Lesson 12 Flashcards
Laboratory diagnosis of an infection is usually confirmed by isolating and culturing microorganisms in what kind of media?
artificial media
are cultured in either liquid (broth) or on solid (agar) artificial media.
Bacteria and fungi
-, developed the Petri dish (plate), a container for solid culture media.
Richard Petri
A nutrient material prepared for the growth of microorganisms in a laboratory
Culture medium
When microbes are introduced into a culture medium to initiate growth,
Inoculum
- The microbes that grow and multiply in or on a culture medium
culture
-: is the process of growing microorganisms in culture
Cultivation
- taking bacteria from the infection site
in vivo environment
- by some means of specimen collection and growing them in the artificial environment of the laboratory
the in vitro environment
- a laboratory culture containing a single species of organism.
Pure culture
Purposes of bacterial cultivation
i. To grow and isolate all bacteria present in an infection.
ii. Infection and contaminants or colonizers: To determine which of the bacteria that
grow are most likely causing infection and which are likely contaminants or
colonizers.
iii. Identification and characterization: To obtain sufficient growth of clinically relevant
bacteria to allow identification and characterization.
Purposes of bacterial cultivation
i. To grow and isolate all bacteria present in an infection.
ii. Infection and contaminants or colonizers: To determine which of the bacteria that
grow are most likely causing infection and which are likely contaminants or
colonizers.
iii. Identification and characterization: To obtain sufficient growth of clinically relevant
bacteria to allow identification and characterization.
is often suitable for culture media, particularly if it has a low
mineral content, however glass-distilled or demineralized water is best used.
Tap water
is prepared from a variety of seaweeds and is now
universally used for preparing solid media
Agar
most bacteriological agars melt at what temperature ?
95°C
Agar solidify only when
cooled in what temperature?
42°C
almost universal ingredient of common media is . It is a
complex mixture of partially digested proteins.
peptone
The important constituents of peptone?
peptones
proteoses
amino acids
a variety of inorganic salts including phosphates,
potassium and magnesium,
certain accessory growth factors such as nicotinic
acid and riboflavin
: It contains a wide range of amino acids, growth factors and
Inorganic salts. is used mainly as a comprehensive source of growth
factors and may be substituted for meat extract in culture media.
Yeast extract
It consists mainly of maltose (about 50%), starch, dextrins and
glucose, and contains about 5 percent of proteins and protein breakdown products,
and a wide range of mineral salts and growth factors
Malt extract:
There are use for enriching culture media. Either human or animal blood can be used
Blood and serum
-the earliest culture media.
Liquid media
-The original media used by Louis Pasteur was liquids such as what?
Urine and broth
are dissolve in water, and bacterial growth is indicated by a change in broth appearance from clear to turbid
Broth media nutrient
-Uses of broth media nutrient
For obtaining bacterial growth from blood and water when large volume has to be tested
Preparing bulk of cultures of antigens or vaccines
-are made by adding a solidify agent to the nutrients and water
Solid media/agar
-are made by adding a solidify agent to the nutrients and water
Solid media/agar
-most common solidifying agent
Agarose
-advantage of solid/agar media
Less sensitive than liquid media
Provide isolated colonies that can be quantified and identified
are clones of cells originating from a single bacterial cell
Colonies
-is the simplest and most common medium used routinely in diagnostic laboratories
Nutrient agar prepared by adding 2% agar to
-for special purposes where agar is added to media in concentration that are too low to solidify them.
Semisolid media
-include nutrient broth and peptone water, which form the basis of other media
Simple or basal media
-nutrient broth is an example a simple liquid media that consists of what?
Peptone
Meat extract
Sodium chloride
Water
-nutrient broth is an example a simple liquid media that consists of what?
Peptone
Meat extract
Sodium chloride
Water
is an example of a simple solid medium. The medium is used routinely for isolation of many bacteria from clinical specimens.
Nutrient agar
-a media that contain some ingredients of unknown chemical composition.
