Lab No (1):-Pure Culture technique.

Aim (goal):

Is getting on pure cultivated for morphological, biochemical study as well as serological description. In addition, it importance in preparation of vaccine and pathogenicity test.

Principle:

Most of means built in getting on pure culture in scientific principle in inhibition growth of some germs, at the same time ithelps growth of another group for purpose it is getting in pure culture. This ascertains either by using chemical factors or utilization physicals characteristics such as O2requirement, optimum temperature and osmotic pressure.

Pure Methods:

  1. Dilutions method.

This method uses for isolation and purification of bacteria from natural sources such as soil, water. There are two types of bacterial dilutions are decimal and double dilutions.

  1. Streaking method.

Frist of all ,streaks full loop or swab use or clinical sample on suitable media , then incubation at 37cfor 24h., after that choose isolated colonies ,and streaks on fresh medium .

  1. Power plate method.

In this method , the sample passes in numbers of decimal and double dilutions. After that, take suitable volume from last dilution ( may use the last three tubes)and add in to test tube contains soluble and cool N.A at 45-50 c and tube moves between hands for mix sample with agar soluble. Finally, media powers in plates by movement of plates for it diffuses in equal form on each media.

  1. Selective media: such as Tetrathionate broth, S.S Agar, Bismuth sulphate Agar for identification and isolation of Salmonella, MacConkey agar or MacConkey broth for isolation and purification of colon rods from water and sewage water.
  2. Selective Treatment: In sometimes, for isolation and purification of germs from clinical cases such as sputum it needs to treat samples within acid or base for facilitation of isolation and purification of mixed bacteria from normal flora for solubility of some mucous matter such as pulmonary T.B patients.
  3. Using of some physical properties of bacteria.
  1. O2 requirement.
  2. Temperature requirement.

Materials and methods

Samples:

Pus, sputum, blood, urine , diarrheal feces.

Materials.

  1. Bacterial Suspension from three types of bacteria are Staphylococcus aureus, Bacillus, E. coli.
  2. Petridishes of N. Agar.

Procedure :

  1. Streaks from bacterial suspension or bacterial nutrient broth on N. A. plates ,and incubation for 24 h. at 37c.
  2. Observe the growth produced on plates and distinguishes bacterial colonies.
  3. Examine typical colony for each bacteria in the this mixed culture and it must be these chosen colonies as single colony.
  4. Take singe colony and it streaks on N. A. medium .
  5. Incubate in bacterial incubation for 24h at 37 c and notes the morphological description for growth of colonies . Then, Staining of smear from these colonies by gram stain.
  6. Draw the mixed and single colony also distinguish each of colony ( single and mixed)
  7. Record results and notes.