| 5.1 |
Safety Precautions: |
| 5.1.1 |
Wear personal protective equipments such as protective hand gloves, nose masks and over gown during operation. |
|
| 5.1.2 |
Do not overheat the smear. |
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| 5.1.3 |
Staining solution to be handled carefully. It should not fall on the floor. |
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| 5.1.4 |
For oil immersion technique, use only one drop of immersion oil. Do not over flood the slide with immersion oil. |
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| 5.2 |
Procedure for Identification and Purity: |
| 5.2.1 |
Media preparation for all the tests has to be performed by referring SOP, Media Preparation and Sterilization. |
|
| 5.2.2 |
Perform the Purity Check on receipt of Mother Culture by staining method by isolating the bacteria. |
|
| 5.2.3 |
The staining procedure differentiate bacteria into gram positive and gram negative based on their ability to retain the primary dye (Crystal violet ) or loose the primary dye and accept the colour of the counter stain (safranin). |
|
| 5.2.4 |
The gram positive bacteria produces blue/purple colour with this staining procedure while gram negative ones are pink or red in colour. |
|
| 5.2.5 |
The staining reagent are:
1) Crystal violet: A primary dye.
2) Grams iodine: A complexing agent.
3) Alcohol: A decoloriser.
4) Safranin: A Counter strain. |
|
| 5.2.6 |
Prepare a thin smear of the culture to be examined on a glass slide. |
|
| 5.2.7 |
Air dry or heat fix the smear and flood the slide with Crystal Violet staining solution for 1 minute. Allow the slide to cool do not burn the slide. |
|
| 5.2.8 |
Wash the smear with 70% v/v Ethanol /Grams decolouriser till all the extra Crystal Violet stain is washed off. |
|
| 5.2.9 |
Wash with water and flood with Grams Iodine solution for 1 minute. |
|
| 5.2.10 |
Flood the smear with safranin solution for 1 to 2 minutes. Wash with water and Air dry the slide. |
|
| 5.2.11 |
Place a drop of cedarwood oil and examine under oil immersion lens 100X of the microscope. |
|
| 5.2.12 |
Gram positive organisms should observed blue in colour and Gram negative organisms should observe pinkish red colour. Record the results. |
|
| 5.3 |
Fungal Staining Procedure: |
| 5.3.1 |
Place a Lactophenol cotton blue reagent on a clean and dry slide and place a small loopful Aspergillus fungal culture into Lactophenol cotton blue reagent and tease the Aspergillus culture into thin preparation. |
|
| 5.3.2 |
Remove the excess stain using tissue paper. |
|
| 5.3.3 |
Wait for 15 minutes and observe under microscope. |
|
| 5.3.4 |
Place a coverslip on the slide before observing under the microscope.
Avoid air bubbles. |
|
| 5.3.5 |
Observe Initially under low power for screening in low intensity and then under high power intensity. |
|
| 5.3.6 |
Aspergillus brasilliensis produce white or yellow growth colonies that are covered by Septate dark asexual fungal spores. Record the results. |
|
| 5.4 |
Procedure for Motility testing: |
| 5.4.1 |
Prepare suspension of the Bacterial culture in normal saline, with the help of sterile nichrome loop place a drop of suspension of Bacterial culture on the cover slip. |
|
| 5.4.2 |
Grease the four corners of the cover slip. |
|
| 5.4.3 |
Place a cavity slide on the top of the cover slip taking care that drop is not disturbed. |
|
| 5.4.4 |
Invert the slide so that the cover slip is on the top of the slide. |
|
| 5.4.5 |
Observe under the microscope, first under low power for screening in low intensity and then under high power. |
|
| 5.4.6 |
For motile organisms eg. S boydii, S.aureus, motility can be seen towards the edge of the drop and for non motile organisms eg. B. Subtilis, E. coli, S. abony. C albicans, P. aeruginosa, the cells will be evenly distributed. |
|
| 5.4.7 |
After confirmation of Purity Check of Culture from colony characteristic, staining and Motility, Carry out the Biochemical test for the Cultures and compare the results obtained, as per Annexure. |
|
| 5.4.8 |
Confirm the growth of cultures on selective media as per SOP – Procedure for Testing Growth Promotion, Inhibitory and Indicative Properties of Culture Media. |
|
| 5.4.9 |
The commonly used Biochemical tests are mentioned below.
