Bacterial Inoculation Method: Introduction, Common types, Inoculation Pr

Bacterial Inoculation Method: Introduction, Common types, Inoculation Procedure, Uses and Keynotes

Introduction of Bacterial Inoculation Method

The bacterial inoculation method is necessary to inoculate the bacteria in the suitable media to study the characteristics of bacteria like isolation of pure culture from mixed, colony morphology, biochemical reactions, serotyping, antimicrobial sensitivity testing, etc. Different inoculation methods used in bacteriology are the streak plating technique, spread plate technique, and agar stab technique.

Types of Bacterial Inoculation Method

Inoculation by streaking
Inoculation by spreading
Inoculation by stabbing

Streak Plating Technique

Use a sterile loop every time: flames it for inoculation and after inoculation.
Place a loopful of the bacterial suspension/specimen on one side of the culture plate near the periphery.
Streak several times with the loop in the upper position to an area of the approximately 1-inch square.
Streak in the second corner of the culture plate. Streak several times as above overlapping the first area from one end.
Continue streaking in the next area several times not touching the upper streaks and coming down all the way in the zigzag fashion.

Use

To isolate most of the pathogens from the sites having plenty of mixed flora.
This method helps to get an isolated colony of bacteria.

Spread Plate Technique

A few loopful of the solid culture are put in the sterile saline, approximately 2 ml volume. The content is mixed to make a homogenous suspension.
This is matched with the turbidity standard 0.5 Mac Farland.
Inoculation of the plate using the sterile swab.
Start from one sector of the plate smoothly spreading up to the bottom area of the plate change 90° angle spread again down to the bottom area.
The last spreading is done around the periphery of the plate so that the bacteria is well spread and is uniform.

Use

This method is done for the sensitivity testing of the isolated organism as shown above image.

Agar Stab Technique

Use a sterile straight wire.
Pick up the organism for testing biochemical reactions.
This method is used for inoculating motility indole urea (MIU) medium and SIM (Sulfide, Indole, Motility) medium, and those are semisolid media.
Inoculated by stabbing in verticle fashion.

Inoculation in the broth medium

2-3 colonies are picked up using the sterile loop.
The broth is inoculated gently from the side of the bottle.
Colonies are mixed and suspended in the broth.
Recap the bottle and label the sample number and date.
Incubate at 37°C for 24 hours in an upright position.

Inoculation in the slant medium

The slope area is streaked using the inoculating loop with the colonies.
The butt area is stabbed gently using a sterile wire.
For practical purposes: It is better to use the straight wire to pick up isolated colonies.
Incubate at 37º C for 24 hours.

The procedure of inoculating of TSI slant

Falme to red heat the inoculating loop and the straight wire.
Allow cooling.
Take a few colonies from the pure culture needing identification.
Stab the butt using a straight wire.
Incubate the triple sugar iron (TSI) agar slant overnight with a loose cap.
Read the result.

Keynotes on Bacterial Inoculation Method

The streak plating technique is preferred for isolation of the pure culture.
For antimicrobial sensitivity testing, the spread plate technique is used.
For biochemical tests like MIU, SIM, the agar stab technique is applied.

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