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STREAKINGInmicrobiology,Streakingis a technique used to isolate a purestrain from a single species of

microorganism, oftenbacteria.Samples can then be taken from the resulting colonies and

amicrobiological culture can be grown on a new plate so that the organism can be identified,

studied, or tested.

The streaking is done using asterile tool, such as acotton swab or commonly aninoculation

loop.This is dipped in aninoculum such as a broth or patient specimen containing many speciesof bacteria.

The streak plate method is a rapid qualitative isolation method. The techniques commonly used

for isolation of discrete colonies initially require that the number of organisms in the inoculumsbe reduced. It is essentially a dilution technique that involves spreading a loopful of culture over

the surface of an agar plate. The resulting diminution of the population size ensures that,

following inoculation, individual cells will be sufficiently far apart on the surface of the agar

medium to effect a separation of the different species present. Although many type of proceduresare performed, the four ways or quadrant streak is mostly done.

The commonly used petri dishes are of hundred millimetre diameter. The agar surface of the

plate should be dry without any moisture such as condensation drops. The source of inoculumscan be clinical specimen, environmental swab, sedimented urine, broth or solid culture.

In the streaking procedure, a sterile loop or swab is used to obtain an uncontaminated microbial

culture. The process is called "picking colonies" when it is done from an agar plate with isolated

colonies and is transferred to a new agar or gelatin plate using a sterile loop or needle. The

inoculating loop or needle is then streaked over an agar surface. On the initial region of thestreak, many microorganisms are deposited resulting in confluent growth or the growth of culture

over the entire surface of the streaked area. The loop is sterilized by heating the loop in the blue

flame of the Bunsen burner, between streaking different sections, or zones and thus lesser microorganisms are deposited as the streaking progresses. The streaking process will dilutes out the

sample that was placed in the initial region of the agar surface. There are two most commonlyused streak patterns, a three sector "T streak " and a four quadrant streak methods.

Pouring the Agar Plate:

The agar is immediately poured into a sterile, dry petri plate while holding the top carefullyabove the petri plate bottom in order to avoid contamination. Replace the top, allow the agar to

cool and harden, and store the petri plates in an inverted position. When storing petri plates, do

not stack them more than three high, or use a special petri plate storage holder. The agar is then

poured into the plate using aseptic technique, preferably in a sterile cabinet (laminar air flow

cabinet.

http://en.wikipedia.org/wiki/Microbiologyhttp://en.wikipedia.org/wiki/Strainhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Microbiological_culturehttp://en.wikipedia.org/wiki/Sterilehttp://en.wikipedia.org/wiki/Cotton_swabhttp://en.wikipedia.org/wiki/Inoculation_loophttp://en.wikipedia.org/wiki/Inoculation_loophttp://en.wikipedia.org/wiki/Inoculumhttp://en.wikipedia.org/wiki/Inoculumhttp://en.wikipedia.org/wiki/Inoculation_loophttp://en.wikipedia.org/wiki/Inoculation_loophttp://en.wikipedia.org/wiki/Cotton_swabhttp://en.wikipedia.org/wiki/Sterilehttp://en.wikipedia.org/wiki/Microbiological_culturehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Strainhttp://en.wikipedia.org/wiki/Microbiology

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