CULTIVATION Flashcards
PRINCIPLE OF CULTIVATION
- To grow and isolate all bacteria present in a clinical specimen
- To determine which of the bacteria that grow are most likely contaminants or colonizers.
- To obtain sufficient growth of clinically relevant bacteria to allow identification and characterization
Process of growing microorganisms in culture by taking bacteria from the infection site
CULTIVATION
bacteria with relatively complex, and exceptional media components must be used.
Fastidious
made from seaweed
AGAR
made by acid or enzymatic hydrolysis of animal or vegetable protein, namely muscle, liver, blood, milk, casein. Lactalbumin, gelatin or soybean
PEPTONE
baker’s yeast
YEAST EXTRACT
contain soluble organic bases, protein degradation, products, vitamin and minerals
MEAT EXTRACT
agarose-containing medium
AGAR
petri dish containing the agar
AGAR PLATE
resulting bacterial population derived from single bacterial cell
COLONY
bacterial cultures derived from a single colony
PURE CULTURE
MEDIA CLASSIFICATION
- Enrichment
- Supportive
- Selective
- Differential
Contain specific nutrients required for the growth of bacterial pathogens
ENRICHED MEDIUM (ENRICHMENT)
Example of enriched media
Buffered charcoal yeast extract agar- Legionella pneumophilia
Contain nutrients that support the growth of most nonfastidious organisms without giving any particular organism a growth advantage.
SUPPORTIVE MEDIA
Contain one or more agents that are inhibitory to all organisms except those being sought.
SELECTIVE MEDIA
Example of inhibitory agents
- Dyes
- Bile salts
- Alcohols
- Acids
- Antibiotics
Has added inhibitors that discourage the growth of certain organisms without inhibiting the growth of organism being sought.
SELECTIVE MEDIUM
inhibit Gram ( + ) bacteria
MacConkey agar
selective for Gram ( + ) bacteria
PEA and CAN
selective for Neisseria gonorrhea.
THAYER MARTIN MEDIUM, MARTIN LEWIS AGAR, NEW YORK CITY AGAR
salt tolerant haloduric bacteria ( S. aureus ).
MANNITOL SALT AGAR
Allows colonies of one bacterial species or type to exhibit certain metabolic or culture characteristics that can be used to distinguish them from other bacteria
DIFFERENTIAL MEDIA
Permits differentiation of organisms that grow on the medium.
DIFFERENTIAL MEDIUM
based on the organisms ability to grow in 40% bile and to hydrolyze esculin to produce esculitin
BILE ESCULIN AGAR
Esculin reacts with _____ to form a brown black precipitate.
FERRIC CITRATE
growth indicates tolerance to 40% bile(40% oxygall) blackening indicates hydrolysis of esculin
POSITIVE
lack of growth indicates inability to grow in 40% bile lack of color change indicates inability to hydrolyze esculin
NEGATIVE
Bile esculin agar
A. Positive -
Entercoccus faecalis
B. Negative -
Streptococcus viridans
Cultivation of non-fastidious organisms
BLOOD AGAR PLATE
Determination of hemolytic reaction
BLOOD AGAR PLATE
Enrichment for Legionella spp.
Buffered Charcoal Yeast Extract (BYCE)
The medium consists of a base containing
protein source, soybean protein, digest (containing a slight amount of natural carbohydrate), sodium chloride, agar, and 5% sheep blood
Certain bacteria produce extracellular enzymes that lyse red blood cells in the agar
HEMOLYSIS