1. Types of culture media
categorized according to their function and use .
In diagnostic microbiology there are four general categories of media.
1.Enrichment media
2.Supportive media
3.Selective media
4.Differential media

2. Enrichment media:
it contain specific nutrients required for the growth of particular bacterial pathogen that may be present alone or with other bacterial species in specimen.
. used to enhance the growth of particular bacterial pathogen from mixture of organism by using nutrient specificity
Eg: blood agar, chocolate agar

4. Supportive media:
it contain nutrients that support growth of most fastidious organisms with out giving any particular organism a growth advantage.
Selective media:
it contain one or more agents that are inhibitory to all organism except preferable one.

6. Inhibitory agents used for this purpose include dyes,bile salt,aclcohol ,acids antibiotics
eg: phenyl ethyl alcohol agar
Differential media: this is used to identify the colonies of one bacterial species or type to exhibit certain metabolic or cultural characteristics in a same agar plate

7. Eg:
Eosin methylene blue (EMB), which is differential for lactose and sucrose fermentation
MacConkey (MCK), which is differential for lactose fermentation
Mannitol Salt Agar (MSA), which is differential for mannitol fermentation

8. Nutrient agar typically contains (w/v
It is a microbiological growth medium commonly used for the routine cultivation of non-fastidious bacteria. Nutrient agar is a solid medium. Very few microbes can degrade agar, so the agar remains solid during microbial growth.
Nutrient agar typically contains (w/v
0.5g peptone
0.3g beef extract
1.5g agar
100ml Distilled water
pH adjusted to neutral at 25 C.

9. Blood agar
It contains mammalian blood (usually sheep or horse), typically at a concentration of 5–10%.
Blood agar are an enriched, differential media used to isolate fastidious organisms and detect hemolytic activity.
β-hemolytic activity will show complete lysis of red blood cells surrounding colony. -

10. hemolytic activity will show complete lysis of red blood cells surrounding colony. Examples include Streptococcus haemolyticus. α-hemolysis will only partially lyse hemoglobin and will appear green

11. On the right is a positive Streptococcus culture; on the left a positive Staphylococcus culture.

12. Chocolate agar:
chocolate agar is essentially the same as blood agar except that during preparation the red blood cells are lysed when added to molten agar base.
This lysis release intracellular nutrient s such as hemoglobuin,hemin and the coenzyme ,nicotinamide adenine dinucleotide into the agar for utilization by fastidious bacteria

13. Blood cell lysis gives the medium a chocolate brown color.
The pathogens require this medium for growth include Neisseria gonorrhoeae,
Haemophilus spp

14. Macconkey Agar:
it is the most frequently used primary selective and differential agar.
This medium contain crystal violet dye to inhibit the growth of gram positive bacteria and fungi.
It allows the growth of many gram negative bacilli to grow.
The medium contains peptone with lactose and neural red pH indicator.

15. Bacterial fermentation of lactose results in acid production which decreases0 medium pH and cause the neutral red indicator to give bacterial colonies as pink to red color.
Sabouraud`s agar
It is used to culture fungi and has a low pH that inhibits the growth of most bacteria; it also contains the antibiotic gentamycin to specifically inhibit the growth of Gram negative bacteria.

16. Transport media
Transport medium inhibits self destruction and multiplication of microorganisms.
Delay during the transport of specimens from the point of collection noticeably affects the viability of such delicate organisms as Nesseria, haemophilus,shigella and anaerobes.
Various media are used for transporting different types of specimen

17. Stuart transport medium:
it is used for CSF and cervical specimens.this medium preserves both Neisseria species and Trichomonas vaginalis..
Cary-Blair and Amies medium:
is used to transport faecal material on rectal swab and are effective in preserving Salmonella, shigella and vibrio