(a) Catalase test, (b) Coagulase test ,(c) Oxidase test,(d) Sugar fermentation test ,(e) Indole test ,(f) Citrate test and (g) Urease test. |
|
| 5.5 |
Biochemical tests for Escherichia coli: |
| 5.5.1 |
Procedure for Acid and Gas Test: |
|
| 5.5.2 |
Transfer a loopful of culture in 5 ml of sterile MacConkey Broth containing durhams tube. Incubate the test tube at 42 to 44°C for 24 hrs. |
|
| 5.5.3 |
Observation: Change in colour of MacConkey Broth from purple to yellow indicates the production of acid and formation of bubble in Durham’s tube indicates the production of gas. |
|
| |
Procedure for Indole Test: |
|
| 5.5.4 |
Transfer a loopful of culture in 5 ml of sterile Peptone water. Incubate the test tube at 42 to 44°C for 24 hours. |
|
| 5.5.5 |
Add a few drops of Kovacs reagent in the test tube and mix the content and allow the test tube to stand for about 2 minutes. |
|
| |
Observation: Formation of red ring in the reagent layer indicates the production of Indole. |
|
| 5.6 |
Biochemical Tests for Salmonella: |
| 5.6.1 |
Procedure for acidic butt and alkaline slant on Triple Sugar Iron (TSI) Agar. |
|
| 5.6.2 |
Streak a loopful of culture on the slant with sterile nichrome loop and stab the butt with straight sterile nichrome loop. |
|
| 5.6.3 |
Incubate at 30 to 35°C for 24 hours. |
|
| 5.6.4 |
Observation: Acidic butt should show Yellow colour and alkaline slant should show pink colour on TSI without production of H2S gas. |
|
| 5.6.5 |
Transfer a loopful of culture in 10 ml of RVSEB. Incubate at 30 to 35°C for 24 hrs. |
|
| |
Observation: Change in colour of the medium from blue to colourless. |
|
| 5.7 |
Biochemical test for Pseudomonas aeruoginosa |
| 5.7.1 |
Procedure for Oxidase Test: |
|
| 5.7.2 |
Place 2 or 3 drops of freshly prepared 1% w/v solution of N,N,N’,N’, Tetramethyl-4-phenylene-diamine dihydrochloride on a filter paper and smear with P. aeuroginosa colonies. For solution Preparation, refer SOP, Preparation and Handling of Laboratory reagents. |
|
| 5.7.3 |
Observation: Development of pink colour should change to purple colour. |
|
| 5.8 |
Biochemical test for Staphyloccocus aureus: |
| 5.8.1 |
Procedure for Coagulase test: |
|
| 5.8.2 |
Transfer a loopful of culture to individual tube containing 0.5 ml of coagulase rabbit or horse plasma. Incubate in water bath at 37°C, examine the tubes after 3 hours and subsequently at a 3 hour interval up to 24 hours. |
|
| 5.8.3 |
Observation: Formation of Clot. |
|
| 5.9 |
Biochemical Tests for Shigella boydii: |
| 5.9.1 |
Procedure for acidic butt and alkaline slant on Triple Sugar Iron (TSI) Agar. |
|
| 5.9.2 |
Streak a loopful of culture on the slant with sterile nichrome loop and stab the butt with straight sterile nichrome loop. |
|
| 5.9.3 |
Incubate at 30 to 35°C for 24 hours. |
|
| 5.9.4 |
Observation: Acidic butt should show Yellow colour and alkaline slant should show pink colour on TSI without production of H2S gas. |
|
| 5.9.5 |
Transfer a loopful of culture in 10 ml of GN Broth. Incubate at 30 to 35°C for 24 hrs. |
|
| 5.9.6 |
Observation: Change in colour from colourless to turbid. |
|
| 5.10 |
KOH String test or Gram Staining Alternative test |
| 5.10.1 |
Place a drop of 3% potassium hydroxide (KOH) on a glass slide. For solution Preparation, refer SOP, Preparation and Handling of Laboratory reagents. |
|
| 5.10.2 |
By using a nichrome loop, place a visible loopful of cells from a single, well isolated colony is mixed into the drop. |
|
| 5.10.3 |
Mix with Nichrome loop for about 60 seconds. |
|
| 5.10.4 |
Observation: If the mixture becomes viscous and a string is formed on lifting the nichrome loop (KOH positive) than the colony is considerd as gram negative. |
|
| 5.10.5 |
Note: This test is simple and can be done effectively on old cultures. This method can be done as a backup to gram staining. |
|
| |
If Purity Check and Identification of any culture is not satisfactory, repeat the test. If Fails after rechecking, procure a new culture. |
|
| 5.10.6 |
After Completion of the activity, decontaminate all the cultures and media by referring to SOP for Decontamination of microbial Waste. |
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