) DCA
2) LJ medium
3) HE
4) MSA
5) XLD
6) BCYE
What is the characteristic of differential media (or why is this called differential)?
This agar is also differential because the appearance of colonies produced by certain bacterial spp is readily distinguishable
What is the purpose (or action) of differential media (or why is it called differential)?
It employs some factors (or factors) that allows colonies of 1 bacterial spp or type to exhibit certain metabolic or culture characteristics that can be used to distinguish them from other bacteria growing on the same agar plate
What are the exs of differential media?
1) McConkey
2) EMB
3) MSA
What is the purpose of transport media?
These are used to maintain the viability of certain delicate organisms in clinical sxs during their transport to the lab
What are the characteristics of transport media?
They typically contain only:
1) Buffers and 2) salt
They lack:
1) Carbon
2) Nitrogen
3) Organic growth factors
Does transport media facilitate microbial multiplication? Why or why not?
No, these type of media does not facilitate microbial multiplication because these lack carbon, nitrogen, and other organic growth factors
Provide an ex of transport medium
Stuart’s transport medium for Neisseria gonorrhea (or gonorrhoeae)
If media are not purchased, can lab personnel prepare agars and broths?
Yes
How does lab personnel prepare agars and broths?
By using dehydrated powders that are reconstituted in H2O (distilled or deionized) accdg to manufacturer’s reccos
What types of H2O are used for preparation of agars and broths?
1) Distilled
2) Deionized
What is the general idea (or concept) for preparing agars?
Generally, media are reconstituted by dissolving specified amt of media powder, w/c usually contains all necessary components, in H2O
Where are the necessary components (in agar preparation) usually present?
In the media powder
Where are the necessary components (in agar preparation) usually present?
In the media powder
What is the importance (or purpose) of boiling (in preparation of agar)?
It is often required to dissolve the powder, but specific manufacturer’s instructions printed in media package inserts should be followed exactly
Where are the specific manufacturer’s instructions placed?
These are printed in media package inserts
Does most media require sterilization?
Yes
Why is sterilization required for most media?
So that only bacteria from pt sxs will grow and not those that are contaminants from H2O or the powdered media
When should the timing of autoclave sterilization start?
The timing of autoclave sterilization should start from the moment the temp reaches 121 DC and usually requires a minimum of 15 mins
What should be done once the sterilization cycle is completed?
Molten agar is allowed to cool to approx 50 DC before being distributed to individual petri plates (usually 25 mL of molten agar per plate)
After the sterilization cycle, the molten agar is cooled to approx what temp?
50 DC
What is the concentration (or density) of molten agar per plate?
Usually 25 mL
What should be done if other ingredients are to be added (to the culture medium)?
They should be incorporated when the molten agar has cooled, just before distribution to plates
What are the exs of other ingredients (that are added to culture medium)?
Supplements such as:
1) Sheep blood or specific vitamins
2) Nutrients
3) Antibiotics
What are the 3 types of hemolysis present in SBA?
1) Beta hemolysis
2) Alpha hemolysis
3) Gamma hemolysis
What is the general purpose of SBA?
For isolation of microorganisms
What are the purposes (and what types of medium) of Mac?
Selective and differential for the isolation of gram (-) bacilli
What are the purposes (or what types of medium) of EMB?
Selective and differential
What are the purposes (or what types of medium) of TCBS?
Selective and differential for Vibrio, Plesiomonas, and Aeromonas
What are the bacteria that can be detected (or can be present) in TCBS?
1) Vibrio cholerae
2) Vibrio parahaemolyticus
What are the purposes (or what types of medium) of Salmonella Shigella agar?
Selective and differential for Salmonella and Shigella spp
What are the bacteria that can be detected (or can be present) in Salmonella Shigella agar?
1) Salmonella
2) Shigella
What are the results in Simmon’s Citrate agar?
1) Negative
2) Positive
What are the results in urea agar?
1) Uninoculated or negative
2) Negative
3) Positive
What are the bacteria that can be detected (or can be present) in SIM?
1) Escherichia coli
2) Micrococcus luteus
3) Proteus mirabilis
What are the results in DNAse agar?
1) (+) : clear zone around inoculation line
2) (-) : no clearing, green colored agar throughout
What are the purposes (or what types of medium) of BHI agar?
Supportive / enrichment media
What are the purposes (or what types of medium) of nutrient agar?
Supportive / enrichment media
What are the purposes (or what types of medium) of Thioglycollate broth?
Supportive / enrichment media
What are the purposes (or what types of medium) of Selenite F?
Enrichment / selective media
What is the meaning of SBA?
Sheep’s (or sheep) Blood Agar
What is the meaning of Mac?
MacConkey Agar
What is the meaning of EMB?
Eosin Methylene Blue
What is the meaning of TCBS?
Thiosulfate Citrate Bile Salts and Sucrose
What is the meaning of LIA?
Lysine Iron Agar
What is the meaning of SIM?
Sulfide Indole Motility
What is the meaning of TSI?
Triple Sugar Iron