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Complex media
-a complex medium contains some ingredients such as?
Meat juices
Digested protein
-the complex media contain what?
Water
Carbon sources such as glucose for bacteria growth
various salt needed for bacterial growth
A source of amino acids and nitrogen (beef and yeast extract)
-is a synthetic kind of medium which contains known quantities of all ingredients used but not contain any animal, yeast or plant tissue
Defined media
-defined media is consist of what?
Trace elements And vitamins
Define carbon source and nitrogen source required by a certain microbes
(Examples are glucosen or glycerol and ammonium salts or nitrates
-are invariably solid media that facilitate growth of certain fastidious bacteria. These media are prepared by adding
substances like blood, serum, and egg to the basal media in order to meet the nutritional requirements of more exacting and more fastidious bacteria.
Enriched media
-examples of enriched media
Blood agar
Chocolate agar
Loefflers serum
LJ medium
-examples of enriched media
Blood agar
Chocolate agar
Loefflers serum
LJ medium
- is an enriched medium in which nutritionally rich whole blood supplements constitute the basic nutrients.
Blood agar
- is enriched with heat-treated blood (80°C), which turns brown and gives the medium the color for which it is named.
Chocolate agar
are liquid media that stimulate the growth of certain bacteria or suppress the growth of others for isolation of desired pathogenic bacteria.
Enrichment media
- present in feces,tend to overgrow pathogenic ones in stool specimen.
Escherichia coli
-example or enrichment media that are used for the isolation of Salmonella typhi and Shigella spp. from feces
selenite-F broth or tetrathionate broth
These are solid media that contain substances that inhibit the growth of all but a few bacteria but at the same time facilitate isolation of certain
bacteria.
Selective media
- selective for the isolation of Vibrio cholerae
Thiosulfate citrate bile salt sucrose agar (TCBS)
- selective for enteric bacilli, such as Salmonella spp. and Shigella spp
Deoxycholate citrate agar (DCA)
- selective for Gram-negative bacteria
Hektoen enteric (HE) agar
- selective for Mycobacterium tuberculosis
LJ medium
selective for Gram-positive bacteria
Mannitol salt agar (MSA)
-selective for Gram-negative bacteria,
Xylose lysine desoxycholate (XLD) agar
-selective for certain Gram-negative bacteria, such as Legionella pneumophila.
Buffered charcoal yeast extract agar
-distinguish one microorganism from another growing on the same media by their growth characteristics
Differential or indicator media
- differential for lactose and sucrose
fermentation
Eosin methylene blue (EMB)
-, differential for lactose fermentation
MacConkey
differential for mannitol fermentation
Mannitol salt agar (MSA)
- differential for lac operon mutants for detection of recombinant strains of bacteria for study in molecular biology.
X-gal plates,
-are used to maintain the viability of certain delicate organisms in clinical specimens during their transport to the
laboratory.
They lack carbon, nitrogen,and organic growth factors, hence do not facilitate microbial multiplication
Transport media
-transport media typically contain this
only buffers and salt
medium for Neisseria gonorrhoeae
Stuart’s transport
-basically contains 1% “sugar”, which in microbiology denotes any fermentable substance, such as glucose, sucrose, lactose, and mannitol that is routinely used for fermentation tests.
Sugar media
-can be used for the short-term storage of bacterial cultures.
Refrigeration
-Is a process in which a pure culture of microbes is placed in a suspending liquid and quick-frozen at temperatures ranging from - 50º to -95°C. The culture can usually be thawed and cultured even several years later.
Deep freezing
- a suspension of microbes is quickly frozen at temperatures ranging from -54º to -95ºC, and the water is removed by a high vacuum (sublimation). The organisms can berevived at any time by hydration with a suitable liquid nutrient medium.
Lyophilization (freeze drying)
is a common method of preserving strains of bacteria
Cold storage
- for drying suspensions of bacteria for preservation purposes have been developed.
Drying methods
