The phenomena of producing immunity and vaccination technique consisting of introducing infectious agents into an absorptive surface of skin, in contrast to introducing the substance in tissues through injecting is inoculation. Broadly, it is to introduce antigenic substances into tissues.

It has a precise definition for processes carried out in vitro which involves the transferring of microbes from and to lab apparatus in research laboratories. It also finds its usage in commercial applications such as baking, brewing, wine making, producing antibiotics and more. A good example is the production of blue cheese through the inoculation of ripening cheese with dedicated molds of bacteria.

In simple terms, inoculation in microbiology is the process of introducing microbes into a culture media so that it reproduces there. Commonly, it is used in the introduction of vaccines, serum or any antigenic substance in the body so as to boost immunity against a particular disease.

This process of Inoculation is carried out in different media such as – plate culture, slant culture, agar plates, stab culture, sweep plate method and so on.

Various Inoculation Methods Used in Bacteriology

In Bacteriology, there are several techniques used for inoculating. Some of the most commonly used techniques are as discussed:

Streak plating method –

This method is used to obtain completely isolated colonies from a culture or specimen inoculum through the creation of sections of increasing dilution on a single plate.

  • Inoculate clinical specimens through the use of sterile inoculation loop into the agar media. Spread the specimen gently on a section of the culture media surface
  • Extract loop from the inoculated area and distribute into a second part
  • Extract loop from the other section and disperse it to the 3rd section. Continue for the 3rd and 4th section. Make sure that sections 1 and 4 are not overlapping. Unload inoculation loop used into suitable containers
  • Substitute the lid followed by incubating the streaked agar plate at the optimum temperature (inverted stance), so as to curb condensation

Agar stab technique –

It is used in the preparation of stab cultures, from a plate select single colonies.

  • Select a well-isolated colony through aseptic technique using an inoculating stab needle (sterile) and stab it a few times via the agar to the base of the tube
  • Substitute the cap and secure loosely during incubation enabling exchange of gases
  • Incubation of this stabbed plate at the suitable temperature is carried out

Spread Plate Technique

It is used for evenly spreading cells to ensure growth of the well isolated separate colonies. Further, it can be used for serial dilutions.

  • Onto the agar media, with the help of a sterile spreader, inoculate the clinical specimen where we spread the bacteria gently on the whole culture media surface. This is done by rotating the plate while spreading it backwards and forward. Refrain from allowing the spreader to touch the edges of the plate
  • Substitute the lid and ensure the plate is standing in an upright position for drying (10-12 minutes)
  • Now incubate the spread agar plate at the optimum temperature with the lid at the base (inverted)

This was a brief on culture media used, some other media such as anaerobic culture techniques, liquid culture techniques and pour plate do exist.

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