Transcript The API 20E System

The API 20E System
• The API 20E System is miniaturized version of
conventional tests that is used for the identification
of members of the family Enterobacteriaceae and
other gram-negative bacteria.
• This system utilizes a plastic strip with 20
separate compartments.
• Each compartment consists of a depression, or
cupule, and a small tube that contains a specific
dehydrated medium
Inculcation
• To inoculate each compartment it is necessary to
first make up a saline suspension of the unknown
organism; then, with syring, each compartment is
filled with the bacterial suspension.
• The cupule receives the suspension and allows it
to flow into the tube of medium.
• The dehydrated medium is reconstituted by the
saline.
• To provide anaerobic conditions for some of the
compartments it is necessary to add sterile mineral
oil to them.
• After incubation for 18–24 hours, the reactions
are recorded, test reagents are added to some
compartments, and test results are tabulated.
Materials
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Agar slant or plate culture of unknown
Test tube of 5 ml 0.85% sterile saline
API 20E test strip
API incubation tray and cover
Squeeze bottle of tap water
Mineral oil
Syringe.
Oxidase test reagent
1. If you haven’t already done the oxidase test on
your unknown, do so at this time.
• It must be established that your unknown is
definitely oxidase negative before using this
system.
2. Prepare a saline suspension of your unknown by
transferring organisms from the center of a wellestablished colony on an agar plate (or from
aslant culture) to a tube of 0.85% saline solution.
3. Dispense about 5 ml of tap water into the tray
with a squeeze bottle. Note that the bottom of the
tray has numerous depressions to accept the water.
4. Vortex mix the saline suspension to get uniform
dispersal
5. Inoculate all the tubes on the test strip with the
pipette by depositing the suspension into the
cupules as you tilt the API tray
Important
• Slightly under fill ADH, LDC, ODC, H2S and URE.
(Note that the labels for these compartments are
underlined on the strip.) Under filling these
compartments leaves room for oil to be added and
facilitates interpretation of the results.
• Since the media in |CIT|, |VP|, and |GEL|
compartments require oxygen, completely fill both
the cupule and tube of these compartments.
• Note that the labels on these three compartments are
bracketed as shown here.
Results
• Each chemical test give specific color
• The result readied as number of 7 digits
• This No is matched with tables or with computer
program to identify the bacteria
Animation