Bacte LAB Streaking Flashcards
> One of the fundamental skills in diagnostic microbiology
> A technique employed for bacterial isolation from clinical or environmental sample
> A sample is spread in a petri dish in the form of a long, thin line over the surface of a solid medium.
Streak Plate Method
Purpose of Streaking (3)
> To produce isolated
colonies of an organism
on an agar plate.
> To produce pure colonies
(from mixed cultures).
Mixed cultures produces
varied colony
morphology
> To specifically identify
the isolated organisms
through biochemical
tests
The inoculum is streaked at one edge and
spread in vertical lines above the edge.
- The vertical lines a cross-streaked
diagonally - Suitable for propagating pure cultures
and dilute specimens
RADIANT STREAK
> The most commonly used and preferred
streaking method
> Four equal—sized sections of the agar
plate is streaked
> An initial streak is performed at the first
section then streak on the succeeding
sections sequentially.
QUADRANT STREAK
-An inoculum is evenly distributed in a single
continuous movement from starting point to
the center of the plate
- Used for diluted specimens (urine) or pure culture
cultivation - Used for semi-quantitation of colonies from urine
samples [using calibrated loop (0.01 or 0.001 ul)]
CONTINUOUS STREAK
- Also known as the “three-sector streak”
- A petri plate is divided into three sections
creating a “T” pattern - when the final section is being streaked,
the inoculum is diluted to the point to
produce isolated colonies - Follows discontinuous streaking (most of
the time
T-STREAK
- Often done in diagnostic laboratories
- Preferred method due to its time and
space efficiency
BI-PLATE STREAKING
Streaked plates are incubated for ___________ at _____. Bacterial growth (colonies on agar
plate) are expected
24 hour, 37 deg C
LIMITATIONS IN STREAKING (4)
Only aerobic or facultative
aerobic bacterial isolates
could be grown
Syntrophic bacteria
can‘t be purified by this
method
The primary suspension
should contain the viable
bacteria
The method is
skill-depended
a ____________________________ is followed where the loop is sterilized at the end of each quadrant prior to streaking over the next quadrant.
discontinuous fashion of streaking
It is routinely followed in urine culture. It is a modified form of continuous streaking. In this method, a calibrated loop (usually a loop of 1 or 2μl) is used to streak a certain volume of the liquid specimen.
Semi-quantitative Streaking
It is another form of continuous streaking where a loopful of the specimen is streaked all over the plate in a zigzag pattern in a single continuous movement. It is commonly done to propagate the pure culture
and culture them in large quantities.
Zigzag Streaking
