Inoculation and Incubation

Inoculation Techniques

Inoculation is a method used to introduce a sample (eg: bacteria) into a growth medium. This paves the way to study the microorganisms under congenial conditions.
Aseptic techniques must be strictly adhered to prevent contamination of the culture or the environment. Sterilized tools and a clean environment are crucial.
Examples of inoculation tools are inoculating loops and needles. These are often made of metal, and may be flame sterilised before and after use.
The source of the microorganisms can be a slant culture, a broth culture, or a plate culture, where bacteria have been growing on a solid or in a liquid medium.
Inoculation in solid media often involves streaking the sample across the surface of the medium to isolate individual colonies.
Inoculation in a liquid medium (broth) typically involves swirling the inoculating loop in the broth.

Incubation refers to maintaining the inoculated media under conditions favourable for the growth of microorganisms.
Proper temperature, pH, and oxygen levels dictate the successful growth of different microorganisms. Optimum conditions vary depending on the microorganism.
The incubation temperature for most human pathogens falls around the human body temperature (37°C).
Incubation time may range from a few hours to several days, depending on the species and growth conditions.
After incubation, colonies of bacteria become visible on solid media and broth media may become turbid due to bacterial growth.
It is crucial that once samples have been incubated, aseptic techniques are used to prevent contamination upon further examination.
The incubation period is also considered as the time between inoculation of microorganisms into a host and the onset of illness.
Gram staining, biochemical tests, and antibiotic susceptibility tests can be performed on the grown colonies for identification and diagnostic purposes.