Isolation of bacteria in pure culture

Isolation of bacteria in pure culture

To identify a bacterial pathogens, it’s necessary to isolate the bacteria in pure culture, many techniques can be used to isolate different microorganisms.
1. Streak plate technique:
Streak method is routinely employed for isolation of bacteria in pure culture. This technique involves the following steps:
1. Put a sterile wire loop over the flame of the burner until be red-hot and allow to cool.
2. Remove very small amount of bacterial culture or clinical materials by sterile wire loop.
3. Hold the late of medium near to the burner by free hand and put the inoculums on peripheral of the plate and spread over a small area.
4. Rotate the plate to 90? and streak over agar surface by making a parallel line vertical to the first one.
5. Sterile the loop again and rotate the plate toward right angle and making another lines of streak vertical toward quarter by touching the previous lines.
6. By the same process, repeat the streaking for 3 to 4 times until the whole surface of the agar plate is inoculated.
7. Streak the center of plate in a zigzag motion.
8. Incubate the plate in an inverted position at 37?C for 18-24hr.
2. Spread plate technique:
In this method take 0.1ml of sample of bacterial culture by pipette place over the surface of agar medium. Spread the bacteria culture over the surface by glass spreader then incubate the plate at 37?C for 18-24hr.
This technique is used for counting bacteria and also for swabbing from clinical lesions such as throat swab, ear swab, vaginal swab and others.
3. Pouring plate technique:
1. Inoculate a sterilized empty Petri dish with 0.1ml of bacterial culture or sample by using sterile pipette.
2. Pour the media into the Petri dish and allow to solidify.
3. Incubate the plate at 37?C for 18-24hr.
To differentiate between aerobic and anaerobic bacteria, aerobic bacteria grow a