Aseptic Techniques and Cell Counting - Essay Example

All bacteria encountered in the laboratory should be regarded as potentially pathogenic, i.e. should they escape from the Petri dish, tube, or flask, etc. and enter a suitable host e.g. humans, they are capable of causing their characteristic disease.

Sterility is the complete absence of living microorganisms or spores. It is an absolute term - even one microbe can replicate to enormous numbers - thus partial sterility does not exist! Several different methods are used for sterilization and some of which we will use today. The maintenance of sterility requires the use of the Aseptic Technique. The object of this is to prevent any form of contact between the sterile growth medium (e.g. petri dish containing nutrient agar) or the pure culture and any source of contaminating organisms.

The new student should be aware that it is very easy to sterilize a pipette or bacteriological loop and then place it on the non-sterile bench whilst picking up something else. Sources of contamination include Any non-sterile surface, liquids, or air. Air is a very important contamination source because of; free-floating fungal or bacterial spores, liquid droplets, dust particles, and dried skin scales, all of which may contain bacteria and/or fungi. Good aseptic technique is crucial for work in microbiology, microbial genetics, or biotechnology.

Flaming using a Bunsen Burner is the classic method for rapid sterilization of bacteriological loops, glass pipettes, and bottle or flask necks. Flaming needs to be done for several seconds, long enough to raise the temperature well above 100 C. Bottlenecks should be rotated in the flame for 5 sec. or so to achieve this. For all basic techniques in microbiology and today’s exercise in liquid transfer and inoculation, manual dexterity in removing screw-on lids is important. The most reliable technique is to use the little finger to unscrew and hold lids and plugs, leaving the other fingers free to hold loops or pipettes, etc. The operator (i.e. you!) is the most likely source of small particles floating in the air and landing on your work.